WO2007074772A1 - X線ct装置 - Google Patents
X線ct装置 Download PDFInfo
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- WO2007074772A1 WO2007074772A1 PCT/JP2006/325777 JP2006325777W WO2007074772A1 WO 2007074772 A1 WO2007074772 A1 WO 2007074772A1 JP 2006325777 W JP2006325777 W JP 2006325777W WO 2007074772 A1 WO2007074772 A1 WO 2007074772A1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
- A61B6/03—Computerised tomographs
- A61B6/032—Transmission computed tomography [CT]
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/40—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis
- A61B6/4035—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis the source being combined with a filter or grating
- A61B6/4042—K-edge filters
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/46—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with special arrangements for interfacing with the operator or the patient
- A61B6/461—Displaying means of special interest
- A61B6/465—Displaying means of special interest adapted to display user selection data, e.g. graphical user interface, icons or menus
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/54—Control of apparatus or devices for radiation diagnosis
- A61B6/542—Control of apparatus or devices for radiation diagnosis involving control of exposure
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S378/00—X-ray or gamma ray systems or devices
- Y10S378/901—Computer tomography program or processor
Definitions
- the present invention relates to an X-ray CT apparatus, and in particular, many parameters to be set at the imaging planning stage prior to imaging when performing diagnosis of the presence of a lesion in an organ of a subject, for example, cancer.
- the present invention relates to an improvement of an X-ray CT apparatus having a function for supporting the setting of an image.
- the contrast, noise amount, and discriminability of the lesion to the background tissue displayed on the display device of the X-ray CT apparatus with respect to the background tissue are set based on the imaging conditions (tube voltage, tube current, orbit Speed, helical pitch, slice thickness, etc.), reconstruction conditions (reconstruction filter, etc.), and the size of the target tissue, etc. It was difficult to estimate the image quality of the target tissue image and determine the parameters to be set optimally. Therefore, whether an image with high discrimination ability can be obtained
- Japanese Patent Laid-Open No. 2004-97778 discloses an X-ray computer equipped with a planning assistance system having a function for constructing a scan plan screen having a graphical user interface (GUI) together with a condition optimization function for solving such a point.
- a tomography device When the dose represented by CTDI (CT Dose Index) is input to the scan plan screen with GUI, the target diameter indicating 50% detection rate (identification rate) is displayed on the reconstructed image.
- CTDI CT Dose Index
- the index DEI Dose Efficiency Index
- its phantom sample image are displayed on the scan plan screen, and the density difference between the target tissue specified by the desired detection rate, target diameter or target diameter and its background tissue
- the target diameter, detection rate, and DEI corresponding to that are displayed on the scan plan screen to assist the shooting plan.
- the object of the present invention is to provide an X-ray having a versatile function that supports setting of other setting parameters only by setting a limited number of simple setting parameters at the imaging planning stage prior to imaging.
- CT equipment is provided.
- X-ray generation means an X-ray detector disposed opposite to the X-ray generation means, and the X-ray generation means and the X-ray detector are rotationally moved on a circular orbit surface having the same rotation center. While rotating and rotating with the rotating means and the rotating means, the X-ray generating means irradiates the subject placed on the rotation center with the X-ray generating means to detect the transmitted X-ray dose in the subject.
- X is provided with control means for controlling the detection by a detector, and reconstruction calculation means for obtaining a tomographic image by performing reconstruction calculation using the transmitted X-ray dose data obtained under the control of the control means.
- Line CT system Line CT system
- Input means for inputting information relating to the target tissue of the subject to be identified in the tomographic image and an index relating to the accuracy of the identification, and imaging for identifying the target tissue with the index input by the input means
- an X-ray CT apparatus comprising an imaging condition determining means for determining a condition.
- An imaging condition determining method in an X-ray CT apparatus is provided.
- an X-ray having a versatile function that supports setting of other setting parameters only by setting a limited number of simple setting parameters at the imaging planning stage prior to imaging. CT device can be provided.
