JP2002214347A - Emission ct apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an emission image and an MRI image correctly match each other in an anatomical positional relationship. SOLUTION: A transmission image and a PET image which are picked up by an image pickup portion 2 at the same time are transmitted to an image processing portion 3, where image conversion is carried out so that the transmission image coincides with the MRI image taken from an MRI device 5. A conversion formula thereof is applied to the PET image to convert the PET image and synthesize it with the MRI image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PET (Positron Emission Tomography) apparatus for capturing an image using a positron emitting nuclide or a single photon emitting nuclide, and a SPECT (Single-Photon Emission Computed T).
The present invention relates to an emission CT apparatus such as an apparatus, and particularly to an emission CT apparatus having an image processing function for determining the position of an affected part.

[0002]

2. Description of the Related Art PET images or SPECT images are used for medical diagnosis of tumors. When a drug that accumulates in a tumor is labeled with a positron-emitting nuclide or a single-photon-emitting nuclide, the drug is administered to a patient, and when the drug accumulates in the tumor, a PET or SECT image is taken. Will show the tumor.

[0003] When a tumor diagnosed by an emission image is removed by surgery or treated with chemotherapy, it is necessary to specify the anatomical position of the tumor. , A CT image or an MRI image is usually used. For example, in the case of a malignant tumor located in the mediastinum or prostate diagnosed by PET examination, a doctor or the like identifies the anatomical position by comparing the emission image with a CT image or MRI image taken for reference. Most often, they rely on human visual judgment.

[0004] Alternatively, there has been proposed a method of improving accuracy by using a marker. Paste the marker on the patient's torso,
PET image or SPECT so that this marker appears
A CT image or MRI image is also taken together with the image, and the position of the tumor is specified on the CT image or MRI image by aligning the emission image with the CT image or MRI image with reference to the marker. I do.

[0005]

However, the conventional method has the following problems. First, in a method relying on human visual judgment, the result differs depending on the person making the judgment, and the objectivity of the judgment is lost. In addition, the method using a marker cannot be applied to a case where the marker moves due to a respiratory motion or the like, and there are few useful clinical examples. Further, in this method, the marker is set not only at the time of capturing the emission image but also at the time of CT.
Since the operation must be performed also at the time of capturing an image and an MRI image, the operation is complicated and the inspection cannot be performed efficiently.

In view of the above, the present invention eliminates the reliance on human subjectivity, facilitates the work without using a marker, and reduces the time required for an inspection image and CT. The image and the MRI image can be accurately associated with the position, and the position of the tumor can be determined more accurately.
It is an object to provide an emission CT device.

[0007]

In order to achieve the above object, an emission CT apparatus according to the present invention comprises:
An imaging unit that simultaneously collects emission data and transmission data from a subject to obtain an emission image and a transmission image of the same site of the subject, and the transmission image matches another medical diagnostic image of the same site. An image processing unit that converts the transmission image so as to perform the conversion, converts the emission image using the relationship of the conversion, and superimposes the emission image on the medical diagnosis image.

Since an emission image and a transmission image of the same site of the subject are obtained, the transmission image shows the anatomical positional relationship of the same site as the emission image. The anatomical positional relationship of the same site is represented in more detail by another medical diagnostic image such as an MRI image. This MR
An image such as an I image and a transmission image should basically match if the scale and the displacement are adjusted. Accordingly, the transmission image is converted so as to match the MRI image or the like by adjusting the scale or the displacement of the transmission image. If the emission image is converted using this conversion relationship, the converted emission image will be free from a difference in scale or displacement from the MRI image, and can be accurately matched in an anatomical positional relationship. . Therefore, by performing image synthesis in which the converted emission image is superimposed on the MRI image or the like, an image of a tumor or the like can be represented on the MRI image or the like in which the anatomical positional relationship is expressed in more detail.
The position of a tumor or the like can be accurately determined.

