WO2015068204A1 - 輪郭画像生成装置および核医学診断装置 - Google Patents
輪郭画像生成装置および核医学診断装置 Download PDFInfo
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Definitions
- the present invention relates to a contour image generating apparatus and nuclear medicine that extract a contour of an imaging target of a subject based on collected data obtained by administering a radiopharmaceutical to the subject and detecting radiation collected from within the subject.
- the present invention relates to a diagnostic device.
- PET positron emission tomography
- the PET apparatus is configured to reconstruct a tomographic image of a subject only when two ⁇ rays (gamma rays) generated by the annihilation of positrons are detected simultaneously by a plurality of detectors.
- a PET apparatus for mammography that images the breast of a subject as a PET apparatus.
- a detector is disposed so as to surround the breast of the subject, and the detection sensitivity can be improved by bringing the detector close to the breast of the subject.
- the ⁇ rays detected by the detector are ⁇ rays released from within the subject to which the radiopharmaceutical has been administered in advance.
- the released ⁇ rays are absorbed by the tissue in the body of the subject. Therefore, the PET apparatus performs absorption correction considering the influence of ⁇ -ray absorption when generating a PET image (see, for example, Patent Document 1).
- Absorption correction is generally performed using data captured by an X-ray CT apparatus or using data detected using an external radiation source that emits ⁇ rays.
- the dynamic contour model is a method of extracting a contour shape by dynamically changing a closed curve set on an image to match the contour of an object.
- the contour extraction process using the dynamic contour model needs to be repeated many times in order to extract the contour shape of the object, and the accuracy of the obtained contour shape varies depending on the number of processing times.
- the operator sets the number of times of processing and extracts the contour shape by performing the contour extraction processing for the set number of times of processing, but the operator visually confirms whether or not an accurate contour shape has been obtained. There is a need. If the obtained contour shape is smaller than the object contour, the number of times of processing is reduced. If the obtained contour shape is larger than the object contour, the number of times of processing is increased. In this way, it is possible to acquire an accurate contour shape of the object.
- Non-Patent Document 1 when contour extraction processing using a dynamic contour model as in Non-Patent Document 1 is applied to extract the contour shape of the subject's breast, a precise contour shape is obtained. There is a problem that cannot be done. That is, since the contour extraction process using the dynamic contour model extracts the contour shape using the gradient information of the two-dimensional reconstructed image, the contour shape should remain where the change in the pixel value of the adjacent pixel is large. That is, if the breast contour of the subject is clear, the contour shape should remain at the breast contour.
- the contour may remain at a gradient (that is, a noise portion) due to the noise. Therefore, an accurate contour shape cannot be obtained unless the contour extraction process is repeated many times.
- an object such as a tumor is present in the breast, where the change in the pixel value of the adjacent pixel is larger than the breast contour.
- the contour extraction process is not completed with an appropriate number of processes, the acquired contour shape enters the inside of the breast contour, and an object contour such as a tumor is extracted as the contour shape, and an unintended contour shape is acquired.
- the operator can visually confirm the obtained contour shape and repeat the setting of several processing times to perform accurate contour shape. Can be acquired relatively quickly.
- the contour extraction process is performed on data having a large number of slices such as a nuclear medicine diagnostic apparatus, the appropriate number of processes may be different for each slice. Therefore, when the operator visually confirms the contour shape for each slice, it takes a lot of time, and it is very difficult to perform the contour extraction processing by setting the number of times of processing.
- An object of the present invention is to provide a contour image generation device and a nuclear medicine diagnosis device.
- the present invention has the following configuration. That is, the contour image generating apparatus according to the present invention is a first preset which is repeatedly performed by a contour extraction model on a two-dimensional reconstructed image of a subject acquired by detecting radiation emitted from the subject.
- a contour extraction processing unit that performs one contour extraction processing, and a change area between the first contour shape and the second contour shape are calculated.
- a change area calculation unit a pixel value total calculation unit that calculates a sum of pixel values of pixels included in the change area; a change rate calculation unit that calculates a change rate that is a ratio of the change area and the total;
- An end determination unit that determines whether or not the change rate is smaller than a preset threshold value, and the second contour shape when the end determination unit determines that the change rate is greater than the threshold value.
- the processing of the contour extraction processing unit, the change area calculation unit, the pixel value total calculation unit, the change rate calculation unit, and the end determination unit is executed again, and the change rate is determined by the end determination unit from the threshold value.
- a control unit that outputs a two-dimensional contour image including the second contour shape when it is determined that the second contour shape is also small.
- the contour extraction processing unit generates a new second contour shape from the preset first contour shape, which is repeatedly performed on the two-dimensional reconstructed image by the contour extraction model. Of the contour extraction processing to be extracted, one contour extraction processing is performed.
- the end determination unit determines whether or not the rate of change is smaller than a preset threshold value.
- the rate of change is calculated as follows.
- the change area calculation unit calculates the change area between the first contour shape and the second contour shape, and the pixel value total calculation unit calculates the sum of the pixel values of the pixels included in the change area.
- the change rate calculation unit calculates a change rate that is a ratio of the change area to the total.
- the repetition control unit sets the second contour shape as the first contour shape when the end determination unit determines that the change rate is greater than the threshold, causes the contour extraction processing unit and the like to execute again, and the end determination unit When it is determined that the change rate is smaller than the threshold value, a two-dimensional contour image including the second contour shape is output.
- the rate of change which is the ratio of the change area and the sum of the pixel values of the pixels included in the change area, has the property of being settled to the same value every time without depending on the data for each two-dimensional reconstructed image.
- a threshold value is set in advance using a plurality of sample data acquired in advance.
- the repetition control unit outputs a two-dimensional contour image including the second contour shape when the end determination unit determines that the change rate is smaller than the threshold value. Accordingly, the contour shape of the subject to be imaged can be automatically extracted accurately with a suitable number of processing times without visual confirmation by the operator.
- the contour image generation apparatus further includes a processing number determination unit that counts the number of times of the contour extraction processing and determines whether or not the processing number has reached the number of breaks.
- the unit calculates a rate of change for each number of breaks, which is a ratio of the sum of the change areas to the sum of the totals, and the control unit is configured so that the number of processes does not reach the number of breaks in the process count determination unit. Is determined, the second contour shape is set as the first contour shape, and the processing of the contour extraction processing unit, the change area calculation unit, the pixel value total calculation unit, and the processing number determination unit is performed again.
- the processing number determination unit determines that the processing number has reached the number of divisions
- the processing number is reset and the determination by the end determination unit is performed.
