JP5930193B2 - SPECT image conversion apparatus, image conversion program, and image conversion method - Google Patents

Description

  The present invention relates to a technique for converting a pixel value of a SPECT image into a general unit of radioactivity per unit capacity. More specifically, the present invention relates to a technique for converting a pixel value of a SPECT image using a conversion coefficient stored in advance in a database or the like.

  SPECT, which is one of the nuclear medicine imaging techniques, is performed by administering a radiopharmaceutical to a subject, detecting γ rays emitted from the radiopharmaceutical with a dedicated camera, and imaging it. SPECT is widely used clinically because it can image the function of a living body like PET.

  However, in SPECT, since γ rays are affected by absorption and scattering by living tissue, it is necessary to perform absorption and scattering correction at the time of image reconstruction. This absorption and scattering correction affects the quality of the reconstructed image. In recent years, a CSPECT program has been developed to unify these correction methods that were not standardized between facilities, and to convert the pixel values in the reconstructed image into a common unit such as Bq / mL that represents the amount of radioactivity per unit volume. (Non-Patent Document 1). This program enabled collaborative research and direct comparison of data at multicenters that were previously difficult, and also allowed absolute quantification of cerebral blood flow using head SPECT images.

  Hidehiro Iida et al. , “Multi-Evaluation of a Standardized Protocol for Rest and Acetazolamide Cerebro Blood Flow Assessment Pro-Sequent Repetitive SPECT. Nucl. Med. , (2010), vol. 51, no. 10, p. 1624-1631

  By the way, in order to convert the pixel value of the SPECT image into a unified unit such as Bq / mL, a conversion coefficient (Becquerel calibration factor, hereinafter referred to as BCF) representing the relationship between the radioactivity amount per unit capacity and the SPECT count. It is necessary to ask. BCF is a procedure in which a count value is measured on a SPECT cross-sectional image obtained using a sample with a known amount of radioactivity per unit volume, and the radioactivity amount per unit volume in the used sample is divided by the count value. Desired. Until now, it was said that the BCF had to be obtained for each inspection at each facility where the SPECT inspection was performed. This is because it has been considered that subtle habits and conditions of the SPECT device used affect the SPECT image. However, the conventional method of performing BCF for each facility has a problem that a separate sample is required for the BCF measurement and a certain time is required for the BCF measurement, which may cause unnecessary exposure. It was.

  The present invention has been made in view of the above circumstances, and a method of converting a pixel value of a SPECT image into a unified unit such as Bq / mL without performing BCF measurement at each facility where a SPECT inspection is performed, and the method An image processing apparatus and a computer program for executing the above are provided.

  As a result of repeated detailed studies using many experimental results, the inventor has found that the value of the BCF is almost equal if the combination of the SPECT apparatus model and the collimator is the same. Based on this knowledge, the BCF value for each combination of SPECT device model and collimator type is made into a database, and the necessary BCF value is read out from this database at the time of inspection, so that the pixel value is not obtained separately for each facility. The present invention was completed by discovering that the conversion into a unit of Bq / mL was possible.

  An image processing apparatus according to the present invention uses a becquerel calibration factor, which is a conversion coefficient for converting a pixel value of a SPECT image into a unit of radioactivity (Bq / mL) per unit volume, and information related to the SPECT apparatus (SPECT apparatus) Model name and collimator type), a database stored in a tagged form, an image acquisition unit having a function of acquiring a SPECT image, a model name of the SPECT apparatus used for capturing the SPECT image, and an installed collimator Using a conversion coefficient acquisition unit having a function of reading a becquerel calibration factor corresponding to a species from the database, and the becquerel calibration factor, a pixel value at each pixel of the SPECT image is calculated as a radioactivity amount per unit capacity (Bq / mL). ) To convert to units Comprising a first pixel value conversion processing unit.

