JP5068334B2 - Medical image conversion apparatus and method, and program - Google Patents

Description

  The present invention provides a medical image obtained by converting a series of medical images acquired by performing imaging using a contrast agent, for example, so that a signal value changes with time, for volume rendering display or the like. The present invention relates to a conversion apparatus and method, and a program for causing a computer to execute a medical image conversion method.

  In recent years, high-quality three-dimensional images have been used for image diagnosis due to advances in medical equipment (for example, multi-detector CT). Here, since a three-dimensional image is composed of a large number of two-dimensional tomographic images and has a large amount of information, it may take time for a doctor to find and diagnose a desired observation site. Accordingly, the structure of interest is recognized by using a method such as a maximum value projection method (MIP method) and a minimum value projection method (MinIP method) from a three-dimensional image including the structure of interest, for example. By creating a 3D image and performing MIP display, 3D image volume rendering (VR) display, or CPR (Curved Planer Reconstruction) display, the entire structure, and further the structure Various techniques for improving the visibility of lesions contained in objects have been proposed.

  By the way, in the multi-detector type CT described above, a large number of tomographic images can be acquired at once using a plurality of detectors, and it is now possible to acquire a tomographic image exceeding 300 slices in one rotation. It has become. Further, since the time required for one rotation of the detector is about 0.3 seconds, it is possible to acquire a plurality of three-dimensional images in time series at short time intervals if only a specific organ is used. In this way, the organs of interest included in the three-dimensional image acquired in time series are displayed in time series order, that is, by displaying the three-dimensional time including the time in three dimensions, the moving image can be displayed as the moving organ of interest. It is possible to observe as seen (see Patent Document 1).

  Thus, by displaying a three-dimensional image four-dimensionally, heart analysis and the like can be performed particularly in the cardiovascular field. Moreover, when acquiring a three-dimensional image using a contrast agent as well as organs with motion such as the heart and lungs, the flow of the contrast agent is displayed in four dimensions, so that the liver, brain, etc. It becomes possible to diagnose a specific organ.

  When a three-dimensional image is displayed in VR, the organ of interest is extracted, and the signal value of each pixel is determined according to the signal value (CT value in the case of a CT image) of each pixel position of the extracted three-dimensional image of the organ. A color (R, G, B) and opacity (opacity) are set for the three-dimensional display. Four-dimensional display of a three-dimensional image is performed by setting a color and opacity for each of a plurality of three-dimensional images, creating a VR image, and displaying the created VR images in chronological order.

JP 2005-322252 A

  By the way, in a series of three-dimensional images obtained by photographing a moving organ such as the heart and lungs in a time series order at short time intervals, the corresponding pixel position of the organ included in each of the three-dimensional images having different time phases is obtained. Signal values are often the same. On the other hand, a three-dimensional image acquired by photographing at a short time interval in time series using a contrast agent is included in each of the three-dimensional images because the purpose is to diagnose temporal changes in signal values. Signal values at pixel positions of the same tissue are often different. Depending on the tissue, the signal value is the same in a three-dimensional medical image in a certain time phase, but the signal value may be different in a three-dimensional medical image in another time phase. As described above, if the signal value is different even in the same tissue according to the time phase, or if the signal value is the same even in different tissues, the different tissues are distinguished when the VR image is displayed four-dimensionally. It cannot be displayed separately. Further, if different tissues cannot be distinguished and displayed in this way, accurate diagnosis may not be possible.

  The present invention has been made in view of the above circumstances, and an object thereof is to make it possible to distinguish different tissues when displaying a series of medical images, for example, in chronological order.

The medical image conversion apparatus according to the present invention includes an image acquisition means for acquiring a series of a plurality of medical images for a specific part;
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. Conversion means for converting to a corresponding display pixel value.

  “A series of medical images” is obtained by continuously capturing specific portions of the same subject at short time intervals, and displaying changes in signal values in the medical images by displaying them in time series order. A plurality of medical images capable of being used can be used. It is also possible to use a plurality of medical images that are acquired by performing imaging using a plurality of types of radiation having different energies and that can display changes in signal values in the medical images by displaying in order of energy. In addition, any type of medical image can be used. Specifically, a three-dimensional image, a three-dimensional specific organ image extracted from the three-dimensional image, a two-dimensional image at a specific slice position including the specific organ in the three-dimensional image, or a specific acquired by simple X-ray imaging An organ image or the like can be used.

In the medical image conversion apparatus according to the present invention, a reference first signal value, a second signal value obtained by changing the first signal value, and a display for the first and second signal values. It further comprises storage means for storing a color template that defines the relationship between pixel values,
The conversion means may be means for converting the signal value of each pixel position of the target medical image into the display pixel value with reference to the color template with the reference medical image as a reference.

The medical image conversion apparatus according to the present invention further includes storage means for storing a reference first signal value and a color template that defines a relationship between display pixel values with respect to the first signal value,
The converting means converts the signal value at each pixel position of the reference medical image into the display pixel value with reference to the color template, and converts the signal value at each pixel position of the target medical image and the reference medical image. The display pixel value corresponding to each pixel position of the reference medical image is corrected according to the index value representing the amount of change from the signal value of the corresponding pixel position, and the signal value of each pixel position of the target medical image is Means for converting the display pixel value to be corrected may be used.