- the end determination unit determines that the rate of change is greater than the threshold
- the second contour shape is set as the first contour shape, the contour extraction processing unit, the change area calculation unit, and the pixel value total It is preferable that the processes of the calculation unit, the change rate calculation unit, the processing number determination unit, and the end determination unit are executed again.
- the rate of change for each number of processes may fluctuate up and down due to statistical noise in the two-dimensional reconstructed image.
- end determination is performed for each processing count, the rate of change once decreases greatly, the rate of change becomes smaller than the threshold value, and the contour extraction process may end before the rate of change settles.
- a processing number determination unit is not provided and end determination is performed for each processing number, but determination processing is performed for each number of separations, that is, for each of a plurality of processing numbers.
- the change rate calculation unit calculates a change rate for each number of divisions, which is a ratio of the total change area and the total pixel value.
- the end determination unit performs determination using the change rate calculated as the average value for each number of breaks. Therefore, it is possible to prevent the contour extraction process from being finished before the change rate is settled due to a change in the change rate for each processing count, and to accurately extract the contour shape with an appropriate number of processing times.
- an example of the contour image generating apparatus is that the number of divisions is variable. That is, when the number of divisions is reached, the next number of divisions may be set to a number different from the previous number of divisions. For example, a relatively large number of processes is set as the number of delimiters for the number of processes where the difference between the threshold and the change rate is large, and a relatively small number of processes is set as the number of delimiters for the number of processes where the difference between the threshold and the change rate is small. As a result, it is possible to accurately extract the contour shape with an appropriate number of processes while reducing the number of end determinations.
- the number of divisions is reduced as the number of processes reaches the number of divisions. That is, when the number of divisions is reached, the next number of divisions is set to a number less than the previous number of divisions or the same number as the previous number of divisions. As a result, it is possible to accurately extract the contour shape with an appropriate number of processes while reducing the number of end determinations.
- an example of the contour image generating apparatus according to the present invention is that the number of divisions is constant. Thereby, the end determination can be simply performed under the same conditions.
- the two-dimensional reconstructed image is any one of a plurality of two-dimensional reconstructed images constituting a three-dimensional reconstructed image generated by reconstruction. It is preferable that the control unit generates a three-dimensional contour image from the plurality of output two-dimensional contour images.
- the contour shape can be accurately extracted with an appropriate number of processes for each two-dimensional reconstructed image (slice).
- a plurality of detectors are arranged in a ring shape, based on a detector unit that detects radiation emitted from a subject, and radiation detected by the detector unit, A data collection unit that collects emission data, a reconstruction processing unit that reconstructs the emission data to obtain a two-dimensional reconstructed image, and is repeatedly performed on the two-dimensional reconstructed image by a contour extraction model in advance.
- a contour extraction processing unit that performs one contour extraction processing, and the first contour shape and the second contour shape
- a change area calculation unit that calculates a change area
- a pixel value total calculation unit that calculates a sum of pixel values of pixels included in the change area
- a change rate that is a ratio of the change area and the total
- an end determination unit that determines whether or not the change rate is smaller than a preset threshold
- the end determination unit that determines that the change rate is greater than the threshold
- the second contour shape is set as the first contour shape, and the processing of the contour extraction processing unit, the change area calculation unit, the pixel value total calculation unit, the change rate calculation unit, and the end determination unit is executed again.
- a control unit that outputs a two-dimensional contour image including the second contour shape when the change rate is determined to be smaller than the threshold value by the end determination unit. It is.
- the contour extraction processing unit obtains a new second contour shape from the preset first contour shape, which is repeatedly performed on the two-dimensional reconstructed image by the contour extraction model. Of the contour extraction processing to be extracted, one contour extraction processing is performed.
- the end determination unit determines whether or not the rate of change is smaller than a preset threshold value.
- the rate of change is calculated as follows.
- the change area calculation unit calculates the change area between the first contour shape and the second contour shape, and the pixel value total calculation unit calculates the sum of the pixel values of the pixels included in the change area.
- the change rate calculation unit calculates a change rate that is a ratio of the change area to the total.
- the repetition control unit sets the second contour shape as the first contour shape when the end determination unit determines that the change rate is greater than the threshold, causes the contour extraction processing unit and the like to execute again, and the end determination unit When it is determined that the change rate is smaller than the threshold value, a two-dimensional contour image including the second contour shape is output.
- the rate of change which is the ratio of the change area and the sum of the pixel values of the pixels included in the change area, has the property of being settled to the same value every time without depending on the data for each two-dimensional reconstructed image.
- a threshold value is set in advance using a plurality of sample data acquired in advance.
- the repetition control unit outputs a two-dimensional contour image including the second contour shape when the end determination unit determines that the change rate is smaller than the threshold value. Accordingly, the contour shape of the subject to be imaged can be automatically extracted accurately with a suitable number of processing times without visual confirmation by the operator.
- the contour shape of the subject to be imaged can be automatically and accurately extracted with an appropriate number of processes without visual confirmation by the operator.
- FIG. 1 is a diagram illustrating a schematic configuration of a mammography PET apparatus according to Embodiment 1.
- FIG. It is a figure which shows the structure of the outline image generation part which concerns on Example 1.
- FIG. It is a figure for demonstrating several 2D reconstruction image which comprises a 3D reconstruction image.
- 6 is a flowchart illustrating an operation of a contour image generation unit according to the first embodiment.
- FIG. 10 is a diagram illustrating a configuration of a contour image generation unit according to a second embodiment. 10 is a flowchart illustrating an operation of a contour image generation unit according to the second embodiment. It is a figure which shows the relationship between the frequency
- FIG. 1 is a diagram illustrating a schematic configuration of a mammography PET apparatus according to the first embodiment.
- the mammography PET apparatus 1 detects emission data E1 based on the detector unit 3 that detects ⁇ rays emitted from the breast B of the subject M to which the radiopharmaceutical is administered, and the ⁇ rays detected by the detector unit 3. And a data collecting unit 5 for collecting.
- a plurality of ⁇ -ray detectors 7 are arranged in a ring shape so as to surround a breast B that is an imaging target of the subject M.
- the ⁇ -ray detector 7 corresponds to the detector of the present invention.
- the ⁇ -ray detector 7 includes a scintillator block, a light guide, and a photomultiplier tube (all not shown).
- a plurality of scintillator blocks are configured, and a plurality of scintillator blocks are arranged in a matrix (for example, 8 rows ⁇ 8 columns). Further, the plurality of scintillator blocks arranged two-dimensionally have a single layer structure composed of one stage or a laminated structure composed of a plurality of stages (for example, two stages).
- the data collection unit 5 has a coincidence circuit (not shown).
