Radiographic imaging method

Abstract

The present invention relates to a radiological imaging method, the method comprising: two radiation sources with mutually orthogonal imaging directions perform a vertical scan on a standing patient (20) along a vertical scan direction (Z), wherein the radiological method comprises at least one operating mode, in which operating mode: a frontal exploration view is obtained to identify a specific bone location (21) within the frontal exploration view, and according to the patient thickness and the identified specific bone location (21) along the vertical scan direction (Z), the drive current intensity of the frontal radiation source is automatically adjusted (11) to improve the compromise between: reducing the overall radiation dose received by the patient (20) during the vertical scan, and at the same time, for the frontal image, maintaining the local image contrast of the identified specific bone location (21) at different imaging positions along the vertical scan direction (Z) at a sufficient level.

Description

Technical Field

[0001] The present invention relates to a radiography method, aiming to reduce the radiation dose received by a patient while still obtaining high-quality images of the patient's body. Background Art

[0002] Scanning stereoradiography systems have shown an interesting ability to simultaneously acquire frontal and lateral images for 3D reconstruction of skeletal anatomical regions such as the spine or pelvis, where the dose is reduced by up to 50% or even up to 100% compared to CT (Computed Tomography) scans, and by up to 10% for single-view images compared to classical CR (Computed Radiography) or DR (Direct Radiography) systems.

[0003] However, this system does not have AEC (Automatic Exposure Control), and thus the parameters of the patient scan can only be manually selected by the operator based on the visual assessment of the patient's anatomical structure that the operator can perform. The operator can only choose between three possible anatomical sizes: small, medium, or large. The spectral characteristics (kV and filters) and intensity of the X-ray beam are adjusted according to the protocol (whole body, whole spine, pelvis,...) and the patient's body size (small, medium, or large) with reference to a simple table. This system is interesting in helping the operator select the parameters, but the main drawback is related to the sole visual selection by the operator.

[0004] This drawback is also well-known in standard 2D radiography, and some automatic exposure controls (AECs) have been developed to achieve an automatic exposure duration. Once the dose target is reached in the dosimeter unit, which is typically a radiation-permeable ionization chamber placed between the patient and the detector (film, CR, DR), this AEC can stop the exposure. This AEC also has some drawbacks. The first drawback is again related to the operator's choice of the spectrum (kV, filter), which is usually selected among three possible cross-selections of the protocol and patient size. The second drawback of this AEC is related to the type of detector used to acquire the image. As long as film is used, this AEC can provide correct results because the effects of overexposure or underexposure that provide too bright or too dark image densities are clearly visible on the film. Therefore, the dose target of the AEC can be set to obtain a standard expected density for a type of film. However, when computed radiography (CR) and direct radiography (DR) capture devices began to become widely used 2D detectors in radiology, other problems emerged because the operator could no longer simply detect overexposure or underexposure by observing light or dark image densities because these detectors and their automatic image processing can provide almost the same type of image density regardless of the dose, and the only difference is the noise in the image. The operator has some difficulties in correctly setting the dose target based on the noise in the image, and using different types or vendor models of CR or DR detectors is also a reason why it is extremely difficult to obtain good results.

[0005] IEC 62494-1 recommends using an exposure index (EI) that depends on noise and thus on the signal-to-noise ratio (SNR) of the image to define the dose target of the AEC as an exposure index target (EIT). IEC 62494-1 also recommends defining a deviation index (DI) as the ratio of the achieved exposure index to the exposure index target, expressed in decibels as DI = 10 × log 10 (EI / EIT).

[0006] Considering a scanning radiography system, known methods for AEC in standard 2D radiography using a dosimeter unit placed between the patient and the detector are difficult to be compatible for different reasons. The first reason is related to the great difficulty or even impossibility of changing the exposure time, which is only related to the scanning speed and the size of the scanning area. For a 2D system, the AEC dosimeter unit does not move relative to the patient, and thus this static measurement for a 2D system can stop the exposure immediately after reaching the exposure target. The second reason is the field of view of such a dosimeter for a scanning radiography system, which only depends on a very small part of the relevant ROI (region of interest) for diagnosing the patient's body, usually only one line of the total image. Using such a small part of the relevant ROI has little chance of providing prior information, which would be needed to process the shooting parameters to obtain an exposure index close to the exposure index target in the relevant ROI and to obtain a satisfactory signal-to-noise ratio (SNR).

[0007] According to a first prior art outside the field of radiological vertical scanning imaging, a computed tomography imaging method in the known patent application US 2011 / 0026668 based on a rotating radiation source emitting a very high radiation dose is known, and the emission is in a spiral path along the horizontal scanning direction of a patient lying on a hospital bed. This radiation source is driven by a current intensity and a voltage intensity. The current intensity is related to the radiation dose emitted by the radiation source per unit time (e.g., one second). The voltage intensity is related to the energy of each photon emitted by the radiation source. In order to perform such a horizontal scan on a given specific lying patient, the voltage intensity is adjusted to adapt to the radiation dose emitted along the horizontal scanning direction, or the current intensity is adjusted along the horizontal scanning direction to adapt to the radiation dose, which is very high anyway for the patient thickness along the horizontal direction and at least fifty times that of the vertical scan of a standing patient, thereby improving the contrast of the overall image with the patient thickness along the horizontal direction. Summary of the Invention

[0008] The object of the present invention is

[0009] To improve the trade-off between

[0010] Reducing the radiation dose received by the patient,

[0011] And maintaining a good image quality level of the patient's body or patient organ, or at least keeping the image quality of the patient's body or patient organ at a sufficient level,

[0012] While using a radiological imaging method:

[0013] ○ The method is overall easier and simpler than the first prior art mentioned above.

[0014] ○ And in particular, the method can use a simpler and cheaper current-regulated radiation generator, because this current-regulated radiation generator will regulate the current intensity without any additional voltage intensity regulation restrictions.

[0015] The present invention proposes to solve the following problem: in the vertical scan of a standing patient, the radiation dose emitted anyway is much lower than that in computed tomography. Still, reduce the radiation dose of this emission, and at the same time, according to the change in patient thickness along the vertical scan direction, find an image contrast that is differently maintained well or at least sufficiently horizontally along the vertical direction by adjusting the amount of emitted radiation particles without changing the beam energy.

[0016] Thus, reduce the radiation dose emitted in the low-thickness area of the patient's body and minimize the radiation dose, while maintaining a still sufficient radiation dose emitted in the high-thickness area of the patient's body. At the same time, use a relatively simple and cheap current intensity-regulated radiation generator to adjust the current intensity, so as to overall increase the radiation dose emitted.

[0017] This compromise between reducing the emitted radiation dose and sufficient image contrast, although making the used radiological imaging method simple and cheap, may be different at each height along the vertical scan direction, or at least generally vary with the change in the thickness of the patient's body along the vertical scan direction.

[0018] In addition, this local image contrast is maintained at a sufficient level or better maintained at the same level (as in the first prior art):

[0019] This depends globally not only on the overall thickness of the patient,

[0020] but also locally maintained in the area of the patient's body with the highest patient thickness, which is actually the most critical area of the patient's body for imaging, guided by the specific bone positioning identified in the exploration view.

[0021] At the same time, use a simpler and cheaper radiological imaging method, especially when using a simpler and cheaper current intensity-regulated radiation generator to adjust the current intensity without any voltage intensity regulation during imaging.

