Radiological Imaging Methods

Abstract

The present invention relates to a radiological imaging method comprising a step of performing a vertical scan of a standing patient (20) along a vertical scanning direction (Z) with two radiation sources having mutually orthogonal imaging directions, said radiological method comprising at least one operating mode in which a frontal scout view is created for identifying specific bone localizations (21) within said frontal scout view, and a drive current intensity modulation (11) of said frontal radiation sources is automatically performed depending on the patient's thickness and the identified specific bone localizations (21) along said vertical scanning direction (Z) to improve the compromise between reducing the overall radiation dose received by the patient (20) during said vertical scanning and at the same time maintaining a sufficient level of local image contrast of said identified specific bone localizations (21) at different imaging positions along said vertical scanning direction (Z) for the frontal images.

Description

[Technical field]

[0001] The present invention relates to radiological imaging methods that desire a lower radiation dose received by the patient, while still obtaining good quality images of the patient's body. [Background technology]

[0002] Scanning stereoscopic radiography systems have demonstrated the exciting ability to simultaneously produce frontal and lateral images for 3D reconstruction of skeletal anatomical parts such as the spine or pelvis, with a dose reduction of up to 50 or even 100 compared to CT (Computed Tomography) scanning, and with a dose reduction of up to 10 for single-view images compared to conventional CR (Computed Radiography) or DR (Direct Radiography) systems.

[0003] However, this system did not have AEC (Automatic Exposure Control) and therefore the parameters of the patient scan were only selected manually by the operator according to the assessment he could make visually on the patient's anatomy. The operator could only choose between three possible anatomical sizes: small, medium and large. The spectral characteristics (kV and filters) and the intensity of the X-ray beam were adjusted by reference to simple tables, according to the choice of the protocol (total body, whole spine, pelvis...) and the size of the patient (small, medium or large). Although this system was interesting in helping the operator to select the parameters, the main drawback was associated with the operator's visual-only selection.

[0004] This drawback was also known for standard 2D radiology, and some automatic exposure controls (AEC) were developed to allow automatic exposure periods. This kind of AEC could stop the exposure as soon as the dose target was reached in the dosimeter cell, which is usually a radiotransparent ionization chamber placed between the patient and the detector (film, CR, DR). This kind of AEC also had some drawbacks. The first drawback is again related to the operator's choice regarding the spectrum (kV, filters), usually chosen by a crossed choice in the protocol and size of the patient, typically among three possibilities. The second drawback of this kind of AEC was related to the type of detector used to acquire the images. As long as film was used, this kind of AEC could provide correct results, since the effects of overexposure or underexposure, which provide too bright or too dark image densities, are clearly visible on the film. The dose target of the AEC could therefore be set to obtain a standard expected density for a certain type of film. However, as computed radiography (CR) and direct radiography (DR) captors started to become popular 2D detectors for radiology, other problems arose, since these detectors and their automatic image processing could provide almost the same kind of image density regardless of dose, the only difference being the noise in the image, so operators could no longer simply detect over- or under-exposure by looking at the light or black image density. Operators had some difficulties in properly setting the dose target according to the noise in the image, and the use of CR or DR detector models of different types or suppliers was also a cause of notable difficulties in obtaining good results.

[0005] IEC 62494-1 proposed to use an Exposure Index (EI) that depends on the noise and thus the image signal to noise ratio (SNR) to define the dose target of AEC as the Exposure Index Target (EIT). IEC 62494-1 defines the exposure index as DI in dB = 10*log 10It was also proposed to define the deviation index (DI) as the ratio of the achieved exposure index to the exposure index target, expressed in (EI / EIT).

[0006] Considering scanning radiography systems, the known method of AEC for standard 2D radiography using a dosimeter cell placed between the patient and the detector is hardly compatible for various reasons. The first reason is related to the fact that it is very difficult or even impossible to change the exposure time, which is related only to the scanning speed and the size of the scanning area; for 2D systems, the AEC dosimeter cell does not move relative to the patient, and therefore this static measurement of 2D systems allows to stop the exposure as soon as the exposure target is reached. The second reason is the field of view of such a dosimeter for scanning radiography systems, which depends only on a very small part of the ROI (Region of Interest) relevant for diagnosis in the patient's body, typically only one line of the full image. The use of such a small part of the relevant ROI has little opportunity to provide the a priori information necessary to process the parameters of the shot in order to obtain an exposure index in the relevant ROI close to the exposure index target and to obtain a sufficient signal-to-noise ratio (SNR).

[0007] According to a first prior art outside the technical field of radiological vertical scanning imaging, a computed tomography method based on a rotating radiation source emitting a very high radiation dose in US Patent Application No. 2011 / 0026668 is known, which performs a spiral path along a horizontal scanning direction of a patient lying on a patient bed. This radiation source is driven by both a current intensity and a voltage intensity. The current intensity is related to the radiation dose emitted by the radiation source in a unit of time, for example one second. The voltage intensity is related to the energy of each photon emitted by the radiation source. To perform such a horizontal scan of a given specific lying patient, the voltage intensity is modulated to match the radiation dose emitted along the horizontal scanning direction, or the current intensity is modulated along the horizontal scanning direction to match the radiation dose emitted, which is anyway very high, at least 50 times higher than in a vertical scan of a standing patient, and the thickness of the patient along the horizontal direction, improving the overall image contrast for the thickness of the patient along the horizontal direction. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent Application No. 2011 / 0026668 [Patent Document 2] PCT / IB2016 / 000273 [Patent Document 3] PCT / IB2017 / 000986 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to is generally simpler and less complex than the first prior art method described above; In particular, since a current-modulated radiation generator must modulate the current intensity without being constrained by additional voltage intensity modulation, a much simpler and less expensive current-modulated radiation generator can be used. Using radiological imaging methods, Reducing the radiation dose received by the patient; and Maintaining a good level of image quality of the patient's body or the patient's organs, or at least maintaining an adequate level of image quality of the patient's body or the patient's tissues. The aim is to improve the compromise between [Means for solving the problem]

[0010] The invention proposes to solve the problem of still reducing the emitted radiation dose in vertical scanning of a standing patient, where the emitted radiation dose is anyway much lower than in computed tomography, by modulating the amount of emitted radiation particles without changing the energy of the beam, while simultaneously seeking to maintain a good or at least sufficient level of image contrast that differs along the vertical direction as the patient's thickness varies along said vertical scanning direction.

[0011] Thereby, while using a fairly simple and inexpensive current intensity modulated radiation generator to modulate the current intensity, the emitted radiation dose is reduced in thin zones of the patient's body and kept to a minimum while still maintaining an adequate emitted radiation dose in thick zones of the patient's body, thereby leading to an overall improvement in the emitted radiation dose.

[0012] Such a compromise between reduced emitted radiation dose and sufficient image contrast while keeping the radiological imaging method used simple and inexpensive may be different at each height along the vertical scan direction, or at least frequently varies with the variable thickness of the patient's body along the vertical scan direction.

[0013] Furthermore, this local image contrast is In particular, when using simpler and less expensive current intensity modulated radiation generators that modulate the current intensity without voltage intensity modulation during imaging, it is possible to achieve a high level of imaging while using simpler and less expensive radiological imaging methods. Not only does it depend on the overall thickness of the patient, Locally, also in the patient's body regions where the patient's thickness is greatest, which are the patient's body regions that are actually most important for imaging, guided by the localization of specific bones identified in the scout view; It is maintained at a sufficient level (as in the first prior art) or better still at the same level.