The medical image conversion apparatus according to the present invention further includes storage means for storing a first signal value serving as a reference and a color template representing a relationship between display pixel values with respect to the first signal value,
The converting means converts the signal value at each pixel position of the reference medical image into the display pixel value with reference to the color template, and converts the signal value at each pixel position of the target medical image and the reference medical image. The display pixel value corresponding to each pixel position of the reference medical image is corrected according to the index value representing the amount of change from the signal value of the corresponding pixel position, and the signal value of each pixel position of the reference medical image is Means for converting the display pixel value to be corrected may be used.

  The “index value representing the amount of change” may be any index value that can represent the difference between the signal value of each pixel position of the target medical image and the signal value of the corresponding pixel position of the reference medical image. In addition to the difference value from the signal value at the corresponding pixel position of the medical image, an absolute value of the difference value, a logarithmic value of the difference value, or the like can be used.

  The medical image conversion apparatus according to the present invention may further include display means for displaying the converted series of medical images in time series when the medical images are acquired in time series. Good.

  In the medical image conversion apparatus according to the present invention, when the medical images are acquired in time series order, the time phase of the target medical image obtained by correcting the converted reference medical image with the corrected display pixel value. In addition, display means for displaying in chronological order may be further provided.

  In the medical image conversion apparatus according to the present invention, the series of medical images may be acquired by performing imaging using a plurality of types of radiation having different energies.

  The medical image conversion apparatus according to the present invention may further include alignment means for aligning pixel positions of the series of medical images between the series of medical images.

  In this case, smoothing means for smoothing the series of medical images may be further provided before the alignment.

  In the medical image conversion apparatus according to the present invention, the medical image may be a three-dimensional medical image.

  In the medical image conversion apparatus according to the present invention, the medical image may be taken using a contrast agent.

The medical image conversion method according to the present invention acquires a series of a plurality of medical images for a specific part,
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. The display pixel value is converted into a corresponding value.

  The medical image conversion method according to the present invention may be provided as a program for causing a computer to execute the method.

  According to the present invention, a series of a plurality of medical images for a specific part is acquired, and for a target medical image to be converted in the series of medical images, a signal value at each pixel position of the target medical image is used as a reference. The reference pixel image is converted into a display pixel value corresponding to the amount of change from the signal value at each corresponding pixel position of the reference medical image. For this reason, even if the signal values of different tissues are the same in a certain target medical image, display can be performed with different display pixel values if they change over time. Therefore, different tissues can be distinguished and displayed by different display pixel values, and as a result, diagnosis using a series of medical images displayed in a predetermined order can be performed accurately.

  Also, refer to a color template that defines a reference first signal value, a second signal value obtained by changing the first signal value, and a relationship between display pixel values with respect to the first and second signal values. By converting the signal value at each pixel position of the target medical image into the display pixel value with reference to the reference medical image, even in a tissue that changes the same signal value over time, for example, the signal in the reference medical image If the values are different, it can be converted into different display pixel values by appropriately setting the color template. Further, even if the signal values of the same tissue are different, the tissues originally have the same signal value. Therefore, if a medical image having the same signal value is used as a reference medical image, the same display pixel value is used. Can be displayed.

  In addition, referring to the first signal value as a reference and the color template representing the relationship between the display pixel value and the first signal value, the signal value at each pixel position of the reference medical image is converted into the display pixel value, and the target The display pixel value corresponding to each pixel position of the reference medical image is corrected according to the index value representing the amount of change between the signal value of each pixel position of the medical image and the signal value of the corresponding pixel position of the reference medical image. By converting the signal value at each pixel position of the target medical image to a corrected display pixel value, the change in the signal value can be reliably reflected in the change in the display pixel value. Therefore, by making a reference medical image a medical image in which the same tissue has the same signal value and different tissue has a different signal value, it is possible to reliably change the signal value in a series of medical images displayed in a predetermined order. Can be recognized.

  In addition, referring to the first signal value as a reference and the color template representing the relationship between the display pixel value and the first signal value, the signal value at each pixel position of the reference medical image is converted into the display pixel value, and the target The reference medical image is corrected by correcting the display pixel value corresponding to each pixel position of the reference medical image according to the amount of change between the signal value of each pixel position of the medical image and the signal value of the corresponding pixel position of the reference medical image. By converting the signal value at each pixel position into the corrected display pixel value, the change in the signal value can be reliably reflected in the change in the display pixel value. Accordingly, the same tissue has the same signal value, and different tissues have different signal values as reference medical images, so that the corrected display pixel values are obtained in a predetermined order in accordance with the target medical image. It is possible to reliably recognize a change in signal value in a series of displayed reference medical images.

1 is a schematic block diagram showing the configuration of a medical image conversion apparatus according to a first embodiment of the present invention. The figure which shows the color template for converting 3D volume data in 1st Embodiment. The figure for demonstrating conversion to a display pixel value The flowchart which shows the process performed in 1st Embodiment. 1 is a schematic block diagram showing the configuration of a medical image conversion apparatus according to a first embodiment of the present invention. The figure which shows the color template for converting 3D volume data in 2nd Embodiment. The figure which shows the part where the signal value change amount becomes the maximum The flowchart which shows the process performed in 2nd Embodiment. The flowchart which shows the process performed in 3rd Embodiment The schematic block diagram which shows the structure of the medical image converter by other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a medical image conversion apparatus according to the first embodiment of the present invention. The configuration of the medical image conversion apparatus 1 shown in FIG. 1 is realized by executing a medical image conversion processing program read into the auxiliary storage device on a computer. At this time, the medical image conversion processing program is stored in a storage medium such as a CD-ROM or distributed via a network such as the Internet and installed in a computer.