[0022] Maintaining the local image contrast of a specific bone of the marker at different imaging positions along the vertical scanning direction at a sufficient level means that the level of the local image contrast is not reduced or deteriorated, or at least not reduced or deteriorated too much such that the level would imply that a practitioner of the radiography method can no longer correctly see the specific bone of the marker.

[0023] In other words, maintaining the local image contrast of a specific bone of the marker at different imaging positions along the vertical scanning direction at a sufficient level means that the level of the local image contrast is sufficient for a practitioner of the radiography method to see and notice possible injuries within the specific bone localization of the marker.

[0024] Maintaining the local image contrast of a specific bone of the marker at different imaging positions along the vertical scanning direction at a sufficient level means ideally maintaining the local image contrast of the specific bone localization of the marker at different imaging positions along the vertical scanning direction.

[0025] Maintaining these local image contrasts at a sufficient level means preferably maintaining the local image contrast at least for the thickest patient region or patient zone.

[0026] Which patient regions or patient zones are the thickest can be learned from scout views.

[0027] This object is achieved by a radiography method, which includes: radiation sources with two imaging directions orthogonal to each other, a front radiation source and a side radiation source, vertically sliding to perform a vertical scan on a standing patient along the vertical scanning direction, wherein the radiography method includes at least one operation mode, in which: a front scout view is obtained by performing a preliminary vertical scan on the standing patient by the front radiation source along the vertical scanning direction, the front scout view is processed to identify a specific bone localization within the front scout view, according to the patient thickness and the specific bone localization identified along the vertical scanning direction, at least the drive current intensity of the front radiation source is adjusted along the vertical scanning direction without adjusting the voltage intensity of the front radiation source along the vertical scanning direction, and the adjustment of the drive current intensity of the front radiation source is automatically performed to improve the trade-off between reducing the overall radiation dose received by the patient during the vertical scan and, for the front image, maintaining the local image contrast of the specific bone localization of the marker at different imaging positions along the vertical scanning direction. Voltage is a synonym for tension.

[0028] This object is also achieved by a radiography method, the method comprising: two radiation sources with orthogonal imaging directions, a front radiation source and a side radiation source, vertically sliding to perform a vertical scan on a standing patient along a vertical scan direction, wherein the radiography method comprises at least one operating mode, in which operating mode: a preliminary vertical scan is performed on the standing patient along the vertical scan direction by the side radiation source to obtain a side exploration view, the side exploration view is processed to identify specific bone localizations within the side exploration view, and based on the patient thickness and the identified specific bone localizations along the vertical scan direction, the drive current intensity of at least the side radiation source is adjusted along the vertical scan direction without adjusting the voltage intensity of the side radiation source along the vertical scan direction, and the adjustment of the drive current intensity of the side radiation source is performed automatically to improve the trade-off between: reducing the overall radiation dose received by the patient during the vertical scan, and at the same time, for side images, maintaining the local image contrast of the identified specific bone localizations at different imaging positions along the vertical scan direction at a sufficient level.

[0029] This object is also achieved by a radiography method, the method comprising: two radiation sources with orthogonal imaging directions, a front radiation source and a side radiation source, vertically sliding to perform a vertical scan on a standing patient along a vertical scan direction, wherein the radiography method comprises at least one operating mode, in which operating mode: a preliminary vertical scan is performed on the standing patient along the vertical scan direction by the front and side radiation sources to obtain front and side exploration views, the front and side exploration views are processed to identify specific bone localizations within the front and side exploration views, and based on the patient thickness and the identified specific bone localizations along the vertical scan direction, the drive current intensity of at least the front and side radiation sources is adjusted along the vertical scan direction without adjusting the voltage intensity of the front or side radiation source along the vertical scan direction, and the adjustment of the drive current intensity of the front radiation source and the adjustment of the drive current intensity of the side radiation source are performed simultaneously, preferably synchronously and automatically, to improve the trade-off between: reducing the overall radiation dose received by the patient during the vertical scan, and at the same time, for front images and side images, maintaining the local image contrast of the identified specific bone localizations at different imaging positions along the vertical scan direction at a sufficient level.

[0030] The preferred embodiments include one or more of the following features, which may be separate from or together with any of the foregoing objects of the present invention, in partial or complete combination.

[0031] Preferably, the identified specific bone localizations include the patient's spine, preferably the patient's spine.

[0032] In fact, the patient's spine is the specific bone location that is of greatest concern for detailed analysis within the patient's body; thus it is used for driving and current intensity regulation.

[0033] Alternatively, the specific bone location can also be the pelvis or an arm or a leg of the standing patient along the vertical scanning direction, depending on the area of interest within the body part of the patient being imaged.

[0034] Preferably, the driving current intensity of the front radiation source is also adjusted to achieve a certain signal-to-noise ratio, which is constant and common for most of the imaging positions along the vertical scanning direction for the front image and / or for the side image, preferably constant and common for all the imaging positions along the vertical scanning direction, but two different values can be taken respectively for the front image and the side image.

[0035] Preferably, for each of the front and / or side images, the signal-to-noise ratio is constant and predetermined for each different patient organ to be imaged.

[0036] Preferably, for the front image of the patient's spine, the standard signal-to-noise ratio corresponds to the number of X-ray photons received by each detector pixel that is between 50 and 70, and the operator of the radiography method preferably has the possibility of deviating from this standard value by at least + or - 20%, more preferably at least + or - 50% by manual command, and / or for the side image of the patient's spine, the standard signal-to-noise ratio corresponds to the number of X-ray photons received by each detector pixel that is between 20 and 40, and the operator of the radiography method preferably has the possibility of deviating from this standard value by at least + or - 20%, more preferably at least + or - 50% by manual command.

[0037] Therefore, in the case of having a constant and optimized signal-to-noise ratio along or even all along the vertical scanning direction, the local image contrast of the identified specific bone location at different imaging positions along the vertical scanning direction is greatly improved because this is the area of actual interest in the front and / or side images.

[0038] Preferably, the front and / or side images are normalized preferably by homogenizing only the area located outside the patient's body contour after undergoing at least the first step of current intensity adjustment, so as to eliminate image artifacts from the driving current intensity adjustment.

[0039] In fact, due to this drive current intensity regulation, there are some artifacts in the frontal and / or lateral images, which superimpose some alternating waves of clear and dark gray levels on the blank part of the image (right outside the patient's body) or on the very thin parts of the patient, making these images less satisfactory for the interpretation by the operator of the radiography method, or at least requiring some training on his or her part.

[0040] Preferably, after normalization, the frontal and / or lateral images undergo a contrast enhancement step.

[0041] Thus, on the one hand, the image artifacts resulting from this drive current intensity regulation are eliminated, while the contrast enhancement improved by this same drive current intensity regulation is not only retained but also fully utilized.

[0042] Preferably, the specific bone localization of the identification excludes metal components, if any, such as metal prostheses in the skeletal part of the patient's body or metal protectors placed on the patient's body, for example, before performing the radiography method.