[0014] Maintaining a sufficient level of local image contrast of the identified specific bone localization at different image positions along the vertical scan direction means that the level of local image contrast does not decrease or deteriorate, or at least does not decrease or deteriorate too much so as to mean that a radiological imaging method expert will not be able to see the identified specific bone correctly.

[0015] In other words, maintaining a sufficient level of local image contrast of the identified specific bone localization at different imaging positions along the vertical scan direction means that the level of local image contrast is sufficient for a radiological imaging method expert to see and notice possible lesions within the identified specific bone localization.

[0016] Maintaining a sufficient level of local image contrast of the identified specific bone localization at different imaging positions along the vertical scanning direction means ideally maintaining the local image contrast of the identified specific bone localization at different image positions along the vertical scanning direction.

[0017] Maintaining these local image contrasts at sufficient levels preferably means maintaining local image contrast for at least the thickest patient regions or zones.

[0018] Knowing which patient area or zone is the thickest can be done via the scout view.

[0019] This object is achieved by a radiological imaging method comprising the step of vertically sliding two radiation sources, one frontal and one lateral radiation source, with mutually orthogonal imaging directions, to perform a vertical scan of a patient standing along a vertical scanning direction, said radiological method comprising at least one operating mode, in which a frontal scout view is created by performing a preliminary vertical scan of a patient standing along said vertical scanning direction by said frontal radiation sources, said frontal scout view being processed to identify the localization of a particular bone within said frontal scout view. and a drive current intensity of at least the frontal radiation source is modulated along the vertical scan direction in response to a patient thickness and a localization of the identified specific bone along the vertical scan direction, and there is no modulation of a voltage intensity of the frontal radiation source along the vertical scan direction, and the drive current intensity modulation of the frontal radiation source is automatically performed to improve the compromise between reducing the overall radiation dose received by a patient during the vertical scan and at the same time maintaining a sufficient level of local image contrast of the identified specific bone localization at different imaging positions along the vertical scan direction for a frontal image. Voltage is a synonym for tension.

[0020] This object is also achieved by a radiological imaging method comprising the step of vertically sliding two radiation sources, one frontal radiation source and one lateral radiation source, with mutually orthogonal imaging directions, to perform a vertical scan of a patient standing along a vertical scanning direction, said radiological method comprising at least one operating mode, in which a lateral scout view is created by performing a preliminary vertical scan of the patient standing along said vertical scanning direction by said lateral radiation sources, said lateral scout view being processed to identify the localization of a particular bone within said lateral scout view. and a drive current intensity of at least the side radiation source is modulated along the vertical scan direction in response to a patient thickness and a localization of the identified specific bone along the vertical scan direction, and there is no modulation of a voltage intensity of the side radiation source along the vertical scan direction, and the drive current intensity modulation of the side radiation source is automatically performed to improve a compromise between reducing the overall radiation dose received by a patient during the vertical scan and at the same time maintaining a sufficient level of local image contrast of the identified specific bone localization at different imaging positions along the vertical scan direction for side images.

[0021] This object is also achieved by a radiological imaging method comprising the step of vertically sliding two radiation sources, one frontal radiation source and one lateral radiation source, with mutually orthogonal imaging directions, to perform a vertical scan of a patient standing along a vertical scanning direction, said radiological method comprising at least one operating mode, in which frontal and lateral scout views are created by performing a preliminary vertical scan of the patient standing along said vertical scanning direction by said frontal and lateral radiation sources, said frontal and lateral scout views are processed in order to identify the localization of a particular bone within both said frontal and lateral scout views, and said frontal and lateral scout views are processed in order to identify the localization of a particular bone within both said frontal and lateral scout views, and The drive current intensity of both the front and side radiation sources is modulated along the vertical scan direction depending on the patient thickness and the localization of the identified specific bone along the vertical scan direction, with no modulation of the voltage intensity of either the front or side radiation sources along the vertical scan direction, the drive current intensity modulation of the front radiation source as well as the drive current intensity modulation of the side radiation source all being performed simultaneously, preferably synchronously and automatically, to improve the compromise between reducing the overall radiation dose received by the patient during the vertical scan and at the same time maintaining a sufficient level of local image contrast of the identified specific bone localization at different imaging positions along the vertical scan direction for front and side images.

[0022] Preferred embodiments comprise one or more of the following features which may be taken separately or together in part or in full combination with any preceding object of the present invention.

[0023] Preferably, said identified specific bone location comprises the patient's spine, preferably is the patient's spine.

[0024] Indeed, the patient's spine is the particular bone location of most interest to analyze in detail within the patient's body and is therefore used to drive the current intensity modulation.

[0025] Alternatively, the particular bone location may be the pelvis, arm, or leg of a patient standing along the vertical scan direction, depending on the region of interest within the portion of the patient's body being imaged.

[0026] Preferably, the drive current intensity modulation of the front radiation source is constant for the front image and / or the side image and is also performed to reach a signal-to-noise ratio value that is constant for the front image and / or the side image and common to a majority of the imaging positions along the vertical scanning direction, preferably common to all the imaging positions along the vertical scanning direction, but which can take two different values ​​for the front image and the side image, respectively.

[0027] Preferably, for each of said frontal and / or lateral images, said signal to noise ratio value is constant and predetermined for different patient organs to be imaged.

[0028] Preferably, for frontal images of the patient's spine, said standard signal-to-noise ratio value corresponds to a number of X-ray photons received per detector pixel comprised between 50 and 70, and the operator of the radiological imaging method preferably has the possibility, via a manual command, to deviate from this standard value by at least + or - 20%, more preferably by at least + or - 50%, and / or for lateral images of the patient's spine, said standard signal-to-noise ratio value corresponds to a number of X-ray photons received per detector pixel comprised between 20 and 40, and the operator of the radiological imaging method preferably has the possibility, via a manual command, to deviate from this standard value by at least + or - 20%, more preferably by at least + or - 50%.

[0029] Therefore, with a constant and optimized signal-to-noise ratio along or all along the vertical scanning direction, the local image contrast of identified specific bone localizations at different imaging positions along the vertical scanning direction is much improved with respect to what was actually the region of interest in the frontal and / or lateral images.

[0030] Preferably, the frontal and / or lateral images, after having undergone at least a first step of current intensity modulation, are preferably normalized by homogenization of areas located just outside the contours of the patient's body in order to remove image artifacts resulting from the drive current intensity modulation.

[0031] In fact, due to this drive current intensity modulation, there were some artifacts in the frontal and / or lateral images, which were some alternating waves of overlapping clear and dark grey levels in the blank parts of the image (just outside the patient) or in very thin parts of the patient, making those images a little less pleasant to interpret for the operator of the radiological imaging method, or at least requiring some training on the part of the operator.

[0032] Preferably, said frontal and / or lateral images are subjected to a contrast enhancement step after being normalized.

[0033] Thus, on the one hand, image artifacts resulting from this drive current intensity modulation are cancelled, but the contrast enhancement improved by this same drive current intensity modulation is not only maintained but also fully exploited.

[0034] Preferably, the identified specific bone localization excludes metallic parts, if any, such as, for example, metallic prostheses of parts of the skeleton of the patient's body or, for example, metallic protection that has been put in place on the patient's body prior to performing the radiological imaging method.

[0035] Indeed, these foreign (to the patient's body) objects introduced into or on the patient's body, since they are metallic and therefore impede much more radiation and x-rays than the rest of the patient's body, may lead to some non-optimization of the emitted dose, with the risk of some overexposure or some underexposure to the emitted radiation for the altitudes corresponding to these foreign objects. Firstly, in a mode in which the drive voltage strength is constant, and secondly, in which both the drive voltage strength and the drive current strength are constant, if the metallic outliers are not excluded, the results may be worse, since more or all parameters will be selected for the maximum thickness, which will result in a higher or much higher radiation dose being emitted than required, which will be very harmful to the patient.