  An image processing program according to the present invention is a SPECT image data and a Becquerel calibration factor which is a conversion coefficient for converting the pixel value of the SPECT image into a unit of radioactivity (Bq / mL) per unit volume, A computer program that can use a Becquerel calibration factor stored in a database constructed in a predetermined storage device and that causes a computer to operate as an image processing device, and obtains a SPECT image in the computer Image acquisition step, and conversion coefficient acquisition step of reading out the Becquerel calibration factor corresponding to the model name of the SPECT device used for capturing the SPECT image and the collimator type mounted from the database constructed in the predetermined storage device When, Here, the becquerel calibration factor is stored in advance in the database by tagging information relating to the SPECT device (model name and collimator type of the SPECT device), and using the read becquerel calibration factor. And a first pixel value conversion step of converting a pixel value in each pixel of the SPECT image into a unit of radioactivity (Bq / mL) per unit capacity.

  Since the image processing apparatus and the image processing program according to the present invention are configured to read out and use the BCF stored in the database in advance, there is an advantage that it is not necessary to perform complicated BCF measurement for each facility.

  The image processing apparatus according to the present invention converts the pixel value of each pixel converted into a unit of the amount of radioactivity per unit volume (Bq / mL) into an SUV (Standardized Uptake value) that represents the amount of radiopharmaceutical taken up per body weight. The image processing program according to the present invention may be further provided with a second pixel value conversion processing unit having a function of converting. Similarly, the image processing program according to the present invention stores an image after execution of the first pixel value conversion step. It may further have a function of executing a second pixel value conversion step of converting the pixel value of each pixel into an SUV (Standardized Uptake value) representing the amount of radiopharmaceutical taken up per body weight.

  An image processing method according to the present invention is a method of performing image processing of a SPECT image using a computer, and an image acquisition step of acquiring a SPECT image by a computer, and a radioactivity amount per unit capacity of the pixel value of the SPECT image. A Becquerel calibration factor that is a conversion coefficient for conversion to a unit of (Bq / mL), and a Becquerel calibration factor corresponding to the model name of the SPECT device used for capturing the SPECT image and the type of collimator installed A conversion coefficient acquisition step of acquiring the BEC, and wherein the becquerel calibration factor is given in advance in association with information related to the SPECT apparatus (model name of the SPECT apparatus and the installed collimator type). Calibration screen Sequentially executed, and a first pixel value conversion step of converting the unit of the amount of radioactivity per unit volume of the pixel values (Bq / mL) at each pixel of the SPECT image using compactors.

  In the image processing method according to the present invention, the Becquerel calibration factor is pre-tagged in a database constructed in a predetermined storage device and tagged with information related to the SPECT device (model name of the SPECT device and mounted collimator type). The conversion coefficient acquisition step stores the model name of the SPECT apparatus used for capturing the SPECT image and the Becquerel calibration factor corresponding to the installed collimator type from the database. It is good also as a structure.

  Also, in the image processing method according to the present invention, the pixel value of each pixel of the image after execution of the first pixel value conversion step is converted by a computer into an SUV (Standardized Uptake value) indicating the amount of radiopharmaceutical taken up per body weight. The second pixel value conversion step of converting to may be further executed.

  According to the present invention, the pixel value of a SPECT image can be converted into a unified unit such as Bq / mL without measuring the BCF at each facility where the SPECT inspection is performed.

6 is a flowchart showing the flow of processing in a preferred embodiment of the image processing apparatus according to the present invention. 1 is a functional block diagram of a preferred embodiment of an image processing apparatus according to the present invention. The system configuration in the desirable mode of the image processing device concerning the present invention. An example of the information stored in the database mounted in the image processing apparatus which concerns on this invention. The figure which shows the structure in a preferable aspect of the image processing program which concerns on this invention.

  The present invention will be described below with reference to the drawings. In addition, the example shown below demonstrates the preferable form to the last, and the content of this invention is not limited at all by these description.