  The medical image conversion apparatus 1 according to the first embodiment includes a volume data acquisition unit 10, a storage unit 20, a registration unit 30, a conversion unit 40, a display control unit 50, and an input unit 60.

  The volume data acquisition unit 10 is a three-dimensional volume data group 110 including a plurality of three-dimensional volume data 100 obtained by photographing a specific part of a subject at a predetermined time interval Δt in a modality 2 such as a CT apparatus or an MRI apparatus. The communication interface function is acquired. The three-dimensional volume data group 110 is transmitted from the modality 2 via the LAN. Further, in the present embodiment, a three-dimensional volume data group 110 representing a state in which the contrast agent flows is obtained by administering a contrast medium to the subject and photographing the abdomen of the subject using a CT apparatus, with the specific region being the liver. Shall be acquired.

  Here, the three-dimensional volume data 100 is obtained by stacking two-dimensional tomographic image data obtained in order along the direction perpendicular to the tomographic plane on the liver to be diagnosed. Is generated by superimposing a plurality of tomographic images taken by a modality 2 such as a CT apparatus or an MRI apparatus. Note that the volume data acquired using the CT apparatus is data that stores the amount of X-ray absorption for each voxel (that is, pixel position), and one signal value for each pixel position (in the case of imaging with the CT apparatus) , A value indicating the amount of X-ray absorption).

  The three-dimensional volume data group 110 includes, for example, a series of three-dimensional volume data 100 acquired by photographing a subject at different time phases t1, t2,..., Tn having a constant time interval Δt. The

  The three-dimensional volume data 100 is appended with incidental information defined by the DICOM (Digital Imaging and Communications in Medicine) standard. The incidental information includes, for example, an image ID for identifying a three-dimensional image represented by each three-dimensional volume data 100, a patient ID for identifying a subject, an examination ID for identifying an examination, and image information. Unique ID (UID) assigned, examination date when the image information was generated, examination time, type of modality used in the examination to obtain the image information, patient information such as patient name, age, gender, Examination site (imaging site, liver in the present embodiment), imaging conditions (contrast agent used, radiation dose, etc.) Information such as series number or collection number when multiple images are acquired in one examination Can be included.

  The storage unit 20 is a large-capacity storage device such as a hard disk, and stores a three-dimensional volume data group 110. Note that the storage unit 20 stores a plurality of three-dimensional volume data groups 110 having different subjects (that is, different patients) or having the same subject and different photographing times. In addition, a color template 120 described later is also stored. Note that a plurality of color templates are prepared according to a part to be extracted and displayed in VR among the parts included in the three-dimensional volume data 100, and a plurality of color templates 120 are stored in the storage unit 20.

  The alignment unit 30 aligns corresponding pixel positions in the liver portion between the three-dimensional volume data 100 for each of the three-dimensional volume data 100. Specifically, `` WM Wells III, P. Viola, H. Atsumi, S. Nakajima, and R. Kikinis, Multi modal volume registration by maximization of mutual information, Med.Image Anal., Vol.1, no.1 , pp. 35 51, 1996. (Reference 1), “Rueckert, D., Sonoda, LI, Hayes, C., Hill, DLG, Leach, MO, Hawkes, DJ, Nonrigid registration using free-form deformations: application to breast MR images. IEEE Transactions on Medical Imaging, vol.18, pp.712? 721, 1999. (Reference 2), “Masumoto J, Sato Y, Hori M, Murakami T, Johkoh T, Nakamura H, `` Tamura S: A similarity measure for nonrigid volume registration using known joint distribution of target tissue: Application to dynamic CT data of the liver, Medical Image Analysis, vol.7, no.4, pp.553-564, 2003. '' Reference 3), “Yongmei Wang, Lawrence H. Staib, Physical model-based non-rigid registration incorporating statistical shape information, Medical Image Analysis (2000) volume 4, number 1, pp 7-21” (reference 4) Corresponding pixel positions can be associated using the described technique.

  The technique described in Reference 1 performs alignment using a rigid registration technique, and the pixel position is set so that the mutual information amount is maximized between three-dimensional medical images acquired by different modalities. This is a method of aligning pixels by adjusting the direction and direction. The method described in Reference 2 performs registration using a non-rigid registration method, and by using a deformation estimation method based on a B-spline function called “free from deformation” (FFT), This is a technique for performing alignment. The technique described in Reference 3 performs registration using a non-rigid registration technique, and in a CT image acquired in time series order, a joint distribution of a target tissue such as a liver (joint distribution). Is used to measure and align the similarity by sliding the tissue at the boundary between the target tissue and the non-target tissue. The technique described in Reference 4 performs alignment using a non-rigid registration technique. The shape of an object is given in advance, and the object is deformed so as to obtain the shape. This is a method of aligning the positions.

  Moreover, it is also possible to use the technique described in the Japanese translations of PCT publication No. 2005-528974 gazette and the Japanese translations of PCT publication 2007-516744 gazette. The technique described in JP 2005-528974 A acquires first and second image data sets from a region of interest of a target, creates a model of physiological motion such as respiration and heart motion with respect to the region of interest, Fit a physiological model to the first image data set, apply an object-specific physiological phantom to the second image data set for conversion, and apply the conversion to the first image data set This is a technique for performing alignment.