[0036] Preferably, the current intensity modulation is maximized so as to also maximize the vertical scan rate at a constant value.

[0037] Thus, for a given amount of radiation emitted kept at the same level, and therefore received by a standing patient during said vertical scan, the total vertical scan time is significantly shortened, which has the advantage of reducing the possibility and effects of movement of a standing patient, thereby somewhat reducing the risk of blurring and distortion of the frontal and lateral images, and thereby further improving the signal-to-noise ratio of these frontal and lateral images.

[0038] Preferably, said operating mode can be manually switched either on or off by an operator of the radiological imaging procedure.

[0039] Thus, this highly advantageous method of operating a radiological imaging device is available, but it can be cancelled if an operator of the radiological imaging device wants to remove it, for example, to operate the radiological imaging device completely manually. The radiological imaging method according to an advantageous embodiment of the invention presents three operating modes: a fully manual mode, an AEC mode without modulation and an AEC mode with modulation.

[0040] Preferably, said mode of operation is dedicated to vertical scanning of large and / or obese patients.

[0041] Preferably, said mode of operation is dedicated to vertical scanning of pediatric patients.

[0042] The radiological imaging method according to the invention is even more interesting in that the patient thickness can be particularly thin or particularly thicker than for average-sized patients. This shows the ability of the radiological imaging method according to the invention to be very patient-specific. Of course, the radiological imaging method according to the invention also works very well for standard-sized patients.

[0043] Preferably, said current intensity modulation rate does not exceed a predetermined threshold of 5 mA per millisecond, preferably a predetermined threshold of 2 mA per millisecond, more preferably a predetermined threshold of 1 mA per millisecond.

[0044] Thus, the radiological imaging method according to the invention may be carried out using relatively simple and inexpensive radiation sources having relatively slow current intensity drive capabilities.

[0045] Preferably, said current intensity modulation is in the range of at least 20mA to 300mA, preferably 10mA to 400mA.

[0046] Thus, the radiological imaging method according to the invention may be carried out using relatively simple and inexpensive radiation sources having a relatively limited range of current strength drive capabilities.

[0047] Preferably, said fixed voltage strength is selected within the range of 50 kV to 120 kV.

[0048] Thus, the radiological imaging method according to the invention can also be carried out using relatively simple and inexpensive radiation sources.

[0049] Preferably, said vertical scan velocity value is in the range of at least 8cm / sec to 20cm / sec, preferably 4cm / sec to 30cm / sec.

[0050] Thus, the radiological imaging method according to the present invention may be performed using relatively simple and inexpensive radiation sources having a relatively limited range of vertical scan speed capabilities, while simultaneously fully utilizing the available range of vertical scan speed capabilities.

[0051] Preferably, each of the frontal scout views and / or lateral scout views is generated by performing a preliminary vertical scan of a patient standing along a vertical scan direction with a reduced overall radiation dose compared to each of the frontal and lateral images prior to generating each of the frontal and lateral images.

[0052] Thus, the modulation of the drive current intensity, and possibly the vertical scan speed, according to the thickness profile and the localization of specific bones of the standing patient's body along the vertical scan direction can be determined immediately prior to performing a vertical scan that results in valid frontal and lateral images of the standing patient's body that are performed with a limited but complete radiation dose sufficient to create high quality frontal and lateral images. The scout view can be performed at the expense of very limited overexposure to the emitted radiation.

[0053] Preferably, the reduced overall radiation dose is less than 10% of the overall radiation dose, preferably less than 5% of the overall radiation dose.

[0054] The benefit is therefore two-fold: not only is overexposure during scout view (+10% or +5%) very limited, but it is also very efficient to optimize the compromise between the overall radiation dose received and the enhancement of image contrast.

[0055] Preferably, pixels in the scout view are grouped together to create an imaging zone, preferably by zones of NxN pixels, more preferably by zones of at least 10x10 pixels, for example by zones of at least 20x20 pixels to create an imaging zone.

[0056] Thus, image quality and image contrast are enhanced for the scout view, despite the very low levels of emitted radiation dose used to perform this scout view.

[0057] Preferably, the image or the imaging zone is processed to identify corner points which are used to calculate the thickness profile and identify the location of the particular bone in a patient standing along the vertical scan direction.

[0058] Therefore, despite the very low levels of emitted radiation dose, from a scout view it is easier and more efficient to calculate the thickness profile and identify the localization of the particular bone of a patient standing along the vertical scan direction.

[0059] Preferably, said images or said imaging zones are processed by a neural network to calculate said thickness profile and to identify the location of said particular bones in a patient standing along said vertical scan direction.

[0060] Therefore, despite the very low level of emitted radiation dose, it is easier and more efficient to identify the localization of the particular bone of a patient standing along the vertical scan direction from a scout view.

[0061] Preferably, the two radiation sources slide vertically to perform a vertical scan of the pelvis, spine, or whole body of a standing patient along a vertical scan direction.

[0062] Preferably, two radiation detectors are associated with the two radiation sources respectively, and the two radiation detectors are two Photon Counting Detectors (PCDs) each associated with an automatic image processing function that automatically balances image density regardless of the amount of radiation received at the sensing surface of the radiation detector to enhance image contrast.

[0063] Thus, overexposure or underexposure to the radiation signal emitted by the radiation source is difficult to manually assess correctly by the operator of the radiological imaging method. Furthermore, photon counting detectors exhibit improved linearity and signal-to-noise ratio compared to gas detectors.

[0064] Preferably, two radiation detectors are associated with the two radiation sources respectively, and the two radiation detectors are two multi-energy counting detectors, preferably two Energy Resolved Photon Counting Detectors (ERPCDs).

[0065] Preferably, the radiation is X-ray.

[0066] A standing patient, or a patient in a standing position, is a patient in a weight-bearing position, as opposed to a lying patient, or a patient in a lying position, as in computed tomography. Another weight-bearing patient position, as an alternative to a standing patient position, is a sitting patient position.

[0067] Moreover, further features and advantages of the invention will become apparent from the following description of embodiments of the invention, given as non-limiting examples, with reference to the attached drawings listed below, in which: [Brief description of the drawings]

