Arrangement for characterising cerebrospinal fluid

Abstract

The invention relates to an arrangement (1) for non-invasively characterising cerebrospinal fluid and other bodily fluids, • comprising a sensor head (7) for emitting terahertz radiation (T) and receiving its reflections (R), which sensor head, during use, is applied to the patient (3) in such a way that the terahertz radiation (T) radiates into the bodily fluid, • comprising an electronic evaluation circuit for calculating measurement data from the emitted and received radiation (T, R), wherein this circuit automatically determines the extinction of different wavelengths and, from this, calculates the concentration of different substances in the bodily fluid, • and comprising a display (8) for optically representing the data calculated by the evaluation circuit as results.

Description

[0001] Arrangement for characterizing cerebrospinal fluid

[0002] Description:

[0003] The invention relates to an arrangement for characterizing body fluids such as the cerebrospinal fluid “CSF”, hereinafter referred to as “CSF”.

[0004] In practice, it is common to perform invasive examinations of cerebrospinal fluid (CSF), for example, using a lumbar puncture or intraoperatively using a ventricular puncture. This examination is used to identify diseases, particularly in many neurological conditions, but it is also used after accidents to identify damage and assess the extent of trauma. Samples of CSF are taken from the patient, and one sample is subsequently analyzed in the laboratory, while additional samples are sent to a microbiology laboratory for bacterial incubation. This allows, for example, the concentrations of blood, protein, leukocytes, and lactate in the CSF to be determined.

[0005] Cerebrospinal fluid examinations carry the risk of bacterial contamination. If the procedure is not completely aseptic, skin-borne pathogens can be introduced into the puncture channel during the puncture, leading to the dangerous complication of meningitis or ventriculitis. Another risk of lumbar puncture is the possibility of cerebrospinal fluid leakage, which can cause the dura mater to leak. Another risk is injury to the spinal cord vessels, which can lead to an intraspinal or epidural hematoma with compression or damage to the spinal cord. Finally, lumbar puncture also carries the risk that, depending on the examiner's experience, the incorrect puncture height may be selected. This, for example, can result in paralysis, sensory disturbances, or bladder / rectal dysfunction for the patient in the case of a spinal cord injury if the puncture is performed in the upper lumbar region.

[0006] When characterizing other body fluids such as blood or urine, an invasive examination is often performed by puncturing a vein or the bladder.

[0007] The invention is based on the object of providing an arrangement for characterising the cerebrospinal fluid which enables the examination of the cerebrospinal fluid to be as simple and risk-free as possible for the practitioner and the patient.

[0008] This object is achieved by an arrangement according to claim 1. Advantageous embodiments are described in the subclaims.

[0009] In other words, the invention proposes a system that enables a non-invasive examination of the cerebrospinal fluid. The invention is based on the idea that the risks previously associated with this examination are due to the invasive nature of the examination, so that they can be virtually eliminated by means of a system according to the invention. According to the invention, the CSF is examined by irradiating it through the skull with electromagnetic radiation in the terahertz range.

[0010] The arrangement according to the invention therefore firstly comprises a sensor head which, on the one hand, has an emitter or transmitter which emits the terahertz radiation, and, on the other hand, has a receiver or receiver which receives reflections of the terahertz radiation.

[0011] To generate the radiation, the sensor head is supplied with electrical energy. The arrangement according to the invention therefore secondly comprises a power supply unit, which can be connected to a mains voltage on the primary side and to the sensor head on the secondary side to supply it with electrical energy. To prevent damage to the sensor head and to ensure consistently high-quality measurement results, the power supply unit is designed as a stabilized power supply with a voltage regulator such that a specific output voltage is reliably maintained and constantly provided.

[0012] The voltage regulator can be physically separate from the power supply, but it can also form an integral part of the entire power supply, inaccessible to an operator. In one embodiment, the voltage regulator can be operated by the operator and set to different voltage values, for example, if the sensor head of the arrangement is replaceable and different sensor heads are operated with different voltages. The different sensor heads can each be equipped with a quick-coupling system, for example, an electrical plug connection, so that the arrangement can be operated with either one of several—at least two—sensor heads, enabling quick and uncomplicated switching between the different sensor heads.As an alternative to the aforementioned power supply, a battery, accumulator, or similar energy storage device can also be used to power the sensor head. This offers several advantages:

[0013] Firstly, even in the event of a power or voltage grid failure, the sensor head can continue to operate, and the energy storage device can be recharged at another time, provided the power or voltage supply allows it. In one embodiment, the sensor head has a data storage device for the recorded measured values, so that these can be temporarily stored in the sensor head and later processed. Alternatively, other components of the arrangement can also be operated independently of the mains using a suitable energy storage device, e.g., a data storage device outside the sensor head, an evaluation circuit, a signal amplifier, and / or a display, so that these components—and possibly the entire arrangement—can be operated independently of the mains.