[0043] In fact, these foreign (to the patient's body) objects introduced into or onto the patient's body, being metallic and thus blocking more radiation and X-rays than the rest of the patient's body, may cause some non-optimization of the emitted dose, which may result in some overexposure or underexposure of the emitted radiation at the height corresponding to these foreign objects. In the following modes, firstly, the drive voltage intensity is constant, and secondly, both the drive voltage intensity and the drive current intensity are constant. If the metal outliers are not excluded, the consequences may be worse because more or all parameters are selected for the maximum thickness, and thus the emitted radiation dose is higher or much higher than the required dose, which is very harmful to the patient.

[0044] Preferably, the current intensity regulation is maximized, so that the vertical scanning speed is also maximized to a constant value.

[0045] Therefore, for a given emitted radiation dose, and thus for a given radiation dose received by the standing patient during the vertical scan, both are maintained at the same level, and the total vertical scan time is significantly reduced, with the advantages of reducing the possibility of movement of the standing patient and the impact of patient movement, thereby reducing to a certain extent the risk of blurring and distortion of the frontal and lateral images, and thus still enhancing the signal-to-noise ratio of these frontal and lateral images.

[0046] Preferably, the operating mode can be manually turned on or off by the operator of the radiography method.

[0047] Thus, this very advantageous way of operating a radiological imaging device is available, and this way can be cancelled if and when the operator of this radiological imaging device wants to remove it, so as to operate this radiological imaging device, for example, completely manually. The radiological imaging method according to an advantageous embodiment of the invention presents three operating modes: full manual mode, AEC mode without adjustment, and AEC mode with adjustment.

[0048] Preferably, the operating mode is dedicated to vertical scanning of large and / or obese patients.

[0049] Preferably, the operating mode is dedicated to vertical scanning of pediatric patients.

[0050] The radiological imaging method according to the invention pays more attention to patients whose thickness can be particularly lower or particularly higher than that of the average body type. This shows the very targeted ability of the radiological imaging method according to the invention for patients. Of course, the radiological imaging method according to the invention is also very effective for patients with a standard body type.

[0051] Preferably, the rate of adjustment of the current intensity does not exceed a predetermined threshold of 5 mA per millisecond, preferably a predetermined threshold of 2 mA per millisecond, and more preferably a predetermined threshold of 1 mA per millisecond.

[0052] Therefore, the radiological imaging method according to the invention can also be carried out with a relatively simple and inexpensive radiation source with a relatively slow current intensity driving ability.

[0053] Preferably, the range of adjustment of the current intensity is at least from 20 mA to 300 mA, and preferably from 10 mA to 400 mA.

[0054] Therefore, the radiological imaging method according to the invention can also be carried out with a relatively simple and inexpensive radiation source with a relatively limited range of current intensity driving ability.

[0055] Preferably, the fixed voltage intensity is selected in the range from 50 kV to 120 kV.

[0056] Therefore, the radiological imaging method according to the invention can also be carried out with a relatively simple and inexpensive radiation source.

[0057] Preferably, the value of the vertical scanning speed ranges from at least 8 cm / s to 20 cm / s, and preferably from 4 cm / s to 30 cm / s.

[0058] Therefore, the radiological imaging method according to the invention can also be carried out with a relatively simple and inexpensive radiation source with a relatively limited range of vertical scanning speed ability, while making full use of the available range of the vertical scanning speed ability.

[0059] Preferably, before obtaining each of the frontal and lateral images, each of the frontal and / or lateral exploration views is obtained by performing a preliminary vertical scan of the standing patient along a vertical scan direction with a reduced overall radiation dose compared to each of the frontal and lateral images.

[0060] Thus, it is possible to determine the adjustment of the drive current intensity and possibly the vertical scan speed only before performing the vertical scan based on the thickness distribution and the specific bone positioning of the standing patient's body along the vertical scan direction, which will result in obtaining effective frontal and lateral images of the standing patient's body with a limited and sufficient radiation dose sufficient to obtain high-quality frontal and lateral images. The exploration views can be produced at the cost of a rather limited overexposure to the emitted radiation.

[0061] Preferably, the reduced overall radiation is less than 10% of the overall radiation dose, preferably less than 5% of the overall radiation dose.

[0062] Thus, the benefits are twofold: not only is the overexposure (+10% or +5%) during the production of the exploration views very limited, but also the compromise between optimizing the received overall radiation dose and enhancing the image contrast is very efficient.

[0063] Preferably, the pixels in the exploration view are grouped together into imaging regions preferably in N×N pixel regions, more preferably in at least 10×10 pixel regions, for example in at least 20×20 pixel regions, to form imaging regions.

[0064] Thus, although the level of the emitted radiation dose used to produce this exploration view is very low, the image quality and image contrast of the exploration view are enhanced.

[0065] Preferably, the image or the imaging region is processed to identify salient points, which are then used to calculate the thickness distribution and identify the specific bone positioning of the standing patient along the vertical scan direction.

[0066] Thus, although the level of the emitted radiation dose is very low, it is easier and more efficient to calculate the thickness distribution from the exploration view and identify the specific bone positioning of the standing patient along the vertical scan direction.

[0067] Preferably, the image or the imaging region is processed by a neural network to calculate the thickness distribution and identify the specific bone positioning of the standing patient along the vertical scan direction.

[0068] Thus, although the level of the emitted radiation dose is very low, it is easier and more efficient to identify the specific bone positioning of the standing patient along the vertical scan direction from the exploration view.

[0069] Preferably, the two radiation sources slide vertically to perform a vertical scan of the pelvis or spine or the whole body of a standing patient along the vertical scan direction.

[0070] Preferably, two radiation detectors are respectively associated with the two radiation sources. The two radiation detectors are two photon counting detectors (PCDs), and each photon counting detector is associated with an automatic image processing function. Regardless of the radiation dose received on the sensitive surface of the radiation detector, the automatic image processing function automatically balances the image density to enhance the image contrast.

[0071] Therefore, it is more difficult for the operator of the radiological imaging method to correctly manually evaluate the overexposure or underexposure of the radiation signal emitted by the radiation source. In addition, compared with gas detectors, photon counting detectors have improved linearity and signal-to-noise ratio.

[0072] Preferably, two radiation detectors are respectively associated with the two radiation sources. The two radiation detectors are two multi-energy counting detectors, preferably two energy-resolved photon counting detectors (ERPCDs).

[0073] Preferably, the radiation is X-ray.

[0074] 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 in computed tomography. Another patient weight-bearing position that can replace the patient standing position can be the patient sitting position.

[0075] Further features and advantages of the present invention will become apparent from the following description of embodiments of the present invention given as non-limiting examples with reference to the accompanying drawings listed below. Description of the Drawings

[0076] Figure 1 An example showing a part of a radiological imaging method according to an embodiment of the present invention, which processes the calculation of the driving current intensity adjustment of a radiation source.

[0077] Figure 2 An example showing a specific bone localization by feature point detection, here the whole body of a patient including the spine extending to the pelvis and legs.

[0078] Figure 3 An example showing the corresponding parameters, which are median signal patch values varying with the vertical position in millimeters along the patient's height.

[0079] Figure 4 An example showing the corresponding thickness distribution varying with the vertical position in millimeters along the patient's height in millimeters.

[0080] Figure 5Examples are shown of the variation of a constant voltage, expressed in kilovolts, with the patient equivalent thickness, expressed in centimeters, for frontal and lateral images respectively.