[0068] [Figure 1] FIG. 2 illustrates an example of a portion of a radiological imaging method according to an embodiment of the present invention that deals with calculating the drive current intensity modulation of a radiation source. [Diagram 2] FIG. 1 is an example of localization of specific bones through detection of corner points, here showing the entire body of a patient including the spine continued by the pelvis and legs. [Diagram 3] FIG. 13 shows an example of a corresponding parameter that is the median signal patch value as a function of vertical position along the patient's height expressed in millimeters. [Figure 4] FIG. 13 shows an example of a corresponding thickness profile expressed in millimeters as a function of vertical position along a patient's height expressed in millimeters. [Diagram 5] FIG. 1 shows an example of constant voltage expressed in kilovolts as a function of equivalent patient thickness expressed in centimeters for frontal and lateral images, respectively. [Figure 6] FIG. 13 shows an example of current modulation expressed in milliamps as a function of equivalent patient thickness expressed in centimeters for frontal and lateral images, respectively. [Figure 7] FIG. 13 shows an example of the number of resulting X-ray photons per detector pixel (representing the signal-to-noise ratio) as a function of the equivalent patient thickness expressed in centimeters for frontal and lateral images, respectively. [Figure 8] FIG. 1 shows an example of the radiation dose received by a patient in μGy (microgray) as a function of the equivalent thickness of the patient expressed in centimeters for frontal and lateral images, respectively. [Figure 9] FIG. 13 shows an example of a filtered frontal scout view after the salient point detection step but before the salient point filtering step. [Figure 10]FIG. 13 shows an example of a filtered frontal scout view after a salient point detection step and after a salient point filtering step. [Figure 11] FIG. 13 shows an example of a filtered side scout view after the salient point detection step but before the salient point filtering step. [Figure 12] FIG. 13 shows an example of a filtered side scout view after a salient point detection step and after a salient point filtering step. [Figure 13] FIG. 13 shows an example of a filtered frontal scout view after the deep neural network detection step. [Figure 14] FIG. 13 shows an example of a filtered side scout view after the deep neural network detection step. [Figure 15] FIG. 13 shows example side view images of constant drive current intensity and constant drive voltage intensity in constant current and constant voltage modes. [Figure 16] FIG. 13 shows an example of a side view image of modulated drive current intensity and constant drive voltage intensity in modulated current and constant voltage mode. [Figure 17] FIG. 13 shows an example of a final lateral image displayed to a radiologist. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] The present invention aims to provide a solution for providing a scanning stereoscopic radiography system with an AEC system, which is compliant with IEC 62494-1, designed to be used in the scanning stereoscopic radiography systems described in applications PCT / IB2016 / 000273 and PCT / IB2017 / 000986, which are incorporated by reference and owned by the same applicant EOS-Imaging.

[0070] In a preferred embodiment, the two detectors of the scanning stereoscopic radiography system are multi-energy counting detectors, also known as energy-resolved photon counting detectors (ERPCDs), having at least two energy bins. In another embodiment, the two detectors of the scanning stereoscopic radiography system are mono-energy counting detectors, also known as photon counting detectors (PCDs).

[0071] The use of photon counting detectors in multi-energy or mono-energy is advantageous compared to gas detectors for two main reasons. The first reason is the fact that the signal of an ERPCD or PCD is linear with respect to the incident flux and directly equal to the number of detected photons, whereas the signal of a gas detector is strongly nonlinear and this nonlinearity was rather complicated to model in order to correct accurately. In ERPCD and PCD, there is still a nonlinear behavior at high fluxes, called the pile-up effect, but this pile-up effect can be successfully modeled and corrected by image calibration software. The second reason is the fact that ERPCD and PCD have a very stable behavior and sensitivity without needing a new calibration for several months, whereas gas detectors are far from stable, require daily calibration, and their behavior and sensitivity can also vary in minutes depending on room temperature changes. The stability of PCD and ERPCD, as well as the photon counting feature, allow the direct use of the counting signal of the incident photons in the detector to evaluate the exposure index and the signal-to-noise ratio. The signal-to-noise ratio is directly equal to the root mean square of the signal. Other types of energy integrating detectors, such as gas detectors, for example, do not exhibit this advantage and require precise calibration in order to assess the SNR and therefore the exposure index.

[0072] The radiological imaging method according to an embodiment of the present invention is based on the use of scout views in mono-energy (ERPCD or PCD). Since one goal of this scanning radiography system is to specialize in bone imaging for orthopedics, the scout views in that case are analyzed to accurately locate the axial skeleton or bones of the selected protocol. However, for some other applications, a soft tissue organ protocol such as lungs may be selected, in which case the scout views are analyzed to locate the organs.

[0073] The relevant ROI for diagnosis according to the definition of IEC 62494-1 is defined by the union of a set of circular sub-ROIs, also called "patches", of approximately the size of the spine (4-5 cm diameter) placed over a set of characteristic detection points or landmarks in the scout view according to a bone or organ search specific protocol. This search for characteristic points can be materialized using two different methods, namely using specific corner point search algorithms or using a trained pose-detection deep neural network.

[0074] The patient's equivalent thickness is then evaluated at each patch, and some protocol of specific selection rules provides a vertical vector of equivalent thickness as a function of Z (vertical) position in the patient. Equivalent thickness is evaluated at the single material PMMA [poly(methyl methacrylate)] equivalent when a mono-energy scout view is used.

[0075] The vertical equivalent thickness vector is then used to process the characteristic thickness, which is a reliable detection of the most likely maximum thickness. The characteristic thickness and equivalent vector thickness are then used to process the parameters of the scan to bring the exposure index at each patch as close as possible to the exposure target.

[0076] The exposure parameters may be generated in several different modes according to operator selection; The first mode, called "Constant Exposure Mode", simply provides the optimum constant kV, mA, filter, and scan speed to use for the scan, providing constant flux exposure control as defined in IEC 60601-2-44; The second mode, called "Flex-Dose", processes the vectors of scan speed, selected filter and time modulation of exposure along the vertical axis, providing Z-axis exposure control following the definition in IEC 60601-2-44.

[0077] "Flex Dose" should be used with the voltage or tension (kV) fixed and the current (mA) modulated along the Z axis. It is this second mode, called "Flex Dose", that is the mode of operation according to the present invention.

[0078] FIG. 1 shows an example of a part of a radiological imaging method according to an embodiment of the invention that deals with calculating the drive current intensity modulation of a radiation source.

[0079] A radiological imaging method according to an embodiment of the present invention includes a method for processing current intensity modulation of a radiation source along a vertical scan direction. Figure 1 shows a functional block diagram of an exemplary implementation using corner points.

[0080] The following successive steps are carried out:

[0081] In step 1, a scout view of a standing patient is acquired with reduced radiation dose. The scout view is required to use "flex dose" and is acquired with a 0.5 mm thick copper filter and a very low dose. The patient dose ratio between this scout view and the main shot is less than 10% for long axis and localization protocols. This step 1 of the method is the acquisition of a scout view at reduced dose by vertical scanning along the patient.

[0082] In step 2, post-processing of the scout view is performed, where the pixels in the scout view are preferably grouped together by zones of N×N pixels, for example, zones of at least 20×20 pixels, to create imaging zones with calibration and average binning. The scout view was acquired here at such a low level of dose that a large binning of 20×20 was applied to sufficiently filter noise and obtain a higher level of confidence in the estimated thickness. This step 2 is a post-processing of the scout view image, including homogeneity correction using detector gain calibration and the use of filters to improve the signal-to-noise ratio without introducing bias to obtain a higher level of confidence in the estimated thickness, for example, an average binning of 20×20 is appropriately adapted.

[0083] In step 3, as will be explained in more detail with respect to Figs. 9 to 12, the corner points are detected, first the points of higher radiation absorption are detected, then some of the detected points are filtered according to a predetermined rule to give the corner points continuity in order to substantially maintain only the desired specific bone localization, for example the spine of the patient's body. A corner point detection algorithm developed to detect bones of the confirmed axial skeleton is then applied to the binned images. The detected corner points are then selected differently in the frontal and lateral images depending on the patient's orientation. The selected corner points mainly follow the axial skeleton, which consists of the lower limbs, pelvis, spine, neck, and head. In step 3, where metal detection is performed, the detection of metal prostheses or metal protections is also used to remove and exclude the corresponding selected corner points, whereas in step 8, only outliers are selected in terms of thickness. This step 3 is the detection of the specific bone localization in the scout view and the removal of the metal parts. As an example, the description of the method using corner point detection is used, but another implementation using a specific neural network can also be used. The corner point detection method used consists of searching at a typical vertebra-sized scale of about 5 cm in diameter to find a set of local maximum attenuation points in the scout view. The detected corner points are then selected differently in the frontal and lateral images depending on the patient's orientation. The selected corner points mainly follow the axial skeleton, which consists of the lower limbs, pelvis, spine, neck, and head. There is only one selected corner point at one Z elevation (one Z position along the vertical scan direction), whereas there can be several different detected corner points at one Z elevation. Figures 9 to 12 show corner point detection and selection in the frontal and lateral scout views of a patient, respectively. Figures 9 and 11 show the detected corner points, and Figures 10 and 12 show the selected corner points. Figures 13 and 14 show an example of skeleton detection using the neural network method with a limited number of landmarks applied to the same patient as Figures 9 to 12.As an example, the limited number of landmarks shown in Figures 13 and 14 correspond to the cervical vertebrae C2 and C7, the thoracic vertebrae T9, the sacrum, and in the lower limbs, the left and right femoral heads, the 1 / 3 shafts, the center of the trochlea, the distal tibia and the proximal tibia. The corner point selection method can also remove points detected in metal parts, including, for example, metal prostheses or metal protections for breasts, gonads, ovaries, or other sensory parts of the body. Metal parts can also be removed using neural network methods.