[0014] Secondly, if the sensor head is not connected to an external energy storage device via a cable, but rather the energy storage device is integrated into the sensor head, the cable connection of the sensor head can be limited to small cable cross-sections, since no electrical power is required to operate the sensor head; instead, only information signals need to be transmitted. These include incoming signals to the sensor head for controlling the sensor head, such as adjusting the frequency and amplitude of the terahertz radiation to be emitted, as well as signals outgoing from the sensor head for transmitting the received measurement signals to an evaluation circuit, a signal amplifier, or a display. The small cable cross-sections result in greater freedom of movement when handling the sensor head. In particular, if the sensor head is configured for wireless signal transmission, the sensor head can be handled with optimal freedom of movement.Since the sensor head is not used to perform an imaging procedure, it generally does not require any mobility along the patient's body during the examination. However, the freedom of movement provided by small cable cross-sections or the complete absence of cables makes it easier to position the sensor head at a specific location and in a specific orientation on the patient's body. In particular, if the sensor head is not guided manually but is placed in a holder that is placed on the patient, interference that could otherwise be caused by a collision between the cable and the holder, as well as interference that could be caused by inadvertent contact with the cable during the examination, can be avoided.

[0015] The signals delivered by the sensor head's receiver are fed to an electronic evaluation circuit, which is also part of the inventive arrangement. The evaluation circuit automatically determines the absorbance of various wavelengths based on the emitted and received radiation and automatically calculates the concentration of various substances in the cerebrospinal fluid.

[0016] Finally, the arrangement according to the invention also includes a display on which the results are visually presented. The results, namely the data calculated by the evaluation circuit, can be displayed alphanumerically, for example, in the form of percentages or absolute values ​​of the respective amounts of substances detected by the sensors and / or calculated from the sensor data. Another type of visual display can be provided in the form of a bar chart, so that a separate bar is displayed for each different substance, representing the percentage or absolute amount of the respective substance.A standard value for the same substance can be represented in an adjacent bar, or within the same bar, a standard value for the substance in question can be displayed using different colors or grayscale values, so that in the bar chart mentioned above, the relationship between the sensor-detected measured values ​​and the standard references for the respective substance can be immediately read. Both of these representations can be combined, so that the results can be displayed both alphanumerically and in diagram form. In any case, the invention provides for the results to be displayed visually, unlike with an imaging method.

[0017] Using the inventive device, an examination of the cerebrospinal fluid in the cranium can be performed by placing the sensor head on the outside of a patient's skull, emitting terahertz radiation, and receiving its reflections for subsequent analysis. Since this type of examination is entirely non-invasive, the risks associated with an invasive examination are eliminated.

[0018] However, the device not only enables a non-invasive examination of the cerebrospinal fluid, but can also be used for non-invasive examinations of other body fluids. The functionality of the device also applies, mutatis mutandis, to the examination of other body fluids. Necessary adjustments include, for example, placing the sensor head not on the skull, but on other suitable parts of the patient's body, so that part of the electromagnetic radiation penetrates another body fluid rather than the cerebrospinal fluid. Accordingly, the concentrations of the same substances, but possibly also the concentrations of other substances contained in the respective fluid, may be determined in other body fluids, e.g.In the cerebrospinal fluid, the concentrations of blood, protein, leukocytes and lactate can be determined, while in the blood, the concentration of, for example, red and white blood cells as well as the Hb and HTC values ​​can be determined.