FIG. 1 is a flowchart showing an outline of processing in a preferred embodiment of the image processing apparatus according to the present invention, and FIG. 2 is a functional block diagram in a preferred embodiment of the image processing apparatus according to the present invention. The image processing apparatus 10 according to the present invention can be configured by a computer that has read the image processing program 300, and the image processing method according to the present invention can be realized by operating the image processing apparatus 10.
In a preferred embodiment, the image processing apparatus 10 includes an imaging information acquisition unit 20, a data acquisition unit 30, a conversion coefficient acquisition unit 40, a first conversion processing unit 50, a second conversion processing unit 60, a database 70, and an output unit 90. It consists of. Here, a plurality of BCF values are stored in the database 70 in a form tagged with the model name of the SPECT apparatus and the installed collimator type. In a preferred embodiment, the image processing apparatus 10 is connected to a nuclear medicine image capturing apparatus 100 such as a SPECT apparatus through an electric communication line.
FIG. 3 shows a system configuration in the most preferable mode of the image processing apparatus 10 according to the present invention. In a preferred embodiment, in the image processing apparatus 10, a CPU 230, a memory 240, an output device 250 such as a monitor, a communication interface 260, an input device 270 such as a keyboard, and a hard disk 220 are connected via a bus 280. ing. In addition, the image processing apparatus 10 may include a CD-ROM drive, a USB interface, and the like. The communication interface 260 is used to connect to the nuclear medicine image capturing apparatus 100. The memory 240 stores an image processing program 300 according to the present invention.

The image processing apparatus 10 causes the imaging information acquisition unit 20 to execute an imaging information acquisition step, and allows the user to input information such as the model name of the SPECT apparatus and information about the installed collimator, the total amount of radiopharmaceutical administered, and the weight of the subject. The information input by the user via the input device 270 is acquired and stored in the memory (step S01). Each acquired information is used in the following processing by the image processing apparatus 10 as necessary.
Depending on the embodiment, each piece of information described above may be given at the same time as the SPECT image in a form tagged with the SPECT image acquired in the next SPECT data acquisition step (step S02). In this case, step S01 can be omitted.

Next, the image processing apparatus 10 causes the data acquisition unit 30 to execute a SPECT data acquisition step, and acquires a SPECT image to be subjected to image processing (step S02). The SPECT image acquired here is a three-dimensional image composed of a plurality of tomographic images. This SPECT image can be obtained by a publicly known method widely and generally used in clinical practice.
In a preferred embodiment, the SPECT image is captured in the image processing apparatus 10 by directly inputting the SPECT image stored in a computer-readable format such as the DICOM format from the nuclear medicine imaging apparatus 100 through a network. The SPECT data is acquired by a method in which data acquired in a state stored in a computer-readable storage medium such as a hard disk, a CD-ROM, or a DVD is read by a reading device provided in the computer system. It may be a thing.

Next, the image processing apparatus 10 causes the conversion coefficient acquisition unit 40 to execute a conversion coefficient acquisition step, and acquires a BCF value corresponding to the combination of the model name of the SPECT apparatus used for SPECT imaging and the installed collimator type ( Step S03). FIG. 4 shows the information stored in the database 70 in the preferred embodiment. As shown in this figure, each BCF is stored in the database 70 in a form tagged with information such as the SPECT apparatus model and collimator type.
In a preferred embodiment, the conversion coefficient acquisition step reads information about the model name of the SPECT device acquired in step S01 and read into the memory and information about the installed collimator type, and accesses the database 70 to read the corresponding BCF value. It is performed by such operations.
In a preferred embodiment, the database 70 is constructed in a hard disk 220 connected to a computer constituting the image processing apparatus 10. The database 70 may be stored in a computer-readable storage medium such as a CD-ROM, DVD, or USB memory. In this case, the storage medium storing the database 70 is inserted into a CD-ROM drive, DVD drive, or USB interface so that the image processing program 300 can access the database 70.

