Methods and systems for analyzing samples using cavity ring-down spectroscopy and methods for generating predictive models

Abstract

The present disclosure discloses methods and systems for analyzing samples using cavity ring-down spectroscopy and generating predictive models. At least a portion of the sample is loaded into a ring-down cavity. For each of a set of wavelengths, a laser beam is generated and directed into the ring-down cavity. The laser beam entering the ring-down cavity is eliminated. Light intensity attenuation data for light leaving the ring-down cavity is recorded via a light intensity sensor system. Using at least indirectly a data set of light intensity attenuation data for previously analyzed samples, the probability that a subject from whom the sample was received has a physiological condition or the extent of a physiological condition is determined from the light intensity attenuation data for the set of wavelengths, wherein the presence or absence of a physiological condition or the extent of a physiological condition has been identified for the previously analyzed sample.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 62 / 828,750, filed on April 3, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present description relates generally to spectroscopy, and more particularly to methods and systems for analyzing samples using cavity ring-down spectroscopy, and methods for generating predictive models. Background Art

[0004] The diagnosis of certain physiological conditions can be challenging. One such physiological condition is lung cancer, which is one of the most prevalent and deadly forms of cancer. Although the prognosis can be improved when lung cancer is found in its early, localized stages, in most cases the cancer is not diagnosed until it has already begun to spread. The survival rate for lung cancer decreases significantly as it spreads from the local area to other areas. Therefore, early detection of lung cancer is critical.

[0005] Currently, low-dose computed tomography (LDCT) is recommended for screening of lung cancer. However, this approach is associated with a high false-positive rate, causing many patients to undergo unnecessary follow-up evaluations. Along with the high costs associated with the technology and patient exposure to radiation, its lack of sensitivity makes LDCT an unattractive solution, as its low specificity can lead to a high false-positive rate.

[0006] A large body of recent research on breath biomarkers for lung cancer detection shows the promise of this alternative form of screening. Thousands of volatile organic compounds ("VOCs") have been identified in exhaled human breath, with concentrations ranging from parts per million by volume (ppmv) to parts per trillion by volume (pptv). Although cancer cells are believed to influence the production of a group of VOCs in the body that enter the lungs through the bloodstream and leave the body in exhaled breath, there is no strong agreement on what those specific VOCs are.

[0007] The most widely used technique for VOC detection in exhaled breath is mass spectrometry, which is often combined with gas chromatography ("GC-MS"). GC-MS is popular because it offers high selectivity and sensitivity in compound detection and strong accuracy in compound identification. The likelihood that two compounds will behave similarly in a mass spectrometer and a gas chromatograph is low, making GC-MS a reliable choice when certainty is necessary. In lung cancer breath analysis, GC-MS was first used to analyze lung cancer breath biomarkers in 1985. Several studies since then have focused on identifying dozens of potential biomarkers. Despite advances in the technology, GC-MS is impractical for widespread clinical use because it is expensive, time consuming, and requires complex sample collection procedures, limiting its use in laboratory research.

[0008] Another technology that has emerged in breath analysis is the electronic nose ("E-nose"), which uses an array of gas-sensitive sensors to detect different groups of VOCs. This VOC detection method has some advantages over GC-MS, such as its relatively low cost, small size, speed, and ability to be used in "online" applications. Online breath analysis has the potential to eliminate the need for sample storage and provide more immediate feedback to clinicians. However, electronic noses are far from ideal. They require frequent calibration, they are sensitive to humidity and temperature changes, and they experience drift and memory effects. They also tend to lack the features that make GC-MS attractive, such as its high sensitivity, high selectivity, and its ability to identify individual compounds.

[0009] Cavity ring-down spectroscopy ("CRDS") is a method commonly used to analyze a sample by its absorption spectrum. A typical CRDS system employs a laser that generates a beam of light that is directed into a cavity of a chamber having two highly reflective mirrors. The beam is typically within the visible or near infrared ("IR") spectrum and is tuned to a single wavelength. The beam is then repeatedly reflected between the mirrors, which allows a portion of the light to escape the ring-down cavity.

[0010] In order to "fill" a ring-down cavity, the length of the cavity must be consistent with the wavelength of the laser. This is usually achieved by adjusting the position of one of the two mirrors. When the laser resonates with the cavity mode, intensity is generated in the cavity due to constructive interference. When the light entering the cavity is eliminated, the intensity of the light in the ring-down cavity decays at a predetermined rate when it is empty. A small portion of the light is not reflected by the mirror and escapes from the ring-down cavity. The intensity of the escaping light is measured by a sensor component to determine the decay rate.

[0011] When a sample is placed in a ring-down cavity, analytes (e.g., volatile organic compounds) present in the sample absorb some of the light, thereby accelerating the decay of the intensity of the light in the ring-down cavity. An absorption spectrum is generated by measuring the decay time of light in the presence of the sample at specific wavelengths relative to the decay time of light in the absence of the sample at these wavelengths. Identification and quantification of individual analytes in a sample can be achieved by a variety of methods, such as linear regression of the measured absorption spectrum of the sample with the known absorption spectra of various analytes.

[0012] While individual analytes can be easily identified, the specific analyte that can be used to positively detect the presence or absence of a particular physiological condition, such as in the case of lung cancer, may be unclear. Breath samples can be collected from patients in a non-invasive manner and analyzed by CRDS, however, since there is no widely accepted protocol for analytes that demonstrate the presence or absence of lung cancer in the breath, and since breath samples contain many confounding components that may make detection of a single analyte difficult, a different approach is required. Summary of the invention

[0013] In one aspect, a method for analyzing a sample using cavity ring-down spectroscopy is provided, the method comprising: loading at least a portion of the sample in a ring-down cavity; for each of a set of wavelengths: generating, via at least one laser, a laser beam at the wavelength that is directed into the ring-down cavity; eliminating the laser beam that enters the ring-down cavity; and recording, via a light intensity sensor system, light intensity attenuation data for light leaving the ring-down cavity; and determining, via at least one processor, at least indirectly using a data set of light intensity attenuation data for previously analyzed samples, a probability that a subject from whom the sample was received has a physiological condition or the extent of a physiological condition from the light intensity attenuation data for the set of wavelengths, wherein the presence or absence of a physiological condition or the extent of a physiological condition has been identified for the previously analyzed sample.

[0014] The determining may include using a predictive model based at least in part on a data set of light intensity attenuation data.

[0015] The physiological condition may be lung cancer.

[0016] The sample and the previously analyzed sample may be a breath sample.

[0017] The group of wavelengths may be a first group of wavelengths, wherein the sample may be loaded from a thermal desorption tube, the at least a portion of the sample may be a first portion of the sample, the first portion of the sample is desorbed from the thermal desorption tube heated to a first desorption temperature so as to load at least the first portion of the sample into a ring-down cavity, and the method may further include: loading a second portion of the sample desorbed from the thermal desorption tube heated to a second desorption temperature; for each of the second group of wavelengths: generating a laser beam at the wavelength directed into the ring-down cavity via at least one laser; eliminating the laser beam entering the ring-down cavity; and recording light intensity attenuation data for light leaving the ring-down cavity via a light intensity sensor system.

[0018] The second set of wavelengths may be equal to the first set of wavelengths.

[0019] The method may also include combining, for each of the first set of wavelengths, light intensity attenuation data from the second portion of the sample with light intensity attenuation data from the first portion of the sample.

[0020] The determination may be performed using a predictive model trained at least in part using a dataset of light intensity attenuation data from previously analyzed samples.

[0021] The generating, eliminating, and recording may be performed until the control module determines that a desired level of light intensity attenuation data has been collected.

[0022] In another aspect, a system for analyzing a sample using cavity ring-down spectroscopy is provided, the system comprising: a ring-down cavity; at least one laser operable to generate a laser beam at each wavelength in a set of wavelengths, the laser beam being directed into the ring-down cavity; a sample loading system for loading at least a portion of a sample into the ring-down cavity for analysis and for unloading the at least a portion of the sample from the ring-down cavity; a light intensity sensor system positioned to record light intensity attenuation data for light exiting the ring-down cavity; at least one processor operably coupled to the sample loading system, the at least one laser, and the light intensity sensor system; a memory storing computer readable instructions, the computer readable instructions The instructions, when executed by the at least one processor, cause the at least one processor to: control a sample loading system to load at least a portion of a sample into a ring-down cavity; for each of the group of wavelengths: operate at least one laser to generate a laser beam directed into the ring-down cavity; eliminate the laser beam entering the ring-down cavity; and record light intensity attenuation data for light leaving the ring-down cavity via a light intensity sensor system; and at least indirectly, cause a data set of light intensity attenuation data for samples previously analyzed to determine, from the light intensity attenuation data for the group of wavelengths, a probability that a subject from whom the sample was received has a physiological condition or a degree of a physiological condition, wherein the presence or absence of a physiological condition or a degree of a physiological condition has been identified for the previously analyzed sample.

[0023] The at least one processor may determine the probability using a predictive model based at least in part on a data set of light intensity attenuation data.

[0024] The physiological condition may be lung cancer.

[0025] The sample and the previously analyzed sample may be a breath sample.

[0026] The group of wavelengths may be a first group of wavelengths, the sample may be set in a thermal desorption tube, at least a portion of the sample may be a first portion of the sample, at least one processor may control a sample loading system to desorb the first portion of the sample by heating the thermal desorption tube to a first desorption temperature to load the first portion of the sample into the ring-down cavity, and wherein the at least one processor may control the sample loading system to desorb the second portion of the sample by heating the thermal desorption tube to a second desorption temperature to load the second portion of the sample into the ring-down cavity after unloading the first portion of the sample from the ring-down cavity, and wherein the at least one processor may, for each of the second group of wavelengths: operate at least one laser to generate a laser beam directed into the ring-down cavity; eliminate the laser beam entering the ring-down cavity; and record light intensity attenuation data for light leaving the ring-down cavity via a light intensity sensor system.

[0027] The second set of wavelengths may be equal to the first set of wavelengths.

[0028] The at least one processor may combine the light intensity attenuation data from the second portion of the sample with the light intensity attenuation data from the first portion of the sample for each of the first set of wavelengths.

[0029] The at least one processor may determine the probability from the light intensity decay data using a predictive model trained at least in part using a dataset of light intensity decay data for previously analyzed samples.

[0030] The at least one processor may repeat the operations of eliminating and recording until the at least one processor determines that a desired level of light intensity attenuation data has been collected.

[0031] On the other hand, a method for analyzing a sample using cavity ring-down spectroscopy is provided, the method comprising: heating a thermal desorption tube to a first desorption temperature to desorb a first portion of a sample contained therein; loading the first portion of the sample into a ring-down cavity; for each of a first set of wavelengths: generating a laser beam at the wavelength directed into the ring-down cavity via at least one laser; eliminating the laser beam entering the cavity; and recording light intensity attenuation data for light leaving the ring-down cavity via a light intensity sensor system; unloading the first portion of the sample from the ring-down cavity; heating the thermal desorption tube to a second desorption temperature to desorb a second portion of the sample contained therein; loading the second portion of the sample into the ring-down cavity; for each of a second set of wavelengths: generating a laser beam at the wavelength directed into the ring-down cavity via at least one laser; eliminating the laser beam entering the cavity; and recording light intensity attenuation data for light leaving the ring-down cavity via a light intensity sensor system; and analyzing the light intensity attenuation data for desorption at the first desorption temperature and the light intensity attenuation data for desorption at the second desorption temperature.