[0081] Figure 6 Examples are shown of the variation of the current regulation, expressed in milliamperes, with the patient equivalent thickness, expressed in centimeters, for frontal and lateral images respectively.

[0082] Figure 7 Examples are shown of the variation of the number of X-ray photons per detector pixel obtained (representing the signal-to-noise ratio) with the patient equivalent thickness, expressed in centimeters, for frontal and lateral images respectively.

[0083] Figure 8 Examples are shown of the variation of the radiation dose received by the patient, expressed in μGy (microgray), with the patient equivalent thickness, expressed in centimeters, for frontal and lateral images respectively.

[0084] Figure 9 Examples are shown of the filtered frontal exploration views after the salient point detection step but before the salient point filtering step.

[0085] Figure 10 Examples are shown of the filtered frontal exploration views after the salient point detection step and after the salient point filtering step.

[0086] Figure 11 Examples are shown of the filtered lateral exploration views after the salient point detection step but before the salient point filtering step.

[0087] Figure 12 Examples are shown of the filtered lateral exploration views after the salient point detection step and after the salient point filtering step.

[0088] Figure 13 Examples are shown of the filtered frontal exploration views after the deep neural network detection step.

[0089] Figure 14 Examples are shown of the filtered lateral exploration views after the deep neural network detection step.

[0090] Figure 15 Examples are shown of lateral images with a constant drive current intensity and a constant drive voltage intensity in the constant current and voltage mode.

[0091] Figure 16 Examples are shown of lateral images with a regulated drive current intensity and a constant drive voltage intensity in the regulated current and constant voltage mode.

[0092] Figure 17An example of the final lateral image presented to the radiologist is shown. Detailed Description

[0093] The present invention aims to provide a solution for an AEC system for a scanning stereoradiography system, the AEC being compliant with IEC 62494-1. This AEC system is designed for the scanning stereoradiography system described in applications PCT / IB2016 / 000273 and PCT / IB2017 / 000986, which are incorporated by reference and owned by the same applicant EOS-Imaging.

[0094] In a preferred embodiment, the two detectors of this scanning stereoradiography system are multi-energy counting detectors, also known as energy-resolving photon counting detectors (ERPCD) with at least 2 energy bins. In another embodiment, the two detectors of this scanning stereoradiography system are mono-energetic counting detectors, also known as photon counting detectors (PCD).

[0095] Using photon counting detectors in multi-energy or mono-energetic form is advantageous compared to gas detectors for two main reasons. The first reason is that the signal of the ERPCD or PCD is linearly related to the incident flux and is directly equal to the number of detected photons, while the signal of the gas detector is strongly non-linear and this non-linearity is quite complex to model for precise correction. In the ERPCD and PCD, there is still non-linear behavior at high fluxes, called pile-up effect, but this pile-up effect can be well modeled and corrected by the image calibration software. The second reason is that the ERPCD and PCD have a very stable behavior and sensitivity, do not require new calibration for several months, and are insensitive to room temperature variations, while gas detectors are far less stable and require daily calibration, and the behavior and sensitivity of said gas detectors may also vary within minutes depending on the room temperature change. The stability of the PCD and ERPCD and the photon counting function enable 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, do not have this advantage and require precise calibration to evaluate the SNR and thus evaluate the exposure index.

[0096] The radiography method according to an embodiment of the present invention is based on using a scout view at mono-energy (ERPCD or PCD). Since one of the objectives of this scanning radiography system is dedicated to skeletal imaging in orthopedics, the scout view in this case is analyzed to precisely find the axial skeleton or bones of the selected scenario. But for some other applications, a soft tissue organ scenario can be selected, such as the lungs, in which case the scout view is analyzed to find the organ.

[0097] The relevant ROIs for diagnosis defined according to IEC 62494-1 are defined by the union of a set of circular sub-ROIs, which are also referred to as "patches" of approximately vertebral size (4-5 cm in diameter), and the set of circular sub-ROIs are placed on a set of feature detection points or landmarks on the exploration view according to a protocol-specific bone or organ search. This search for feature points can be implemented in two different ways: a specific salient point search algorithm or using a trained pose detection deep neural network.

[0098] Then the equivalent thickness of the patient is evaluated in each patch, and a certain specific selection rule scheme provides a vertical vector of the equivalent thickness according to the patient's Z (vertical) position. When using a monoenergetic exploration view, the equivalent thickness is evaluated in a single-material PMMA [poly(methyl methacrylate)] equivalent.

[0099] Then the vertical equivalent thickness vector is used to process the characteristic thickness, which is a safety detection of the most likely maximum thickness. Then the characteristic thickness and the equivalent vector thickness are used to process the scanning parameters to obtain an exposure index as close as possible to the exposure target in each patch.

[0100] According to the operator's selection, the exposure parameters can be generated in several different modes:

[0101] The first mode, called the "constant exposure mode", only provides the best constant kV, mA, filter, and scanning speed for the scan and will provide constant flux exposure control according to the definition of IEC 60601-2-44;

[0102] The second mode, called "elastic dose", will process the scanning speed, the selected filter, and the exposure time adjustment vector along the vertical axis and will provide Z-axis exposure control according to the definition of IEC 60601-2-44.

[0103] "Elastic dose" is used when the voltage or tension (kV) is fixed and the current (mA) is adjusted along the Z-axis. The operating mode according to the present invention is this second mode called "elastic dose".

[0104] Figure 1 An example of a part of a radiography method according to an embodiment of the present invention is shown, which processes the calculation of the drive current intensity adjustment of a radiation source.

[0105] The radiography method according to an embodiment of the present invention includes a method for processing the current intensity adjustment of a radiation source along a vertical scanning direction. Figure 1 A functional block diagram of an example implementation using salient points is presented.

[0106] Perform the following consecutive steps:

[0107] In step 1, obtain a scout view of a standing patient at a reduced radiation dose. The scout view is necessary for using the "elastic dose" mode and is obtained using a 0.5 mm thick copper filter and a very low dose. For the long axis and local protocols, the patient dose ratio between this scout view and the main photograph is less than 10%. This step 1 of the method is to obtain the scout view by vertically scanning the patient at a reduced dose.

[0108] In step 2, perform post-processing on the scout view, where preferably the pixels in the scout view are grouped together in N×N pixel regions, for example in at least 20×20 pixel regions, to obtain an imaging region with calibration and average binning. Here, the scout view is obtained at such a low level of dose that a large binning of 20×20 is applied to filter sufficient noise and obtain a higher confidence level for the estimated thickness. This step 2 is the post-processing of the scout view image, including performing uniformity correction using the gain calibration of the detector and using a filter to improve the signal-to-noise ratio without introducing any bias to obtain a high confidence level for the estimated thickness, for example, a 20×20 average binning is very suitable.