[0084] In step 4, from the corner points, a signal profile is obtained as a function of vertical position expressed in mm. This step 4 is the processing of the signal profile along the vertical scan of the patient. The median signal of the scout view image is processed in each circular patch centered on the selected corner point and related to the altitude z of the corresponding corner point in the vertical scan reference. The patch size represents an area roughly similar to the size of a vertebra, about 5 cm in diameter. The resulting signal profile function in z is sparse, and interpolation and extrapolation of this sparse signal profile provides a complete vertical profile sampling of the signal according to the vertical altitude z throughout the required vertical scan height of the patient, including some lower and upper extension of the scan area for optional selection by the operator.

[0085] In step 5, the patient thickness profile is calculated from the preceding signal profiles. This step 5 is in fact the processing of the thickness profile along the vertical scan of the patient. The logarithm of the z signal profile function is processed using a calibrated quadratic polynomial function to provide the corresponding PMMA thickness equivalent value according to Equation 1.

[0086]

number

[0087] mAs = mA scout view *time_per_line MaxThickness=600mm for PMMA The coefficients a, b, and c of the polynomial are processed using a calibration.

[0088] Optionally, new upper and / or lower scan limits may be manually selected by the radiology imaging modality operator in step 6. The operator may use a selection tool on the scout view image in the interface software to increase or decrease the scan height by a small amount.

[0089] In step 7, optionally, the patient thickness profile is cropped according to the preceding new upper and / or lower scan limits. The processed thickness profile function in z is then cropped according to operator selection of upper and lower limits of the vertical scan along the patient.

[0090] In step 8, the characteristic patient thickness is calculated from the preceding thickness profile, after filtering outliers such as metal prostheses or metal protections has already been performed in step 3. This step 8 is the processing of the characteristic thickness. Simply considered, the maximum value of the thickness profile previously determined in step 5 does not represent the patient's thickness when he is sitting or when he has his legs on the support or his arms folded. In order to define the patient's representative thickness, the derivative of the thickness profile is processed to define statistical parameters using the mean and standard deviation to remove the outliers, and then the characteristic thickness is defined as the maximum thickness without taking into account the outliers.

[0091] In step 9, image acquisition parameters are obtained from a reference table according to both the exact location of a particular bone, e.g., the patient's spine along the vertical scanning direction, and the change in the patient's thickness along the vertical scanning direction, i.e., along the patient's height. In fact, the processed characteristic PMMA equivalent thickness and the selected profile are used to obtain image acquisition parameters (kV, filter, scan speed) according to the reference anatomical parameter table. Step 9 is the selection in the table of image acquisition parameters according to the processed characteristic thickness and the selected protocol. The parameter set includes, for example, a signal target, and a reference kV. If the operator chooses to disable modulation but maintain AEC, the reference kV, mA, and speed may be used to acquire the patient's image, in which case constant values ​​of scan speed and current are processed according to the signal target and the characteristic thickness. The reference voltage (kV) is used to acquire the patient's image with current modulation by a constant voltage (kV). As an example, the signal target for spine examination is different for frontal and lateral images, typically about 60 photons / pixel for frontal views and about 30 photons / pixel for lateral views, respectively. These values ​​can be adjusted by the radiologist within limited tolerances.

[0092] In step 10, depending on the selected operating mode, either a constant value of the current intensity or preferably a variable modulation of the current intensity along the vertical direction is selected as a function of both the exact position of the patient's spine along the vertical scanning direction and the variation of the patient's thickness along the vertical scanning direction in order to reach a constant and common signal-to-noise ratio along the vertical scanning direction, i.e. a constant target number of X-ray photons per detector pixel along the vertical scanning direction, this constant target number of X-ray photons per detector pixel along the vertical scanning direction preferably has different values, e.g. 60 for frontal images and 30 for lateral images. The last step of "flex dose" is the processing of the current (mA) modulation vector of the image along the scanned patient's body part to match as closely as possible the exposure index target in all patches of the ROI. A matrix was calibrated to establish the relationship between the measured signal values ​​as a function of the set of voltage (kV) values ​​and the PMMA equivalent thickness. The algorithm used to determine the current (mA) performs ID interpolation within this matrix.

[0093] More precisely, in this step 10, depending on the selected operating mode, a variable modulation of the current intensity along the vertical direction is selected as a function of both the exact position of the patient's spine along the vertical scanning direction and the variation of the patient's thickness along the vertical scanning direction, so as to obtain an equivalent patient thickness variation along the vertical scanning direction (bones attenuate more radiation and therefore correspond to a thickness superior to their actual thickness compared to soft tissues) in order to reach a constant and common signal-to-noise ratio along the vertical scanning direction, i.e. a constant target number of X-ray photons per detector pixel along the vertical scanning direction, which preferably has different values, e.g. 60 for frontal images and for lateral images, e.g. 30.

[0094] It is known that contrast is better at low voltages (kV), but the use of low voltages (kV) is not efficient in terms of the useful dose that provides some signal at the detector compared to the dose received in thicker parts of the body. If one or more voltage values ​​are available (at least three of them, preferably exactly three), the selection of a specific value of the voltage (kV) constant along the complete vertical scan is guided by a compromise between better contrast leading to lower voltages (kV) and more efficient dose use leading to higher voltages (kV). The thickness profile and a 1D table representing the expected signal for the selected constant voltage value and thickness for the reference current and scan speed are used to process the current profile required at the reference scan speed to reach the signal target. The current profile can then be adjusted proportionally to the specific scan speed. For example, to double the scan speed relative to the reference scan speed, a doubling of the current profile is required. The source with the maximum output power allowed for a given scan speed, the maximum current profile can be estimated by the ratio of the maximum power and the selected constant voltage value. The optimum scan speed is found by looking at the higher allowable current profile.

[0095] The final step of "FlexDose" is the processing of the image current (mA) modulation vector along the scanned patient body-part to meet as closely as possible the exposure index target in all patches of the ROI.

[0096] Voltage (kV) and current (mA) can be treated only as scalar values ​​with respect to the corresponding characteristic thickness in constant AEC mode, or as current modulation vectors in "flex dose" mode, to optimize the x-ray flux according to the estimated patient thickness along the vertical scan. The "flex dose" mode allows significant dose reduction for long axis protocols compared to the constant current (mA) mode, which is based only on the maximum patient thickness.

[0097] The overall goal of the "flex dose" mode is to reach a constant and repeatable signal level at the maximum thickness of the scanned area of ​​the patient in a constant mode, and further to reach a constant and repeatable signal level along the scanned axial skeleton of the patient, regardless of the patient's morphology and thickness for this mode.