[0032] The first set of wavelengths may be equal to the second set of wavelengths.

[0033] The method may also include combining, for each of the first set of wavelengths, light intensity attenuation data from the second portion of the sample with light intensity attenuation data from the first portion of the sample.

[0034] The second desorption temperature may be greater than the first desorption temperature.

[0035] The first desorption temperature may be equal to the second desorption temperature.

[0036] The analysis may include at least indirectly using a data set of light intensity attenuation data for a previously analyzed sample to determine, from the light intensity attenuation data for a first portion of the sample and the light intensity attenuation data for a second portion of the sample, a probability that a subject from whom the sample was received has a physiological condition or the extent of the physiological condition, wherein the presence or absence of the physiological condition or the extent of the physiological condition has been identified for the previously analyzed sample.

[0037] The determination may be performed using a predictive model trained at least in part using a dataset of light intensity attenuation data for previously analyzed samples.

[0038] In yet another aspect, a system for analyzing a sample using cavity ring-down spectroscopy is provided, the system comprising: a ring-down cavity; at least one laser operable to generate a laser beam directed into the ring-down cavity; a sample loading system for loading at least a portion of the sample into the ring-down cavity for analysis and for unloading at least a portion of the sample from the ring-down cavity, the sample loading system comprising a heater configured to heat a thermal desorption tube containing the sample; a light intensity sensor system positioned to record light intensity attenuation data for light exiting the ring-down cavity; at least one processor operably coupled to the sample loading system, the at least one laser, and the light intensity sensor system; a storage device storing computer-readable instructions that, when executed by the at least one processor, cause the at least one processor to: control the sample loading system to heat the thermal desorption tube to a first desorption temperature to desorb a first portion of the sample contained therein; The invention relates to a method for preparing a thermal desorption tube according to the present invention and comprising the steps of: controlling the thermal desorption tube to heat the thermal desorption tube to a second desorption temperature so as to desorb the second portion of the sample contained therein, and loading the first portion of the sample into the ring-down cavity; for each of the first set of wavelengths: operating at least one laser to generate a laser beam at the wavelength guided into the ring-down cavity; eliminating the laser beam entering the ring-down cavity; and recording light intensity attenuation data for the light leaving the ring-down cavity via a light intensity sensor system; unloading the first portion of the sample from the ring-down cavity; controlling the sample loading system to heat the thermal desorption tube to a second desorption temperature so as to desorb the second portion of the sample contained therein, and loading the second portion of the sample into the ring-down cavity; for each of the second set of wavelengths: operating at least one laser to generate a laser beam at the wavelength guided into the ring-down cavity; eliminating the laser beam entering the ring-down cavity; and recording light intensity attenuation data for the light leaving the ring-down cavity via a light intensity sensor system; and analyzing the light intensity attenuation data of the desorption at the first desorption temperature and the light intensity attenuation data of the desorption at the second desorption temperature.

[0039] The first set of wavelengths may be equal to the second set of wavelengths.

[0040] The computer executable instructions, when executed by the at least one processor, may cause the at least one processor to combine light intensity attenuation data from the second portion of the sample with light intensity attenuation data from the first portion of the sample for each of the first set of wavelengths.

[0041] The second desorption temperature may be greater than the first desorption temperature.

[0042] The first desorption temperature may be equal to the second desorption temperature.

[0043] The computer executable instructions, when executed by at least one processor, may cause the at least one processor to at least indirectly use a data set of light intensity attenuation data for a previously analyzed sample to determine, from the light intensity attenuation data for a first portion of the sample and the light intensity attenuation data for a second portion of the sample, a probability that a subject from whom the sample was received has a physiological condition or the extent of the physiological condition, wherein the presence or absence of the physiological condition or the extent of the physiological condition has been identified for the previously analyzed sample.

[0044] The determination may be performed using a predictive model trained at least in part using a dataset of light intensity attenuation data for previously analyzed samples.

[0045] In yet another aspect, a method for generating a predictive model for cavity ring-down spectroscopy is provided, comprising: for each of a plurality of samples identified as having a physiological condition or a degree of a physiological condition, each of the samples being stored in at least two thermal desorption tubes, and for each of at least two mutually unique desorption temperature sequences: selecting a previously unselected one of the at least two thermal desorption tubes containing the sample; for each desorption temperature in the sequence, in order: heating the previously unselected one of the at least two thermal desorption tubes to a desorption temperature to desorb a portion of the sample contained therein; loading the portion of the sample into a ring-down cavity; for each of a set of wavelengths: generating via at least one laser a laser beam at the wavelength directed into the ring-down cavity; eliminating the laser beam entering the ring-down cavity; and recording light intensity decay data for the wavelength for the portion of the sample; and unloading the portion of the sample from the ring-down cavity; and identifying for which of the at least two mutually unique desorption temperature sequences the light intensity decay data has a greater correlation with the presence or absence of the physiological condition that the plurality of samples have been identified as having or the degree of the physiological condition.

[0046] Each subsequent desorption temperature in at least one of the at least two desorption temperature sequences may be higher than a previous desorption temperature in at least one of the at least two desorption temperature sequences.

[0047] In another aspect, a system for generating a predictive model for cavity ring-down spectroscopy analysis is provided, comprising: a ring-down cavity; at least one laser operable to generate a laser beam directed into the ring-down cavity; a sample loading system for loading at least a portion of the sample into the ring-down cavity for analysis and for unloading at least a portion of the sample from the ring-down cavity, the sample loading system comprising a heater configured to heat a thermal desorption tube containing the sample; a light intensity sensor system positioned to record light intensity attenuation data for light exiting the ring-down cavity; at least one processor operably coupled to the sample loading system, the at least one laser, and the light intensity sensor system; a storage device storing computer readable instructions that, when executed by the at least one processor, causes the at least one processor to: for each of a plurality of samples identified as having a physiological condition or a degree of a physiological condition, each sample is stored in at least two thermal desorption tubes, and ... For each of at least two mutually unique desorption temperature sequences: selecting a previously unselected one of at least two thermal desorption tubes containing a sample; for each desorption temperature in the sequence, in order: heating the previously unselected one of the at least two thermal desorption tubes to a desorption temperature to desorb a portion of the sample contained therein; loading the portion of the sample into a ring-down chamber; for each of a set of wavelengths: generating via at least one laser a laser beam at the wavelength directed into the ring-down chamber; eliminating the laser beam entering the ring-down chamber; and recording light intensity decay data for the wavelength for the portion of the sample; and unloading the portion of the sample from the ring-down chamber; and identifying for which of the at least two mutually unique desorption temperature sequences the light intensity decay data has a greater correlation with the presence or absence or degree of a physiological condition that a plurality of samples have been identified as having.

[0048] Each subsequent desorption temperature in at least one of the at least two desorption temperature sequences may be higher than a previous desorption temperature in at least one of the at least two desorption temperature sequences.

[0049] On the other hand, a method for analyzing a sample using cavity ring-down spectroscopy is provided, comprising: heating a thermal desorption tube to a first desorption temperature to desorb a first portion of a sample contained therein; discharging the first portion of the sample without performing cavity ring-down spectroscopy analysis thereon; heating the thermal desorption tube to a second desorption temperature different from the first desorption temperature to desorb a second portion of the sample contained therein; loading the second portion of the sample into a ring-down cavity; for each of a second set of wavelengths: generating, via at least one laser, a laser beam at the wavelength that is directed into the ring-down cavity; eliminating the laser beam entering the cavity; and recording, via a light intensity sensor system, light intensity attenuation data for light leaving the ring-down cavity; and analyzing the light intensity attenuation data.

[0050] The analysis may include at least indirectly using a data set of light intensity attenuation data for a previously analyzed sample to determine from the light intensity attenuation data for a second portion of the sample a probability that a subject from whom the sample was received has a physiological condition or the extent of a physiological condition, the presence or absence of the physiological condition or the extent of the physiological condition having been identified for the previously analyzed sample.

[0051] In another aspect, a system for analyzing a sample using cavity ring-down spectroscopy is provided, the system comprising: a ring-down cavity; at least one laser operable to generate a laser beam directed into the ring-down cavity; a sample loading system for loading at least a portion of the sample into the ring-down cavity for analysis and for unloading at least a portion of the sample from the ring-down cavity, the sample loading system comprising a heater configured to heat a thermal desorption tube containing the sample; a light intensity sensor system positioned to record light intensity attenuation data for light exiting the ring-down cavity; at least one processor operably coupled to the sample loading system, the at least one laser, and the light intensity sensor system; and a storage device storing computer-readable instructions, the The computer-readable instructions, when executed by at least one processor, cause the at least one processor to: heat the thermal desorption tube to a first desorption temperature to desorb a first portion of a sample contained therein; discharge the first portion of the sample without performing cavity ring-down spectroscopy thereon; heat the thermal desorption tube to a second desorption temperature different from the first desorption temperature to desorb a second portion of the sample contained therein; load the second portion of the sample into a ring-down cavity; and for each of a second set of wavelengths: generate, via at least one laser, a laser beam at the wavelength directed into the ring-down cavity; eliminate the laser beam entering the cavity; and record, via a light intensity sensor system, light intensity attenuation data for light exiting the ring-down cavity; and analyze the light intensity attenuation data.

[0052] The computer executable instructions, when executed by the at least one processor, cause the at least one processor to at least indirectly use a data set of light intensity attenuation data for a previously analyzed sample to determine from the light intensity attenuation data for the second portion of the sample a probability that a subject from whom the sample was received has a physiological condition or a degree of the physiological condition, wherein the presence or absence of the physiological condition or the degree of the physiological condition has been identified for the previously analyzed sample.

[0053] Other technical advantages will become apparent to one of ordinary skill in the art after reviewing the following drawings and description. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] For a better understanding of one or more embodiments described herein and to more clearly show how the same may be implemented, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0055] Figure 1 is a schematic diagram of various optical and pneumatic components of a CRDS system according to one embodiment;

[0056] Figure 2 is used to load the breath sample into Figure 1 and 2 A cross-sectional view of the thermal desorption tube in the ring-down chamber of the CRDS;

[0057] Figure 3 It is used to control Figure 1 Schematic diagram of the electrical control system for the various optical and pneumatic components of the CRDS system shown;

[0058] Figure 4 According to one embodiment, the use Figure 1 General method for analyzing samples using the CRDS system;

[0059] Figure 5 The use of the embodiment is shown Figure 1 Method for generating prediction model of CRDS system;

[0060] Figure 6 The use according to another embodiment is shown Figure 1 Method for analyzing light intensity attenuation data of samples using a CRDS system;

[0061] Fig. 7A A CRDS analysis system according to another embodiment is shown, wherein a computing device is in communication with the CRDS system; and

[0062] Figure 7B yes Fig. 7A Schematic diagram of a computing device.