[0109] In step 3, as will be referenced Figures 9 to 12Detecting the salient points as explained in more detail, where first the points with higher radiation absorption are detected, and then a part of the detected points are filtered out according to a predetermined rule so as to actually retain only the desired specific bone localizations, such as the spine of the patient's body, to make the salient points continuous. The salient point detection algorithm developed for detecting the verified axial bones is applied to the binned images. Then the detected salient points are selected in different ways in the frontal and lateral images according to the patient orientation. The selected salient points mainly follow the axial skeleton composed of the lower limbs, pelvis, spine, neck and head. Metal prosthesis or metal protection detection is also used to remove and exclude the salient points correspondingly selected during metal detection in step 3, while in step 8, only outliers are selected regarding the thickness. This step 3 is to detect the specific bone localizations and reject metal components in the scout view. As an example, we adopt the description of the method using salient point detection, but another implementation using a specific neural network can also be adopted. The salient point detection method used includes searching within the range of the typical vertebra size, i.e., with a diameter of about 5 cm, to find a set of local maximum attenuation points in the scout view. Then the detected salient points are selected in different ways in the frontal and lateral images according to the patient orientation. The selected salient points mainly follow the axial skeleton composed of the lower limbs, pelvis, spine, neck and head. There is only one selected salient point at one Z-height (one Z-position along the vertical scanning direction), while there can be several different detected salient points at one Z-height. Figures 9 to 12 Salient point detection and selection on the patient's frontal and lateral scout views are presented respectively. Figure 9 and 11 present the detected salient points, and Figure 10 and 12 present the selected salient points. Figure 13 and 14 present an example of skeleton detection using the neural network method, including a limited number of landmarks, compared with Figures 9 to 12 applied to the same patient. As an example, Figure 13 and 14 the limited number of landmarks presented correspond to the cervical vertebrae C2 and C7, thoracic vertebra T9, sacrum, and the left and right femoral heads, 1 / 3 diaphysis, trochlear center, distal tibia and proximal tibia of the lower limbs. The method of selecting salient points is also capable of removing the points detected on metal components, including, for example, metal prostheses or metal protection for the breast, gonads, ovaries or other sensitive parts of the body. Metal components can also be removed using the neural network method.

[0110] In step 4, based on the prominent points, a signal distribution in millimeters as a function of the vertical position is obtained. This step 4 processes the signal distribution scanned vertically along the patient. The median of the signals in the exploration view image is processed in each circular patch centered on the selected prominent points and associated with the height z of the corresponding prominent points in the vertical scan reference. The area represented by the patch size is approximately equivalent to the size of a vertebra with a diameter of about 5 cm. The resulting signal distribution function of z is sparse, and the interpolation and extrapolation of this sparse signal distribution provide a complete sampling of the signal vertical distribution over the entire height of the patient where vertical scanning is required, including some bottom and top extensions of the scanned area selected by the operator.

[0111] In step 5, based on the previous signal distribution, the patient thickness distribution is calculated. In fact, this step 5 processes the thickness distribution scanned vertically along the patient. The logarithm of the signal distribution function of z is processed using a calibrated quadratic polynomial function to provide the corresponding PMMA thickness equivalent value according to Equation 1:

[0112]

[0113] where mAs = mA 探查视图 × time / line and the maximum thickness = 600 mm of PMMA.

[0114] The coefficients a, b, and c of the polynomial are processed using calibration.

[0115] In step 6, optionally, a new scan upper limit and / or lower limit can be manually selected by the operator of the radiography method. The operator can slightly decrease or increase the scan height using the selection tool on the exploration view image in the interface software.

[0116] In step 7, optionally, the patient thickness distribution is cropped according to the previous new scan upper limit and / or lower limit. Then, the processed thickness distribution function of z is cropped according to the operator's selection of the upper and lower limits of the vertical scan along the patient.

[0117] In step 8, based on the previous thickness distribution, after outliers such as metal prostheses or metal protectors have been filtered out in step 3, the characteristic patient thickness is calculated. This step 8 processes the characteristic thickness. Considering only the maximum value of the thickness distribution determined previously in step 5 does not represent the patient thickness when the patient is sitting or has their legs on a support or their arms crossed. To define the representative thickness of the patient, the derivative of the thickness distribution is processed to define statistical parameters using the mean and standard deviation to remove outliers, and then the characteristic thickness is defined as the maximum thickness without considering outliers.

[0118] In step 9, image acquisition parameters are obtained from a reference table based on a specific bone localization (e.g., the exact position of the patient's spine along the vertical scan direction) and the patient thickness variation along the vertical scan direction (i.e., along the patient's height). In fact, the processed characteristic PMMA equivalent thickness and the selected protocol are used to obtain the image acquisition parameters (kV, filter, scan speed) according to a reference anatomical parameter table. Step 9 is to select in the image acquisition parameter table according to the processed characteristic thickness and the selected protocol. The parameter set includes, for example, a signal target and a reference kV. The reference kV, mA, and speed can be used to acquire an image of the patient in the case where the operator chooses to disable the adjustment, but maintain AEC. In this case, the constant values of the scan speed and current will be processed according to the signal target and the characteristic thickness. The reference voltage (kV) is used to acquire an image of the patient with a constant voltage (kV) current regulation. As an example, the signal targets for a spine examination are different for anterior and lateral images and are typically about 60 photons / pixel for anterior images and about 30 photons / pixel for lateral images, respectively. The radiologist can adjust these values within a limited allowable range.

[0119] In step 10, according to the selected operating mode, a constant current intensity value along the vertical direction, or preferably a variable adjustment of the current intensity, is selected as a function of the exact position of the patient's spine along the vertical direction and the patient thickness variation along the vertical scan direction, in order to achieve a constant and common signal-to-noise ratio along the vertical scan direction, i.e., a constant target number of X-ray photons per detector pixel along the vertical scan direction. The constant target number of X-ray photons per detector pixel along the vertical scan direction preferably has different values for anterior images (e.g., 60) and lateral images (e.g., 30). The last step of the "elastic dose" mode is to process the current (mA) adjustment vector of the image scanned along the patient's body part to fit as closely as possible to the exposure index target in each patch of the ROI. A calibration matrix is established to relate the measured signal value to the PMMA equivalent thickness as a function of a set of voltage (kV) values. The algorithm for determining the current (mA) performs 1D interpolation in this matrix.

[0120] More precisely, in this step 10, a variable adjustment of the current intensity in the vertical direction is selected as a function of the precise position of the patient's spine in the vertical scan direction and the change in the patient's thickness in the vertical scan direction according to the selected operation mode, in order to obtain an equivalent change in the patient's thickness in the vertical scan direction (bones attenuate more radiation, so compared to soft tissues, the bones are equivalent to a thickness that is thicker than their actual thickness), in order to achieve a constant and common signal-to-noise ratio in the vertical scan direction, that is, a constant target number of X-ray photons for each detector pixel in the vertical scan direction. The constant target number of X-ray photons for each detector pixel in the vertical scan direction preferably has different values for frontal images (e.g., 60) and lateral images (e.g., 30).

[0121] It is known that the contrast is better at low voltage (kV), but using low voltage (kV) does not efficiently view the useful dose that provides a certain signal in the detector compared to the dose received in the thick parts of the body. When one or more voltage values are available (at least 3, and preferably exactly 3 are available), the selection of a specific value of the voltage (kV) constant for the full vertical scan is guided by the following trade-off, that is, the trade-off between better contrast leading to lower voltage (kV) and more efficient dose use leading to higher voltage (kV). The thickness distribution and a 1D table representing the expected signal with respect to the selected constant voltage value and the thickness for the reference current and scan speed are used to process the required current distribution at the reference scan speed to achieve the signal target. Then the current distribution can be adjusted in a way proportional to the specific scan speed. For example, with respect to the reference scan speed, the current distribution needs to be doubled to double the scan speed. In the case where the source has a maximum output power, the maximum allowable current distribution for a given scan speed can be inferred by the ratio of the maximum power to the selected constant voltage value. The best scan speed can be found by looking at the higher allowable current distribution.