[0098] Fig. 2 is an example of localization of specific bones through detection of corner points, here showing the whole body of a patient including the spine continued by the pelvis and legs. Fig. 2 shows a typical example of selected corner points in a lateral scout view.

[0099] A series of circles generally follow the patient's spine in the vertical direction. The series of corner points SP are spotted on a lateral image of the patient's body. The lateral image of the patient's body is plotted for altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the figure, and both altitude and width w are expressed in mm.

[0100] Figure 3 shows an example of the corresponding parameter P, which is the median signal patch value as a function of vertical position Z along the patient's height expressed in millimeters. Figure 3 shows the corresponding fully sampled signal profile along a vertical scan of the patient. The selected corner points are indicated on the lateral scout view in Figure 2 by circular dots representing circular patches of approximately 5 cm diameter.

[0101] 4 shows an example of a corresponding thickness profile th expressed in millimeters as a function of vertical position Z along the patient's height expressed in millimeters. FIG. 4 shows the determination of the characteristic thickness in the lateral profile shown in FIG.

[0102] The patient thickness profile is plotted on Figure 4. The patient thickness th, expressed in mm, is represented as a function of the vertical position Z, also expressed in mm.

[0103] Figures 5 and 6 show simulations of standard relationships of voltage (kV) and current (mA) as a function of equivalent PMMA thickness for the whole spine protocol in "flex dose" mode for characteristic thicknesses of 225 mm in the front and 335 mm in the side measured on the anthropomorphic phantom of Figures 15, 16, and 17 taken as examples.

[0104] Figure 5 shows examples of constant voltages V expressed in kilovolts as a function of the patient's equivalent thickness th expressed in centimeters for the frontal and lateral images, respectively. These constant voltages can be selected according to the characteristic thickness measurements in the frontal and lateral scout views.

[0105] For the frontal curve F, the voltage constant value was chosen at 90 kV (corresponding to a characteristic thickness of 225 mm measured in a frontal scout view of the anthropomorphic phantom) and is independent of the characteristic patient thickness, which ranges from about 10 cm to about 50 cm.

[0106] For the lateral curve L, the voltage constant value was chosen at 120 kV (corresponding to a characteristic thickness of 335 mm measured in the frontal scout view of the anthropomorphic phantom) and is independent of the characteristic patient thickness, which ranges from about 10 cm to about 50 cm.

[0107] FIG. 6 shows an example of the current modulation I expressed in milliamperes as a function of the equivalent thickness th of the patient expressed in centimeters for the frontal and lateral images, respectively.

[0108] For the frontal curve F, the current increases steadily from about 10 mA to about 400 mA for equivalent patient thicknesses ranging from about 10 cm to about 30 cm, and then remains constant at about 400 mA for equivalent patient thicknesses ranging from about 30 cm to about 50 cm.

[0109] For the profile curve L, the current increases steadily from about 10 mA to about 400 mA for equivalent patient thicknesses ranging from about 10 cm to about 37 cm, and then remains constant at about 400 mA for from about 37 cm to about 50 cm. The increase in the F curve is steeper than that of the L curve.

[0110] FIG. 7 shows an example of the resulting number of X-ray photons S (representing the signal-to-noise ratio) per detector pixel as a function of the equivalent patient thickness th expressed in centimeters for frontal and lateral images, respectively.

[0111] For the front curve F, the number of x-ray photons per detector pixel is rather constant at about 60 for equivalent patient thicknesses ranging from about 15 cm to about 30 cm, then drops sharply from about 60 to about 5 for equivalent patient thicknesses ranging from about 30 cm to about 40 cm, and continues to drop more gently from about 40 cm to about 50 cm, tending toward zero without actually reaching zero. Below 15 cm, between 15 cm and 10 cm, the number increases sharply to about 140.

[0112] For the side curve L, the number of x-ray photons per detector pixel remains rather constant at about 27 for equivalent patient thicknesses ranging from about 20 cm to about 37 cm, and then continues to decrease more gently as it tends toward zero, without actually reaching zero, for equivalent patient thicknesses ranging from about 40 cm to about 50 cm. Below 20 cm, between 20 cm and 10 cm, this number increases sharply to about 20.

[0113] FIG. 8 shows an example of the radiation dose D received by the patient in μGy as a function of the equivalent thickness th of the patient expressed in centimeters for frontal and lateral images, respectively.

[0114] For the frontal curve F, the radiation dose received by the patient first increases slowly from about 0 to about 100 microGrays for equivalent patient thicknesses ranging from about 10 cm to about 20 cm, then increases much more rapidly from about 100 microGrays to about 850 microGrays for equivalent patient thicknesses ranging from about 20 cm to about 30 cm, and then remains approximately constant at about 850 microGrays for equivalent patient thicknesses ranging from about 30 cm to about 50 cm.

[0115] For the profile curve L, the radiation dose received by the patient first increases slowly from about 0 to about 130 microGrays for equivalent patient thicknesses ranging from about 10 cm to about 25 cm, then increases much more rapidly from about 130 microGrays to about 1700 microGrays for equivalent patient thicknesses ranging from about 25 cm to about 37 cm, and then remains approximately constant at about 1700 microGrays for equivalent patient thicknesses ranging from about 37 cm to about 50 cm. The L curve increases more slowly than the F curve in a first slowly increasing phase, but then the L curve increases faster than the F curve in a second abrupt (or rapid) increasing phase.

[0116] In all Figures 9 to 16, for the scout view, the scale along the horizontal and vertical axes is in mm after the scout view image is binned (meaning each zone of the original 20x20 square pixels is collected into a new pixel); there is no such binning in the front and side images taken after the scout view.

[0117] Figures 9 to 12 show frontal and side images using a corner point detection step both before and after filtering to focus on the patient's spine (or the patient's spine followed by one of the patient's legs) and exclude other bones in order to enhance image contrast in the zone of interest, which in this case is the patient's spine.

[0118] This filtering step aims to select only corner points that are likely to be located approximately in the axial skeleton, here the spine and one leg following the spine.

[0119] 9 shows an example of a filtered frontal scout view after the corner point detection step but before the corner point filtering step. This image of a patient's body is plotted for altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the view, and both altitude and width w are expressed in mm.

[0120] 10 shows an example of a filtered frontal scout view after the corner point detection step and after the corner point filtering step. This image of a patient's body is plotted for altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the view, and both altitude and width w are expressed in mm.

[0121] Bones 21-25 are spotted in a patient 20. The patient 20 is plotted in terms of the patient's height Z, expressed in mm, against the patient's width, expressed in mm.

[0122] The rules for the frontal image filtering step are as follows:

[0123] For each Z (vertical position) value, the corner point with the maximum thickness is selected.

[0124] Metallic portions are excluded (which correspond to very steep attenuation or absorption in their vicinity within the patient's body), even if they correspond to corner points with maximum thickness.

[0125] If the filtering is performed in a frontal image of the patient 20, then:

[0126] Only the spine 21, the left leg 23, and a small portion of the right leg 22 are left.

[0127] On the other hand, the arm 24, shoulder 25 and most of the right leg 33 have been filtered out and thereby eliminated.

[0128] Figure 11 shows an example of a filtered side scout view after the corner point detection step but before the corner point filtering step. This image of a patient's body is plotted in terms of altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the view, and both altitude and width w are expressed in mm.

[0129] 12 shows an example of a filtered lateral scout view after the corner point detection step and after the corner point filtering step. This image of a patient's body is plotted for altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the view, and both altitude and width w are expressed in mm.