[0063] Unless otherwise specifically noted, the articles shown in the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0064] For simplicity and clarity of explanation, reference numerals in the drawings may be repeated, where deemed appropriate, to indicate or similar elements. In addition, in order to provide a thorough understanding of one or more embodiments or multiple embodiments described herein. However, those skilled in the art will appreciate that the embodiments described herein may be practiced without these specific details. In other cases, well-known methods, processes, and components are not described in detail to avoid confusing the embodiments described herein. First, it should be understood that although exemplary embodiments are shown in the drawings and described below, any number of technologies may be used to implement the principles of the present disclosure, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and technologies shown in the drawings and described below.

[0065] The various terms used throughout this specification may be read and understood as follows, unless the context dictates otherwise: "or" as used throughout is inclusive, as if written as "and / or"; singular articles and pronouns as used throughout include their plural forms and vice versa; similarly, gendered pronouns include their counterparts, such that the pronouns should not be construed as limiting anything described herein to use, implementation, performance, etc. by a single gender; "exemplary" should be understood as "illustrative" or "exemplary" and not necessarily as "preferred" over other embodiments. Further definitions of terms may be set forth herein; these may apply to prior and subsequent instances of these terms, as will be understood by reading this specification.

[0066] Without departing from the scope of the present disclosure, the systems, devices and methods described herein may be modified, added to or omitted. For example, the components of the systems and devices may be integrated or separated. In addition, the operations of the systems and devices disclosed herein may be performed by more, fewer or other components, and the methods described may include more, fewer or other steps. In addition, the steps may be performed in any suitable order. As used herein, "each" refers to each member of a set or each member of a subset of a set.

[0067] Any module, unit, component, server, computer, terminal, engine or device illustrated herein that executes instructions may include or otherwise access computer-readable media, such as storage media, computer storage media or data storage devices (removable and / or non-removable), such as, for example, disks, optical disks or tapes. Computer storage media may include volatile and non-volatile, removable and non-removable media implemented by any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical storage, cassettes, tapes, disk storage or other magnetic storage devices, or any other medium that can be used to store required information and can be accessed by applications, modules or both. Any such computer storage medium may be part of a device or accessible or connectable thereto. In addition, unless the context clearly indicates otherwise, any processor or controller set forth herein may be implemented as a single processor or multiple processors. Multiple processors may be arrayed or distributed, and any processing function mentioned herein may be performed by one or more processors, even if a single processor may be illustrated. Any methods, applications, or modules described herein may be implemented using computer-readable / executable instructions, which may be stored or otherwise held by such computer-readable media and executed by one or more processors.

[0068] The following disclosure presents a novel method for analysis using CRDS. Unlike conventional methods in which light intensity attenuation data is compared to light intensity attenuation data for a single known analyte, a data set of light intensity attenuation data for a set of previously analyzed samples that have been identified as having a physiological condition or a degree of a physiological condition is used to at least indirectly analyze the light intensity attenuation data recorded for the sample. In a preferred embodiment, this is accomplished by using a predictive model generated on a set of training data using machine learning. In addition, the process of incrementally desorbing samples from a thermal desorption tube can be used to provide additional information about the sample. Further, the predictive model can be improved by using machine learning to determine which combinations of desorption temperatures and / or wavelengths provide light intensity attenuation data that has a greater correlation with a physiological condition or a degree of a physiological condition, using the physiological condition or the degree of a physiological condition to identify multiple samples.

[0069] A physiological condition is any type of condition that a subject may be in. A physiological condition may include a disease, an infection, a functional state of one or more organs or body systems, etc. The extent of a physiological condition may include severity, stage (such as cancer stage), growth size, glandular output, etc. In some cases, the extent of a physiological condition may be binary, to indicate the presence or absence of a physiological condition in a subject. The degree may be discrete or may be continuous.

[0070] The various components of the CRDS system 20 for analyzing a sample according to a particular embodiment are shown in FIG. Figure 1 2 is shown in FIG. A CO2 laser 24 and a carbon 13O2 laser 28 are provided. The CO2 laser 24 and the carbon 13O2 laser 28 are gas tube lasers that emit at a series of quasi-uniformly spaced known frequencies that can be quickly selected using an adjustable diffraction grating arrangement. Gas tube laser technology has a long history and is a stable and robust way to generate infrared radiation at precisely known frequencies. Both the CO2 laser 24 and the carbon 13O2 laser 28 emit light in the mid-IR spectrum.

[0071] Each of the CO2 laser 24 and the Carbon 13O2 laser 28 has an actuator and output coupler that enables adjustment of the length of the laser cavity and an actuator to change the angle of the grating at the back of the cavity, thereby changing its pitch to adjust the wavelength it reflects. By adjusting the length of the laser cavity and changing the angle of the grating, the laser can be very accurately tuned to a specific wavelength and desired mode quality.

[0072] The CO2 laser 24 generates a first laser beam 32 and the carbon 13O2 laser 28 generates a second laser beam 36. Depending on the desired optical frequency, the CO2 laser 24 is either tuned and the first laser beam 32 is generated while the carbon 13O2 laser 28 is detuned, or the carbon 13O2 laser 28 is tuned and the second laser beam 36 is generated while the CO2 laser 24 is detuned. In this way, at most only one of the CO2 laser 24 and the carbon 13O2 laser 28 outputs a beam at any particular time, so that the first beam 32 and the second beam 36 are not combined at the same time. Mid-infrared, particularly long-wavelength infrared, is selected as the type of light because most volatile organic compounds absorb light in this range. As a result, a variety of volatile organic compounds can be measured by a single system. The CO2 laser operates in this range and has sufficient power and line width narrowness for ring-down spectroscopy. The use of two lasers increases the range and number of available wavelengths that the CRDS system 20 can use to analyze samples.

[0073] The first laser beam 32 is redirected via a mirror 40 on the optical mount to a beam splitter 44. The beam splitter 44 is partially reflective and partially transmissive and splits each of the first laser beam 32 and the second laser beam 36 into two beams, a sampling beam 48 and a working beam 52, the working beam 52 having the same characteristics as the sampling beam 48 and may have a similar intensity as the sampling beam 48.

[0074] The sampling beam 48 is received by a fast infrared detector 56. The fast infrared detector 56 measures the amplitude and beat frequency of the sampling beam 48 using an oscilloscope. The beat frequency may indicate the presence of higher order modes caused by suboptimal tuning of the CO2 laser 24 or the carbon 13O2 laser 28. In response to detecting an undesirable beat frequency, the corresponding laser 24 or 28 is tuned until the amplitude of the beat frequency is minimized or eliminated while maximizing the intensity. If the amplitude of the beat frequency cannot be reduced below an acceptable level, the laser may be tuned to a different wavelength.

[0075] The working beam 52 continues to the first optical modulator 60, which then deflects the working beam 52 to a reflector 64 on an optical mount. The reflector 64 redirects the light to the second optical modulator 68, which in turn deflects the working beam 52 to a focusing lens 72. The optical modulators are used to control the intensity of the beam generated by the laser. In the present embodiment, the first optical modulator 60 and the second optical modulator 68 are acousto-optic modulators ("AOM"), also known as Bragg devices. An AOM is a type of optical modulator that uses a piezoelectric transducer coupled to a material such as germanium or glass. In the described embodiment, the material is germanium. When an oscillating electrical signal is applied to the piezoelectric transducer, the piezoelectric transducer vibrates, generating acoustic waves in the material. These acoustic waves expand and compress the material, thereby generating periodic changes in the refractive index and allowing Bragg diffraction. Light entering the AOM at a first-order Bragg angle relative to a plane perpendicular to the axis of propagation of the acoustic wave will be deflected by an amount equal to twice the Bragg angle at maximum efficiency. Eliminating the electrical signal eliminates the Bragg diffraction properties of the material and allows the light to pass through undeflected, effectively attenuating the light along the deflected optical path. A byproduct of the AOM is that the frequency of the deflected light is shifted.

[0076] In other embodiments, the light modulator may also be an electro-optic modulator. An electro-optic modulator is another type of light modulator that applies a DC or low-frequency electric field to a material to distort the position, orientation, and / or shape of the material's molecules. As a result, the refractive index is changed to change the phase of the outgoing light beam as a function of the applied field. By sending the light beam through a polarizer, the phase modulation is converted into an intensity modulation. In another approach, a phase modulator can act as an intensity modulator when placed in a branch of an interferometer.

[0077] Furthermore, although the CRDS system 20 is described as having two optical modulators, in other embodiments, the CRDS system may have a fewer or greater number of optical modulators.

[0078] The first optical modulator 60 and the second optical modulator 68 act as attenuators to adjust the intensity of the working beam 52 and eliminate the beam at the beginning of a ring-down event. A ring-down event includes the elimination of the working beam 52 irradiating the ring-down cavity or the detuning of the laser of the ring-down cavity, and the collection of light intensity data from the ring-down cavity. Because they are AOMs, the first optical modulator 60 and the second optical modulator 68 use the acousto-optic effect to diffract light using acoustic waves (usually at radio frequencies). In each of the first optical modulator and the second optical modulator, a piezoelectric transducer is coupled to a material such as germanium or glass, and an oscillating electrical signal is used to oscillate the piezoelectric transducer. The vibrating piezoelectric transducer generates an acoustic wave in the material, which expands and compresses the material, thereby generating a periodic change in the refractive index and allowing Bragg diffraction. Light entering the AOM at a Bragg angle relative to a plane perpendicular to the propagation axis of the acoustic wave will be deflected at maximum efficiency by an amount equal to twice the Bragg angle. Eliminating the electrical signal eliminates the Bragg diffraction characteristics of the material and allows the light to pass through without deflection, effectively eliminating the light along the deflected optical path. Therefore, the intensity of the sound can be used to modulate the intensity of the light in the deflected beam.

[0079] The intensity of the light deflected by each of the first optical modulator 60 and the second optical modulator 68 can be between about 85%, which represents the maximum deflection efficiency of the optical modulators 60, 68, and the attenuation limit of each of the first optical modulator 60 and the second optical modulator 68 is about 0.1% of the input light intensity. When the acoustic wave applied to the germanium is turned off, the deflected beam loses about 30dB or 99.9% of the previous intensity. The attenuation limit means the upper limit of how much the optical modulator can reduce the input light intensity.

[0080] Optical modulators are asymmetric because, as a side effect, when receiving input light at their first end, they Doppler shift the frequency of the light in a first mode, and when receiving input light at their second end, they Doppler shift the frequency of the light in a second mode that is opposite to the first mode and attenuates the same power. However, the Doppler shift of the frequency of the light is in the same direction regardless of whether the light enters at the first or second end.

[0081] Conventional CRDS systems use a single optical modulator and therefore have a frequency-shifted operating beam. These frequency shifts are typically small relative to the frequency of the light and can change the way the light is absorbed by the material in the cavity, but this frequency shift can be compensated for during analysis. If the diffraction is toward the source of the acoustic wave in the AOM, the frequency shift is downward, while if the diffraction is away from the source of the acoustic wave, the frequency shift is upward. As discussed, the effect is minimal.