  The technique described in JP-T-2007-516744 is a technique for aligning images by aligning the positions of the landmarks based on the similarity of the positions of the landmarks between the two images. .

  The alignment unit 30 aligns the three-dimensional image represented by the three-dimensional volume data 100 using these methods. Thereby, pixels representing the same position are associated with each other between the three-dimensional images.

  The alignment method is not limited to the above-described various methods, and any known method can be used. Alternatively, the three-dimensional volume data 100 may be sequentially displayed on the monitor 4, and the operator may perform alignment by input from the input unit 60. Further, not only the liver portion but also all pixel positions of the three-dimensional volume data 100 may be aligned.

  The conversion unit 40 converts the signal value at each pixel position of the three-dimensional volume data 100 into a display pixel value for volume rendering (VR) display. FIG. 2 is a diagram showing a color template for converting the three-dimensional volume data 100. A plurality of color templates 120 are prepared and stored in the storage unit 20 in accordance with the parts to be extracted and displayed in the VR among the parts included in the three-dimensional volume data 100. In the present embodiment, the color template 120 for liver VR display is selected. In the first embodiment, the color template 120 has a second signal value obtained by changing the first signal value with the first signal value serving as a reference as the first axis X as shown in FIG. Is set on the second axis Y, and the color (R, G, B) and opacity for the first and second signal values are set on the third axis Z. Although only one color template is shown in FIG. 2, actually, four color templates are prepared for each of R, G, and B colors and opacity.

  Hereinafter, creation of a two-dimensional lookup table will be described. In the case of a CT image, the unit of signal value is HU (Hounsfield unit), and HU is a fixed value according to the tissue. For example, when the imaging region is the abdomen as in the present embodiment, the signal value is a fixed value according to tissues such as the liver, spleen, and blood vessels. That is, the signal value differs depending on the tissue. On the other hand, how to change the signal value of each tissue by administration of a contrast agent is also known. In the case of an MRI image, the signal value differs depending on the imaging apparatus, but the signal value is fixed according to the tissue by correcting the difference in the signal value between the apparatuses. Can do. Therefore, using the signal value of the three-dimensional volume data 100 before the contrast agent is administered, the signal value of the three-dimensional volume data 100 on the first axis X and the color (R corresponding to the tissue on the third axis Z) , G, B) and a one-dimensional reference look-up table B0 serving as a reference in which opacity is set, a signal value that changes due to administration of a contrast agent or the like is set as the second axis Y, and the signal value A two-dimensional look is obtained by setting the tissue color and opacity in response to changes in a two-dimensional manner in the direction of the third axis Z with respect to the plane defined by the first and second axes X and Y. You can create uptables.

  The conversion unit 40 refers to the color template 120 and converts the signal value at each pixel position of the three-dimensional volume data 100 into a display pixel value including R, G, B, and opacity. At this time, the conversion unit 40 selects one reference time phase B serving as a reference among the time phases of the plurality of three-dimensional volume data 100. For the three-dimensional volume data 100 of the reference time phase B (hereinafter referred to as the reference three-dimensional volume data 130), the signal value at each pixel position is changed to the color using the portion of the reference lookup table B0 in the color template 120. And a display pixel value composed of opacity. On the other hand, for the three-dimensional volume data 100 in a time phase other than the reference time phase, the signal value at each pixel position is set to the second axis Y of the color template 120 and the signal value at the corresponding pixel position in the reference three-dimensional volume data 130. Are plotted on the first axis X, and the color and opacity corresponding to the plot are determined on the third axis Z and converted to display pixel values consisting of that color and opacity.

  Specifically, referring to FIG. 3, when the signal value at a certain pixel position (target pixel position) of the reference three-dimensional volume data 130 is n0, the signal value at the target pixel position is referred to by referring to the color template 120. Is converted to a display pixel value D0. When the signal value of the corresponding pixel position corresponding to the target pixel position changes to n1 in the three-dimensional volume data 100 of other time phases, the signal value of the corresponding pixel position is the display pixel value with reference to the color template 120. Converted to D1.

  The selection of the reference time phase B is, for example, the acquisition of the three-dimensional volume data 100 with the least time, the first time phase, the intermediate time phase, the last time phase, or the noise in the time phase of the three-dimensional volume data group 110. A predetermined time phase such as a time phase may be selected. In addition, selection of which time phase is set as the reference time phase B may be accepted by input from the input unit 60. In this embodiment, since the change in the signal value due to the administration of the contrast agent is observed, the effect of the contrast agent does not appear as the reference time phase B, and the same tissue has the same signal value. It is preferable to select the leading time phase in which different tissues have different signal values.

  Then, the conversion unit 40 converts the signal values at the respective pixel positions of all the three-dimensional volume data 100 into display pixel values with reference to the color template 120. As a result, the three-dimensional volume data 100 represents a VR image from which the liver is extracted.

  The display control unit 50 displays the VR images represented by the converted series of three-dimensional volume data 100 on the display 4 in chronological order. In the present embodiment, since the liver at the time of contrast medium administration is displayed, a state in which the contrast medium flows in the liver is displayed on the display 4.

  The input unit 60 includes a known input device such as a keyboard and a mouse.