- an inexperienced user of an X-ray CT apparatus can input a simple input item via the input device at the imaging planning stage prior to imaging, and the visibility (desired by the user) An image having an image quality having a recognition ability can be easily obtained.
- FIG. 1 is an external view of an X-ray CT apparatus to which the present invention is applied.
- FIG. 2 is an overall configuration diagram of the X-ray CT apparatus shown in FIG.
- FIGS. 3 (a) and 3 (b) are diagrams for explaining the principle applied in the present invention.
- FIGS. 4 (a), 4 (b) and 4 (c) are diagrams for explaining the principle applied in the present invention.
- FIG. 5 is a diagram showing imaging operations sequentially performed by an arithmetic unit using data stored in the storage device in FIG. 2 at an imaging planning stage prior to actual imaging of a subject examination site according to the present invention.
- Fig. 6 shows the contents of input related to the target tissue of the examination site, which is input via the input device in Fig. 2 in the imaging planning stage prior to actual imaging of the examination site of the subject in accordance with the present invention. And a display example on the display device of the estimated reconstructed image of the examination site including the target tissue, which is the result of the calculation executed by the calculation device according to the input content.
- FIG. 7 is a diagram of each examination part of the standard human body, which is stored in the storage device in FIG. An example of the standard time density
- FIG. 8 is a diagram for explaining the attenuation of X-rays until the X-ray generator force in FIG. 2 is generated and detected by the opposing detector.
- FIG. 9 shows the X-ray effective energy corresponding to the irradiation X-ray effective spectrum for each tube voltage of the X-ray generator in the flow of FIG.
- the contrast between the target tissue and the background tissue corresponding to each X-ray attenuation coefficient corresponding to each tube voltage, the X-ray attenuation coefficient corresponding to each tube voltage, and the respective contrast The figure explaining the setting of the tube voltage based on this.
- FIG. 10 identifies the tomographic imaging position of the subject at the beginning of the imaging planning stage prior to actual imaging, and obtains an ellipsoid that approximates the cross-sectional size of the subject at the identified imaging position. Scanning the subject's scanogram, and then calculating the tube current time product mAs that defines the irradiation dose of the X-ray generator calculated based on the obtained approximate ellipsoid and the amount of noise obtained in step S6 in Fig. 5. Illustration to explain.
- FIG. 11 shows the generation of standard image data of the standard projection data force for each examination region stored in the database in the storage device according to the present invention, and the target tissue pseudo-projection data to the standard projection data. Addition of the noise amount obtained in step S6 of Fig. 5 to the standard projection data on which the superimposition and target tissue pseudo-projection data are superimposed, and the target tissue on which the noise is added.
- FIG. 1 is a schematic view showing the external appearance of an X-ray CT apparatus 1 to which the present invention is applied.
- a scanner 10 used for imaging and a bed 20 for moving a subject 40 (see FIG. 2), It consists of a mouse and keyboard, etc., and measures data such as bed movement speed information and reconstruction position, and processes data obtained from the input device 311 and detector 12 (see Fig. 2) for inputting reconstruction parameters
- the operation unit 32 includes a configuration unit), and the operation unit 30 includes a display unit 312 that displays a reconstructed image.
- FIG. 2 is an overall configuration diagram of the X-ray CT apparatus 1 shown in FIG.
- the scan method is a rotate one-bit one-tate method (third generation), and mainly comprises the scanner 10, the bed 20, and the operation unit 30 as described above.
- the scanner 10 includes an X-ray generator 11, a high-voltage switching unit 18a, a high-voltage generator 18b, an X-ray controller 18c, an X-ray detector 12, a preamplifier 17, a collimator 13, a collimator controller 13a, and an X-ray generator 11 And a drive device 14 that rotationally drives the X-ray detector 12, a drive device 14 and a scanner control device 15 that controls the collimator control device 13a, and raising and lowering the bed 20
- the bed control device 21 performs movement control in the body axis direction, the bed movement measurement device 22 that measures the movement amount of the bed 20, the central control device 16 that controls the scanner 10 and the operation unit 30, and the like.