[0082] The working beam 52 deflected by the second light modulator 68 is focused by a focusing lens 72. The laser beam, and therefore the working beam 52, continues to diverge as it travels from the CO2 laser 24 or the carbon 13O2 laser 28. The focusing lens 72 focuses the working beam 52 downward.

[0083] A mirror 76 on the optical mount then redirects the working beam 52 to the ring-down chamber 80. The two mirrors 64, 76 extend the path length of the working beam 52.

[0084] The ring-down chamber 80 is an elongated tube in which a resonant cavity, referred to as a ring-down cavity 84, is defined. A front cavity mirror 88a and a rear cavity mirror 88b (also referred to herein as cavity mirrors 88) are located at the longitudinal ends of the ring-down cavity 84. The cavity mirror 88 is highly reflective, both for light directed to the cavity mirror 88 from outside the ring-down cavity 84 and for light directed to the cavity mirror 88 within the ring-down cavity 84. As a result, a portion (about 0.1%) of the working light beam 52 is directed to the front cavity mirror 88a, passes through the front cavity mirror 88a, and enters the ring-down cavity 84, while a majority (about 99.9%) of the working light beam 52 is reflected back to the mirror 76.

[0085] The cavity mirror 88 is mounted on a mirror mount 92, which can be actuated to adjust the position and orientation of the cavity mirror 88. In particular, the front cavity mirror 88a, which faces the front of the ring-down cavity 84, is mounted on the mirror mount 92, which can be actuated by three mechanized micrometers 96a. The rear cavity mirror 88b, which faces the rear of the ring-down cavity 84, is mounted on the mirror mount 92, which can be actuated by three piezoelectric micrometers 96b, which can be manually adjusted for optical alignment or actuated by a piezoelectric device that allows them to be further adjusted by a piezoelectric driver.

[0086] The angle of each cavity mirror 88 can be changed so that they are sufficiently aligned so that the light beam does not deviate when it enters the ring-down cavity 84. If one of the cavity mirrors 88 is askew, some of the light is reflected to the side of the ring-down cavity 84, losing light intensity and generating higher-order modes. The micrometer 96 can also be adjusted simultaneously to change the length of the ring-down cavity 84 without affecting the angular alignment. This allows the ring-down cavity 84 to be tuned so that the ring-down cavity 84 resonates at the frequency of the light entering the ring-down cavity 84.

[0087] The focusing lens 72 focuses the laser to match the optical mode of the ring-down cavity 84 so that the minimum beam waist of the beam is located at the same position as the minimum beam waist of the ring-down cavity 84. The position of the focusing lens 72 can be adjusted to match the optical mode of the laser wavelength range.

[0088] A light intensity sensor system in the form of a liquid nitrogen cooled detector 100 is located behind the rear cavity mirror 88b to receive light escaping therethrough. The liquid nitrogen cooled detector 100 measures the intensity of light escaping from the ring down cavity 84. Other types of light intensity sensor systems for measuring the intensity of escaping light may be used in place of the liquid nitrogen cooled detector 100.

[0089] The sample is loaded into the ring-down chamber 84 from a thermal desorption tube 104 for collecting samples for testing.

[0090] Now refer to Figure 2 , an exemplary thermal desorption tube 104 is shown. The thermal desorption tube 104 has a tubular stainless steel shell 105, defining an orifice 106 at each end thereof. The receiving end 107 of the thermal desorption tube 104 receives the sample. In the exemplary described embodiment, the sample is human breath collected from a human body for testing. The foam separator 108 is positioned toward the receiving end and is configured to distribute the fluid pressure more evenly across the cross-section of the stainless steel shell 105. The adsorbent material 109 is located near the foam separator 108 and another foam separator 110. The separators can also be made of wire mesh or other suitable materials. The adsorbent material 109 is very porous, has a relatively high surface area, and is selected for sampling specific compounds to capture and retain the compounds of interest, even in the presence of other compounds. In addition, the adsorbent material 109 allows the collected compounds to be easily desorbed or extracted for analysis. In addition, the selected solid adsorbent does not react with the sample. In a specific example, the solid adsorbent is Tenax or a carbon material. As the sample is received via the receiving end 107, the sample is more concentrated toward the receiving end 107 of the thermal desorption tube 104. In other embodiments, the composition and configuration of the thermal desorption tube may vary, as will be appreciated by those skilled in the art.

[0091] During the sample collection process, breath is collected by a breath collection device in which a thermal desorption tube 104 is mounted. The breath collection device can be relatively small, such as a wearable mask, or can be relatively large, such as a tabletop unit into which a person breathes. The breath sample is received by a receiving end 107 of the thermal desorption tube 104. Human breath contains a variety of small molecules and macromolecules, which are then captured by the adsorbent material 109 in the thermal desorption tube 104. In other embodiments, other types of gaseous samples can be collected by the thermal desorption tube.

[0092] Reference again Figure 1, the sample loading system 112 is used to load the sample from the thermal desorption tube 104 into the ring-down chamber 84, and to evacuate the sample loading system 112 containing the ring-down chamber 84. During the loading of the sample, the sample loading system 112 fills the ring-down chamber 84 with at least a portion of the sample that has been collected (i.e., desorbs the sample from the thermal desorption tube 104 and allows the sample to enter the ring-down chamber 84 without introducing contaminants), brings the pressure and temperature in the ring-down chamber to one atmosphere and 50 degrees Celsius, and seals the ring-down chamber 84. In this embodiment, the absorption spectra of a set of samples to which the measured absorption spectra are at least indirectly compared are determined at this pressure and temperature to ensure consistency between these parameters, which can affect the results. However, in other embodiments, the pressure and temperature can be fixed at other levels for the known and measured absorption spectra. During the evacuation of at least part of the sample, the sample loading system 112 cleans the previously provided sample from the ring-down chamber 84 and the various conduits used to guide the sample from the thermal desorption tube 104 to the ring-down chamber 84.

[0093] The sample loading system 112 has an inlet portion that includes a nitrogen source 116. The nitrogen source 116 is a very clean nitrogen supply that is pressurized or can pressurize nitrogen to at least one atmosphere. In the present embodiment, the nitrogen source 116 is pressurized at a pressure of 5 psi above ambient pressure, but can be changed as long as the pressure is sufficient to pressurize the ring-down chamber 84 to one atmosphere, or some other selected atmospheric pressure for analysis. In the illustrated embodiment, the nitrogen source 116 is nitrogen that has evaporated from a liquid nitrogen storage. The nitrogen source 116 is connected to a gas inlet valve 124a by a conduit 120. Auxiliary gas inlet valve 124b can be connected to other gases, but is not often used. The gas inlet and auxiliary gas inlet valves 124a, 124b are connected to the inlet line 120a. A pressure gauge 128 is positioned along the inlet line 120a and the inlet line valve 124c. A filter 130a is positioned along the inlet line 120a before the cavity inlet valve 124d, which seals the inlet line 120a from the ring-down cavity 84. The filter 130a blocks contaminants from entering the ring-down cavity 84, where they can deposit on the cavity mirror 88 and interfere with reflections.

[0094] The gas inlet valve 124a and the auxiliary gas inlet valve 124b are in communication with the access valve 124e. The access valve 124e allows or prohibits direct access to the desorption tube pipeline 120b and the sample outlet pipeline 120c.

[0095] The desorption line 120b includes a front valve 124f and a rear valve 124g. The thermal desorption tube 104 is located between the front valve 124f and the rear valve 124g, and the receiving end 107 of the thermal desorption tube 104 is positioned toward the rear valve 124g. The thermal desorption tube 104 is located in a controllable heater 132 to heat the thermal desorption tube 104 to a certain temperature range.

[0096] The sample outlet line 120 c includes a sample outlet valve 124 h and a mass flow controller 136 .

[0097] The sample loading system 112 also has an outlet portion that includes a chamber outlet valve 124i that communicates with the ring-down chamber 84. An outlet line 140 is in communication with the chamber outlet valve 124i. A pressure gauge 144 is located along the outlet line 140. A vacuum shutoff valve 124j is located between the pressure gauge 144 and a vacuum pump 148. A vacuum suction valve 124k is in communication with the vacuum pump 148 and draws air through a pump suction line 150. A filter 130b is located in the pump suction line 150 to prevent contaminants that may interfere with the operation of the vacuum pump 148 from entering.

[0098] Valves 124a - 124k may also be referred to herein as valves 124 .

[0099] Although the chamber inlet valve 124d and the chamber outlet valve 124i are shown coupled to the ring-down chamber 84 at certain locations for convenience, it should be understood that the locations at which the valves 124d, 124i are coupled to the ring-down chamber 84 may vary. In a preferred configuration, the chamber inlet valve 124d communicates with the ring-down chamber 84 toward its end adjacent to the front chamber mirror 88a, and the chamber outlet valve 124i communicates with the ring-down chamber 84 toward its end adjacent to the rear chamber mirror 88b.

[0100] When a new sample is to be loaded into the ring-down chamber 84, the thermal desorption tube 104 containing the new sample is coupled to the sample loading system 112, such as Figure 1 shown.

[0101] During the evacuation phase, the vacuum intake valve 124k is opened and the vacuum pump 148 is turned on. The vacuum intake valve 124k is then closed, and the vacuum shut-off valve 124j, the chamber outlet valve 124i, the chamber inlet valve 124d, the inlet line valve 124c, and the access valve 124e are opened in sequence. The contents of the pipelines along the path and the ring-down chamber 84 are evacuated from the CRDS system 20 by the vacuum pump 148. The pressure gauge 144 is able to determine when the system is sufficiently evacuated, particularly when the pressure gauge 128 is disconnected from the vacuum pump 148. When it is determined that the system has been sufficiently evacuated, these same open valves 124j, 124i, 124d, 124c, and 124e are then closed in reverse order. Thereafter, during the nitrogen filling phase, valves 124a, 124c, 124d, 124i, and 124j are opened to allow nitrogen from the nitrogen source 116 to fill the pipelines 120a and 140. Another evacuation phase is then used to purge the nitrogen. The nitrogen filling phase and evacuation phase may be repeated as needed to clear the line. The CRDS system 20 is thus evacuated of the previously tested sample.

[0102] During the loading of a new sample, the thermal desorption tube 104 is flushed to remove carbon dioxide and water from the thermal desorption tube 104 to minimize the amount of carbon dioxide and water loaded into the ring-down chamber 84. To flush the thermal desorption tube 104, the gas inlet valve 124a, the gas inlet line valve 124c, and the back valve 124g are opened to provide a path to nitrogen gas to flush forward the thermal desorption tube 104. The thermal desorption tube 104 is selected to inhibit the collection of carbon dioxide and water with the sample, and some carbon dioxide and water are usually still present in the thermal desorption tube 104.

[0103] 500 ml of nitrogen is passed through the thermal desorption tube to remove the carbon dioxide and water remaining in the thermal desorption tube 104 from the original sample. Then the forward valve 124f and the sample outlet valve 124h are opened to provide a path to the mass flow controller 136. The mass flow controller 136 allows the nitrogen and the entrained carbon dioxide and water to be released at a specified flow rate. In this configuration, the flow rate is 500 ml / min. Then all valves 124 are closed.