[0122] The last step of the "elastic dose" mode is to process the current (mA) adjustment vector of the image scanned along the patient's body part to fit as closely as possible to the exposure index target in each patch of the ROI.

[0123] The voltage (kV) and current (mA) can only be processed as scalar values corresponding to the characteristic thickness in the constant AEC mode, or as a current adjustment vector in the "elastic dose" mode, in order to optimize the X-ray flux according to the estimated patient thickness along the vertical scan. Compared with the constant current (mA) mode based only on the patient's maximum thickness, the "elastic dose" mode achieves a significant dose reduction in the long-axis protocol.

[0124] The overall goal of the "elastic dose" mode is to achieve a constant and reproducible signal level at the maximum thickness position of the patient's scan area in the constant mode, and in addition to achieve a constant and reproducible signal level along the patient's scan axial skeleton and independent of the patient's morphology and thickness in this mode.

[0125] Figure 2 An example of a specific bone localization detected by prominent points is shown, here the whole body of a patient including the spine extending to the pelvis and legs. Figure 2 Typical examples of the selected prominent points in the lateral exploration view are presented.

[0126] The continuous circles are along the patient's spine in the overall vertical direction. This continuous prominent point SP is found on the lateral image of the patient's body. This lateral image of the patient's body is plotted against the height Z (height along the vertical scan direction) as a function of the patient's width, with the patient thickness th perpendicular to the plane of the figure, and both the height and width w are in mm.

[0127] Figure 3 An example of the corresponding parameter P is shown, which is the median signal patch value varying with the vertical position Z in mm along the patient's height. Figure 3 The corresponding full-sampled signal distribution along the patient's vertical scan is presented. The selected prominent points are represented by dots in Figure 2 the lateral exploration view, and the dots represent circular patches with a diameter of approximately 5 cm.

[0128] Figure 4 An example of the corresponding thickness distribution varying with the vertical position Z in mm along the patient's height as th is shown. Figure 4 The presentation is in Figure 2 the characteristic thickness determination on the lateral distribution presented in.

[0129] The patient thickness distribution is plotted in Figure 4 The patient thickness th in mm is represented as a function of the vertical position Z also in mm.

[0130] Figure 5 and 6 present simulations of the standard relationship between voltage (kV) and current (mA) of the equivalent PMMA thickness for the full-spine protocol in the "elastic dose" mode, taking the anthropomorphic models of Figure 15 , 16 and 17 as examples, with the measured anterior characteristic thickness of 225 mm and the lateral characteristic thickness of 335 mm.

[0131] Figure 5An example is shown of the variation of a constant voltage V, expressed in kilovolts, with the patient equivalent thickness th, expressed in centimeters, for a frontal image and a lateral image respectively. These constant voltages can be selected based on the characteristic thickness measurements in the frontal and lateral exploration views.

[0132] For the frontal curve F, the voltage constant value has been selected as 90 kV (corresponding to a characteristic thickness of 225 mm measured in the frontal exploration view of the anthropomorphic model), and is independent of the characteristic patient thickness ranging from approximately 10 cm to approximately 50 cm.

[0133] For the lateral curve L, the voltage constant value has been selected as 120 kV (corresponding to a characteristic thickness of 335 mm measured in the frontal exploration view of the anthropomorphic model), and is independent of the characteristic patient thickness ranging from approximately 10 cm to approximately 50 cm.

[0134] Figure 6 An example is shown of the variation of the current regulation I, expressed in milliamperes, with the patient equivalent thickness th, expressed in centimeters, for a frontal image and a lateral image respectively.

[0135] For the frontal curve F, for an equivalent patient thickness ranging from approximately 10 cm to approximately 30 cm, the current regularly increases from approximately 10 mA to approximately 400 mA, and then remains constant at approximately 400 mA for an equivalent patient thickness from approximately 30 cm to approximately 50 cm.

[0136] For the lateral curve L, for an equivalent patient thickness ranging from approximately 10 cm to approximately 37 cm, the current regularly increases from approximately 10 mA to approximately 400 mA, and then remains constant at approximately 400 mA for an equivalent patient thickness from approximately 37 cm to approximately 50 cm. The increase of the F curve is steeper than that of the L curve.

[0137] Figure 7 An example is shown of the variation of the number S of X-ray photons per detector pixel obtained (representing the signal-to-noise ratio) with the patient equivalent thickness, expressed in centimeters, for a frontal image and a lateral image respectively.

[0138] For the frontal curve F, for an equivalent patient thickness ranging from approximately 15 cm to approximately 30 cm, the number of X-ray photons per detector pixel is quite constant, approximately 60, and for an equivalent patient thickness from approximately 30 cm to approximately 40 cm, then the number of photons suddenly decreases from approximately 60 to approximately 5, and for an equivalent patient thickness from approximately 40 cm to approximately 50 cm, the number of photons continues to decrease more slowly towards zero, but does not actually reach zero. Below 15 cm, between 15 cm and 10 cm, this number suddenly increases to approximately 140.

[0139] For the lateral curve L, for an equivalent patient thickness ranging from about 20 cm to about 37 cm, the number of X-ray photons per detector pixel is fairly constant, about 27, and for an equivalent patient thickness ranging from about 40 cm to about 50 cm, then the number of photons slowly decreases towards zero, not actually reaching zero. Below 20 cm, between 20 cm and 10 cm, this number suddenly increases to about 250.

[0140] Figure 8 Examples are shown of the radiation dose D received by the patient in μGy as a function of the equivalent patient thickness th in cm, for the anterior and lateral images respectively.

[0141] For the anterior curve F, for an equivalent patient thickness ranging from about 10 cm to about 20 cm, the radiation dose received by the patient first slowly increases from about zero to about 100 microgray, then for an equivalent patient thickness ranging from about 20 cm to about 30 cm, the radiation dose received by the patient suddenly increases from about 100 microgray to about 850 microgray, and for an equivalent patient thickness ranging from about 30 cm to about 50 cm, the radiation dose received by the patient then remains roughly constant at about 850 microgray.

[0142] For the lateral curve L, for an equivalent patient thickness ranging from about 10 cm to about 25 cm, the radiation dose received by the patient first slowly increases from about zero to about 130 microgray, then for an equivalent patient thickness ranging from about 25 cm to about 37 cm, the radiation dose received by the patient suddenly increases from about 130 microgray to about 1700 microgray, and for an equivalent patient thickness ranging from about 37 cm to about 50 cm, the radiation dose received by the patient then remains roughly constant at about 1700 microgray. The L curve increases more slowly than the F curve in the first stage of slow increase, but the L curve increases faster than the F curve in the second stage of sudden (or rapid) increase.

[0143] In all Figures 9 to 16 On, the scales along the horizontal and vertical axes are in mm. After binning of the scout view image (which means that each 20×20 original square pixel area has been collected into a new pixel), for the scout view, the anterior and lateral images taken after the scout view do not have such binning.

[0144] Figures 9 to 12 Anterior and lateral images are shown using a salient point detection step, before and after filtering, to focus on the patient's spine (or on the patient's spine extending to one of his or her legs) and exclude other bones, thus enhancing the image contrast of the region of interest (here the patient's spine).