[0130] Bones 31-35 are spotted in a patient 30. The patient 30 is plotted in terms of the patient's height Z, expressed in mm, against the patient's width, expressed in mm.

[0131] The rules for the side image filtering step are as follows:

[0132] For each Z (vertical position) value, the corner point closest to the patient's back is selected (here, since the patient is facing left, it corresponds more to the corner point on the right of the profile image, but if the patient were facing right, it would correspond more to the corner point on the left of the profile image).

[0133] Metallic portions are excluded (which correspond to very steep attenuation or absorption in their vicinity within the patient's body), even if they correspond to corner points with maximum thickness.

[0134] It still excludes some isolated corner points that are too close to the patient's back, farther than the patient's spine facing to the right in the lateral image, for example some isolated corner points that are lost in soft tissue zones such as in the buttocks or fleshy parts of the back.

[0135] If filtering is performed in a lateral image of the patient 30, then:

[0136] Only the spine 31 and the left leg 32 remain.

[0137] On the other hand, the arms 33 and 34 and the jaw 35 have been filtered out and thereby excluded.

[0138] The current intensity modulation can be calibrated.

[0139] A particular image, either front or side, may also be modified.

[0140] The profile of the drive current intensity modulation is calculated from the scout view.

[0141] The calculated modulation profile is then used to acquire an image.

[0142] The acquired images are then corrected by calibration software by homogenizing the detector and correcting its non-linearity.

[0143] Then, for each line j of the captured image, the feedback measurement file of the generator after emission of radiation is used to identify the value of the current mA(j) effectively delivered by the generator in this line j.

[0144] The image is then normalized and the signal in each line j of the captured image is divided by mA(j).

[0145] Figure 13 shows an example of a filtered frontal scout view after the deep neural network detection step. This image of the patient's body is plotted for altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the view, and both altitude and width w are expressed in mm.

[0146] There is a patient 40 represented on a frontal image with landmarks 41 plotted by a deep neural network.

[0147] Figure 14 shows an example of a filtered lateral scout view after the deep neural network detection step. This image of the patient's body is plotted for altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the view, and both altitude and width w are expressed in mm.

[0148] There is a patient 50 depicted on a lateral image with landmarks 51 plotted by a deep neural network.

[0149] Figure 15 shows an example of a side view image of constant drive current and voltage strength in constant current and voltage modes. Figure 15 shows a lateral scan of an anthropomorphic phantom when modulation is disabled.

[0150] A patient 60 is depicted on a lateral image. The image of the patient's body is plotted with respect to altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the figure, and both altitude and width w are expressed in mm. There is a constant drive current strength 61 all along the vertical scan direction Z, for example at about 350 mA. There is a constant drive voltage strength 62 all along the vertical scan direction Z, for example at about 120 kV. The lateral image of the patient 60 is of average quality.

[0151] Figure 16 shows an example of a side view image of modulated drive current intensity and constant drive voltage intensity in modulated current and constant voltage mode. Figure 16 shows a lateral scan of an anthropomorphic phantom with modulation enabled but using a fixed voltage (kV).

[0152] A patient 70 is depicted on the lateral image. The image of the patient's body is plotted with respect to altitude Z (height along the vertical scan direction) as a function of the patient's width, where the patient's thickness th is perpendicular to the plane of the figure, and both altitude and width w are expressed in mm. There is a drive current intensity modulation 71 all along the vertical scan direction Z, varying, for example, between about 10 mA and about 350 mA. There is a constant drive voltage intensity 72 all along the vertical scan direction Z, for example at about 120 kV. The lateral image of patient 70 is of particularly similar quality to the lateral image of patient 60, but taken with a lower radiation dose and adjusted to obtain an appropriate level of signal at each position along the vertical scan direction.

[0153] In comparison with the image of Figure 15, in the image shown in Figure 16 it can be seen that the blank or void parts of the image outside the patient are modulated in accordance with the applied modulation profile. The image is then corrected by normalization with a filtered out signal without attenuation to remove this modulation of the blank parts in the image, to avoid compromising the radiologist's analysis of the image. The demodulated image is then subjected to standard contrast enhancement before being presented to the radiologist.

[0154] Fig. 17 shows an example of a final lateral image displayed to a radiologist. Fig. 17 shows, for example, a lateral scan image acquired using current modulation only including demodulation and contrast enhancement processing as presented to a radiologist. This final lateral image is of good quality.

[0155] The invention has been described with reference to preferred embodiments, however, many variations are possible within the scope of the invention. [Explanation of symbols]

[0156] 20 patients 21 bones, spine 22 bones, right leg 23 bones, left leg 24 bones, arm 25 bones, shoulders 31 bones, spine 32 bones, left leg 33 bones, right leg, arm 34 Bone, Arm 35 Bones, Jaws 40 patients 41 Landmark 50 patients 51 Landmark 60 patients 61 Constant drive current strength 62 Constant driving voltage strength 70 patients 71 Drive current intensity modulation 72 Constant driving voltage strength

Claims

1. 1. A radiological imaging method comprising the steps of vertically sliding two radiation sources having mutually orthogonal imaging directions, one frontal radiation source and one lateral radiation source, to perform a vertical scan of a standing patient (20) along a vertical scanning direction (Z), The radiological imaging method includes at least one mode of operation, the mode of operation comprising: a frontal scout view is created by performing (1) a preliminary vertical scan of a standing patient (20) along the vertical scan direction (Z) with the frontal radiation source; The frontal scout view is processed (2, 3) to identify specific bone locations (21) within the frontal scout view; a drive current intensity (11) of at least the frontal radiation source is modulated along the vertical scan direction (Z) in response to a patient thickness and a location (21) of the identified specific bone along the vertical scan direction (Z); There is no modulation of the driving voltage intensity of the front radiation source along the vertical scanning direction (Z), The modulation of the driving current intensity (11) of the front radiation source, reducing the overall radiation dose received by the patient (20) during said vertical scan; At the same time, for the en face images, the local image contrast of the identified specific bone localization (21) at different imaging positions along the vertical scanning direction (Z) is maintained at a sufficient level, so that the emitted radiation dose is reduced in thin zones of the patient's body and still maintained at a sufficient radiation dose in thick zones of the patient's body. This is done automatically to improve the compromise between Radiological imaging methods.

2. 1. A radiological imaging method comprising the steps of vertically sliding two radiation sources having mutually orthogonal imaging directions, one frontal radiation source and one lateral radiation source, to perform a vertical scan of a standing patient (30) along a vertical scanning direction (Z), The radiological imaging method includes at least one mode of operation, the mode of operation comprising: a lateral scout view is created by performing (1) a preliminary vertical scan of a standing patient (30) along the vertical scan direction (Z) with the lateral radiation source; The lateral scout view is processed (2, 3) to identify specific bone locations (31) within the lateral scout view; a drive current intensity (11) of at least the side radiation source is modulated along the vertical scan direction (Z) in response to a patient thickness and a location (31) of the identified specific bone along the vertical scan direction (Z); There is no modulation of the driving voltage intensity of the side radiation source along the vertical scan direction (Z); Modulating the drive current intensity of the side radiation source comprises: reducing the overall radiation dose received by the patient (30) during said vertical scan; At the same time, for lateral images, the local image contrast of the identified specific bone localization (31) at different imaging positions along the vertical scanning direction (Z) is maintained at a sufficient level, so that the emitted radiation dose is reduced in thin zones of the patient's body and still maintained at a sufficient radiation dose in thick zones of the patient's body. This is done automatically to improve the compromise between Radiological imaging methods.