[0019] The invention is based on the idea that an examination of other body fluids can also be carried out by placing the sensor head on the outside of the skin of a human or animal patient, for example in an examination of blood or urine, by placing the sensor head on the skin of a patient where a vein runs beneath the skin or where the stomach, bladder or another body part filled with blood or another fluid is located, whereby in these cases too the terahertz radiation is emitted and its reflections are received so that they can then be evaluated.The application of an arrangement according to the invention is particularly well suited for the examination of the aforementioned body fluids, cerebrospinal fluid and blood, and, as expected, also of urine or other fluids, since these fluids are located at a sufficiently close distance from the epidermis, so that the examination can be carried out with a low radiation intensity that is gentle on the patient by placing the sensor head externally against the epidermis or, if necessary, against the scalp hair. Since this type of examination is exclusively non-invasive, the risks associated with an invasive examination are eliminated. Aspects of invasive examination procedures, e.g., with regard to the required penetration depth into the body, can, as expected, be approximately transferred to the application of terahertz radiation, although the respective absorption influences, for example, determine the penetration depth.

[0020] While the emitter emits terahertz radiation in a specific frequency range, the receiver receives reflections from the various substances contained in the cerebrospinal fluid. The measurement method is based on spectroscopy and Lambert-Beer's law. The method performed with the inventive arrangement makes it possible to determine an unknown concentration based on the absorption of the emitted rays. Part of the electromagnetic radiation is absorbed by solutions such as the cerebrospinal fluid, while another part of the radiation penetrates the solution and is reflected back to the sensor head.

[0021] The reflected radiation is detected by the receiver of the sensor head and can either be temporarily stored for data transmission or transmitted directly to the evaluation circuit.

[0022] The transmission T indicates the extent to which the radiation intensity Io radiated into the CSF passes through the CSF at a specific wavelength. The ratio of the radiation intensity before entering the CSF (Io) and after exiting (I) is described by the equation T = I / Io. The extinction E, on the other hand, describes the transmission at a specific wavelength:

[0023] E = -log (I / Io).

[0024] The propagation of electromagnetic waves, with their specific characteristics such as frequency and wavelength, is used to identify substances. Lambert-Beer's law states that absorption can be determined by the decrease in intensity as they pass through a medium. The absorbance of a wavelength is defined by its intensity. This absorption can be identified by the ratio between the transmitted radiation intensity and the incident radiation intensity. This process is also known as extinction. Extinction varies depending on the concentration of the absorbing substance, the wavelength of the radiation in the material being irradiated, and the decadic extinction coefficient.

[0025] E Ä = logw (I / Io) = C*d* e Ä where

[0026] Ex = extinction for a specific wavelength X

[0027] I = transmitted light in W / m 2

[0028] Io = incident light in W / m 2

[0029] C = concentration in mol / m 3 d = wavelength in cm, and ex = extinction coefficient for the specific wavelength X

[0030] According to the invention, the cerebrospinal fluid is examined in the skull and using radiation in the terahertz range of the electromagnetic wave spectrum. This radiation has the property of being able to penetrate the skull and reach the cerebrospinal fluid. In order to counteract the potential risk of damage to human body tissue that could be caused by the radiation, the radiation intensity of the emitter can be set as low as possible, and the radiation can be bundled similar to an optical lens so that it penetrates the tissue over a larger area, with a correspondingly low area intensity, and so that the radiation only reaches the desired intensity in the area of ​​its focus in the cerebrospinal fluid. In order to avoid an undesirably high radiation intensity and also to generate more reflections, which couldWhile this can positively influence the examination accuracy, an alternative configuration of the arrangement can deliberately not focus the radiation, but rather emit it as a parallel or even diverging beam. Depending on the design of the emitter, this can be achieved without a lens or by inserting a diverging lens into the beam path.

[0031] The individual components of the arrangement according to the invention do not have to be combined in a single device. For example, the power supply can have its own housing, and the sensor head can be connected to the power supply via a cable, thus allowing limited freedom of movement. The evaluation circuit can be arranged in the same housing as the power supply, e.g., as a device that can be placed on a table. In this case, the cable serves to transmit power to the sensor head and to transmit the measurement signals from the sensor head to the evaluation circuit.

[0032] An amplifier can be located in the sensor head to amplify the measurement signals emitted by the receiver before they are transmitted wirelessly or via cable.

[0033] Depending on space requirements, the evaluation circuit can be housed in the sensor head itself, allowing electrical signals from the sensor head's receiver to be processed with as little loss and interference as possible. In this case, the aforementioned cable can be used not only to transmit power to the sensor head but also to transmit the data calculated by the evaluation circuit.