- the data collecting unit 5 collects one event determined to be simultaneously counted based on the electrical signal output from the detector unit 3 by detecting ⁇ rays as emission data E1. That is, the data collection unit 5 considers that two ⁇ -rays emitted from the subject M in the opposite direction by 180 ° are simultaneously counted only when the two ⁇ -ray detectors 7 detect the ⁇ -rays within a certain period, Collect that information.
- the emission data E1 is collected three-dimensionally, but in some cases, two-dimensional collection may be used.
- a contour image generation unit 9 that generates a three-dimensional contour image Gr that is an image including the contour shape of the breast B of the subject M from the collected emission data E 1, and a contour image generation unit 9
- An absorption correction unit 11 is provided that generates an absorption coefficient map based on the generated three-dimensional contour image Gr and performs absorption correction on the emission data E1 using the absorption coefficient map.
- the absorption coefficient map used for absorption correction is obtained by uniformly assigning an absorption coefficient equivalent to the breast B of the subject M within the outline of the breast B of the three-dimensional outline image Gr.
- the absorption coefficient is set in advance.
- the absorption correction unit 11 performs absorption correction on the emission data E1, and generates emission data E2 after absorption correction.
- the contour image generation unit 9 corresponds to the contour image generation device of the present invention.
- a reconstruction processing unit 13 that reconstructs the emission data E2 after the absorption correction and generates the PET image Gp is provided at the subsequent stage of the absorption correction unit 11.
- the reconstruction processing by the reconstruction processing unit 13 uses a two-dimensional or three-dimensional reconstruction method.
- a three-dimensional iterative reconstruction method is used for the reconstruction process.
- the absorption correction unit 11 may be included in the system model of the reconstruction processing unit 13.
- the mammography PET apparatus 1 includes a main control unit 15 that comprehensively controls each component of the apparatus 1, a display unit 17 that displays the PET image Gp generated by the reconstruction processing unit 13, and an operator
- An input unit 19 that performs input settings and various operations and a storage unit 21 that stores a PET image Gp and the like are provided.
- the main control unit 15 includes a central processing unit (CPU).
- the display unit 17 includes a liquid crystal monitor or the like.
- the input unit 19 includes a keyboard, a mouse, and the like.
- the storage unit 21 includes a storage medium such as a ROM (read-only memory), a RAM (random-access memory), or a hard disk. The storage medium may be removable from the mammography PET apparatus 1.
- FIG. 2 is a diagram illustrating a configuration of the contour image generation unit 9 according to the first embodiment. First, an outline of the contour image generation unit 9 will be described.
- the contour image generation unit 9 reconstructs emission data E1 collected by detecting two ⁇ rays emitted from the breast B of the subject M, and generates a three-dimensional reconstructed image G of the breast B of the subject M.
- a reconstruction processing unit 31 to be generated and a storage unit 33 to store the generated three-dimensional reconstruction image G are provided.
- the repetitive control unit 39 to be described later is one of the two-dimensional reconstruction images G1 constituting the three-dimensional reconstruction image G among the three-dimensional reconstruction images G stored in the storage unit 33.
- the configuration image G1 is read (see FIG. 3).
- the contour image generation unit 9 determines the contour shape of the breast B of the subject M in the read two-dimensional reconstructed image G1 and outputs the two-dimensional contour image Gr1, and the output 2
- a contour image collecting unit 37 that collects the three-dimensional contour image Gr1 and outputs a three-dimensional contour image Gr, and a repetitive control unit 39 that comprehensively controls each component of the contour image generating unit 9 are provided.
- the repetition control unit 39 corresponds to the control unit of the present invention.
- the contour determination unit 35 includes a contour extraction process for extracting a new second contour shape Wb from a preset first contour shape Wa, which is repeatedly performed by the contour extraction model, in the acquired two-dimensional reconstructed image G1.
- a contour extraction processing unit 41 that performs one contour extraction processing is provided.
- the contour determination unit 35 calculates a change area calculation unit 43 that calculates a change area S between the first contour shape Wa and the second contour shape Wb, and calculates a total V of pixel values of pixels included in the change area S.
- the contour determination unit 35 includes an end determination unit 49 that determines whether the change rate Ra is smaller than a preset threshold value P.
- the iterative control unit 39 sets the second contour shape Wb as the first contour shape Wa when the end determination unit 49 determines that the change rate Ra is greater than the threshold value P, and calculates the contour extraction processing unit 41 and the change area calculation.
- the unit 43, the pixel value total calculation unit 45, the change rate calculation unit 47, and the end determination unit 49 are executed again. Further, when the end determination unit 49 determines that the change rate Ra is smaller than the threshold value P, the iterative control unit 39 outputs a two-dimensional contour image Gr1 including the second contour shape Wb.
- the reconstruction processing unit 31 reconstructs emission data E1 collected by detecting two ⁇ rays emitted from the breast B of the subject M, and generates a three-dimensional reconstruction image G of the breast B of the subject M. Generate.
- the reconstruction process is performed by a known method such as a two-dimensional reconstruction method or a three-dimensional reconstruction method.
- the reconstruction processing it is possible to reconstruct the three-dimensionally collected emission data E1, such as a rebinning method, a FORE (Fourier rebinning) method, and an OS-EM (ordered subsets-expectation maximization) method.
- a combination with a construction method may be used.
- a list mode three-dimensional DRAMA dynamic RAMRAM
- the contour extraction processing unit 41 is a part of the contour extraction processing repeatedly performed by the contour extraction model in each of a plurality of two-dimensional reconstruction images G1 constituting the three-dimensional reconstruction image G generated by the reconstruction processing unit 31.
- One contour extraction process is performed.
- the one-time contour extraction process based on the contour extraction model is a process of extracting a new second contour shape Wb from a preset first contour shape Wa.
- a level set method or a snake method is used as the contour extraction model.
- the level set method has the following effects over the snake method. For example, when the subject M is small, both breasts B may be reflected.
- the contour method cannot extract individual contour shapes by the snake method, but the contour shape can be individually extracted by the level set method.
- the contour extraction processing sets an initial contour W (0) so as to largely surround the breast B of the subject M, and repeatedly executes the contour extraction processing.
- Outline W (1), outline W (2), outline W (3),..., Outline W (n) are obtained in order.
- the contour extraction process is performed for the first time, the first contour shape Wa becomes the contour W (0), and the new second contour shape Wb becomes the contour W (1).
- the contour extraction process is performed for the second time, the first contour shape Wa is the contour W (1), and the new second contour shape Wb is the contour W (2).
- the change rate Ra is used for the end determination.
- the change rate Ra is a ratio between the change area S of the first contour shape Wa and the second contour shape Wb and the sum V of the pixel values of the pixels included in the change area S.