- the operation unit 30 includes an input / output device 31 and an arithmetic device 32.
- the input / output device 31 stores display data such as an input device 311 including a mouse and a keyboard, a display device 312 having a monitoring power for displaying a reconstructed image, a reconstructed image displayed on the display device 312, and the like.
- a display memory for storing the configuration program, a main memory, and a storage device 313 such as a hard disk drive are provided.
- the arithmetic device 32 includes an image processing means 321 that performs image processing such as preprocessing, filter processing, and postprocessing based on the projection data sent from the scanner 10, and a reconfiguration arithmetic device that reconstructs the projection data described above. 322.
- the device From the input device 311 in the operation unit 30, the device conditions (X-ray tube target angle, target material, target density, X-ray tube specific X-ray filtration aluminum equivalent, scintillator material, scintillator density, scintillator thickness, bow tie filter shape , Its material, copper filter shape, etc.), imaging target site information (test site target tissue, its size, its recognition rate)
- Imaging conditions tube current, tube voltage, circular velocity, helical pitch, etc.
- reconstruction conditions image FOV, reconstruction filter, image slice thickness, reconstruction slice position, etc.
- reference information for each examination site under standard imaging conditions
- the CT value of the target tissue and background tissue or the difference between the CT values, or the density (concentration) of the target tissue and background tissue and the X-ray attenuation characteristics of each target tissue and background tissue are input.
- a control signal necessary for imaging is sent from the central control device 16 to the X-ray control device 18c, the couch moving device 21, and the scanner control device 15, and imaging is started upon receipt of the imaging start signal.
- Device conditions, reference information, and the like are input in advance via the input device 311 and stored in the storage device 313.
- the X-ray controller 18c sends a control signal to the high-voltage generator 18b, and a high voltage is applied to the X-ray generator 11 via the high-voltage switching boot 18a. X-rays are emitted from 11 to the subject 40. At the same time, a control signal is sent from the scanner control device 15 to the drive device 14, and the X-ray generator 11, X-ray detector 12, and preamplifier 17 rotate around the subject 40.
- the bed 20 with 40 is stationary (when scanning a circle) Or it is translated in the direction of the rotation axis of the X-ray generator 11 or the like (during helical scanning).
- the irradiated X-ray is limited in the irradiation area by the collimator 13, absorbed (attenuated, attenuated) by each tissue in the subject 40, passes through the subject 40, and is detected by the X-ray detector 12.
- X-rays detected by the X-ray detector 12 are converted into current, amplified by the preamplifier 17, and input to the arithmetic unit 32 as a projection data signal.
- the projection data signal input to the calculation device 32 is subjected to image reconstruction processing by the reconstruction calculation device 322 in the calculation device 32.
- the reconstructed image is stored in the storage device 313 in the input / output device 31 and displayed as a CT image on the display device 312. Alternatively, after being processed by the image processing means 321, it is displayed as a CT image on the display device 312.
- FIG. 3 shows the normal distribution, where the peak values PV and PV of the normal distribution curve F of the target tissue A and the normal distribution curve F of the background tissue B are the same.
- the difference that is, the CT value difference corresponds to the contrast between the target tissue A and the background tissue B, and the normal distribution curve F of the target tissue A and the normal distribution curve F of the background tissue B.
- Deviation ⁇ ⁇ corresponds to the amount of noise in target tissue ⁇ and background tissue ⁇ ⁇ ⁇ ⁇ , respectively.
- the areas S and S converted to the number of pixels obtained by integrating each are the target tissues.
- the ratio (area ratio) of the entire target tissue A to the normal distribution of the background tissue B in the normal distribution corresponds to the discrimination ability, that is, the recognition rate D.