  Next, processing performed in the first embodiment will be described. FIG. 4 is a flowchart showing processing performed in the first embodiment. It is assumed that the three-dimensional volume data group 110 is acquired by the volume data acquisition unit 10 and stored in the storage unit 20. It is assumed that a plurality of color templates 120 are also stored in the storage unit 20. When the operator operates the input unit 60 to select a three-dimensional image to be displayed (Yes in step ST1), the alignment unit 30 selects the three-dimensional volume data group 110 corresponding to the selected three-dimensional image. Is read from the storage unit 20, and the pixel positions between the three-dimensional volume data 100 constituting the three-dimensional volume data group 110 are aligned (step ST2). Thereby, the pixel position between the three-dimensional volume data 100 is matched.

  Then, the conversion unit 40 selects the reference time phase B (step ST3), and further selects the color template 120 used for conversion (step ST4). Next, the conversion unit 40 converts the signal value at each pixel position of the reference three-dimensional volume data 130 in the reference time phase B into a display pixel value with reference to the part of the reference lookup table B0 included in the color template 120. (Step ST5). Further, the signal value at each pixel position in the other three-dimensional volume data 100 other than the reference three-dimensional volume data 130 is converted into a display pixel value by the selected color template 120 (step ST6). Then, the display control unit 50 displays the VR images represented by the converted three-dimensional volume data 100 on the display 4 in chronological order (step ST7), and ends the process.

  Thus, in the first embodiment, the reference first signal value is on the first axis X, and the second signal value obtained by changing the first signal value is on the second axis Y. The reference three-dimensional volume data 130 is obtained from a color template 120 including a two-dimensional lookup table in which the colors (R, G, B) and opacity for the first and second signal values are set to the third axis Z. As a reference, the signal value at each pixel position in the three-dimensional volume data 100 is converted into a display pixel value. Therefore, by selecting an appropriate color template 120, even if the tissue changes in the same signal value over time, if the signal value is different in the reference three-dimensional volume data 130, a different display pixel value is obtained. Can be converted. In addition, even if the signal values of the same tissue are different, the tissues originally have the same signal value. Therefore, if the time phase having the same signal value is set as the reference time phase B, the same display pixel is obtained. Can be displayed by value. Therefore, according to the first embodiment, diagnosis using the three-dimensional volume data group 110 displayed in chronological order can be performed accurately.

  Next, a second embodiment of the present invention will be described. FIG. 5 is a schematic block diagram showing the configuration of the medical image conversion apparatus according to the second embodiment of the present invention. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted here. The medical image conversion apparatus 1A according to the second embodiment replaces the color template 120 including a two-dimensional lookup table, and a pair color template 160 including a reference color template 140 including a one-dimensional lookup table and a difference color template 150 thereof. Is different from the first embodiment in that the signal value of the three-dimensional volume data 100 is converted into the display pixel value using the pair color template 160 in the storage unit 20. Note that a plurality of pair color templates 160 are prepared and stored in the storage unit 20 according to the part to be extracted and displayed in the VR among the parts included in the three-dimensional volume data 100. Also in the second embodiment, the pair color template 160 for the VR display of the liver is selected.

  FIG. 6 is a diagram showing a reference color template and a difference template. As shown in FIG. 6, the reference color template 140 is a one-dimensional lookup table in which the horizontal axis represents the signal value of the three-dimensional volume data 100, and the vertical axis represents color (R, G, B) and opacity. . The difference color template 150 is a one-dimensional lookup table in which the horizontal axis represents the signal value variation and the vertical axis represents the color and opacity variation. In FIG. 6, only one reference color template and difference template are shown, but in actuality, a pair color composed of four reference color templates and difference templates for each of R, G, and B colors and opacity, respectively. A template 160 is prepared.

  The conversion unit 40 selects one reference time phase B serving as a reference among the time phases of the plurality of three-dimensional volume data 100. For the reference three-dimensional volume data 130 of the reference time phase B, the signal value at each pixel position is converted into a display pixel value composed of color and opacity with reference to the reference color template 140. On the other hand, for the three-dimensional volume data 100 in a time phase other than the reference time phase, first, the signal value S0 of each pixel position of the three-dimensional volume data 100 and the signal of the corresponding pixel position of the reference three-dimensional volume data 130 are used. The difference value (S0−SB) from the value SB is calculated as the signal value change amount ΔS, and the display pixel value (referred to as D10) at the corresponding pixel position in the reference three-dimensional volume data 130 is referred to the difference color template 150. Is calculated. Next, the corrected display pixel value (D10 + ΔD) is calculated by correcting the display pixel value D10 at the corresponding pixel position of the reference three-dimensional volume data 130 with the calculated change amount ΔD of the display pixel value. Then, the signal value S0 at each pixel position in the three-dimensional volume data 100 is converted into a corrected display pixel value (D10 + ΔD).

  Specifically, considering the case where the signal value is converted to opacity, there is no change in the signal value at each pixel position in the three-dimensional volume data 100 with the corresponding pixel position in the reference three-dimensional volume data 130. The signal value is converted so that the opacity does not change. On the other hand, the pixel value that changes so that the signal value becomes larger becomes more opaque, and the signal value that changes so that the pixel position that changes so that the signal value becomes smaller becomes more transparent. Also, when converting the signal value to the R color, if there is no change in the signal value from the corresponding pixel position of the reference three-dimensional volume data 130 at each pixel position in the three-dimensional volume data 100, the redness is The signal value is converted so as not to change. On the other hand, the pixel value that changes so that the signal value becomes larger becomes reddish, and the signal value that changes so that the pixel position that changes so that the signal value becomes smaller becomes less reddish.