[0145] This filtering step aims to select only the prominent points that are most likely to lie on the axial skeleton, here the spine, and on one of the legs that continues the spine.

[0146] Figure 9 An example of a filtered anterior scout view after the prominent point detection step but before the prominent point filtering step is shown. This patient body image is plotted with respect to the height Z (height along the vertical scan direction) as a function of the patient width, with the patient thickness th perpendicular to the plane of the figure, and both the height and width w are in mm.

[0147] Figure 10 An example of a filtered anterior scout view after the prominent point detection step and after the prominent point filtering step is shown. This patient body image is plotted with respect to the height Z (height along the vertical scan direction) as a function of the patient width, with the patient thickness th perpendicular to the plane of the figure, and both the height and width w are in mm.

[0148] Bones 21 to 25 were found in patient 20. Patient 20 is plotted with respect to his or her height Z in mm and with respect to his or her width also in mm.

[0149] The rules for the anterior image filtering step are as follows:

[0150] For each Z (vertical position) value, the prominent point with the maximum thickness is selected.

[0151] Even if the metal part corresponds to the prominent point with the maximum thickness (the metal part corresponds to a very steep attenuation or absorption change near it in the patient's body), the metal part is excluded.

[0152] When filtering the anterior image of patient 20:

[0153] Only the spine 21, a small part of the left leg 23, and a small part of the right leg 22 remain.

[0154] While most of the arm 24, the shoulder 25, and the right leg 22 have been filtered and thus excluded.

[0155] Figure 11 An example of a filtered lateral scout view after the prominent point detection step but before the prominent point filtering step is shown. This patient body image is plotted with respect to the height Z (height along the vertical scan direction) as a function of the patient width, with the patient thickness th perpendicular to the plane of the figure, and both the height and width w are in mm.

[0156] Figure 12An example of a filtered lateral exploration view after the prominent point detection step and after the prominent point filtering step is shown. This patient body image is plotted against the patient width as the height Z (height along the vertical scanning direction) varies, with the patient thickness th perpendicular to the plane of the figure, and both the height and the width w are expressed in mm.

[0157] Bones 31 to 35 were found in patient 30. Patient 30 is plotted against his or her height Z in mm and against his or her width also in mm.

[0158] The rules for the lateral image filtering step are as follows:

[0159] For each Z (vertical position) value, the prominent point closest to the patient's back is selected (since the patient is looking to the left, this corresponds more to the prominent points on the right side of the lateral image here, but if the patient is looking to the right, it corresponds more to the prominent points on the left side of the lateral image).

[0160] Even if the metal part corresponds to the prominent point with the maximum thickness (the metal part corresponds to a very steep attenuation or absorption change near it in the patient's body), the metal part is excluded.

[0161] Some isolated prominent points that are too close to the patient's back and further from the right side of the lateral image than the patient's spine are still excluded, such as some isolated prominent points lost in soft tissue areas such as the buttocks or back muscle parts.

[0162] When filtering the lateral image of patient 30:

[0163] Only the spine 31 and the left leg 32 are retained.

[0164] While the arms 33 and 34 and the upper and lower jaws 35 have been filtered and are thus excluded.

[0165] The current intensity adjustment can be calibrated.

[0166] Specific images in the front or side can also be corrected:

[0167] Calculate the distribution for driving the current intensity adjustment from the exploration view.

[0168] Then use the calculated adjustment distribution to obtain the image.

[0169] Then, the obtained image is corrected by homogenizing the detector and correcting its non-linearity through calibration software.

[0170] Then, using the feedback measurement file of the radiation emission post - generator, identify the value effectively sent by the generator of the current mA(j) at each line j of the captured image.

[0171] Then normalize the image: divide the signal of each line j of the captured image by mA(j).

[0172] Figure 13 An example of a filtered anterior exploration view after the deep neural network detection step is shown. This patient body image is plotted against the height Z (height along the vertical scanning direction) as a function of the patient width, with the patient thickness th perpendicular to the plane of the figure, and both the height and width w are in mm.

[0173] Patient 40 is represented on the anterior image, which has a marker 41 drawn by the deep neural network.

[0174] Figure 14 An example of a filtered lateral exploration view after the deep neural network detection step is shown. This patient body image is plotted against the height Z (height along the vertical scanning direction) as a function of the patient width, with the patient thickness th perpendicular to the plane of the figure, and both the height and width w are in mm.

[0175] Patient 50 is represented on the lateral image, which has a marker 51 drawn by the deep neural network.

[0176] Figure 15 An example of a lateral image with a constant drive current intensity and a constant drive voltage intensity in constant current and voltage mode is shown. Figure 15 A lateral scan of the anthropomorphic model with regulation disabled is presented.

[0177] Patient 60 is represented on the lateral image. This patient body image is plotted against the height Z (height along the vertical scanning direction) as a function of the patient width, with the patient thickness th perpendicular to the plane of the figure, and both the height and width w are in mm. There is a constant drive current intensity 61, e.g., about 350 mA, along the vertical scanning direction Z. There is a constant drive voltage intensity 62, e.g., about 120 kV, along the vertical scanning direction Z. The lateral image of patient 60 has medium quality.

[0178] Figure 16 An example of a lateral image with a regulated drive current intensity and a constant drive voltage intensity in regulated current and constant voltage mode is shown. Figure 16 A lateral scan of the anthropomorphic model with regulation enabled but with a fixed voltage (kV) is presented.

[0179] Patient 70 is represented on a lateral image. This patient body image is plotted as a function of the patient width along the height Z (height along the vertical scan direction), with the patient thickness th perpendicular to the plane of the figure, and both the height and the width w are expressed in mm. There is a drive current intensity adjustment 71 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 along the vertical scan direction Z, for example about 120 kV. The lateral image of patient 70 has a significantly similar quality to the lateral image of patient 60, but is taken at a lower radiation dose and is adjusted to obtain the correct signal level at each position along the vertical scan direction.

[0180] Compared with Figure 15 the images in Figure 16 it can be seen that in the images presented in

[0181] Figure 17 the blank or empty parts of the external patient image are adjusted corresponding to the applied adjustment distribution. The image is then corrected by normalizing with an exception signal without attenuation to remove such adjustments to the blank parts in the image, so as not to impair the radiologist's analysis of the image. The demodulated image follows a standard contrast enhancement process before being presented to the radiologist. Figure 17 An example of the final lateral image presented to the radiologist is shown.

[0182] The present invention has been described with reference to preferred embodiments. However, many variations are possible within the scope of the present invention.

Claims

1. A radiological imaging method, comprising: Two radiation sources with orthogonal imaging directions, a front radiation source and a side radiation source, the radiation sources sliding vertically to perform a vertical scan on a standing patient (20) along a vertical scan direction (Z), wherein the radiological imaging method includes at least one operation mode, in which: Performing a preliminary vertical scan on a standing patient (20) by the front radiation source along the vertical scan direction (Z) to obtain a front exploration view, Processing (2, 3) the front exploration view to identify a specific bone location (21) within the front exploration view, Adjusting at least the drive current intensity of the front radiation source along the vertical scan direction (Z) according to the patient thickness and the identified specific bone location (21) along the vertical scan direction (Z), Not adjusting the drive voltage intensity of the front radiation source along the vertical scan direction (Z), The adjustment of the drive current intensity of the front radiation source is performed automatically to improve the trade-off between: Reducing the overall radiation dose received by the patient (20) during the vertical scan, At the same time, for the front image, maintaining the local image contrast of the identified specific bone location (21) at different imaging positions along the vertical scan direction (Z) at a sufficient level.