3. 1. A radiological imaging method comprising the steps of: vertically sliding two radiation sources having mutually orthogonal imaging directions, one frontal radiation source and one lateral radiation source, along a vertical scanning direction (Z) to perform a vertical scan of a standing patient (20, 30), The radiological imaging method includes at least one mode of operation, the mode of operation comprising: frontal and lateral scout views are generated by performing (1) a preliminary vertical scan of a standing patient along the vertical scan direction with the frontal and lateral radiation sources; The frontal scout view and the lateral scout view are processed (2, 3) to identify specific bone locations (21, 31) within both the frontal scout view and the lateral scout view; the drive current intensity (11) of both the front radiation source and the side radiation source is modulated along the vertical scan direction (Z) in response to a patient thickness and a location (21, 31) of the identified specific bone along the vertical scan direction; There is no modulation of the driving voltage intensity of either the front radiation source or the side radiation source along the vertical scanning direction (Z); The modulation of the drive current intensity of the front radiation source and the modulation of the drive current intensity of the side radiation source include: reducing the overall radiation dose received by a patient (20, 30) during said vertical scan; At the same time, the local image contrast of the identified specific bone localization (21, 31) at different imaging positions along the vertical scanning direction (Z) for the frontal image and the lateral image is maintained at a sufficient level, so that the emitted radiation dose is reduced in thin zones of the patient's body and still maintained at a sufficient radiation dose in thick zones of the patient's body. all run simultaneously or synchronously and automatically to improve the compromise between Radiological imaging methods.

4. 4. The radiological imaging method according to any one of claims 1 to 3, wherein the identified specific bone localization (21, 31) comprises or is the patient's spine.

5. A radiological imaging method according to claim 1, wherein the drive current intensity (11) of the front radiation source and / or the lateral radiation source is modulated, and wherein the modulation of the drive current intensity (11) of the front radiation source and / or the lateral radiation source is also performed to reach, for the front image and / or the lateral image, a signal-to-noise ratio value which is constant and common to a majority of the imaging positions along the vertical scanning direction (Z) or common to all the imaging positions along the vertical scanning direction (Z), but which can take two different values ​​for the front image and the lateral image, respectively.

6. 6. The radiological imaging method according to claim 5, wherein for each of the frontal and / or lateral images, the value of the signal-to-noise ratio is constant and predetermined for different patient (20, 30) organs to be imaged.

7. For a frontal image of the patient's spine, said signal-to-noise ratio value corresponds to a number of X-ray photons received per detector pixel comprised between 50 and 70, and / or the human operator of the radiological imaging method has the available capability to deviate from this standard value by at least + or - 20%, or at least + or - 50%, via a manual command, and / or for a lateral image of the patient's spine, said signal-to-noise ratio value is referred to as a standard signal-to-noise ratio value and corresponds to a number of X-ray photons received per detector pixel comprised between 20 and 40, and / or a human operator of said radiological imaging method has the available capability to deviate from this standard value by at least + or - 20%, or at least + or - 50%, via a manual command, A radiological imaging method according to claim 5 or 6.

8. 8. The radiological imaging method according to any one of claims 1 to 7, wherein the frontal and / or lateral images, after having undergone at least a first step of modulation of the current intensity, are normalized by homogenization of an area located just outside the contour of the patient's body in order to remove image artefacts resulting from the modulation of the drive current intensity (11).

9. 9. The radiological imaging method according to claim 8, wherein the frontal and / or lateral images are subjected to a contrast enhancement step after being normalized.

10. 10. The radiological imaging method according to any one of claims 1 to 9, wherein the identified specific bone localization (21, 31) excludes metallic parts, if any, such as metallic prostheses of a part of the skeleton of the patient's body or metallic protections that have been put in position on the patient's body before performing the radiological imaging method.

11. 11. The radiological imaging method according to any one of the preceding claims, wherein the modulation of the current intensity (11) is maximized so as to also maximize the vertical scan speed at a constant value.

12. 12. The radiological imaging method according to any one of the preceding claims, wherein said operating mode can be manually switched either on or off by an operator of the radiological imaging method.

13. 13. The radiological imaging method according to any one of the preceding claims, wherein said mode of operation is dedicated to vertical scanning of large and / or obese patients.

14. 14. The radiological imaging method according to any one of claims 1 to 13, wherein said mode of operation is dedicated to vertical scanning of pediatric patients.

15. 15. The radiological imaging method according to any one of claims 1 to 14, wherein the modulation rate of the current intensity does not exceed a predetermined threshold of 5 mA per millisecond, or a predetermined threshold of 2 mA per millisecond, or a predetermined threshold of 1 mA per millisecond.

16. 16. The radiological imaging method according to any one of claims 1 to 15, wherein the modulation of the current intensity is in the range of at least 20 mA to 300 mA, or 10 mA to 400 mA.

17. A radiological imaging method as claimed in any one of claims 1 to 16, wherein the voltage intensity is fixed since there is no voltage modulation, and the voltage intensity is selected within the range of 50 kV to 120 kV.

18. 18. The radiological imaging method according to any one of the preceding claims, wherein said vertical scan velocity values ​​are in the range of at least 8 cm / sec to 20 cm / sec, or 4 cm / sec to 30 cm / sec.

19. 19. The radiological imaging method according to any one of claims 1 to 18, wherein each of the frontal scout views and / or lateral scout views is generated by performing (1) a preliminary vertical scan of a standing patient (20, 30) along a vertical scanning direction (Z) with a reduced overall radiation dose compared to each of the frontal and lateral images, prior to generating each of the frontal and lateral images.

20. 20. The radiological imaging method of claim 19, wherein the reduced overall radiation is less than 10% of the overall radiation dose, or less than 5% of the overall radiation dose.

21. 21. The radiological imaging method according to any one of claims 1 to 20, wherein pixels in the scout view are grouped together (2) to create imaging zones, and / or preferably by zones of NxN pixels and / or by zones of at least 10x10 pixels.

22. 22. The radiological imaging method according to claim 21, wherein the image or the imaging zone is processed (3) to identify corner points used to calculate the thickness profile and to identify the localization (21, 31) of the particular bone of a standing patient (20, 30) along the vertical scanning direction (Z).

23. 22. The radiological imaging method according to claim 21, wherein the images or the imaging zones are processed by a neural network in order to calculate the thickness profile and to identify the localization (21, 31) of the specific bones of a patient (20, 30) standing along the vertical scanning direction (Z).

24. 24. The radiological imaging method according to any one of claims 1 to 23, wherein the two radiation sources slide vertically to perform a vertical scan of the pelvis, spine, spine or whole body of a standing patient (20, 30) along a vertical scanning direction (Z).

25. 25. The radiological imaging method according to any one of claims 1 to 24, wherein two radiation detectors are two photon counting detectors (PCDs) associated with the two radiation sources, respectively, the two radiation detectors being a first photon counting detector associated with an automatic image processing function that automatically balances image density regardless of the amount of radiation received at the sensing surface of the radiation detector to enhance image contrast, and a second photon counting detector associated with an automatic image processing function that automatically balances image density regardless of the amount of radiation received at the sensing surface of the radiation detector to enhance image contrast.

26. 26. The radiological imaging method according to any one of claims 1 to 25, wherein two radiation detectors are associated with the two radiation sources, respectively, and the two radiation detectors are two multi-energy counting detectors or two energy-resolving photon counting detectors (ERPCDs).

27. 27. The radiological imaging method according to any one of claims 1 to 26, wherein the radiation is an X-ray.

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