  In the above description, the difference value (S0−SB) between the signal value S0 at each pixel position in the three-dimensional volume data 100 and the signal value SB at the corresponding pixel position in the reference three-dimensional volume data 130 is used as the signal value change amount ΔS. Although it is calculated, the index is not limited to the difference value (S0−SB) as long as it is an index representing the amount of change in the signal value between pixel positions. For example, the absolute value of the difference value or the logarithmic value of the difference value may be used instead of the difference value (S0-SB). In this case, the difference color template 150 may be created so as to define the relationship between the absolute value of the difference value or the logarithmic value of the difference value and the change amount of the display pixel value.

  Further, the signal value change amounts of a plurality of time phases are calculated, the signal value change amounts are plotted as shown in FIG. 7, and a portion where the gradient of the signal value change amount in the plot is maximized is obtained, and the display at the portion is displayed. The difference color template 150 may be modified so that the change amount of the pixel value is larger than that of other portions. Thereby, since the change of the display pixel value becomes large in the portion where the change of the signal value is large, the change can be recognized more easily.

  Next, processing performed in the second embodiment will be described. FIG. 8 is a flowchart showing processing performed in the second embodiment. It is assumed that the three-dimensional volume data group 110 is acquired by the volume data acquisition unit 10 and stored in the storage unit 20. In addition, it is assumed that a plurality of pair color templates 160 are also stored in the storage unit 20. When the operator operates the input unit 60 to select a 3D image to be displayed (Yes in step ST11), the alignment unit 30 selects the 3D volume data group 110 corresponding to the selected 3D image. Are read from the storage unit 20, and pixel positions between the three-dimensional volume data 100 constituting the three-dimensional volume data group 110 are aligned (step ST12). Thereby, the pixel position between the three-dimensional volume data 100 is matched.

  Then, the conversion unit 40 selects the reference time phase B (step ST13), and further selects the pair color template 160 used for the conversion (step ST14). Next, the converting unit 40 converts the signal value at each pixel position of the reference three-dimensional volume data 130 in the reference time phase B with reference to the reference color template 140 included in the color template 160 (step ST15). ). Then, for all three-dimensional volume data 100 other than the reference time phase, the difference value between the signal value at each pixel position and the signal value at the corresponding pixel position in the reference three-dimensional volume data 130 is calculated as a signal value change amount ( Step ST16). Then, the display pixel value corresponding to each pixel position in the reference three-dimensional volume data 130 is corrected with reference to the difference color template 150 according to the signal value change amount (step ST17). The signal value at each pixel position in the other three-dimensional volume data 100 is converted into a corrected display pixel value (step ST18). Then, the display control unit 50 displays the VR images represented by the converted three-dimensional volume data 100 on the display 4 in chronological order (step ST19), and ends the process.

  Thus, in the second embodiment, with reference to the reference color template 140, the signal value at each pixel position of the reference three-dimensional volume data 130 is converted into a display pixel value, and the other three-dimensional volume data 100 is converted. The display pixel value is corrected with reference to the difference color template 150 based on the amount of change of the signal value of each pixel position from the signal value of the corresponding pixel position in the reference three-dimensional volume data 130, and the corrected display pixel value The signal value at each pixel position is converted so that For this reason, the change in the signal value in each of the three-dimensional volume data 100 can be reliably reflected in the change in the display pixel value. Therefore, the change in signal value in the three-dimensional volume data group 110 displayed in chronological order by setting the time phase in which the same tissue has the same signal value and the different tissue to have a different signal value as the reference time phase B. Can be reliably recognized.

  In the second embodiment, the pair color template 160 including the reference color template 140 and the difference color template 150 is used. However, instead of the difference color template 150, a signal value change amount is used as an input to display pixel values. The amount of change in the display pixel value may be calculated using an arithmetic expression that outputs the amount of change in. In this case, only the reference color template 140 is stored in the storage unit 20.

  In the second embodiment, the signal value at each pixel position in the other three-dimensional volume data 100 other than the reference three-dimensional volume data 130 is converted to the corrected display pixel value. The signal value at each pixel position in the dimensional volume data 130 may be converted to be a corrected display pixel value. This will be described below as a third embodiment. Note that the third embodiment differs from the second embodiment only in the processing that is performed, and thus a detailed description of the device is omitted.

  FIG. 9 is a flowchart showing processing performed in the third embodiment. It is assumed that the three-dimensional volume data group 110 is acquired by the volume data acquisition unit 10 and stored in the storage unit 20. It is assumed that a plurality of color templates 160 are also stored in the storage unit 20. When the operator operates the input unit 60 to select a three-dimensional image to be displayed (Yes in step ST21), the alignment unit 30 selects the three-dimensional volume data group 110 corresponding to the selected three-dimensional image. Are read from the storage unit 20, and pixel positions between the three-dimensional volume data 100 constituting the three-dimensional volume data group 110 are aligned (step ST22). Thereby, the pixel position between the three-dimensional volume data 100 is matched.