- Such a change rate Ra has a relationship as shown in FIG.
- FIG. 5 is a diagram showing the relationship between the number T of contour extraction processes and the rate of change Ra.
- the horizontal axis indicates the number of times T of contour extraction processing that is repeatedly performed, and the vertical axis indicates the rate of change Ra.
- the contour W (n) gradually approaches the breast B contour of the subject M as shown in FIG. , Once rising, falling, and tend to settle around a certain value.
- the contour extraction process is performed with the number of processing times T near a certain value at which the change rate Ra is settled, an accurate contour shape is obtained.
- the rate of change Ra has a property of being settled to the same value every time without depending on the data for each two-dimensional reconstructed image G1.
- the contour extraction process searches the two-dimensional reconstructed image G1 for a pixel value gradient that occurs at the boundary between the accumulation amount of RI contained in the radiopharmaceutical in the breast B (skin of the breast B) and the noise of the pixels outside the breast B. Then, the contour shape of the breast B is extracted. Pixel noise in the vicinity of the breast B is caused by scattered radiation from the breast B or body, and the amount of scattered radiation is closely related to the amount of RI accumulated in the breast B.
- the amount of change S of the contour area in one contour extraction process decreases as the pixel value gradient increases as it approaches the breast B contour.
- the rate of change Ra in one contour extraction process has a property that it does not depend on the data for each two-dimensional reconstructed image (slice) G1 and settles to the same value every time.
- a threshold value P is set in advance using a plurality of sample data acquired in advance. The contour extraction process can be automatically performed at an appropriate number of processes T for each two-dimensional reconstructed image G1.
- some threshold values P are preset in the storage units 21, 33, etc., depending on the imaging conditions such as the conditions of the apparatus 1, the patient's body size, and the administration conditions of the radiopharmaceutical, and the repetitive control unit 39 stores the storage units 21, 33, etc. Read from and use properly. As a result, the contour extraction process can be automatically performed with the appropriate number of processes T for each imaging condition.
- the change rate Ra is calculated by the change area calculation unit 43, the pixel value total calculation unit 45, and the change rate calculation unit 47 as described above. That is, the change area calculation unit 43 calculates the change area S between the first contour shape Wa and the second contour shape Wb as shown in FIG.
- the pixel value total calculation unit 45 calculates the total V of the pixel values of the pixels included in the change area S.
- the end determination unit 49 determines whether or not the change rate Ra is smaller than a preset threshold value P.
- the repetition control unit 39 sets the second contour shape Wb as the first contour shape Wa when the end determination unit 49 determines that the change rate Ra is larger than the threshold value P. For example, when the second contour shape Wb is the contour W (1) in FIG. 4, the first contour shape Wa is set as the contour W (1) in FIG. Then, the repetition control unit 39 causes the contour extraction processing unit 41, the change area calculation unit 43, the pixel value total calculation unit 45, the change rate calculation unit 47, and the end determination unit 49 to execute again. When the end determination unit 45 determines that the change rate Ra is smaller than the threshold value P, the iterative control unit 39 outputs a two-dimensional contour image Gr1 including the second contour shape Wb.
- a contour image collection unit 37 that collects the two-dimensional contour image Gr1 and outputs the three-dimensional contour image Gr is provided at the subsequent stage of the contour determination unit 35.
- the iterative control unit 39 sequentially reads a plurality of two-dimensional reconstructed images G1 constituting the three-dimensional reconstructed image G, generates a two-dimensional contour image Gr1 from the two-dimensional reconstructed image G1, and generates a plurality of 2
- a three-dimensional contour image Gr is generated from the three-dimensional contour image Gr1.
- the end determination unit 49 may output a two-dimensional contour image Gr1 including the second contour shape Wb, the contour extraction processing unit 41, and the like. The above process may be executed again.
- the operation of the mammography PET apparatus 1 will be described. First, the overall operation of the mammography PET apparatus 1 will be described, and then the operation of the contour image generation unit 9 of the mammography PET apparatus 1 will be described.
- the operation of the mammography PET apparatus 1 will be described.
- a radiopharmaceutical is administered to the subject M, and the subject M is placed in the mammography PET apparatus 1.
- the breast B that is the imaging target of the subject M is housed between the plurality of ⁇ -ray detectors 7 arranged in a ring shape of the detector unit 3.
- Gamma rays are emitted from the breast B of the subject M.
- Two ⁇ rays are emitted in the opposite directions of 180 °.
- the two ⁇ rays are detected by the detector unit 3.
- the data collection unit 5 collects, as emission data E1, an event indicating that two ⁇ -ray detectors 7 have detected two ⁇ -rays within a certain period.
- the emission data E1 collected by the data collection unit 5 is subjected to absorption correction by the absorption correction unit 11.
- Absorption correction is performed using the three-dimensional contour image Gr generated by the contour image generator 9. That is, the absorption correction unit 11 performs absorption correction on the emission data E1 using an absorption map in which a preset absorption coefficient is uniformly assigned in the outline of the three-dimensional outline image Gr. Thereby, emission data E2 after absorption correction is obtained.
- the emission data E2 after the absorption correction is reconstructed into a three-dimensional PET image Gp by the reconstruction processing unit 13.
- the reconstructed three-dimensional PET image Gp is displayed on the display unit 17 and stored in the storage unit 21.
- the image displayed on the display unit 17 may be an arbitrary cross section in the three-dimensional PET image Gp, for example.
- the reconstruction processing unit 13 performs image reconstruction and absorption correction on the emission data E1 to generate a three-dimensional PET image Gp. .
- FIG. 7 is a flowchart illustrating the operation of the contour image generation unit 9 according to the first embodiment.
- the reconstruction processing unit 31 reconstructs the emission data E1 collected by the data collection unit 5, and generates a three-dimensional reconstruction image G of the breast B of the subject M.
- the generated three-dimensional reconstructed image G is stored in the storage unit 33.
- the repetitive control unit 39 is a plurality of two-dimensional reconstructed images G1 constituting the three-dimensional reconstructed image G stored in the storage unit 33 (see FIG. 3).
- One sheet of the two-dimensional reconstructed image G1 is read and sent to the contour extraction processing unit 41.
- the repetition control unit 39 sends the initial contour W (0) to the contour extraction processing unit 41 from the storage units 21 and 33 that store information such as the initial contour W (0) and the threshold P, and ends the threshold P.
- the data is sent to the determination unit 49.
- Step ST02 Contour Extraction Processing
- the contour extraction processing unit 41 starts a new one from the preset first contour shape Wa, which is repeatedly performed by the contour extraction model (for example, level setting method) in the acquired two-dimensional reconstructed image G1.