[0104] Once the carbon dioxide and water are removed from the thermal desorption tube 104, the sample loading system 112 is evacuated again using the same method described above to remove the nitrogen that was just introduced into the lines of the sample loading system 112. The heater 132 surrounding the thermal desorption tube 104 then heats the thermal desorption tube 104 to the desired temperature to thermally desorb at least a portion of the new sample within the thermal desorption tube 104. The gas inlet valve 124a, the passage valve 124e, the front valve 124f, the rear valve 124g, and the chamber inlet valve 124d are then opened to provide a direct path for nitrogen from the nitrogen source 116 through the thermal desorption tube 104 having the desorbed compound of interest to the ring-down chamber 84.

[0105] It is desirable to obtain a pressure of one atmosphere within the ring-down chamber 84 because all reference data collected and analyzed is at this pressure level, thereby ensuring that the results are repeatable.

[0106] The gas inlet valve 124a is triggered to open and close by the system, and then the system waits for the pressure reading at the pressure gauge 128 to stabilize and reach one atmosphere. If the pressure reading is still below one atmosphere when the pressure gauge 128 stabilizes, the gas inlet valve 124a is switched again to repeat the process until the pressure reading is one atmosphere. When the pressure gauge 128 shows that the pressure level in the ring-down chamber 84 is one atmosphere, the valves are all closed.

[0107] If desorption at multiple temperatures is desired, the vacuum pump 148 is turned on, the chamber outlet valve 124i and the vacuum shut-off valve 124j are opened to evacuate the ring-down chamber 84. The chamber outlet valve 124i is then closed before repeating the desorption process.

[0108] Since some sample may be lost between back valve 124g and chamber inlet valve 124d, full evacuation is not typically performed between desorptions.

[0109] By pressurizing a fixed volume ring-down chamber containing a sample to a desired pressure level in this manner, the surface area within the ring-down chamber to which compounds can adhere can be reduced compared to a variable volume ring-down chamber that can be used to raise the pressure within the chamber to a desired level.

[0110] Furthermore, the pressure gauge 128 is located upstream of the path of the sample from the thermal desorption tube 104 to the ring-down chamber 84, thereby preventing sample contamination.

[0111] Figure 3 is a schematic diagram of an electronic control subsystem 200 for various components of the CRDS system 20 also illustrated. All lines represent electrical or electronic signals, arrows represent one-way communications, voltage settings, etc., and lines without arrows represent two-way communications.

[0112] The control module 204 includes one or more processors for controlling Figure 1 The control module 204 has one or more processors 205 and a memory 206 storing computer executable instructions that, when executed by the processor 205, cause the processor 205 to direct the other components of the CRDS system 20 as described herein. The control module 204 can be any type of component that includes at least one processor that executes computer executable instructions to control the operation of the other components of the CRDS system 20 as described herein.

[0113] A pair of RF drivers 208 sends a signal of approximately 40 MHz to power the CO2 laser 24 and the carbon 13O2 laser 28. Each of the lasers 24, 28 is tuned using an output coupler and a diffraction grating. A grating actuator 212 actuates (rotates) the diffraction grating. Another actuator actuates (translates) the output coupler. Each output coupler is driven by a 1000V output coupler piezoelectric 216. The dual-channel high-voltage amplifier 220 that powers the output coupler piezoelectric 216 can be adjusted between 0V and 1000V. The high-voltage amplifier 220 is provided with an analog output signal from a data acquisition ("DAQ") card 224 in the control module 204. The DAQ generates an output between 0V and 10V, and the high-voltage amplifier 220 multiplies the signal by 100 to generate a signal from 0V to 1000V, thereby powering the output coupler piezoelectric 216. Each grating actuator 212 that changes the grating angle is driven by an actuator driver 228 which is commanded by the control module 204 via RS-232. Each grating actuator 212 moves a number of millimeters which is converted into the pitch angle of the laser 24,28.

[0114] Data signals from the pressure gauges 128, 144 of the sample loading system 112 are received via RS-232.

[0115] The fast infrared detector 56 is connected to a small amplifier 232 and an oscilloscope 236 which can be used to read the amplitude and frequency of the beat signal used to tune the lasers 24 , 28 .

[0116] The temperature controller 240 for the thermal desorption tube heater 132 is controlled by the control module 204 via RS-232. The tube heater 132 contains a temperature sensor and an aluminum sheet with a heating tape wrapped around it. Both the heating tape and the temperature sensor are connected to the temperature controller 240 which is a PID (Proportional Integral Derivative) controller. The PID controller reads the temperature back to the main control module 204 via RS-232.

[0117] The relay board 244 is connected to the control module 204 and is used to open and close all of the solenoid valves 124 and the vacuum pump 148 .

[0118] The three-channel piezo driver 248 drives the piezo actuator 252, which actuates the micrometer 96b to adjust the length of the ring-down cavity 84. Each channel has two components: communication with the piezo driver via RS-232, and analog input from the DAQ card 224. In other embodiments, two or more piezo drivers may be used.

[0119] Each optical modulator 60, 68 is driven by an RF driver 256 that sends a signal of approximately 40MHz. Changing the frequency of the RF driver 256 changes the Bragg angle of a given wavelength of light, or changes the wavelength of light to which a given or fixed Bragg angle is tuned. If the RF driver 256 is tuned to a specific frequency and set to full power, most of the working beam 52 (about 85%) passes through. If adjusted to 80%, 70%, the optical modulator 60, 68 will attenuate. If the RF driver 256 is set to zero, the optical modulator 60, 68 is completely turned off. The frequency of the RF driver 256 is set via the RS232 pass component. Analog and digital components can set the amplitude and on / off conditions of the RF driver 256. Specifically, the DAQ card 224 sends a signal to the timing circuit 260 through a digital output ("DO"), which in turn generates the four necessary signals required to enable and set the amplitude of the RF driver. The timing circuit 260 also communicates with the control module 204 via the digitizer 264, enabling the control module 204 to control its operation under steady-state conditions or ring-down trigger conditions, wherein the timing circuit 260 sets the four voltages to zero and then returns to the previous voltage level after a predetermined amount of time. The digitizer 264 sends a trigger pulse to the timing circuit 260 to cause the optical modulators 60, 68 to eliminate the laser light provided to the ring-down cavity 84 during the ring-down event.

[0120] Figure 4 The use of Figure 1 Method 300 for analyzing a sample using a CRDS system 20. Conventionally, samples analyzed using CRDS are desorbed at a single temperature. In method 300, a portion of the sample in the thermal desorption tube is first desorbed at a first temperature, and then at least one additional portion of the sample can be desorbed from the thermal desorption tube at at least one additional temperature. In some cases, it may be desirable to separate portions of the sample for analysis using the CRDS system 20. For example, acetone and ammonia can be desorbed from the thermal desorption tube at a lower temperature. Since acetone and ammonia can overwhelm the spectrum and blur other substances in the sample, it may be necessary to desorb and analyze portions of the sample at different temperatures to separate various substances from other substances. In other embodiments, it may be desirable to desorb the sample twice or more at the same temperature because some components of the sample may be easily desorbed at the temperature for the first time, while other components of the sample may not be easily desorbed at the temperature for the first time, but may be equally easy to desorb at the second time. Since other components can be easily desorbed, they are less present in the second desorption, so the other components are more separated. The ordered set of desorption temperatures may therefore include a single desorption temperature or an ordered set of two or more desorption temperatures.

[0121] Reference now Figure 1 , 34, the method 300 begins by setting the temperature of the heater 132 to the first desorption temperature in the ordered set of desorption temperatures (310). In this particular configuration, a set of one or more temperatures to be used to desorb the sample from the thermal desorption tube 104 can be sorted. In a preferred method, the desorption temperatures are sorted from lowest to highest. In another embodiment, the ordered set of desorption temperatures may include two desorption temperatures that are the same or similar. Desorbing a portion of the sample at a certain temperature to release easily desorbed components / compounds and then analyzing, and then desorbing another portion of the sample at the same temperature to release less easily desorbed components / compounds, can be analyzed with a reduced amount of more easily desorbed components / compounds.

[0122] A first desorption temperature in the ordered set of desorption temperatures is selected, and the heater 132 is operated to heat the thermal desorption tube 104 to the first desorption temperature. Once the thermal desorption tube 104 is heated to the first desorption temperature by the heater 132, the portion of the sample that has been desorbed at the first temperature is loaded into the ring-down chamber 84, as previously described (320). Once a portion of the sample is loaded into the ring-down chamber 84, a laser beam is generated by one of the lasers 24, 28 that has been tuned to one of a set of wavelengths (330). The set of wavelengths can be selected from the wavelengths at which the lasers 24, 28 can generate beams in any desired manner. The generated laser beam is directed through the first optical modulator 60, reflected by the reflector 64, passed through the second optical modulator 68, and reflected by the reflector 72 into the ring-down chamber 80. The optical modulators 60, 68 slightly attenuate the working beam 52 to modulate its intensity.

[0123] When the working beam 52 reaches the front cavity mirror 88a, a portion of about 0.1% penetrates the front cavity mirror 88a and enters the ring-down cavity 84. The majority of the working beam, about 99.9%, is initially reflected back to the working laser 24 or 28 along the same path.

[0124] Initially, the ring-down cavity 84 is not illuminated. Light enters the ring-down cavity 84, and when most of the light in the ring-down cavity 84 is reflected between the two cavity mirrors 88, the amount of light or power in the ring-down cavity 84 begins to increase as further light is introduced from the outside via the working beam 52. A portion of the light leaks out through the cavity mirror 88. It takes a certain duration to "fill" the ring-down cavity 84 with light, and this may occur when the cavity length is equal to the adjacent resonant length of the ring-down cavity 84 of the tuned laser. At this point, there is a balance between the incident light and the leakage.

[0125] Once this equilibrium is reached, the laser beam directed into the ring-down cavity 84 is eliminated (340). The laser beam entering the ring-down cavity 84 can be eliminated in a variety of ways. In certain embodiments, the digitizer 264 sends a trigger pulse to the timing circuit 260 to cause the optical modulators 60, 68 to eliminate the laser light provided to the ring-down cavity 84. In other embodiments, the laser can be turned off or detuned so that it is not resonant for the configured cavity length, etc.

[0126] The timing circuit 260 simultaneously directs the first optical modulator 60 and the second optical modulator 68 to attenuate the light beam at or near the attenuation limit of the optical modulators 60, 68 to reduce the intensity of the light beam from the first optical modulator 60. In the CRDS system 20, by directing the two optical modulators 60, 68 to be turned off simultaneously, the amount of light deflected by the first optical modulator 60 during a short time interval is significantly reduced by the second optical modulator 68 when the second optical modulator 68 is turned off.