[0034] The display can be housed in the same housing as the power supply, e.g., as a monitor in the aforementioned desktop device. It can also be configured as a separate monitor mounted on a wall or on a dedicated mount. The image signals can be transmitted to the display via a cable. A video circuit can be located within the power supply housing, which generates image signals from the data calculated by the evaluation circuit, which are then transmitted to the display.

[0035] The transmission of signals can be wireless, e.g., measurement signals from the sensor head to the evaluation circuit, and / or data calculated by the evaluation circuit to the display or an upstream video circuit, and / or image data from the video circuit to the display can be transmitted wirelessly.

[0036] The terahertz radiation is directed by the emitter onto the cerebrospinal fluid, with a portion of the radiation being absorbed by the CSF. The remaining portion, which passes through the CSF, is reflected, and returns to the sensor head, is received by the receiver located in the sensor head. The individual parameters are determined and analyzed based on the absorption. The parameters are identified by the characteristic properties of the absorption bands. According to the invention, terahertz radiation in the range of 0.1 to 10 terahertz of the electromagnetic spectrum is used, preferably radiation in the lower frequency range of 0.1 to 4 THz. At a frequency of 10 THz, a radiation-related temperature exposure of a patient in the range of approximately 13°C to 14°C can be expected, which is well below a critical temperature exposure that could potentially be hazardous to health, e.g.by potentially leading to protein denaturation. In one configuration, the device uses terahertz radiation in the range of 0.1 to 3 or 4 terahertz. The individual peaks indicate the strength of absorption in this range. The assignment of the characteristic properties to these peaks can be used to determine the concentration of substances in the cerebrospinal fluid.

[0037] In a preferred embodiment of the arrangement, it is designed to use terahertz radiation in the range of 0.3 to 3 terahertz. This frequency range, the so-called "fingerprint," is characterized by a unique wavelength signature, similar to a fingerprint, and enables the identification of parameters based on reference values. This fingerprint range is used to identify vibration spectra. The measured values ​​provided by the sensor head reproduce the individual wave patterns like a fingerprint. The fingerprint range is therefore particularly well-suited for the application of low radiation intensities, which can be used preferentially, for example, to ensure the greatest possible protection for the patient.The fingerprint area can be used very effectively to determine concentrations and assign individual parameters, allowing the concentrations of blood, protein, leukocytes, and lactate in the cerebrospinal fluid (CSF) to be determined non-invasively using the device according to the invention. This procedure enables precise analysis and measurement of substances contained in the CSF, thereby improving medical diagnosis and treatment. Precise analysis of the CSF is particularly important before the implantation of foreign material, such as ventriculoperitoneal or ventriculoatrial shunts.

[0038] The sensor head is not handled invasively, but simply applied externally to the patient's skull. This can be done manually by a person referred to as the "operator" or automatically by a handling robot. In one embodiment of the arrangement, the sensor head is arranged in a headband, cap, hat, or similar holder that can be pulled onto the patient's head. The various different designs are collectively and simply referred to as a holder. The holder ensures that the sensor head maintains its position on the skull during the examination without the sensor head having to be held specifically for this purpose—e.g., by the aforementioned operator.

[0039] For the non-invasive characterization of other body fluids, the sensor head can be arranged on a correspondingly differently designed holder, which can be applied to a patient's skin, for example: the holder can be designed as a band, e.g. an elastic band, which can be placed around the patient's skull, an arm, a leg or the torso, for example, or the sensor head is arranged in or on a piece of clothing, such as the cap or hat mentioned above, on a glove, jacket or trousers or a similar holder that can be applied to the patient, whereby the various different embodiments are collectively and simply referred to as a holder, which in each case ensures that the sensor head maintains its position on the patient during the examination without the sensor head having to be held specifically for this purpose - e.g. by the person providing the treatment.

[0040] To deliver reliable results, the inventive device is first calibrated. The calibration is based on a conventional laboratory analysis of the cerebrospinal fluid to determine the corresponding values. Furthermore, the same cerebrospinal fluid is characterized using the inventive device. Measuring the absorbance for the known concentrations is of great importance for the functionality of the device. The results are then presented in a graph in which the absorbance is plotted as a function of the concentration. This determines the solution to the general linear equation y = m*x+b, where m denotes the slope and b the y-intercept in the corresponding graph. In the inventive application, the general variable x represents the concentration C and the general variable y represents the absorbance E, so that the equation within the scope of the present invention is:

[0041] Ex = m*C+b.