- Fig. 3 (a) shows the case where the size of the target tissue A and the background tissue B are almost equal
- Fig. 3 (b) shows the case where the size of the target tissue A is relatively small compared to the background tissue B.
- the size of the background tissue B is selected to be approximately equal to the size of the target tissue A.
- the recognition rate D of the target tissue A is the size S and S of the target tissue A and the background organization B, the contrast C between the target tissue A and the background tissue B, and the target
- Figure 4 (a) shows the discrimination performance with respect to contrast.
- the recognition rate is low due to the influence of noise.
- the recognition rate increases drastically when the contrast increases to some extent, and the recognition rate becomes constant (100%) when the contrast further increases.
- Figure 4 (b) shows the discrimination performance against noise. If the noise is significantly lower than the contrast, the recognition rate will be high even if the noise increases slightly, but if the noise increases to some extent, the discrimination will drop sharply, and if the noise further increases, the recognition rate will be constant ( 0%).
- Figure 4 (c) shows the discriminability characteristics with respect to size.
- the recognition rate is low due to noise, but when the size is increased to some extent, the recognition rate improves rapidly, and when the size is increased, the recognition rate becomes constant (100%).
- the recognition rate increases even when the size is small.
- the recognition rate decreases when the size is small.
- the X-ray CT system has a function that supports the setting of parameters that should be set by the user at the imaging planning stage prior to imaging.
- the liver of the subject 40 is used as an imaging target examination site, and the target tissue is known to be present.
- a cancer contrast medium of 2 cm or more which may not be present.
- step S1 the user first inputs a cancer of 2 cm or more from the input device 311 to the liver as the target tissue A of the examination site to be imaged, and is an index value indicating the desired image quality. Enter an identification rate, for example, 80%.
- an identification rate for example, 80%.
- Fig. 6 shows a display example displayed on the screen 120 of the display device 312 at that time.
- the field 121 and the imaging target tissue name and size field 122 display the entered information, and the left tomogram 123 is displayed after the calculation described below is performed based on these inputs.
- This is a display example of an estimated reconstructed image of the examination site including the target tissue A and the background tissue B having an input recognition rate of 80% for evaluation of the user to be performed.
- the database in the storage device 313 includes the size of the background tissue corresponding to the target tissue size for each examination site, the X-ray attenuation characteristics and density of both tissues, and the target tissue and background tissue for each examination site under standard imaging conditions. CT value is stored.
- a standard human body whose parameter is the elapsed time from the injection of the contrast medium into the subject during the contrast examination of the target tissue using the contrast medium (iodine).
- a standard time concentration curve representing the concentration of contrast medium for each target tissue at each examination site and X-ray attenuation characteristics at each concentration are stored.
- Each standard time density curve is displayed on the contrast imaging display device 312 of the target tissue according to the user's needs, and the user depends on the imaging conditions (injection speed, injection amount, etc.) and the body type of the subject. It is used to determine the timing of contrast imaging, that is, the contrast phase such as early contrast, peak, and late contrast.
- step S2 the target tissue A and background tissue B set in step S1 are irradiated with 11 X-ray generators, and the irradiation X-ray effective spectrum and X-ray effective for each tube voltage detected by the detector 12 are detected. Calculate energy.
- the irradiation X-ray effective spectrum and the X-ray effective energy for each tube voltage are calculated in advance!
- the results may be stored in advance in the storage device 313 as a database.
- FIG. 8 is a diagram for explaining the effective spectrum, effective energy, and attenuation of X-rays generated from the X-ray generator 11 and detected by the opposing detector 12.
- the braking X-ray spectrum is estimated from Equation 1 and the characteristic X-ray spectrum is estimated from Equation 2 on the basis of the apparatus conditions and the imaging conditions, and these are combined to estimate the irradiation X-ray spectrum.