The BCF value stored in the database 70 is measured by a known method using a plurality of SPECT apparatuses equipped with various collimators. More specifically, for example, it can be determined by the following procedure.
First, a radiopharmaceutical having a known radioactivity per unit volume (Bq / mL) is prepared as a sample. The amount of radioactivity per unit capacity here is an amount of radioactivity that does not cause counting down in SPECT imaging. Such a radiopharmaceutical with a known radioactivity can be a radiopharmaceutical attenuated for 1 to 2 days, for example. This sample is fixed to the center of the SPECT apparatus, SPECT imaging is performed, and image reconstruction is performed to obtain a transverse image. Then, the integrated value of the pixel values of the entire central slice is measured, and the radioactivity amount per unit volume in the sample is divided by that value, thereby obtaining the BCF value. Here, the same value is used for the slice thickness of the transverse image used for the measurement of the BCF and the slice thickness of the SPECT image of the subject.

  When the BCF value is acquired by the conversion coefficient acquisition step, the image processing apparatus 10 causes the first conversion processing unit to execute the first conversion processing step, and the pixel value in the SPECT image of the subject acquired in the data acquisition step The (original pixel value) is converted into a unit such as Bq / mL (step S04). This process is performed by a method in which the BCF value obtained in the conversion coefficient acquisition step is multiplied by the pixel value in each pixel of the SPECT image. Therefore, the first conversion processing step is performed by executing the calculation according to the following Equation 1 for each pixel value.

  When the first conversion processing step is completed, the image processing apparatus 10 executes the second conversion processing step, and converts the pixel value into an SUV (Standardized Uptake Value) representing the amount of radiopharmaceuticals taken up per body weight (Step S05). This process is performed by executing an operation according to the following Equation 2 for each pixel.

  When the second conversion processing step is completed, the image processing apparatus 10 distributes each SUV to the corresponding pixel and outputs it to an output device such as a display (step S06). In a preferred embodiment, the output is performed with luminance and color according to the SUV value. Depending on the embodiment, it is of course possible to set a certain region of interest, calculate the average value of SUVs of pixels included in the region, and display the values numerically.

  Note that the image processing apparatus 10 may be configured to output pixel values converted to Bq / mL units instead of SUVs. In this case, the pixel value after the first conversion process can be arranged in the corresponding pixel and displayed on an output device such as a display. Also in this case, the magnitude of the pixel value converted into Bq / mL can be expressed by a method such as luminance or color.

Next, the image processing program 300 according to the present invention will be described. As described above, the image processing apparatus 10 can be configured as a computer that has read the image processing program 300.
The image processing program 300 may be a program stored in a computer-readable storage medium such as a hard disk, CD-ROM, or DVD, and read into the computer via a corresponding drive. The image processing program 300 may be read into a computer through a network as a computer data signal superimposed on a carrier wave.
FIG. 5 shows a configuration of a preferred embodiment of the image processing program 300 according to the present invention. In a preferred embodiment, the image processing program 300 includes a main module 310 that controls processing, an imaging information acquisition module 320, a data acquisition module 330, a conversion coefficient acquisition module 340, a first conversion processing module 350, and a second conversion module. The conversion processing module 360 and the output module 370 are configured.

  The imaging information acquisition module 320 causes the computer to execute the process according to step S01. The data acquisition module 330 causes the computer to execute the process according to step S02. The conversion coefficient acquisition module 340 causes the computer to execute the process according to step S03. The first conversion processing module 350 causes the computer to execute the process according to step S04. The second conversion processing module 360 causes the computer to execute processing related to step S05. The output module 370 causes the computer to execute the process according to step S06.

  The image processing apparatus 10 according to the present invention can convert a SPECT image into a unit pixel value such as Bq / mL that does not depend on the model used for imaging or imaging conditions without performing BCF measurement for each examination. It becomes. This makes it possible to compare data between facilities and perform absolute quantification more easily.

  The present invention can be used in the fields of image processing software and diagnostic imaging equipment.