  Then, the conversion unit 40 selects the reference time phase B (step ST23), and further selects the pair color template 160 used for the conversion (step ST24). Next, the converting unit 40 converts the signal value at each pixel position of the reference three-dimensional volume data in the reference time phase B with reference to the reference color template 140 included in the color template 160 (step ST25). . Then, for all three-dimensional volume data 100 other than the reference time phase, the difference value between the signal value at each pixel position and the signal value at the corresponding pixel position in the reference three-dimensional volume data 130 is calculated as a signal value change amount ( Step ST26). Then, the display pixel value corresponding to each pixel position in the reference three-dimensional volume data 130 is corrected with reference to the difference color template 150 according to the signal value change amount (step ST27). The signal value at the pixel position is converted into a corrected display pixel value for each corresponding three-dimensional volume data 100 (step ST28).

  In this case, a plurality of reference three-dimensional volume data 130 whose signal values have been converted into corrected display pixel values are created corresponding to other three-dimensional volume data 100 other than the reference three-dimensional volume data 130. Then, the display control unit 50 displays the VR images represented by the converted three-dimensional volume data 100 on the display 4 in chronological order (step ST29), and ends the process. In the third embodiment, the display pixel value of the VR image created from the reference three-dimensional volume data 130 changes in the same time phase as the three-dimensional volume data 100 from which the corrected display pixel value is obtained. Are displayed in chronological order.

  Thereby, also in 3rd Embodiment, the change of a signal value can be reliably recognized in the three-dimensional volume data group 110 displayed in time series order.

  In the first to third embodiments, the three-dimensional volume data group for the abdomen is used, but the three-dimensional volume data group for the head or neck may be used. In this case, the VR image is displayed in a four-dimensional manner so that a change due to the injection of the contrast agent into the blood vessel in the head or the neck appears.

  Further, in the first embodiment, as shown in FIG. 10, a smoothing unit 70 is provided, and each three-dimensional volume data 100 is smoothed before the pixel positions between the three-dimensional volume data 100 are aligned. You may do it. Specifically, the average value of the signal values at the respective pixel positions of the three-dimensional volume data 100 is calculated using a smoothing filter of a predetermined size (for example, 3 × 3 × 3), whereby each three-dimensional volume data 100 is calculated. Can be smoothed. Thereby, when performing alignment, since the influence of the noise contained in the three-dimensional volume data 100 can be reduced, alignment can be performed more accurately. In the second and third embodiments, the smoothing unit 70 may be provided similarly.

  In the first to third embodiments, the positioning unit 30 performs positioning of each three-dimensional volume data 100. However, the abdomen or the head, neck, and other parts have little movement. Or there is little movement. Therefore, for the three-dimensional volume data 100 of such a part, signal value conversion may be performed without performing alignment.

  In the first to third embodiments, the case where the abdominal three-dimensional volume data group 110 is VR-displayed in chronological order has been described. However, the three-dimensional volume data 100 on the slice plane at the same position is described. Of course, the present invention can also be applied to a case where a two-dimensional image representing a cross section of the abdomen is extracted from the three-dimensional volume data 100 and the density and / or color of the extracted two-dimensional image is converted and displayed in time series. It is. Further, the time series images are not limited to the three-dimensional volume data 100, and an image group including a series of images acquired at a predetermined time interval by simple X-ray imaging can be used.

  In addition, as described in, for example, Japanese Patent Application Laid-Open No. 2009-178493, the present invention is also used when sequentially displaying a plurality of three-dimensional volume data captured by a CT apparatus using a plurality of types of X-rays having different energies. Can be applied. In this case, as in the first to third embodiments, by converting the signal values of a plurality of three-dimensional volume data having different energies into display pixel values, it is possible to change the energy of radiation used for imaging. The display pixel value is changed in accordance with the change in the signal value, and the three-dimensional volume data can be sequentially displayed in accordance with the change in the X-ray energy at the time of imaging.

DESCRIPTION OF SYMBOLS 1 Medical image conversion apparatus 2 Modality 4 Display 10 Volume data acquisition part 20 Storage part 30 Positioning part 40 Conversion part 50 Display control part 60 Input part 70 Smoothing part 100 Three-dimensional volume data 110 Three-dimensional volume data group 120 Color template 130 Reference three-dimensional volume data 140 Reference color template 150 Difference color template 160 Pair color template

Claims (17)