2. A radiological imaging method, comprising: Two radiation sources with orthogonal imaging directions, a front radiation source and a side radiation source, the radiation sources sliding vertically to perform a vertical scan on a standing patient (30) along a vertical scan direction (Z), wherein the radiological imaging method includes at least one operation mode, in which: Performing a preliminary vertical scan on a standing patient (30) by the side radiation source along the vertical scan direction (Z) to obtain a side exploration view, Processing (2, 3) the side exploration view to identify a specific bone location (31) within the side exploration view, Adjusting at least the drive current intensity of the side radiation source along the vertical scan direction (Z) according to the patient thickness and the identified specific bone location (31) along the vertical scan direction (Z), Not adjusting the drive voltage intensity of the side radiation source along the vertical scan direction (Z), The adjustment of the drive current intensity of the side radiation source is performed automatically to improve the trade-off between: Reducing the overall radiation dose received by the patient (30) during the vertical scan, At the same time, for the side image, maintaining the local image contrast of the identified specific bone location (31) at different imaging positions along the vertical scan direction (Z) at a sufficient level.

3. A radiological imaging method, comprising: Two radiation sources with orthogonal imaging directions, a front radiation source and a side radiation source, the radiation sources sliding vertically to perform a vertical scan on standing patients (20, 30) along a vertical scan direction (Z), wherein the radiological imaging method includes at least one operation mode, in which: Performing a preliminary vertical scan on a standing patient by the front and side radiation sources along the vertical scan direction to obtain front and side exploration views, Processing (2, 3) the front and side exploration views to identify specific bone localizations (21, 31) within the front and side exploration views, Adjusting the drive current intensity of the front and side radiation sources along the vertical scan direction according to the patient thickness and the identified specific bone localizations (21, 31) along the vertical scan direction (Z), Not adjusting the drive voltage intensity of the front or side radiation source along the vertical scan direction (Z), The adjustment of the drive current intensity of the front radiation source and the adjustment of the drive current intensity of the side radiation source are carried out simultaneously, or simultaneously, synchronously and automatically, to improve the trade-off between: Reducing the overall radiation dose received by the patient (20, 30) during the vertical scan, At the same time, for the front image and the side image, maintaining the local image contrast of the identified specific bone localizations (21, 31) at different imaging positions along the vertical scan direction (Z) at a sufficient level.

4. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The adjustment of the drive current intensity of the front radiation source is also carried out to achieve a certain signal-to-noise ratio, which is constant and common for all the imaging positions along the vertical scan direction (Z) for the front image if there is a front image and / or for the side image if there is a side image, but can take two different values for the front image and the side image respectively.

5. The radiographic imaging method according to claim 4, wherein For each of the front and / or side images, for each different patient (20, 30) organ to be imaged, the signal-to-noise ratio is constant and predetermined.

6. The radiography method according to claim 4, wherein: For the front image of the patient's spine, the standard signal-to-noise ratio corresponds to the number of X-ray photons received by each detector pixel between 50 and 70, and / or the operator of the radiography method has the possibility of deviating from this standard value by at least + or - 20%, or at least + or - 50% through a manual command, And / or for the side image of the patient's spine, the standard signal-to-noise ratio corresponds to the number of X-ray photons received by each detector pixel between 20 and 40, and / or the operator of the radiography method has the possibility of deviating from this standard value by at least + or - 20%, or at least + or - 50% through a manual command.

7. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, If there is a front image, the front image and / or if there is a side image, the side image is normalized by homogenizing only the area located outside the patient's body contour after undergoing at least the first step of current intensity adjustment, so as to eliminate image artifacts from the drive current intensity adjustment.

8. The radiographic imaging method according to claim 7, characterized in that, After normalization, the front and / or side images undergo a contrast enhancement step.

9. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The specific bone localization (21, 31) of the identification excludes metal components, if any, or metal prostheses in the patient's body skeleton part, if any, or metal protectors placed on the patient's body before performing the radiography method, if any.

10. The radiological imaging method according to any one of claims 1 to 3, characterized in that, The current intensity adjustment is maximized so that the vertical scanning speed is also maximized to a constant value.

11. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The operation mode can be manually turned on or off by the radiography method operator.

12. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The rate of change of the current intensity adjustment 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.

13. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The range of the current intensity adjustment is at least from 20 mA to 300 mA, or from 10 mA to 400 mA.

14. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The voltage intensity is fixed and selected within the range from 50 kV to 120 kV.

15. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The value range of the vertical scanning speed is at least from 8 cm / s to 20 cm / s, or from 4 cm / s to 30 cm / s.

16. The radiological imaging method according to any one of Claims 1 to 3, characterized in that, Before obtaining each of the frontal image and the lateral image, each of the frontal and / or lateral exploration views is obtained by performing a preliminary vertical scan of the standing patient (20, 30) along the vertical scan direction (Z) with a reduced overall radiation dose compared to each of the frontal image and the lateral image.

17. The radiographic imaging method according to claim 16, wherein The reduced overall radiation dose is less than 10% of the overall radiation dose, or less than 5% of the overall radiation dose.

18. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, Pixels in the exploration view are grouped together in an N × N pixel area to form an imaging area.

19. The radiographic imaging method according to claim 18, wherein Pixels in the exploration view are grouped together in at least a 10 × 10 pixel area to form an imaging area.

20. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The exploration view is processed (3) to identify prominent points, which are then used to calculate the thickness distribution and identify the specific bone localization (21, 31) of the standing patient (20, 30) along the vertical scan direction (Z).

21. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, The exploration view is processed by a neural network to calculate the thickness distribution and identify the specific bone localization (21, 31) of the standing patient (20, 30) along the vertical scan direction (Z).

22. The radiological imaging method according to any one of claims 1 to 3, characterized in that, The two radiation sources slide vertically so as to perform a vertical scan of the pelvis or spine or spinal column or whole body of the standing patient (20, 30) along the vertical scan direction (Z).

23. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, Two radiation detectors are respectively associated with the two radiation sources. The two radiation detectors are two photon counting detectors (PCDs), and each photon counting detector is associated with an automatic image processing function. Regardless of the radiation dose received on the sensitive surface of the radiation detector, the automatic image processing function automatically balances the image density to enhance the image contrast.

24. The radiographic imaging method according to any one of claims 1 to 3, characterized in that, Two radiation detectors are respectively associated with the two radiation sources. The two radiation detectors are two multi-energy counting detectors, or two energy-resolved photon counting detectors (ERPCDs).

25. The radiographic imaging method according to claim 18, characterized in that, The imaging area is processed (3) to identify prominent points, which are then used to calculate the thickness distribution and identify the specific bone localization (21, 31) of the standing patient (20, 30) along the vertical scan direction (Z).

26. The radiographic imaging method according to claim 18, characterized in that, The imaging region is processed by a neural network to calculate a thickness distribution and identify the specific bone localization (21, 31) of the standing patient (20, 30) along the vertical scan direction (Z).

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