[0009]

Next, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, an emission CT apparatus 1 according to the present invention
The imaging unit 2 includes an imaging unit 2 that captures an emission image, an image processing unit 3 that performs image processing, and an image display unit 4 that displays the processed image. The image processing unit 3 converts an MRI (or CT) image from the MRI apparatus (or X-ray CT apparatus) 5
It is captured by ICOM communication (a communication protocol that handles medical data including image data in common).

As the image pickup section 2, a PET image pickup section is used here. This is a type of simultaneous collection of emission data and transmission data. A PET imaging unit of the emission and transmission data simultaneous acquisition type is configured, for example, as shown in FIG. 2 (see Japanese Patent Application No. Hei 9-184885). In FIG. 2, a number of radiation detectors 11 are arranged in a ring shape, and a subject (patient) 3 is arranged in the ring-shaped array 10.
0 is arranged. These detectors 11
Are output to the coincidence circuit 12, and it is detected that radiation is incident on any two detectors 11 at the same time and outputs are simultaneously generated from these. When outputs are simultaneously generated from the two detectors 11 and detected by the coincidence circuit 12, outputs from the coincidence circuit 12 are output from the address converters 13, 1 and 2.
4 and the address is converted in accordance with the combination of the two detectors 11.
Is counted for each address.

In this address conversion, when outputs are simultaneously generated from the two detectors 11, the addresses are converted into position information on a line connecting the two detectors 11. The information representing the position of the line connecting the two detectors 11 is represented by, for example, an angle θ and a distance d from the center, as shown in FIG. That is, when a detection signal is simultaneously generated by two certain detectors 11, conversion to an address consisting of θ and d representing a line connecting the two detectors 11 is performed.

When an output from the coincidence circuit 12 indicating that a detection signal is simultaneously generated in two detectors 11 is generated, the output is sent to both address converters 13 and 14, so that the data collection memories 15 and 16 are output. , Counting at the same address is performed in parallel. However, these address converters 13 and 14 have different first and second masks, respectively, and output only addresses that have passed the masks.
In steps 5 and 16, data passing through different masks are counted. The first mask of the address converter 13 allows only transmission data to pass.
On the other hand, the second mask of the address converter 14 allows only the emission data to pass.

These masks are changed depending on the position of the line source 21. The line radiation source 21 is a radiation source formed in a line shape, and is disposed so as to be orthogonal to a slice plane (a plane including the detector ring type array 10) (in the figure, disposed perpendicular to the paper surface). . This line source 21 is formed of a positron emitting nuclide. The line source 21 is rotated in a stepwise manner along the detector ring-shaped array 10 by a predetermined small angle along the detector ring-shaped array 10 by a mechanism not shown in the drawing. The rotational position is read by a rotational position reading device 22 composed of, for example, a pulse encoder and a counter.
Sent to

Here, since the position of the radiation source is indicated by a straight line (represented by θ and d) connecting a pair of detectors 11 which are simultaneously incident, the position of the radiation source may be known. It can be seen that the count at which address (θ, d) is from that source. That is, the source and address (θ,
There is a correspondence with d). Utilizing this relationship, when the line source 21 is at a certain position, the first mask assumes that only the address (θ, d) corresponding to that position is passed, and the first mask sets the address (θ) corresponding to that position. , D), a second mask is created to pass addresses (θ, d) other than the second mask. Since the line source 21 moves stepwise on a predetermined circular orbit at small angles, the first and second masks are previously formed at each angle, and the rotational position reading device 22 These masks for each angle are selected according to the information read by.

Therefore, when the line source 21 completes one rotation, only the data (transmission data) from the line source 21 is stored in the data collection memory 15 and the data (transmission data) from the subject 30 is stored in the data collection memory 16. Emission data) only.

Since the transmission data is obtained by counting the radiation that has passed through the subject 30, the transmission data is affected by the absorption by the subject 30. Therefore, if this transmission data is used, an absorption distribution image (transmission image) of the subject 30 on the same tomographic plane as the plane on which the detector ring 10 is located can be reconstructed. From the emission data, a positron-emitting radionuclide concentration distribution image (PET image) on the same tomographic plane can be reconstructed. These image reconstruction calculation processes are performed by the image reconstruction device 17, and a transmission image and a PET image are obtained at the same time.