Image acquisition means for acquiring a series of medical images for a specific part;
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. Conversion means for converting into a display pixel value according to,
A reference first signal value, a second signal value obtained by changing the first signal value, and a color template that defines a relationship of display pixel values with respect to the first and second signal values are stored. Storage means,
The converting means is means for converting a signal value at each pixel position of the target medical image into the display pixel value with reference to the color template with the reference medical image as a reference. Conversion device. Image acquisition means for acquiring a series of medical images for a specific part;
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. Conversion means for converting into a display pixel value according to,
Storage means for storing a first template signal value serving as a reference and a color template that defines a relationship between display pixel values with respect to the first signal value;
The conversion means converts the signal value at each pixel position of the reference medical image into the display pixel value with reference to the color template, and converts the signal value at each pixel position of the target medical image and the reference medical image. The display pixel value corresponding to each pixel position of the reference medical image is corrected according to the index value representing the amount of change from the signal value of the corresponding pixel position, and the signal value of each pixel position of the target medical image is A medical image conversion apparatus which is a means for converting to a corrected display pixel value. Image acquisition means for acquiring a series of medical images for a specific part;
Storage means for storing a first template signal value serving as a reference and a color template defining a relationship between display pixel values relative to the first signal value ;
Converting the signal values at each pixel position in relation to the standard reference medical image of said series of medical image on the display pixel values by referring to the color template, except the reference medical image of said series of medical images Display corresponding to each pixel position of the reference medical image according to an index value representing a change amount between the signal value of each pixel position of the other medical image and the signal value of the corresponding pixel position of the reference medical image A medical image conversion apparatus comprising: a conversion unit that corrects a pixel value and converts a signal value at each pixel position of the reference medical image so as to be the corrected display pixel value.   3. The medical image according to claim 1, further comprising: a display unit configured to display the converted series of medical images in time series when the medical images are acquired in time series. Conversion device.   When the medical images are acquired in time series, display means for displaying the converted reference medical images in time series in accordance with the time phase of the target medical image from which the corrected display pixel value is obtained. The medical image conversion apparatus according to claim 3, further comprising:   In the case where the medical images are acquired in time series order, the conversion means uses, as the reference medical image, one reference time phase medical image as a reference from each time phase of the plurality of medical images. 6. The medical image conversion apparatus according to claim 1, wherein the medical image conversion apparatus is a selection unit.   4. The medical image conversion apparatus according to claim 1, wherein the series of medical images is acquired by performing imaging using a plurality of types of radiation having different energies. 5.   8. The medical image conversion apparatus according to claim 1, further comprising an alignment unit configured to align pixel positions of the series of medical images between the series of medical images. 9.   9. The medical image conversion apparatus according to claim 8, further comprising a smoothing unit that smoothes the series of medical images before the alignment.   The medical image conversion apparatus according to claim 1, wherein the medical image is a three-dimensional medical image.   The medical image conversion apparatus according to claim 1, wherein the medical image is captured using a contrast agent. Acquire a series of multiple medical images for a specific site,
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. When converting to the corresponding display pixel value, with the reference medical image as a reference, a reference first signal value, a second signal value obtained by changing the first signal value, and the first and the first A medical image conversion method comprising: converting a signal value at each pixel position of the target medical image into the display pixel value with reference to a color template that defines a relationship between the display pixel value and the signal value of 2. Acquire a series of multiple medical images for a specific site,
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. When converting to a display pixel value corresponding to the reference pixel value, a color template that defines a signal value at each pixel position of the reference medical image as a reference first signal value and a relationship between the display pixel value and the first signal value The reference pixel value is converted to the display pixel value with reference to the reference value according to an index value representing the amount of change between the signal value of each pixel position of the target medical image and the signal value of the corresponding pixel position of the reference medical image. A medical image conversion method, wherein display pixel values corresponding to respective pixel positions of a medical image are corrected, and signal values at respective pixel positions of the target medical image are converted to become the corrected display pixel values. Acquire a series of multiple medical images for a specific site,
A color template that defines a signal value at each pixel position of a reference medical image serving as a reference in the series of medical images, a first signal value serving as a reference, and a relationship between display pixel values with respect to the first signal value. Refer to and convert to the display pixel value,
According to an index value representing a change amount between a signal value of each pixel position of a medical image other than the reference medical image in the series of medical images and a signal value of a corresponding pixel position of the reference medical image. , Correcting the display pixel value corresponding to each pixel position of the reference medical image,
A medical image conversion method, wherein a signal value at each pixel position of the reference medical image is converted to be the corrected display pixel value. Acquiring a series of multiple medical images for a specific site;
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. The display pixel value according to the procedure,
The converting step includes a first signal value serving as a reference with respect to the reference medical image, a second signal value obtained by changing the first signal value, and the first and second signal values. A method for converting a medical image into a computer by referring to a color template that defines a relationship of display pixel values with respect to the image, and converting a signal value at each pixel position of the target medical image into the display pixel value. A program to be executed. Acquiring a series of multiple medical images for a specific site;
For the target medical image to be converted in the series of medical images, the signal value of each pixel position of the target medical image is changed to the amount of change from the signal value of each corresponding pixel position of the reference standard medical image. The display pixel value according to the procedure,
The converting step is performed by referring to a color template that defines a signal value at each pixel position of the reference medical image as a reference first signal value and a relationship between display pixel values with respect to the first signal value. Each of the reference medical images is converted into a display pixel value according to an index value representing a change amount between the signal value of each pixel position of the target medical image and the signal value of the corresponding pixel position of the reference medical image. A medical image conversion method comprising: correcting a display pixel value corresponding to a pixel position and converting a signal value at each pixel position of the target medical image to the corrected display pixel value. A program to make it run. Acquiring a series of multiple medical images for a specific site;
A color template that defines a signal value at each pixel position of a reference medical image serving as a reference in the series of medical images, a first signal value serving as a reference, and a relationship between display pixel values with respect to the first signal value. A procedure for converting to the display pixel value with reference,
According to an index value representing a change amount between a signal value of each pixel position of a medical image other than the reference medical image in the series of medical images and a signal value of a corresponding pixel position of the reference medical image. Correcting a display pixel value corresponding to each pixel position of the reference medical image;
Program for executing the medical image conversion method characterized in that it comprises a procedure for converting a signal value of each pixel position of the reference medical image such that the corrected display pixel values to the computer.

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