[0127] The second optical module 68 greatly increases the attenuation achieved by the first optical modulator 60 alone. In the currently described embodiment, if the first optical modulator 60 can attenuate 30 dB, and the second optical modulator 68 can attenuate an additional 30 dB, the total attenuation achieved via the optical modulators 60, 68 is the sum of their attenuations, i.e., 60 dB. During the filling of the ring-down cavity 84 with light, the optical modulators 60, 68 attenuate the working beam 52 to modulate its intensity. In the present configuration, each optical modulator 60, 68 attenuates the working beam 52 by 5 dB, for a total attenuation of 10 dB. As a result, each of the optical modulators 60, 68 can also further attenuate the working beam 52 by 25 dB, for a total further attenuation of 50 dB. In a conventional setup, one optical modulator must attenuate the working beam by 10 dB, leaving 20 dB of further attenuation available to eliminate the working beam. As will be appreciated, the further attenuation of 50 dB via two optical modulators 60, 68 may extinguish the operating light beam 52 more quickly than one optical modulator with a further attenuation of 20 dB. As a result, the amount of additional light introduced into the ring-down cavity 84 after the optical modulators 60, 68 have been directed off is a fraction of the further light introduced by a single optical modulator arrangement in a conventional CRDS system. By extinguishing the operating light beam 52 more quickly, the optical attenuation measured in the ring-down cavity 84 is less affected by the additional light during the ramp-down time of the optical modulators 60, 68, thus providing greater accuracy when matching the observed decay time to the known decay time.

[0128] The elimination of the laser supplied to the ring-down cavity 84 initiates the ring-down event. In alternative embodiments, the resonant laser supplied to the ring-down cavity 84 may be eliminated in other ways, such as by detuning the laser. By initiating the triggering of the ring-down event via a threshold, the ring-down event may be timed to occur during the peak while the ring-down cavity 84 is resonant with the laser, rather than on one side of the peak. In addition, since the bandwidth of the resonance is approximately 10 millivolts, the resolution of the piezoelectric driver 248 is insufficient to accurately track the peak.

[0129] During the ring-down event, the control module 204 records the light intensity decay data (350) reported by the liquid nitrogen cooled detector 100 exiting the back end of the ring-down cavity 84. In the present configuration, the ring-down event lasts approximately 10 microseconds, but may last longer or shorter in other embodiments. The light decay time is approximately 2 microseconds.

[0130] It is then determined whether to repeat the ring-down event (360). In this embodiment, the CRDS system 20 is configured to collect light intensity decay data for 500 ring-down events.

[0131] Approximately 100 microseconds after triggering the ring-down event, the timing circuit 260 directs the optical modulators 60, 68 to resume allowing the working light beam 52 to pass through to the ring-down cavity 84. If the light intensity decay data from the 500 ring-down event has been captured, the control module 204 stops the operation of the piezoelectric driver 248 and then determines the decay rate based on the ring-down event data, which refers to the light intensity decay data and can be used interchangeably herein. Conversely, if it is determined at 360 that additional light intensity decay data is to be collected, the control module 204 continues to direct the piezoelectric driver 248 to actuate the rear cavity mirror 88b. When the total voltage reaches a maximum or minimum value, it begins to proceed in the opposite direction. That is, if the total voltage AV increases before reaching the maximum voltage within its range, the total voltage AV then decreases back toward the voltage corresponding to the resonant length RL. Alternatively, if the total voltage AV decreases before reaching the minimum voltage within its range, the total voltage AV then increases back toward the voltage corresponding to the resonant length RL. In this way, ring-down events are triggered in both directions.

[0132] The light intensity decay data is collected as quickly as possible because the various outputs may drift. For example, the piezoelectric actuator 252 may have a settling time known as piezoelectric creep.

[0133] In other embodiments, any number of ring-down events may be employed at each wavelength and desorption temperature. In one embodiment, ring-down events at a wavelength and desorption temperature may be performed until a desired level of light intensity decay data is collected. The light intensity decay data collected so far may be analyzed quickly as it is collected to determine if it appears valid. After the desired number of ring-down events for valid light intensity decay data has been collected, the system may consider that sufficient data has been collected at that wavelength and desorption temperature. This may shorten the time required to perform the analysis in many cases.

[0134] When collecting light intensity decay data at the selected wavelength, the control module 204 can process the light intensity decay data for a particular sample, desorption temperature, and wavelength, such as by determining the decay rate for each ring-down event and averaging these values. Other methods can be used to process the ring-down event data.

[0135] It is then determined whether there are additional wavelengths in the group to be laser generated (370). If there are additional wavelengths to be generated, the method 300 returns to 330 where the lasers 24, 28 are tuned to generate laser beams of the newly selected wavelength.

[0136] The process is repeated for other wavelengths of light to generate an absorption spectrum of the sample at a specific desorption temperature. The light intensity data from the liquid nitrogen cooled detector 100 actually provides or is easily converted into light intensity decay data indicating how quickly light of a specific wavelength is absorbed by the sample portion loaded into the ring-down cavity 84.

[0137] For example, the light generated by the CO2 laser 24 provides an absorption coefficient for a range of wavelengths. Similarly, an absorption coefficient can be generated for a range of wavelengths of light from the carbon 13O2 laser 28. In this way, an absorption spectrum of the sample can be generated.

[0138] Once the portion of the sample that desorbed at the first temperature generates an absorption spectrum spanning the set of wavelengths, the portion of the sample is unloaded from the ring-down chamber (375). It is determined whether there are other temperatures in the ordered set to which the thermal desorption tube 104 will be heated to desorb other portions of the sample for analysis in the ring-down chamber 84 (380). If it is determined that there are other temperatures to be used to desorb a portion of the sample, the heater is set to a next desorption temperature at 310. In this embodiment, the next desorption temperature to which the thermal desorption tube 104 is heated is higher than the previous desorption temperature (S) to which the thermal desorption tube 104 was heated. If the ordered set of desorption temperatures contains a single desorption temperature, the method 300 does not return to 310.

[0139] As previously described, desorption of a sample contained in the thermal desorption tube 104 at another temperature that is higher than other temperatures at which the thermal desorption tube 104 previously desorbed may generate a different subset of compounds / species in the sample.

[0140] Once the light intensity attenuation data for each desorption temperature is collected, the CRDS system 20 analyzes the light intensity attenuation data for the set of wavelengths and the set of desorption temperatures to determine a probability that the patient from whom the sample was drawn has a particular physiological condition or degree of a physiological condition (390). The probability is determined at least indirectly using a dataset of light intensity attenuation data for previously analyzed samples for which the presence or absence of a physiological condition or degree of a physiological condition (i.e., lung cancer in the exemplary embodiment) has been identified. The determination of the probability may use a predictive model based at least in part on a dataset of light intensity attenuation data for previously analyzed samples.

[0141] CRDS system 20 can determine the probability that the subject from which the analysis sample was drawn has one of a set of discrete degrees of physiological conditions, and then present the most likely degree of physiological condition or the entire probability group. In addition, CRDS system 20 can also provide a confidence level for each result.

[0142] The light intensity attenuation data collected at each desorption temperature can be analyzed at least indirectly using a dataset of light intensity attenuation data of previously analyzed samples separated by the same or similar desorption temperatures. Preferably, the dataset of light intensity attenuation data of previously analyzed samples is collected using the same or similar temperature sequence used to desorb portions of the sample. In an alternative embodiment, the light intensity attenuation data from two or more desorption temperatures of a sample can be combined together and analyzed using a predictive model generated at least in part based on the light intensity attenuation data of previously analyzed samples, which were processed in the same or similar manner (i.e., the light intensity attenuation data for corresponding desorption temperatures). The predictive model can be generated from the dataset of light intensity attenuation data of previously analyzed samples. A preferred method is to use supervised machine learning.

[0143] The data set of light intensity decay data for previously analyzed samples represents the spectrum of the entire portion of the previously collected sample, rather than the spectrum of any one specific volatile organic compound. By taking this more holistic approach to analyzing samples, there is less reliance on identifying the abundant volatile organic compounds to predict the likelihood that the sample currently being analyzed is from a subject with a physiological condition. The subject may be a human or another animal or organism.

[0144] The predictive model is generated using machine learning techniques, at least in part, by using a dataset of light intensity attenuation data as a training set.

[0145] Obtaining a large enough sample data set to predict the presence or absence of certain physiological conditions may be challenging. In this case, some pre-processing steps may be helpful. This is especially true for certain physiological conditions.

[0146] To manage missing values ​​in the spectrum, interpolation techniques using adjacent absorbance values ​​in the spectrum can be employed, such as spline interpolation. If the available wavelengths are not evenly spaced, average values ​​from comparable subjects identified by k-nearest neighbor search can be used, such as VOC regression methods that can use average values ​​to approximate missing values.

[0147] When high variability is observed in previously collected data, it can be attributed to natural VOC variation and other confounding variables. Baseline correction can be used to remove any unwanted trends, such as by using common spectroscopic detrending techniques (e.g., linear, quadratic, and Savitzky-Golay detrending). Spectral subtraction techniques can also be used for highly concentrated VOCs, such as acetone and ammonia, which are common to all subjects and can mask small, important details in the spectra.

[0148] Similarly, common normalization techniques can be used to improve sample consistency.In addition to those methods based on a single spectrum (e.g., min-max, peak, standard normal variate normalization), methods that normalize over all spectra (such as multiplicative scatter correction) can be employed.

[0149] A comprehensive analysis of spectral and clinical factors was used to identify relationships and confounders that were not obvious in the data set of light intensity attenuation data of previously analyzed samples to improve data interpretation and identify subgroups to be incorporated into predictive models. There are many confounders in breath VOC analysis, including age, sex, smoking, alcohol consumption, medication use, and other diseases. These factors were evaluated using unsupervised clustering techniques as well as supervised predictive models that classified spectra according to possible confounders. Similarly, spectral data from different subgroups can be used to train separate models for lung cancer detection.

[0150] Features such as spectral derivative-based features, projection features, and wavelet transform-based features are being used for feature extraction. Derivative-based features are particularly useful because they apply some inherent baseline and scale corrections to inter-individual variability. Barcode features and one-dimensional forms of local binary patterns (1D-LBP) can also be used. In addition, features obtained from time series of sample desorption at different temperature series can also be used.

[0151] Various preprocessing and feature extraction methods can be combined with the information discovered in the confounder and subset analyses to create the final classification system. In order to reduce the dimensionality of the system and remove redundant features that are not helpful, several feature selection techniques can be used. Statistical-based filtering methods such as minimum redundancy maximum relevance ("mRMR") selection can be employed, as well as classification-based wrapper methods such as sequential feature selection ("SFS") and genetic algorithm ("GA") selection. Simple support vector machines ("SVM"), discriminant analysis (LDA and QDA), and KNN classifiers can be used to evaluate features in wrapper selection methods and to build and validate numerous classification models.

[0152] Various alternative approaches and methods can be employed to generate predictive models.

[0153] Figure 5 A method 400 for generating a prediction model is shown. In this method, a set of desorption temperature sequences is determined for exploration. The desorption temperature sequence is a set of ordered temperatures to which the thermal desorption tube is heated to desorb the sample portion contained therein. Desorption of the sample using a specific temperature sequence enables different selective parts of the sample to be desorbed and analyzed separately, which enables different aspects of the sample to be more easily identified. Certain features of the sample can be more easily seen from the light intensity decay data captured for certain desorption temperature sequences. For example, if a first component / compound can be desorbed from the thermal desorption tube 104 at a certain temperature and is mixed with a second component / compound that can be desorbed at a slightly elevated temperature, then a desorption temperature sequence having a desorption temperature equal to the first component / compound is used, and then a subsequent desorption temperature equal to or higher than the desorption temperature of the second component / compound is used, and the features of the light intensity decay data of the sample can become more obvious. These relationships between the desorption temperature sequence and the exposed features may not be obvious in some cases. As a result, the specific sequence that produces the best correlation with presence or absence may not be obvious without exploration. On the other hand, for example, if light intensity decay data recorded at two desorption temperature sequences yields substantially equal correlations with a subset of samples drawn from subjects having a physiological condition or degree of a physiological condition, it may be desirable to select the shorter desorption temperature sequence.