- the contour extraction model for example, level setting method
- one contour extraction processing is performed.
- the initial contour W (0) is set in the first contour shape Wa, and a new contour extraction process results in a new contour extraction process.
- a contour W (1) is obtained as the second contour shape Wb.
- Step ST03 Calculation of Change Area
- the change area calculation unit 43 calculates a change area S between the first contour shape Wa and the second contour shape Wb.
- the change area S is obtained from the difference between the second contour shape Wb and the first contour shape Wa.
- the change area S is a region indicated by diagonal lines.
- Step ST04 Calculation of Total Pixel Value
- the pixel value total calculation unit 45 calculates the total V of the pixel values of the pixels included in the change area S. That is, the pixel value total calculation unit 45 calculates the sum (total) V of the pixel values of the pixels included in the change area S as shown in FIG.
- Step ST05 Calculation of Change Rate
- Step ST10 End determination (change rate ⁇ threshold)
- the end determination unit 49 determines whether or not the change rate Ra is smaller than a preset threshold value P.
- the repetition control unit 39 first sets the second contour shape Wb as the first contour shape Wa.
- the repetition control unit 39 sets the contour W (1) as the first contour shape Wa.
- the repetition control unit 39 causes the contour extraction processing unit 41, the change area calculation unit 43, the pixel value total calculation unit 45, the change rate calculation unit 47, and the end determination unit 49 to be executed again. That is, the repetition control unit 39 executes the above-described steps ST02 to ST10 again.
- Step ST11 Output of two-dimensional contour image
- the end determination unit 49 determines that the repetition control unit 39 is smaller than the threshold value P (see FIG. 5)
- the iterative control unit 39 performs the process on all or necessary two-dimensional reconstructed images G1 constituting the three-dimensional reconstructed image G, and outputs a plurality of two-dimensional contour images Gr1. Since each two-dimensional contour image Gr1 is determined based on the threshold value P, the contour extraction process is automatically performed with an appropriate number of processes, and the accuracy is high.
- the contour image collection unit 37 collects each output two-dimensional contour image Gr1 and outputs a three-dimensional contour image Gr. Each two-dimensional contour image Gr1 has a contour shape extracted with high accuracy. Therefore, the output three-dimensional contour image Gr also has a precise contour shape.
- the contour extraction processing unit 41 starts a new one from the preset first contour shape Wa, which is repeatedly performed on the two-dimensional reconstructed image G1 by the contour extraction model.
- the contour extraction processing for extracting the second contour shape Wb one contour extraction processing is performed.
- the end determination unit 49 determines whether or not the change rate Ra is smaller than a preset threshold value P.
- the change rate Ra is calculated as follows.
- the change area calculation unit 43 calculates the change area S between the first contour shape Wa and the second contour shape Wb, and the pixel value total calculation unit 45 calculates the total V of the pixel values of the pixels included in the change area S. To do.
- the change rate calculation unit 47 calculates a change rate Ra that is a ratio of the change area S to the total V.
- the repetition control unit 39 sets the second contour shape Wb as the first contour shape Wa when the end determination unit 49 determines that the change rate Ra is greater than the threshold value P, and performs processing such as the contour extraction processing unit 41 and the like.
- the end determination unit 49 determines that the change rate Ra is smaller than the threshold value P, the two-dimensional contour image Gr1 including the second contour shape Wb is output.
- the rate of change Ra which is the ratio of the changed area S and the total pixel value V of the pixels included in the changed area S, has the same value every time without depending on the data for each two-dimensional reconstructed image G1. It has a calming nature.
- a threshold value P is set in advance using a plurality of sample data acquired in advance.
- the iterative control unit 39 outputs a two-dimensional contour image Gr1 including the second contour shape Wb.
- the two-dimensional reconstructed image G1 is one of a plurality of two-dimensional reconstructed images G1 constituting the three-dimensional reconstructed image G generated by reconstruction (see FIG. 3), and the repetitive control unit 39. Generates a three-dimensional contour image Gr from the plurality of output two-dimensional contour images Gr1. For example, when the contour extraction processing is performed with the processing count T fixed, even if the processing count T is appropriate for a certain image, the processing count T is high or low for other images.
- the two-dimensional contour image Gr1 can be generated with an appropriate number of processing times T for each two-dimensional reconstructed image (slice) G1.
- the two-dimensional reconstructed image G1 at both ends of the code H has a lower statistical accuracy because the sensitivity is lower than the two-dimensional reconstructed image G1 at the center of the code C due to the configuration of the detector unit 3. . Therefore, if the contour extraction process is performed with the same number of processes T as the two-dimensional reconstructed image G1 at the center of the code C, the accuracy of the contour shape to be acquired is deteriorated.
- the rate of change Ra is calculated for each two-dimensional reconstructed image (slice) G1, and the end determination is performed based on the threshold value P. Therefore, only the two-dimensional reconstructed image G1 at the center of the code C is used.
- the contour shape can be accurately extracted even in the two-dimensional reconstructed image G1 at the end of the symbol H.
- FIG. 8 is a diagram illustrating a configuration of the contour image generation unit 9 according to the second embodiment. Note that description of the same components as those in the first embodiment is omitted.
- Example 1 in the contour image generation unit 9, the determination by the end determination unit 49 is performed for each contour extraction process.
- the determination by the end determination unit 49 is performed for each of a plurality of contour extraction processes.
- the contour image generation unit 9 of the present embodiment further counts the number of times T of the contour extraction process, and determines the number of times of processing to determine whether the number of times T has reached the number of breaks K.
- a determination unit 51 is provided. For example, when the number of breaks K is set to 5, the processing count determination unit 51 counts the number of times T of the contour extraction processing in the contour extraction processing unit 41, and the contour extraction processing unit 41, the change area calculation unit 43, The determination is performed so that the processes of the pixel value total calculation unit 45 and the change rate calculation unit 47 are repeated five times.
- FIG. 9 is a flowchart illustrating the operation of the contour image generation unit 9 according to the second embodiment.
- the description which overlaps with Example 1 shall be abbreviate
- Step ST01 Reading of two-dimensional reconstructed image
- the repetitive control unit 39 among the plurality of two-dimensional reconstructed images G1 constituting the three-dimensional reconstructed image G stored in the storage unit 33 (see FIG. 3), 1
- the two two-dimensional reconstructed images G1 are read out and sent to the contour extraction processing unit 41.
- the repetition control unit 39 reads the initial contour W (0) from the storage units 21 and 33 that store information such as the initial contour W (0), the threshold value P, and the number of breaks K, and the like to the contour extraction processing unit 41.
- the threshold value P is read and sent to the end determination unit 49
- the number of breaks K is read and sent to the processing number determination unit 51. Note that before the processing, the processing count T is “0”.