- N is the Avogadro number
- A is the target's dense ch
- m is the mass of the electron
- c is the speed of light
- T is the energy of the incident electron
- Q is one
- dT / dl is the theoretical formula for stopping power by Bethe et al., 1 is the electron , T is K, L electron orbital force t K, L required to remove electrons
- the cathode (filament) 1 la is irradiated with thermionic electrons on the anode (target) l ib having the target angle a, and the photon force generated by the target l ib It occurs at an angle approximately perpendicular to the angle.
- the photon passes through the X-ray tube's intrinsic filtration aluminum equivalent l lc, the compensation filter (bowtie filter) 11 d, and the copper filter l ie, and is irradiated to the examination site including the target tissue and background tissue of the subject.
- the effective spectrum of X-rays is calculated taking into account the X-ray irradiation path, and X-ray absorption such as the scanogram force taken at the beginning of the radiography planning stage and the water equivalent ellipsoid 41 generated as a pseudo subject. It passes through the body, enters the scintillator 12a, and is converted into light. The light is detected by the photodiode 12b.
- FIG. 9 is a diagram for explaining the setting of the tube voltage in step S3.
- the effective energy at each tube voltage obtained in step S2 and the corresponding examination site stored in the database in the storage device 313 are shown.
- X-ray attenuation characteristics of the target tissue at the time of contrast imaging with a certain contrast agent concentration and the X-ray attenuation characteristics of the background tissue are obtained, and the X-ray attenuation coefficients of the target tissue are compared with each other.
- the tube voltage that maximizes the difference between the coefficient and the X-ray attenuation coefficient of the background tissue is selected.
- a graph 150 in FIG. 9 is a graph showing the distribution of the effective X-ray effective spectrum obtained when the tube voltages are 100 kv, 120 kv, and 140 kv, as a dotted line, a solid line, and a one-dot chain line, respectively.
- Graphs 155 and 156 in Fig. 9 show the X-ray attenuation coefficient ( ⁇ ) of the target tissue imaged with a contrast medium (iodine) having a vertical axis and the liver X-ray attenuation coefficient ( ⁇ ), which is the background tissue.
- the horizontal axis is a graph showing X-ray attenuation characteristics defined as photon energy. Find the intersection of the X-ray attenuation characteristics of Daraf 155 and each of the effective energies 151, 152, 153 and the intersection of the X-ray attenuation characteristics of graph 156 and each of the effective energies 151, 152, 153.
- the X-ray attenuation characteristics / z A and each effective energy 151, 152, 153 in graph 155 and the X-ray attenuation characteristics / z B and each effective energy 151, 152, 153 of Daraf 156 are displayed on the display device 312. It may be configured so that the tube voltage corresponding to the effective energy desired by the user can be selected by clicking with the mouse. This allows the user to select the effective energy under the conditions desired by the user, such as prioritizing low exposure over discriminating ability after confirming the X-ray attenuation coefficient difference.
- step S4 when the densities D and D of the target tissue A and background tissue B of the examination site are not stored in the database in the storage device 313, for example, a contrast agent is used as in this example.
- this step S4 is omitted.
- step S4 CT values PV, PV and attenuation coefficients, ⁇ and ⁇ of the contrast target tissue A and the background tissue B corresponding to the standard imaging conditions (for example, tube voltage 120 kv) stored in the database in the storage device 313 are stored.
- the standard imaging conditions for example, tube voltage 120 kv
- step S5 (D ⁇ ⁇ ⁇ ) ⁇ 1000 /, ⁇ ⁇ ' ⁇ (3 ⁇ 2)
- step S5 the density D of the contrast target tissue A and background tissue B calculated in step S4
- step S6 the size of the target organization A set in step SI, its recognition rate, the size of the background organization B from which the database power in the storage device 313 is also read based on the size of the target organization A, selected in step S3
- the target tissue A is stored in the database in the storage device 313 using the contrast C between the target tissue A and the background tissue B calculated in step S5 corresponding to the measured tube voltage.