[0154] Although the general method will be described with reference to the CRDS system 20, it should be understood that the method may be implemented using multiple local or distributed CRDS systems and other computers using a common set of parameters and standard practices.

[0155] Method 400 begins with the selection of a sample (404). The sample is selected from a group of samples from subjects who have been identified as having a physiological condition and not having a physiological condition. A desorption temperature sequence is then selected from a group of desorption temperature sequences (408). A group of desorption temperature sequences can be selected based on scientific evidence, randomly, etc. The desorption temperature of heater 132 is set to the next desorption temperature in the sequence (412). If the sequence has not been processed, the first desorption temperature in the sequence is selected.

[0156] Next, a portion of the sample is then desorbed and loaded ( 416 ). The heater 132 is heated to a desorption temperature selected from the sequence, and a portion of the sample is desorbed. The sample loading system 112 loads the desorbed portion of the sample into the ring-down chamber 84 .

[0157] The control module 204 then operates one of the lasers 24, 28 to generate a laser beam of the selected wavelength. The laser beam is directed into the ring-down cavity 84 to "fill" the ring-down cavity 84 with light.

[0158] Once control module 204 determines that there is sufficient light in ring-down cavity 84 , control module 204 directs the optical modulator to eliminate the laser beam directed into ring-down cavity 84 ( 424 ).

[0159] The liquid nitrogen cooled detector 100 records the intensity of light exiting the ring-down cavity 84 via the back cavity mirror 88b (428). The light intensity decay data corresponds to the detected intensity of light exiting the ring-down cavity 84 over time and is transmitted to the control module 204. After the ring-down is completed, the control module 204 determines whether to repeat the ring-down event (430). The ring-down event can be repeated multiple times to reduce the impact of anomalies. If another ring-down event is to be performed at the selected wavelength, the method 400 returns to 420, where a laser beam at the selected wavelength is generated. It is then determined whether there are other wavelengths in the group to be used (432). If there are other wavelengths, the method 400 returns to 420, where a laser beam is generated at the next selected wavelength. Conversely, if it is determined that there are no other wavelengths in the group, it is determined whether there is another desorption temperature in the sequence (436). If there is at least one other desorption temperature in the sequence, the next desorption temperature in the sequence is selected, and the heater 132 is heated to that temperature at 412 to desorb another portion of the sample.

[0160] Conversely, if it is determined at 436 that there are no other desorption temperatures in the sequence, then it is determined whether there are other desorption temperature sequences to be explored (440). If there are other unexplored desorption temperature sequences, then the next desorption temperature sequence is selected at 408. When a new desorption temperature sequence is selected, a new thermal desorption tube from the same subject is used because the sample in the previously used thermal desorption tube 104 has already been at least partially desorbed.

[0161] Once all desorption temperature sequences have been studied, it is determined whether there are any other samples in the group that have not been analyzed (444). If there are unanalyzed samples in the group, then another sample is selected for analysis at 404.

[0162] In contrast, if it is determined at 444 that all samples have been analyzed, then the correspondence between the light intensity attenuation data and the identification of the subject from which the sample was extracted as having a physiological condition or the degree of the physiological condition is subsequently determined for each desorption temperature sequence (448). When there is a significantly more common set of features in the sample from the subject identified as having a physiological condition or the degree of the physiological condition, the correspondence between the light intensity attenuation data and the identification of the sample as having a physiological condition or the degree of the physiological condition is stronger. That is, if for a particular desorption temperature sequence, there is a specific set of features that each appear in 85% of the subjects with the physiological condition and 20% of the subjects without the physiological condition, the light intensity attenuation data of the desorption temperature sequence may have a relatively good correlation with the presence or absence of the physiological condition in the subject from which the sample was obtained. Although this is an example, any pattern between the light intensity attenuation data and the presence of a physiological condition or the degree of the physiological condition may indicate the presence of a correlation between the light intensity attenuation data and the presence of a physiological condition or the degree of the physiological condition.

[0163] Then, a desorption temperature sequence is selected for each desorption temperature sequence based on the correspondence between the light intensity decay data and the identification of the subject from which the sample was drawn, the subject having the physiological condition or the degree of the physiological condition (452). The desorption temperature sequence can be selected based solely on the measured correlation or based on the correlation in combination with other factors. Other factors can determine the selection of the desorption temperature sequence, such as the number of desorption temperatures in the sequence, thereby determining the amount of time to perform the analysis.

[0164] A predictive model is then generated using the selected desorption temperature series selected based at least in part on the correlation (452).

[0165] In cases where a range of temperatures is used to desorb a sample from a thermal desorption tube, it may be disadvantageous to analyze portions of the sample that desorb at certain temperatures. Desorption may be performed at certain temperatures to remove species that are less interesting than those that desorb at other temperatures.

[0166] Figure 6 A method 500 of analyzing a sample by CRDS is shown. In method 500, a portion of the sample is desorbed at a first temperature and, in effect, discarded because it may have little relevance to the presence or absence of a physiological condition in a patient. A second portion of the sample is desorbed at a second temperature. The second portion of the sample is believed to have a relatively high relevance to the presence or extent of a physiological condition and, therefore, is analyzed by CRDS.

[0167] The method 500 begins with the control module 204 setting the temperature of the heater 132 to a first desorption temperature (510). Heating the heater 132 to the first desorption temperature causes the thermal desorption tube 104 to be heated and a first portion of the sample to be desorbed. The control module 204 then directs the sample loading system 112 to discharge the first portion of the sample without performing CRDS on the first portion. The first portion of the sample may be discharged into the surrounding atmosphere, discharged into a collection container, or may be removed from the path between the thermal desorption tube 104 and the ring-down chamber 84 by any other suitable method. In a currently preferred embodiment, the first sample is discharged through the mass flow controller 136 by closing valves 124b and 124d, and by opening valves 124a, 124c, 124g, 124f, and 124h, in substantially the same manner as carbon dioxide and water are discharged from the thermal desorption tube 104.

[0168] After the first portion of the sample is discharged, the heater is heated to a second desorption temperature (530). The second desorption temperature is typically higher than the first temperature, thereby causing different substances to desorb from the thermal desorption tube 104. In other embodiments, the second desorption temperature is the same as or lower than the first desorption temperature. Although a good portion of some components / compounds may have been desorbed at the previous desorption temperature, in fact all other mixed substances may also have been desorbed, thereby facilitating the separation of these components / compounds. The second portion of the sample is then loaded into the ring-down cavity 84 for analysis, as described above (540). Next, the control module 204 operates one of the lasers 24, 28 to generate a laser beam at a selected wavelength (550). The laser beam is directed into the ring-down cavity 84 to fill the cavity with light. Once the ring-down cavity 84 is filled, the laser beam is eliminated (560). The liquid nitrogen-cooled detector 100 then records the intensity of the light emitted from the ring-down cavity 84 via the rear cavity mirror 88b (570). The light emitted from the ring-down cavity 84 represents light intensity decay data recorded by the liquid nitrogen cooled detector 100 and transmitted to the control module 204 .

[0169] Once the ring-down event is complete, it is determined whether to repeat the ring-down event again (580). As described above, it may be desirable to repeat the ring-down event multiple times and then determine one or more collective metrics by determining the decay rate of the light intensity decay data for each ring-down and then modifying the decay rate to minimize the effects of aberrations. If another ring-down event is to be repeated, a laser beam is generated at the selected wavelength at 550. Conversely, if no more ring-down events are to be performed, it is determined whether there are additional wavelengths in the set of wavelengths to be analyzed (590). If it is determined that there are additional wavelengths to be analyzed, a laser beam of the next wavelength is generated at 550. Conversely, if there are no more wavelengths to generate a laser beam for performing CRDS, the light intensity decay data collected at 570 is analyzed (595), after which the method 500 ends. The collected light intensity decay data is then analyzed.

[0170] Although the at least one processor that analyzes the light intensity attenuation data and generates the predictive model is shown and described as being fully integrated with the other elements of the CRDS system, in other embodiments, one or more of the at least one processor may be provided in a separate computer system having a memory and performing some or all of the functions of the control module in the above-described and illustrated embodiments.

[0171] Fig. 7A A system 600 for analyzing a sample using CRDS in another embodiment is shown. The system 600 includes a Figure 1 The CRDS system 604 of the present invention is provided. The CRDS system 604 has a control module 608 having at least one processor for controlling the operation of the various elements of the CRDS system 604. The control module 608 communicates with a computer system 612 via a data communication network 616. The computer system 612 can be any single computer or multiple computers coupled together locally and / or remotely to provide the described functionality. The data communication network 616 can be any suitable medium that enables the control module 608 and the computer system 612 to communicate at least the light intensity attenuation data and any related parameters related thereto, such as wavelength, the temperature at which at least a portion of the sample is desorbed, and any other subject specific data, such as the above-mentioned confounding factors, subject identifiers, time and location information of the time and place of analysis of the sample, etc.

[0172] Figure 7BSeveral physical and logical components of a computer system 612 are shown, including a central processing unit ("CPU") 624, a random access memory ("RAM") 628, an input / output ("I / O") interface 632, a communication interface 636, a non-volatile memory 640, and a local bus 644 that enables the CPU 624 to communicate with other components. The CPU 624 may include one or more processors and execute at least an operating system and a spectrum assessment application. The RAM 628 provides relatively responsive volatile storage to the CPU 624. The I / O interface 632 allows input to be received from one or more devices such as a keyboard, mouse, etc., and information to be output to output devices such as a display and / or speakers. The communication interface 636 allows communication with other computing devices such as the control module 608 over a computer network such as the data communication network 616. The non-volatile memory 640 stores an operating system and programs, including computer executable instructions for implementing the spectrum assessment application. During operation of the computer system 612, the operating system, programs, and data may be retrieved from the nonvolatile storage 640 and placed in the RAM 628 to facilitate execution.

[0173] Although in the above embodiments, the light sources are two lasers that generate light in the mid-infrared range, it should be understood that other light sources may be used. For example, lasers that generate light in the visible spectrum or near-infrared lasers may be used. In addition, in some cases, the CRDS system may include only one laser, or three or more lasers to generate the working beam.

[0174] Electro-optic modulators can be used in place of acousto-optic modulators.

[0175] The AOM can be configured to shift the frequency of the working beam up or down. As long as the net frequency shift achieved by the AOM causes the frequency of the working beam to deviate significantly from the frequency of the working beam generated by the laser, such that the reflected light is outside the bandwidth of the generated laser light, the amount of interference between the reflected light and the generated working beam can be minimized.