- the contour extraction processing unit 41 performs one contour extraction processing using a contour extraction model (for example, a level set method) on the acquired two-dimensional reconstructed image G1. That is, the contour extraction processing unit 41 extracts the contour W (1) that is the second contour shape Wb from the initial contour W (0) that is the first contour shape Wa.
- a contour extraction model for example, a level set method
- Step ST03 Calculation of Change Area
- the change area calculation unit 43 calculates the change area S between the first contour shape Wa and the second contour shape Wb for each processing count T. For example, if the number of breaks K is 5, the change area S is calculated for each processing number T, and the change areas S1 to S5 for 5 times are calculated.
- the total pixel value calculation unit 45 calculates the total pixel value V of the pixels included in the change area S for each processing count T. For example, if the number of divisions K is 5, the total V of pixel values is calculated for each processing number T, and the total V1 to V5 for 5 times is calculated.
- the change rate calculation unit 47 calculates the change rate Ra for each delimiter count K, which is the ratio of the sum of the change areas S and the sum of the total Vs. For example, as described above, when the number of breaks K is 5, there are 5 change areas S1 to S5 and 5 times total V1 to V5.
- Step ST06 Determination of number of processes (number of processes ⁇ number of breaks)
- the repetition control unit 39 sets the second contour shape Wb as the first contour shape Wa. Then, the repetition control unit 39 causes the contour extraction processing unit 41, the change area calculation unit 43, the pixel value total calculation unit 45, the change rate calculation unit 47, and the processing number determination unit 51 to be executed again. That is, the repetition control unit 39 performs the above-described steps ST02 to ST06 again.
- Step ST10 End Determination
- the end determination unit 49 determines whether or not the rate of change Ra is smaller than a preset threshold value P.
- the repetition control unit 39 first sets the second contour shape Wb as the first contour shape Wa.
- the repetition control unit 39 sets the contour W (5) as the first contour shape Wa.
- the iterative control unit 39 causes the contour extraction processing unit 41, the change area calculation unit 43, the pixel value total calculation unit 45, the change rate calculation unit 47, and the end determination unit 49 to be executed again. That is, the repetition control unit 39 executes the above-described steps ST02 to ST10 again.
- Step ST11 Output of a two-dimensional contour image
- the repeat control unit 39 outputs a two-dimensional contour image Gr1 including the second contour shape Wb when the end determination unit 49 determines that the threshold value P is smaller than the threshold value P.
- steps ST01 to ST11 in FIG. 9 are performed on all or a plurality of necessary two-dimensional reconstructed images G1 constituting the three-dimensional reconstructed image G, and a plurality of two-dimensional contour images Gr1 are output. .
- the processing number determination unit 51 is not provided and the end determination is performed for each processing number T, but the determination processing is performed for each number of separations K, that is, for each of a plurality of processing times T. Is going.
- the change rate calculation unit 47 calculates a change rate Ra for each delimiter count K, which is a ratio of the sum of the change areas S and the sum of the pixel value sums V. Therefore, the end determination unit 49 performs determination using the rate of change Ra calculated as the average value for each number of breaks K. As a result, it is possible to prevent the contour extraction process from being finished before the change rate Ra is settled due to a change in the change rate Ra for each processing count, and to generate the two-dimensional contour image Gr1 with the appropriate processing count T. it can.
- the change rate Ra is calculated by the change rate calculation unit 47 for each processing count T.
- the change amount calculation unit 47 is provided between the processing count determination unit 51 and the end determination unit 49.
- the processing number determination unit 51 determines that the processing number T has reached the delimiter number K, the change rate Ra may be calculated.
- the processing number determination unit 51 is not limited to the position of FIG. 8 as long as the change rate Ra for each number of divisions K can be calculated.
- the present invention is not limited to the above embodiment, and can be modified as follows.
- the number of breaks K in the second embodiment described above may be variable. That is, when the number of divisions K is reached, the next number of divisions K may be set to a number different from the previous number of divisions K.
- the processing number T in which the difference between the change rate Ra and the threshold value P is large a relatively large number of processing times T is set as the separation number K
- a small processing count T is set as the delimiter count K.
- the number of breaks K may be decreased as the number of processes T reaches the number of breaks K. That is, when the number of breaks K is reached, the next number of breaks K is set to a number less than the previous number of breaks K or the same number as the previous number of breaks K. As a result, it is possible to accurately extract the contour shape with an appropriate number of processing times T, while reducing the number of end determinations.
- the contour image generation unit 9 generates a three-dimensional contour image Gr from the three-dimensional reconstructed image G.
- the contour image generation unit 9 may generate the two-dimensional contour image Gr1 from the two-dimensional reconstruction image G1.
- the mammography PET apparatus 1 has been described as an example of a nuclear medicine diagnostic apparatus, but is not limited thereto.
- the nuclear medicine diagnostic apparatus may be a modality such as a head PET apparatus that images the head of the subject M, a head PET / CT apparatus, or a head PET / SPECT apparatus. That is, the present invention can be applied to a nuclear medicine diagnostic apparatus that images an object that can be regarded as a relatively single absorber.