[0042] Dear Ms. Lala: After we have explained C and Ex, we should also explain what m and b stand for in the formula; at the latest here or already above in the equation in line 11

[0043] The equation can be rearranged according to the concentration C:

[0044] C = (Ex - b) / m.

[0045] During calibration, the measurement limits are determined. Using the system according to the invention, the presence of red blood cells, hemoglobin, or hematocrit in the CSF can be automatically detected. To avoid falsification, it is important that calibration using laboratory values ​​is performed on the same day as the sample collection for the laboratory values.

[0046] By applying Lambert's law and calculating the extinction Ex = Iog10 (I / IO), the concentration of the parameters can be determined:

[0047] E = absorbance of the various substances CERY = (EAERY - Y-intercept) I slope C leukocytes = (E leukocytes - Y-intercept) I slope C protein = (E Protein - Y-intercept) I Slope Lactate = (Ex Lactate - Y-intercept) I Slope Cducose = (ExGlucose - Y-intercept) I Slope

[0048] In the case of hemoglobin and hematocrit, the values ​​can be calculated based on the sensory measurements as follows:

[0049] CHemoglobin = 3* CERY CHematocrit = 9* CERY

[0050] The result of these equations serves as the basis for the development of a software program called an evaluation circuit, which is capable of determining the concentration from the measured values ​​provided by the sensor head and outputting this data for presentation on a display. In a further development, the evaluation circuit can also automatically statistically analyze this data. Using the inventive arrangement, it is also possible to examine glucose, leukocytes, protein, and lactate in the cerebrospinal fluid. To achieve this, the individual parameters are analyzed in the frequency range from 0.1 to 3 terahertz by measuring their absorption bands, and their characteristic properties are incorporated into the concentration formula for calculating the extinction for calibration.

[0051] Aside from the fact that the non-invasive examination method made possible by the invention allows patients to avoid painful needle pricks in the head area during neurological treatment, a key advantage of this non-invasive examination is the minimization of potential complications such as bleeding, infection, and scarring. Compared to invasive procedures, the non-invasive method therefore offers increased safety. Furthermore, patients benefit from a shorter recovery time. Furthermore, the non-invasive examination allows physicians to act more quickly, which not only leads to significant time and cost savings, but can also be life-saving in acute emergency situations.

[0052] The arrangement according to the invention is explained in more detail below using a purely schematic representation.

[0053] Fig. 1 shows the structure of an arrangement for characterizing the cerebrospinal fluid in the form of a block diagram.

[0054] Fig. 1 shows a schematic block diagram of an arrangement 1 used to examine the cerebrospinal fluid (CSF), whereby the CSF is examined in the cranium 2 of a patient 3. The arrangement 1 used for this purpose has a power supply 4, the primary side of which can be connected to a power or voltage network via a power plug 5, and whose output voltage is stabilized by a voltage regulator 6. The transmission of electrical energy is symbolized by energy arrows E.

[0055] The stabilized output voltage is supplied by the voltage regulator 6 to a sensor head 7 of the arrangement 1, wherein the sensor head 7 contains an emitter for terahertz radiation and a receiver for reflected portions of the emitted terahertz radiation reaching the sensor head 7. The terahertz radiation emitted by the sensor head 7 is symbolized by an arrow T. It penetrates the skull of the patient 1 and there encounters the cerebrospinal fluid and substances contained in the cerebrospinal fluid. The reflected radiation, which reaches the receiver of the sensor head 7, is marked R in Fig. 1. A distance between the sensor head 7 and the cranium 2 is shown purely as an example, however only to be able to arrange the terahertz and reflection arrows T and R graphically. When performing an examination, the sensor head 7 is intended to be placed against the skull of the patient 3.

[0056] In the illustrated embodiment, the measurement signals output by the receiver of the sensor head 7 are processed directly in the sensor head 7 in an evaluation circuit. For this purpose, a chip is arranged in the sensor head 7, on which a software program runs, which represents the evaluation circuit. Deviating from the illustrated embodiment, it can be provided that the measurement signals output by the receiver of the sensor head 7 are transmitted from the sensor head 7 to a remote evaluation circuit, either unchanged or as amplified signals by means of a signal amplifier arranged in the sensor head 7. In any case, signals symbolized by signal arrows S reach a display 8 in unchanged or processed form, where the examination results are visually displayed.At the latest immediately before the display 8, the signals are processed into image signals in order to enable the desired optical representation.