- Size D converted to the number of pixels of rate D, target tissue A, and background tissue B, contrast C between target tissue A and background tissue B
- the noise amounts ⁇ ⁇ of each of the target organization A and its background tissue B are calculated according to the approximate curves that define these relationships exemplified in FIGS. 4 (a), 4 (b), and 4 (c).
- step S7 based on the amount of noise calculated in step S6, the tube current time product mAs that defines the X-ray irradiation dose irradiated from the X-ray generator 11 is calculated.
- the procedure for calculating m As will be described below with reference to FIG.
- a scanogram image 101 is obtained by scanning 100. For each line 101a, 101b orthogonal to the body axis of this scanogram image 101, find the maximum value b of the projection value 102 and the integral value RS of the projection value, and calculate the approximate ellipse with the major axis A and the minor axis B Estimate model 103 (homogeneous ellipsoid of material close to human attenuation coefficient).
- the attenuation coefficient ⁇ of the approximate human body elliptic model is determined in consideration of the effective spectrum corresponding to the selected tube voltage.
- mAs (tube current X orbital velocity) is the major and minor axis lengths (A, B), helical pitch, reconstruction view weight, reconstruction filter, and noise calculated in step S7. Determined based on the amount of Specifically, first, the transmission distance 1 ( ⁇ ) of the X-ray beam passing through the center of the approximate human body ellipse model 103 irradiated from the circular phase ⁇ is calculated based on Equation 5.
- a function that modulates mAs ( ⁇ ) in the circulation direction so that the noise corresponding to the noise amount (dispersion value ⁇ 2 ) is constant is generated by modifying the equation in FIG. 10 (104).
- 105 schematically shows the change in the level of the tube current when a helical scan is performed in the direction of lines 101a to 101b on the scanogram.
- ⁇ 2 ⁇ 2 XCXCXCXCXC (6)
- C, C, C, C, and C are the slice thickness, irradiation dose (tube current X orbital velocity), transparency
- This term is used to consider the effects of differences in overrange, reconstruction view weight, and reconstruction filter.
- mAs, and ST are approximate human body circles that have been measured in advance for each tube voltage base base base
- the noise (dispersion value) obtained from the image obtained by 360-degree reconstruction without performing view weighting on the projected projection data, ⁇ ⁇ 2 is the noise of the reconstruction filter, and the reference
- RW is 1 when reconstruction view weighting is not performed, and becomes larger when reconstruction view weight is added.
- the reconstruction view weight is also related to the helical pitch, and if the helical pitch is large, the amount of data that can be used for reconstruction decreases, so C increases.
- control of irradiation dose based on the amount of noise is not limited to the above method, and any method such as conventional technology may be used.
- step S8 a scanogram previously captured by the subject from a plurality of standard projection data for each examination region of the human body imaged under the standard imaging conditions stored in the database in the storage device 313. Select the standard projection data of the body shape close to the projection value of, and perform size correction of the selected standard projection data based on the integral value of the projection value of the scanogram, and step 1 into the size-corrected standard projection data.
- the pseudo-projection data of the target tissue having the size input in step (5) is superimposed, and each noise amount calculated in step 6 is converted into projection data and added to the standard projection data on which the pseudo-projection data is superimposed.
- the standard projection data superimposed on the pseudo-projection data to which the noise converted into the projection data is added is displayed on the display device 312 for evaluation by the operator. It is displayed as an estimated reconstructed image with a recognition rate of 80% (where the amount of noise calculated in step 6 is converted to that in the projection data in advance. Create as a function the relationship between the value of the projection data obtained by shooting a phantom and the value of the image noise at that time, and how much noise should be added to the projection data based on that function! , Or just decide,)
- Reference numeral 111 denotes standard projection data whose size has been corrected.
- Reference numeral 110 denotes a standard image when the size-corrected standard projection data is reconstructed.
- Reference numeral 112 denotes a target tissue added by the user to an arbitrary position of the examination region of the reconstructed standard image 110 whose contour is emphasized via an input device such as a mouse.