- contour S (S1, S2, S3-Sn) ... Change area V (V1, V2, V3 to Vn) ... Sum of pixel values of pixels included in change area Ra ... Change rate P ... Threshold Gr1 ... Two-dimensional contour image Gr ... Three-dimensional wheel Guo image K ... Number of breaks T ... Number of processes
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Abstract
Description
すなわち、本発明に係る輪郭画像生成装置は、被検体から放出された放射線を検出して取得した被検体の2次元再構成画像に対し、輪郭抽出モデルにより繰り返し行われる、予め設定された第1輪郭形状から新たな第2輪郭形状を抽出する輪郭抽出処理のうち、1回の輪郭抽出処理を行う輪郭抽出処理部と、前記第1輪郭形状と前記第2輪郭形状との変化面積を算出する変化面積算出部と、前記変化面積に含まれる画素の画素値の合計を算出する画素値合計算出部と、前記変化面積と前記合計との比である変化率を算出する変化率算出部と、前記変化率が予め設定された閾値よりも小さいか否かを判定する終了判定部と、前記終了判定部で前記変化率が前記閾値よりも大きいと判定された場合に前記第2輪郭形状を前記第1輪郭形状として設定し、前記輪郭抽出処理部、前記変化面積算出部、前記画素値合計算出部、前記変化率算出部および前記終了判定部の処理を再度実行させ、前記終了判定部で前記変化率が前記閾値よりも小さいと判定された場合に、前記第2輪郭形状を含む2次元輪郭画像を出力する制御部と、を備えていることを特徴とするものである。
次に、本発明の特徴部分である輪郭画像生成部9の構成を具体的に説明する。図2は、実施例1に係る輪郭画像生成部9の構成を示す図である。まず、輪郭画像生成部9の概要を説明する。
マンモグラフィ用PET装置1の動作を説明する。被検体Mに放射性薬剤を投与し、マンモグラフィ用PET装置1に被検体Mを配置する。このとき、被検体Mの撮像対象である***Bは、検出器ユニット3のリング状に配置した複数のγ線検出器7の間に収められる。被検体Mの***Bからγ線が放出される。放出するγ線は、180°反対方向に2本される。この2本のγ線を検出器ユニット3で検出する。データ収集部5は、一定期間内に2つのγ線検出器7で2本のγ線を検出したことを示す事象をエミッションデータE1として収集する。
次に、本発明の特徴部分である輪郭画像生成部9の動作を説明する。図7は、実施例1に係る輪郭画像生成部9の動作を示すフローチャートである。輪郭画像生成部9において、再構成処理部31は、データ収集部5で収集したエミッションデータE1を再構成し、被検体Mの***Bの3次元再構成画像Gを生成する。生成された3次元再構成画像Gは、記憶部33に記憶される。
繰り返し制御部39は、記憶部33に記憶された3次元再構成画像Gを構成する複数の2次元再構成画像G1のうち(図3参照)、1枚の2次元再構成画像G1を読み出し、輪郭抽出処理部41に送る。また、繰り返し制御部39は、初期輪郭W(0)および閾値Pなどの情報を記憶する記憶部21,33等から、初期輪郭W(0)を輪郭抽出処理部41に送り、閾値Pを終了判定部49に送る。
輪郭抽出処理部41は、取得した2次元再構成画像G1において、輪郭抽出モデル(例えばレベルセット法)により繰り返し行われる、予め設定された第1輪郭形状Waから新たな第2輪郭形状Wbを抽出する輪郭抽出処理のうち、1回の輪郭抽出処理を行う。図4の2次元再構成画像G1において、例えば、輪郭抽出処理が1回目の場合、第1輪郭形状Waには、初期輪郭W(0)が設定され、1回の輪郭抽出処理により、新たな第2輪郭形状Wbとして輪郭W(1)が得られる。
変化面積算出部43は、第1輪郭形状Waと第2輪郭形状Wbとの変化面積Sを算出する。変化面積Sは、第2輪郭形状Wbと第1輪郭形状Waとの差分により求められる。図6において、変化面積Sは、斜線で示される領域である。
変化面積算出部43で変化面積Sが算出された後、画素値合計算出部45は、その変化面積Sに含まれる画素の画素値の合計Vを算出する。すなわち、画素値合計算出部45は、図6のような変化面積Sに含まれる画素の画素値の合計(総和)Vを算出する。
変化率算出部47は、変化面積Sと合計Vとの比である変化率Ra(=S/V)を算出する。
終了判定部49は、変化率Raが予め設定された閾値Pよりも小さいか否かを判定する。繰り返し制御部39は、終了判定部49で変化率Raが閾値Pよりも大きいと判定された場合に、まず、第2輪郭形状Wbを第1輪郭形状Waとして設定する。例えば、第2輪郭形状Wbが輪郭W(1)の場合、繰り返し制御部39は、輪郭W(1)を第1輪郭形状Waとして設定する。そして、繰り返し制御部39は、輪郭抽出処理部41、変化面積算出部43、画素値合計算出部45、変化率算出部47および終了判定部49を再度実行させる。すなわち、繰り返し制御部39は、上述のステップST02~ステップST10を再度実行する。
繰り返し制御部39は、終了判定部49で閾値Pよりも小さいと判定された場合に(図5参照)、第2輪郭形状Wbを含む2次元輪郭画像Gr1を出力する。
次に、本実施例の輪郭画像生成部9の動作を説明する。図9は、実施例2に係る輪郭画像生成部9の動作を示すフローチャートである。なお、実施例1と重複する説明は、適宜省略するものとする。
繰り返し制御部39は、記憶部33に記憶された3次元再構成画像Gを構成する複数の2次元再構成画像G1のうち(図3参照)、1枚の2次元再構成画像G1を読み出して、輪郭抽出処理部41に送る。また、繰り返し制御部39は、初期輪郭W(0)、閾値Pおよび区切り回数Kなどの情報を記憶する記憶部21,33等から、初期輪郭W(0)を読み出して輪郭抽出処理部41に送り、閾値Pを読み出して終了判定部49に送り、そして、区切り回数Kを読み出して処理回数判定部51に送る。なお、処理前は、処理回数Tは“0”である。
輪郭抽出処理部41は、取得した2次元再構成画像G1において、輪郭抽出モデル(例えばレベルセット法)による1回の輪郭抽出処理を行う。すなわち、輪郭抽出処理部41は、第1輪郭形状Waである初期輪郭W(0)から第2輪郭形状Wbである輪郭W(1)を抽出する。
変化面積算出部43は、処理回数Tごとに第1輪郭形状Waと第2輪郭形状Wbとの変化面積Sを算出する。例えば、区切り回数Kが5回であれば、処理回数Tごとに変化面積Sを算出し、5回分の変化面積S1~S5が算出される。
画素値合計算出部45は、処理回数Tごとに変化面積Sに含まれる画素の画素値の合計Vを算出する。例えば、区切り回数Kが5回であれば、処理回数Tごとに画素値の合計Vを算出し、5回分の合計V1~V5が算出される。
変化率算出部47は、変化面積Sの総和と合計Vの総和との比である区切り回数Kごとの変化率Raを算出する。例えば、上述のように、区切り回数Kが5回の場合、5回分の変化面積S1~S5と5回分の合計V1~V5とが存在する。変化率Raは、Ra=(S1+S2+S3+S4+S5)/(V1+V2+V3+V4+V5)で算出される。