DESCRIPTION OF SYMBOLS 10 Image processing apparatus 20 Imaging information acquisition part 30 Data acquisition part 40 Conversion coefficient acquisition part 50 1st conversion process part 60 2nd conversion process part 70 Database 90 Output part 220 Hard disk 230 CPU
240 Memory 250 Output device 260 such as monitor Communication interface 270 Input device 280 such as keyboard Bus 300 Image processing program 310 Main module 320 Imaging information acquisition module 330 Data acquisition module 340 Conversion coefficient acquisition module 350 First conversion processing module 360 Second Conversion processing module 370 output module

Claims (7)

Information on the SPECT device (model name of the SPECT device and the type of collimator mounted), a Becquerel calibration factor, which is a conversion coefficient for converting the pixel value of the SPECT image into a unit of radioactivity (Bq / mL) per unit capacity ) And a database stored in a tagged form, an image acquisition unit having a function of acquiring a SPECT image,
A conversion coefficient acquisition unit having a function of reading a becquerel calibration factor corresponding to the model name of the SPECT apparatus used for capturing the SPECT image and the type of the collimator mounted thereon;
A first pixel value conversion processing unit having a function of converting a pixel value in each pixel of the SPECT image into a unit of radioactivity (Bq / mL) per unit capacity using the Becquerel calibration factor;
An image processing apparatus comprising: A second pixel having a function of converting a pixel value of each pixel converted into a unit of the amount of radioactivity per unit volume (Bq / mL) into an SUV (Standardized uptake value) representing a radiopharmaceutical uptake amount per body weight The image processing apparatus according to claim 1, further comprising a value conversion processing unit. SPECT image data and a Becquerel calibration factor, which is a conversion coefficient for converting the pixel value of the SPECT image into a unit of radioactivity (Bq / mL) per unit volume, and is constructed in a predetermined storage device A computer program for using a Becquerel calibration factor stored in a database and operating a computer as an image processing device,
On that computer,
An image acquisition step of acquiring a SPECT image;
A conversion coefficient acquisition step of reading out a Becquerel calibration factor corresponding to a model name of the SPECT apparatus used for capturing the SPECT image and a mounted collimator type from the database constructed in the predetermined storage device;
Here, the becquerel calibration factor is stored in advance in the database by tagging information related to the SPECT device (model name of the SPECT device and the installed collimator type),
A first pixel value conversion step of converting a pixel value in each pixel of the SPECT image into a unit of radioactivity (Bq / mL) per unit capacity using the read Becquerel calibration factor;
An image processing program for executing On the computer,
A second pixel value conversion step of converting the pixel value of each pixel of the image after execution of the first pixel value conversion step into an SUV (Standardized Uptake value) representing a radiopharmaceutical uptake amount per body weight is further executed. The image processing program according to claim 3, wherein A method of performing image processing of a SPECT image using a computer,
By computer
An image acquisition step of acquiring a SPECT image;
A Becquerel calibration factor that is a conversion coefficient for converting a pixel value of a SPECT image into a unit of radioactivity (Bq / mL) per unit capacity, and the model name of the SPECT device used for imaging the SPECT image, and A conversion coefficient acquisition step for acquiring a Becquerel calibration factor corresponding to the mounted collimator type;
Here, the becquerel calibration factor is given in advance in association with information related to the SPECT device (model name of the SPECT device and the installed collimator type), and the SPECT image is obtained using the becquerel calibration factor. A first pixel value conversion step for converting a pixel value in each pixel of the pixel into a unit of radioactivity (Bq / mL) per unit capacity;
Are sequentially executed. The becquerel calibration factor is stored in advance in a database built in a predetermined storage device, tagged with information about the SPECT device (model name of the SPECT device and the type of collimator installed),
In the conversion coefficient acquisition step, a becquerel calibration factor corresponding to a model name of a SPECT apparatus used for capturing the SPECT image and a mounted collimator type is read from the database by the computer. The image processing method as described. By computer
A second pixel value conversion step of converting the pixel value of each pixel of the image after execution of the first pixel value conversion step into an SUV (Standardized Uptake value) representing a radiopharmaceutical uptake amount per body weight is further executed. The image processing method according to claim 5 or 6.

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