- the size of the target tissue is input in step S1.
- 113 is pseudo projection data of the target tissue generated based on the added target tissue 112.
- 1 14 is projection data obtained by superimposing the target tissue pseudo-projection data 113 on the size-corrected standard projection data 111 and converting each noise amount calculated in Step 6 into projection data.
- 115 is an estimated reconstructed image of the examination site including the target tissue and the background tissue with a recognition rate of 80%, in which the projection data 114 is reconstructed according to the reconstruction conditions set in advance. 6 re-estimated reconstructed images 123 are supported. The user evaluates the estimated reconstructed image 123 displayed on the screen 120, and if satisfied, presses the execution button, and shifts to actual shooting according to the setting conditions. If unsatisfied, repeat steps SI-S8 by changing the recognition rate, target tissue size, reconstruction conditions, contrast conditions, etc. that were input and set earlier.
- noise corresponding to the data value of the projection data is added, so that it is possible to obtain a more realistic image quality (noise, artifacts, etc.).
- data obtained by actually photographing the human body is used as the standard data.
- a virtual human body model generated by computer simulation or phantom data for image quality and spatial resolution evaluation may be used. ,.
- the effect of a compensation filter or a copper filter having a different shape or material can be evaluated based on an estimated image or a recognition rate, and used to determine an optimum scanner configuration.
- the scanner can be realized by preparing a plurality of compensation filters, copper filters, and lead filters, and switching them according to the setting.
- it can be used to determine the optimal reconstruction conditions, such as changing the shape of the reconstruction filter according to the setting parameter and evaluating the effect of the reconstruction filter with the estimated image or the recognition rate.
- the present invention can also be used as a simulator for optimizing imaging conditions, apparatus conditions, contrast conditions, and reconstruction conditions.
- discrimination ability is defined as an index of how accurately the target tissue is identified, and this is the ratio of the portion of the normal distribution of the target tissue that does not overlap with the normal distribution of the background region.
- the present invention is not limited to this.
- the TPF True Positive Fraction
- the noise amount (standard deviation amount) for TPF of 0.8 can be obtained based on the data.
- the function that represents the pixel distribution may be a Poson distribution that does not have to be a normal distribution!
Abstract
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JP2007551957A JP4937927B2 (ja) | 2005-12-28 | 2006-12-25 | X線ct装置とx線ct装置における撮像条件決定方法 |
US12/095,072 US7715522B2 (en) | 2005-12-28 | 2006-12-25 | X-ray CT apparatus |
CN2006800494274A CN101346102B (zh) | 2005-12-28 | 2006-12-25 | X射线ct装置 |
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Cited By (7)
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WO2009107658A1 (ja) * | 2008-02-25 | 2009-09-03 | 株式会社 日立メディコ | X線ctスキャンシミュレータ及びx線ct装置 |
JP2009261519A (ja) * | 2008-04-23 | 2009-11-12 | Hitachi Medical Corp | X線ct装置 |
JP2009273745A (ja) * | 2008-05-16 | 2009-11-26 | Toshiba Corp | X線ct装置 |
JP2009285147A (ja) * | 2008-05-29 | 2009-12-10 | Ge Medical Systems Global Technology Co Llc | X線ct装置 |
JP2015226764A (ja) * | 2014-05-08 | 2015-12-17 | 信示 芦田 | X線診断装置 |
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CN113520426A (zh) * | 2021-06-28 | 2021-10-22 | 上海联影医疗科技股份有限公司 | 同轴度测量方法、医疗设备机架调整方法、设备和介质 |
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JPWO2007074772A1 (ja) | 2009-06-04 |
US7715522B2 (en) | 2010-05-11 |
CN101346102B (zh) | 2012-08-22 |
US20090245459A1 (en) | 2009-10-01 |
CN101346102A (zh) | 2009-01-14 |
JP4937927B2 (ja) | 2012-05-23 |
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