処理回数判定部51は、輪郭抽出処理の処理回数Tをカウントし、処理回数Tが区切り回数Kに達したか否かを判定する。例えば、処理回数判定部51は、処理回数Tが1回(T=1)の場合は、処理回数Tが区切り回数Kに達していないと判定する。繰り返し制御部39は、処理回数判定部51で処理回数Tが区切り回数Kに達していないと判定した場合には、第2輪郭形状Wbを第1輪郭形状Waとして設定する。そして、繰り返し制御部39は、輪郭抽出処理部41、変化面積算出部43、画素値合計算出部45、変化率算出部47および処理回数判定部51を再度実行させる。すなわち、繰り返し制御部39は、上述のステップST02~ステップST06を再度実行する。
繰り返し制御部39は、処理回数判定部51で処理回数Tが区切り回数Kに達した(T≧K)と判定した場合には、処理回数Tをリセットする(T=0)。そして、繰り返し制御部39は、ステップST10の終了判定部49による判定を行う。
終了判定部49は、変化率Raが予め設定された閾値Pよりも小さいか否かを判定する。繰り返し制御部39は、終了判定部41で閾値Pよりも大きいと判定された場合に、まず、第2輪郭形状Wbを第1輪郭形状Waとして設定する。繰り返し制御部39は、例えば、第2輪郭形状Wbが輪郭W(5)の場合、輪郭W(5)を第1輪郭形状Waとして設定する。そして、繰り返し制御部39は、輪郭抽出処理部41、変化面積算出部43、画素値合計算出部45、変化率算出部47および終了判定部49を再度実行させるようになっている。すなわち、繰り返し制御部39は、上述のステップST02~ステップST10を再度実行する。
繰り返し制御部39は、終了判定部49で閾値Pよりも小さいと判定された場合に、第2輪郭形状Wbを含む2次元輪郭画像Gr1を出力する。
3 … 検出器ユニット
5 … データ収集部
7 … γ線検出器
9 … 輪郭画像生成部
15 … 主制御部
31 … 再構成処理部
39 … 繰り返し制御部
41 … 輪郭抽出処理部
43 … 変化面積算出部
45 … 画素値合計算出部
47 … 変化率算出部
49 … 終了判定部
51 … 処理回数判定部
M … 被検体
B … ***
E1 … エミッションデータ
G … 3次元再構成画像
G1 … 2次元再構成画像
Wa … 第1輪郭形状
Wb … 第2輪郭形状
W(0),W(1),W(2),…,W(n)… 輪郭
S(S1,S2,S3~Sn)… 変化面積
V(V1,V2,V3~Vn)… 変化面積に含まれる画素の画素値の合計
Ra … 変化率
P … 閾値
Gr1 … 2次元輪郭画像
Gr … 3次元輪郭画像
K … 区切り回数
T … 処理回数
Claims (7)
- 被検体から放出された放射線を検出して取得した被検体の2次元再構成画像に対し、輪郭抽出モデルにより繰り返し行われる、予め設定された第1輪郭形状から新たな第2輪郭形状を抽出する輪郭抽出処理のうち、1回の輪郭抽出処理を行う輪郭抽出処理部と、
前記第1輪郭形状と前記第2輪郭形状との変化面積を算出する変化面積算出部と、
前記変化面積に含まれる画素の画素値の合計を算出する画素値合計算出部と、
前記変化面積と前記合計との比である変化率を算出する変化率算出部と、
前記変化率が予め設定された閾値よりも小さいか否かを判定する終了判定部と、
前記終了判定部で前記変化率が前記閾値よりも大きいと判定された場合に前記第2輪郭形状を前記第1輪郭形状として設定し、前記輪郭抽出処理部、前記変化面積算出部、前記画素値合計算出部、前記変化率算出部および前記終了判定部の処理を再度実行させ、前記終了判定部で前記変化率が前記閾値よりも小さいと判定された場合に、前記第2輪郭形状を含む2次元輪郭画像を出力する制御部と、を備えていることを特徴とする輪郭画像生成装置。 - 請求項1に記載の輪郭画像生成装置において、
前記輪郭抽出処理の処理回数をカウントし、前記処理回数が区切り回数に達したか否かを判定する処理回数判定部を更に備え、
前記変化率算出部は、前記変化面積の総和と前記合計の総和との比である区切り回数ごとの変化率を算出し、
前記制御部は、前記処理回数判定部で前記処理回数が前記区切り回数に達していないと判定した場合には、前記第2輪郭形状を前記第1輪郭形状として設定し、前記輪郭抽出処理部、前記変化面積算出部、前記画素値合計算出部および前記処理回数判定部の処理を再度実行させ、前記処理回数判定部で前記処理回数が前記区切り回数に達したと判定した場合には、前記処理回数をリセットすると共に前記終了判定部による判定を行い、
前記制御部は、前記終了判定部で前記変化率が前記閾値よりも大きいと判定された場合に前記第2輪郭形状を前記第1輪郭形状として設定し、前記輪郭抽出処理部、前記変化面積算出部、前記画素値合計算出部、前記変化率算出部、前記処理回数判定部および前記終了判定部の処理を再度実行させることを特徴とする輪郭画像生成装置。 - 請求項2に記載の輪郭画像生成装置において、
前記区切り回数は、可変であることを特徴とする輪郭画像生成装置。 - 請求項3に記載の輪郭画像生成装置において、
前記区切り回数は、前記処理回数が前記区切り回数に達するほど少なくすることを特徴とする輪郭画像生成装置。 - 請求項2に記載の輪郭画像生成装置において、
前記区切り回数は、一定であることを特徴とする輪郭画像生成装置。 - 請求項1から5のいずれかに記載の輪郭画像生成装置において、
前記2次元再構成画像は、再構成して生成された3次元再構成画像を構成する複数枚の2次元再構成画像のいずれかであり、
前記制御部は、出力された複数枚の前記2次元輪郭画像から3次元輪郭画像を生成することを特徴とする輪郭画像生成装置。 - 複数の検出器がリング状に配置し、被検体から放出された放射線を検出する検出器ユニットと、
前記検出器ユニットで検出された放射線に基づき、エミッションデータを収集するデータ収集部と、
前記エミッションデータを再構成して2次元再構成画像を取得する再構成処理部と、
前記2次元再構成画像に対し、輪郭抽出モデルにより繰り返し行われる、予め設定された第1輪郭形状から新たな第2輪郭形状を抽出する輪郭抽出処理のうち、1回の輪郭抽出処理を行う輪郭抽出処理部と、
前記第1輪郭形状と前記第2輪郭形状との変化面積を算出する変化面積算出部と、
前記変化面積に含まれる画素の画素値の合計を算出する画素値合計算出部と、
前記変化面積と前記合計との比である変化率を算出する変化率算出部と、
前記変化率が予め設定された閾値よりも小さいか否かを判定する終了判定部と、
前記終了判定部で前記変化率が前記閾値よりも大きいと判定された場合に前記第2輪郭形状を前記第1輪郭形状として設定し、前記輪郭抽出処理部、前記変化面積算出部、前記画素値合計算出部、前記変化率算出部および前記終了判定部の処理を再度実行させ、前記終了判定部で前記変化率が前記閾値よりも小さいと判定された場合に、前記第2輪郭形状を含む2次元輪郭画像を出力する制御部と、を備えていることを特徴とする核医学診断装置。
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