[0057] Separately shown components of the arrangement 1 can be combined into a single device. For example, the power supply 4 and the voltage regulator 6 can be arranged in a common housing, or a desktop device can contain the power supply 4, the voltage regulator 6, and also the display 8. Reference symbols:

[0058] 1 arrangement

[0059] 2 Cranium

[0060] 3 patients

[0061] 4 Power supply

[0062] 5 power plugs

[0063] 6 voltage regulators

[0064] 7 Sensor head

[0065] 8 Display

[0066] E electrical energy

[0067] T Terahertz radiation

[0068] R reflected radiation

[0069] S Signal

Claims

Patent claims: 1 . Arrangement (1 ) for the non-invasive characterization of cerebrospinal fluid, • with a sensor head (7), o which has an emitter which, in use, emits terahertz radiation (T), o and which has a complementary receiver which, in use, receives reflections (R) of the terahertz radiation, o and which is intended, in use, to be applied to the skull of a patient (3) in such a way that the terahertz radiation (T) radiates into the cerebrospinal fluid, • and with an electronic evaluation circuit, o which, in use, calculates measurement data based on the radiation (T, R) emitted and received by the sensor head (7), o wherein the evaluation circuit is designed in such a way that it automatically determines the extinction of different wavelengths based on the emitted and received radiation (T, R) and calculates the concentration of different substances in the cerebrospinal fluid therefrom, • and with a display (8) for the optical representation of the data calculated by the evaluation circuit as results.

2. Arrangement according to claim 1, characterized by a power supply unit (4) which can be connected to a mains voltage on the primary side and can be connected to the sensor head (7) on the secondary side for supplying electrical energy to the sensor head.

3. Arrangement according to claim 2, characterized by a voltage regulator (6) which is connected between the power supply (4) and the sensor head (7) in such a way that the voltage for supplying electrical energy to the sensor head (7) is adjustable.

4. Arrangement according to claim 1, characterized by a device for supplying energy to the sensor head, which has an energy storage device.

5. Arrangement according to claim 4, characterized in that the energy storage device is integrated into the sensor head.

6. Arrangement according to one of the preceding claims, characterized in that the emitter is designed in such a way that, in use, it emits radiation in the range between 0.1 THz and 10 THz, preferably between 0.1 THz and 4 THz, particularly preferably between 0.3 THz and 3 THz.

7. Arrangement according to one of the preceding claims, characterized in that the data calculated by the evaluation circuit are presented as results in alphanumeric form.

8. Arrangement according to one of the preceding claims, characterized in that the data calculated by the evaluation circuit are presented as results in the form of a diagram.

9. Arrangement according to one of the preceding claims, characterized in that the sensor head is arranged in a holder, the holder being adapted to bear against the patient in use and to hold the sensor head in a predetermined position on the patient.

10. Arrangement according to one of the preceding claims, characterized in that the sensor head (7) is arranged in a holder, wherein the holder is designed to rest against the head of a patient (3) in use and to hold the sensor head (7) in a predetermined position on the head. 11 . Arrangement according to one of the preceding claims, characterized in that the arrangement has more than one sensor head (7), wherein the sensor head (7) is interchangeable by means of a quick coupling in such a way that it can be exchanged for another sensor head (7) and the arrangement can be operated selectively with one of the several different sensor heads (7).

12. Arrangement according to claim 3, characterized in that the voltage regulator (6) is adjustable to different output voltages.

13. Arrangement according to one of the preceding claims, characterized in that the evaluation circuit is designed in such a way that the extinction for a specific wavelength is automatically calculated as follows: E Ä = logw (I / Io) = C*d* e Ä where Ex = extinction for a specific wavelength X I = transmitted light in W / m 2 Io = incident light in W / m 2 c = concentration in mol / m 3 d = wavelength in cm, and ex = extinction coefficient for wavelength X.

14. Arrangement according to one of the preceding claims, characterized in that the evaluation circuit is designed in such a way that the concentration for a specific substance contained in the cerebrospinal fluid is automatically calculated as follows: C = (Ex - b)Zm. where Ex = absorbance for a specific wavelength XC = concentration of the substance in mol / m 3b = y-intercept, and m = slope.

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