[0176] In other embodiments, more than two optical modulators may be employed in the CRDS system to provide further cancellation capability to more quickly cancel the operating beam at the onset of a ring-down event. Additionally, in other embodiments, a single optical modulator may be employed.

[0177] In other embodiments one or more focusing lenses may be employed and translated to allow repositioning of the lens to allow mode matching of each wavelength of the laser.

[0178] The same approach can be used for other types of resonant cavities, especially optical resonant cavities.

[0179] Other types of events can be triggered because the cavity length is close to the resonant length of the cavity for a particular selected wavelength.

[0180] In other embodiments, analysis of the sample may be performed at a pressure level other than one atmosphere. The width of the absorption spectrum may vary accordingly.

[0181] While specific advantages are enumerated above, various embodiments may include some, none, or all of the enumerated advantages.

[0182] Although in the above embodiments, the resonant cavity is a ring-down cavity, in other embodiments, other types of resonant cavities may be used.

[0183] Those skilled in the art will appreciate that there are many more possible alternative implementations and modifications, and the above examples are only illustrations of one or more implementations. Therefore, the scope of the present disclosure is limited only by the appended claims.

[0184] Reference numerals list

[0185] 20 CRDS system

[0186] 24 CO2 laser

[0187] 28 Carbon 13O2 Laser

[0188] 32 First laser beam

[0189] 36 Second laser beam

[0190] 40 Reflector

[0191] 44 Beam Splitter

[0192] 48 Sampling beam

[0193] 52 Output beam

[0194] 56 Fast Infrared Detector

[0195] 60 First light modulator

[0196] 64 Transmitter

[0197] 68 Second light modulator

[0198] 72 Focusing lens

[0199] 76 Reflector

[0200] 80 Ring-down Chamber

[0201] 84 Ring-down cavity

[0202] 88 Laparoscope

[0203] 88a Anterior cavity mirror

[0204] 88b Rear cavity mirror

[0205] 92 Reflector Mounting

[0206] 96 Micrometer

[0207] 96a Mechanized Micrometer

[0208] 96b Piezoelectric Micrometer

[0209] 100 Liquid nitrogen cooled detector

[0210] 104 Thermal Desorption Tube

[0211] 105 stainless steel housing

[0212] 106 Orifice

[0213] 107 Receiver

[0214] 108 Foam separator

[0215] 109 Adsorption material

[0216] 110 Foam separator

[0217] 112 Sample loading system

[0218] 116 Nitrogen source

[0219] 120 Catheter

[0220] 120a Gas input line

[0221] 120b Desorption line

[0222] 120c Sample output line

[0223] 124 Solenoid valve

[0224] 124a Gas inlet valve

[0225] 124b Auxiliary gas inlet valve

[0226] 124c Inlet line valve

[0227] 124d Cavity inlet valve

[0228] 124e Access valve

[0229] 124f Forward valve

[0230] 124g rear valve

[0231] 124h Sample outlet valve

[0232] 124i Cavity Outlet Valve

[0233] 124j Vacuum cut-off valve

[0234] 124k Vacuum Suction Valve

[0235] 128 Pressure gauge

[0236] 130a, 130b Filters

[0237] 132 Heater

[0238] 136 Mass Flow Controller

[0239] 140 Exit Line

[0240] 144 Pressure gauge

[0241] 148 Vacuum Pump

[0242] 150 Pump suction line

[0243] 200 Electronic control subsystem

[0244] 204 Control Module

[0245] 205 Processor

[0246] 206 Storage

[0247] 208 RF Driver

[0248] 212 Grating Actuator

[0249] 216 Output Coupler Piezo

[0250] 220 High Voltage Amplifier

[0251] 224 DAQ Card

[0252] 228 Actuator Driver

[0253] 232 Amplifier

[0254] 236 Oscilloscope

[0255] 240 Temperature Controller

[0256] 244 Relay Board

[0257] 248 Three-Channel Piezoelectric Driver

[0258] 252 Piezoelectric Actuator

[0259] 256 RF Driver

[0260] 260 Timing Circuit

[0261] 264 Digitizer

[0262] RL Resonance length

[0263] 300 Methods

[0264] 310 Selecting and Setting Temperature

[0265] 320 Load at least a portion of the sample

[0266] 330 Generates a laser beam at a selected wavelength

[0267] 340 Eliminate laser beam

[0268] 350 Record light intensity attenuation data

[0269] Will 360 repeat the downturn?

[0270] 370 Other wavelengths?

[0271] 375 Unload sample section

[0272] 380 Other temperatures in the sequence?

[0273] 390 Determining the probability of physiological conditions

[0274] 400 Methods

[0275] 404 Select Sample

[0276] 408 Select Temperature Series

[0277] 412 Set heater temperature

[0278] 416 Loading a portion of the sample

[0279] 420 Generates a laser beam at wavelength

[0280] 424 Eliminate laser beam

[0281] 428 Record light intensity attenuation data

[0282] 430 Repeated collapse event?

[0283] 432 Other wavelengths?

[0284] 436 Other temperatures?

[0285] 436 Determining the probability of physiological conditions

[0286] 440 Other temperature series?

[0287] 444 Other samples?

[0288] 448 Identifying Temperature Series with Greater Correlation

[0289] 452 Select temperature sequence

[0290] 456 Generate Prediction Model

[0291] 500 Methods

[0292] 510 Set the heater to the first temperature

[0293] 520 Discharge the first part of the sample

[0294] 530 Set the heater to the second temperature

[0295] 540 Loading the second part of the sample

[0296] 550 Generates a laser beam at a selected wavelength

[0297] 560 Eliminate laser beam

[0298] 570 Record light intensity attenuation data

[0299] 580 Repeated collapse event?

[0300] 590 Other wavelengths?

[0301] 595 Analyze the collected light intensity attenuation data

[0302] 600 System

[0303] 604 CRDS system

[0304] 608 Control Module

[0305] 612 Computer Systems

[0306] 616 Data Communication Network

[0307] 624 processors

[0308] 628 RAM

[0309] 632 I / O interface

[0310] 636 Communication Interface

[0311] 640 Non-volatile memory

[0312] 644 Bus

[0313] 648 Database

Claims

1. A method for analyzing a sample using cavity ring-down spectroscopy, comprising: heating the thermal desorption tube to a first desorption temperature to desorb a first portion of the sample contained therein; loading the first portion of the sample into a ring-down cavity; For each of the first set of wavelengths: generating, via at least one laser, a laser beam at the wavelength directed into the ring-down cavity; eliminating said laser beam from entering said cavity; as well as recording light intensity decay data for light exiting the ring-down cavity via a light intensity sensor system; unloading the first portion of the sample from the ring-down cavity; heating the thermal desorption tube to a second desorption temperature to desorb a second portion of the sample contained therein; loading the second portion of the sample into the ring-down cavity; For each of the second set of wavelengths: generating, via the at least one laser, a laser beam at the wavelength directed into the ring-down cavity; eliminating said laser beam from entering said cavity; as well as recording light intensity decay data for light exiting the ring-down cavity via the light intensity sensor system; as well as The light intensity decay data desorbed at the first desorption temperature and the light intensity decay data desorbed at the second desorption temperature are analyzed.

2. The method according to claim 1, wherein: The sample is a breath sample.

3. The method according to claim 1, wherein: The first set of wavelengths is equal to the second set of wavelengths.

4. The method according to claim 3, further comprising: For each of the first set of wavelengths, light intensity attenuation data from the second portion of the sample is combined with light intensity attenuation data from the first portion of the sample.

5. The method according to claim 1, wherein: The second desorption temperature is greater than the first desorption temperature.

6. The method according to claim 1, wherein: The first desorption temperature is equal to the second desorption temperature.

7. The method according to claim 1, wherein: The analysis includes at least indirectly using a data set of light intensity attenuation data for a previously analyzed sample to determine, from the light intensity attenuation data for the first portion of the sample and the light intensity attenuation data for the second portion of the sample, a probability that a subject from whom the sample was received has a physiological condition or the extent of a physiological condition, wherein the presence or absence of the physiological condition or the extent of the physiological condition has been identified for the previously analyzed sample.

8. The method according to claim 7, wherein: The determining is performed using a predictive model trained at least in part using the dataset of light intensity attenuation data for previously analyzed samples.

9. The method according to claim 7, wherein: The physiological condition is lung cancer.

10. A system for analyzing a sample using cavity ring-down spectroscopy, comprising: Ring-down cavity; at least one laser operable to generate a laser beam directed into the ring-down cavity; a sample loading system for loading at least a portion of a sample into the ring-down chamber for analysis and for unloading the at least a portion of the sample from the ring-down chamber, the sample loading system comprising a heater configured to heat a thermal desorption tube containing the sample; a light intensity sensor system positioned to record light intensity decay data for light exiting the ring-down cavity; at least one processor operably coupled to the sample loading system, the at least one laser, and the light intensity sensor system; a memory storing computer readable instructions that, when executed by the at least one processor, cause the at least one processor to: controlling the sample loading system to heat the thermal desorption tube to a first desorption temperature to desorb a first portion of a sample contained therein, and loading the first portion of the sample into the ring-down chamber; For each of the first set of wavelengths: operating the at least one laser to generate the laser beam at the wavelength directed into the ring-down cavity; Eliminating the laser beam entering the ring-down cavity; as well as recording light intensity decay data for light exiting the ring-down cavity via the light intensity sensor system; unloading the first portion of the sample from the ring-down cavity; controlling the sample loading system to heat the thermal desorption tube to a second desorption temperature to desorb a second portion of the sample contained therein, and loading the second portion of the sample into the ring-down chamber; For each of the second set of wavelengths: operating the at least one laser to generate a laser beam at the wavelength directed into the ring-down cavity; Eliminating the laser beam entering the ring-down cavity; as well as recording light intensity decay data for light exiting the ring-down cavity via the light intensity sensor system; as well as The light intensity decay data desorbed at the first desorption temperature and the light intensity decay data desorbed at the second desorption temperature are analyzed.

11. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 10, wherein: The first set of wavelengths is equal to the second set of wavelengths.

12. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 11, wherein: The computer executable instructions, when executed by the at least one processor, cause the at least one processor to combine light intensity attenuation data from the second portion of the sample with light intensity attenuation data from the first portion of the sample for each of the first set of wavelengths.

13. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 10, wherein: The second desorption temperature is greater than the first desorption temperature.

14. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 10, wherein: The first desorption temperature is equal to the second desorption temperature.

15. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 10, wherein: The computer executable instructions, when executed by the at least one processor, cause the at least one processor to at least indirectly use a data set of light intensity attenuation data for a previously analyzed sample to determine, from the light intensity attenuation data for the first portion of the sample and the light intensity attenuation data for the second portion of the sample, a probability that a subject from whom the sample was received has a physiological condition or the extent of a physiological condition, wherein the presence or absence of the physiological condition or the extent of the physiological condition has been identified for the previously analyzed sample.

16. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 15, wherein: The determining is performed using a predictive model trained at least in part using the dataset of light intensity attenuation data for previously analyzed samples.

17. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 10, wherein: The sample is a breath sample.

18. The system for analyzing a sample using cavity ring-down spectroscopy according to claim 15, wherein: The sample is a respiratory sample and the physiological condition is lung cancer.

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