On the other hand, the MRI apparatus (X-ray CT apparatus) 5 obtains an MRI image (CT image) on the same tomographic plane for the same subject 30 as described above, and the image is obtained by the emission CT apparatus 1. Is taken in the image processing unit 3. The above transmission image and their M
Since the RI image (CT image) represents the same tomographic plane of the same subject 30, it should be basically the same except for the nature of the image as representing the same anatomically. .

The image processing unit 3 firstly sets the scale of the transmission image, the position in the vertical and horizontal directions, and the position of the transmission image so that the transmission image matches the MRI image (CT image).
Change the position in the rotation direction and the pixel size.
Letting Φ (s, r, p) be the transformation function when they match, it can be expressed by the following equation. Tnew (i, j) = Φ (s, r, p) * Torg (i, j) where Torg (i, j) is the original transmission image,
Tnew (i, j) represents the transmission image after conversion.

Next, the image processing unit 3 converts the emission image (PET image) using the conversion function Φ (s, r, p) as shown by the following equation. Enew (i, j) = Φ (s, r, p) * Eorg (i, j) where Eorg (i, j) is the original emission image,
(i, j) represents the converted emission image.

Thereafter, the image processing section 3 performs an image synthesis process for superimposing the converted emission image on the MRI image (CT image). The image thus synthesized is displayed on the image display unit 4. In the displayed image,
An emission image (PET image) that has been accurately positioned and scaled is superimposed on the MRI image (CT image). By observing this image by a doctor or the like, the anatomical position of the affected part such as a tumor can be determined. It can be determined accurately.

In this case, the process of converting and matching the scale and position of the image is performed automatically, so that the process is objectively and accurately performed without depending on the subjectivity of the operator.
If you paste a marker, it can be inaccurate,
The accuracy can be improved without performing such inaccurate work, and the work is also facilitated. Since the transmission image is picked up at the same time as the emission image, there is no need to separately pick up the two and the examination time is lengthened, so that no burden is imposed on the patient.

In the above description, the imaging unit 2 collects the PET image and the transmission image at the same time. However, the imaging unit 2 may collect the SPECT image and the transmission image at the same time. To simultaneously acquire a SPECT image and a transmission image, for example, a detector is arranged at a position where radiation from a radiation source arranged outside the subject is not incident, and these are integrally rotated around the subject. What is necessary is just to make it the structure made to make it.

As other medical images to be taken into the image processing unit 3 of the emission CT apparatus 1, an ultrasonic image or the like can be considered in addition to an MRI image and an X-ray CT image. In addition, it goes without saying that the specific configuration and the like can be variously changed without departing from the spirit of the present invention.

[0024]

As described above, according to the emission CT apparatus of the present invention, it is possible to accurately associate an emission image with another medical image such as a CT image and an MRI image in an anatomical positional relationship. it can. Therefore, the position of an affected part such as a tumor can be determined with higher accuracy. Accurate because you can eliminate relying on human subjectivity. In addition, since no marker is used, the operation can be facilitated, and the inspection time does not become longer. Therefore, the burden on the patient does not increase.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of an imaging unit of the emission CT device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Emission CT apparatus 2 Imaging part 3 Image processing part 4 Image display part 10 Detector ring type arrangement 11 Detector 12 Coincidence circuit 13, 14 Address converter 15, 16 Data acquisition memory 17 Image reconstruction device 21 Line source 22 Rotation Position reading device 30 subject

Claims (1)

[Claims] An imaging unit for simultaneously collecting emission data and transmission data from a subject to obtain an emission image and a transmission image of the same site of the subject, and an image for another medical diagnosis of the same site. The transmission image is converted so that the transmission image matches, and an image processing unit that performs a process of converting the emission image using the relationship of the conversion and superimposing the emission image on the medical diagnostic image. Emission CT device.