JPH0434114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an emission CT device, in particular, a method for injecting a radioactive isotope into a subject and detecting radiation emitted from the radioisotope with a radiation detector. This invention relates to an improved emission CT device that synthesizes desired tomographic images of a region.

Background Art In the field of nuclear medicine that utilizes radioactive isotopes (hereinafter referred to as RI), for example, the anatomical form and physiological functions of various organs can be determined by measuring the concentration distribution of RI administered into the human body. We are conducting a diagnosis.

Generally, an emission CT device is widely used to measure such RI distribution in a living body, and this emission CT device has a plurality of radiation detectors arranged in a ring frame shape, and a radiation detector placed within the frame. Radiation emitted from the RI injected into the examination site is detected by each of the radiation detectors, and a tomographic image of the examination site is synthesized.

PRIOR ART FIG. 1 shows an emission CT device that has been used conventionally. A plurality of radiation detectors 1 provided outside the collimator frame 12
a detection frame 16 formed by arranging 4 cells at equal intervals in a substantially ring frame shape, and a detection frame 16 for detecting radiation emitted from the injection RI of the test site 18 placed inside the collimator frame 12 through the collimator 10. The radiation is received by each radiation detector 14.

Here, the collimator 10
Among the radiation emitted from the injection RI inside the collimator 8, only the radiation emitted in the direction parallel to the collimator 10 is transmitted toward the radiation detector 14. This conventional device forms the collimator frame 12. The plurality of collimators 10 are divided into two groups, and the direction of each collimator 10 is set so that the direction of the central axis of each collimator gradually changes.

With the above configuration, in this conventional emission CT device, the collimator frame 12 is rotated and scanned in the direction of the arrow in the figure, and at this time, the information obtained by each radiation detector 14 is processed by a predetermined calculation processing algorithm. By calculating according to
Eight desired tomographic images can be synthesized.

FIG. 2 shows another emission CT device that has been used in the past.
The collimator frame 12 used in the apparatus shown in FIG. 1 is replaced by a rotatable cylindrical shielding plate 20 having eight small slits.

Therefore, when the test region 18 into which RI is injected is placed inside the cylindrical shielding plate 20, the radiation emitted from the injected RI inside the test region 18 will pass through the slits of the cylindrical shielding plate 20. The light is transmitted and received by the radiation detector 14.

At this time, by rotating and scanning the cylindrical shielding plate 20 and moving the slit, this radiation detector 1
It is understood that the radiation incident on the detector 4 is sector-scanned at an angle indicated by θ in the figure, and the data received by each detector 14 is equivalent to that of X-ray CT using a fan beam.

Therefore, with this conventional emission CT device,
By simply rotating and scanning the cylindrical shielding plate 20 so that the slits provided on the cylindrical shielding plate 20 move the distance between the slits, each radiation detector 14 receives a tomographic image of the subject area from the subject area 18. By processing the data thus obtained using a well-known reconstruction algorithm, it is possible to obtain the data necessary to synthesize the
It becomes possible to synthesize desired tomographic images.

However, in the conventional emission CT device shown in FIGS. 1 and 2, the collimator frame 1
2 or the cylindrical shielding plate 20 is separated from the detection frame 16 and rotated and scanned separately, so that the radiation emitted from the injection RI of the test region 18 is efficiently transmitted to each radiation detector 14 forming the detection frame 16. The light was not well received, and this was an obstacle to displaying a tomographic image of the region to be examined 18 in a short time and with high resolution.

That is, in the conventional device shown in FIG. 1, each collimator forming the collimator frame 12 is divided into two groups, and the direction of the central axis of the collimators in each group is set to gradually change. The radiation 300 incident on the radiation detector 14 from the collimators 10 located at both ends of the collimator group is
As shown in FIG. 3, the radiation is obliquely incident on the light-receiving surface 14a of the radiation detector 14 along the pores of the collimator 10, and out of the length d of the radiation detector 14, only the length represented by d' is the radiation. This will not contribute to the detection of Therefore, in such a conventional device, the entire area of each radiation detector 14 cannot be fully utilized to receive radiation, and therefore the radiation detection efficiency is not sufficient.

Furthermore, in the conventional device shown in FIG. 2, the radiation incident on the radiation detector 14 is sector-scanned at an angle indicated by θ in the figure by rotating and scanning the cylindrical shielding plate 20. If the angle is large, the radiation will enter the slit of the cylindrical shielding plate 20 obliquely, as shown in _FIG. I get confused. Therefore, as the sector scanning angle increases, the amount of radiation received by the radiation detector 14 decreases, resulting in a disadvantage that the detection efficiency cannot be sufficiently increased.

Purpose of the Invention The present invention was made in view of such conventional problems, and its purpose is to detect radiation emitted from RI injected into a test site with high efficiency by each radiation detector. An object of the present invention is to provide an emission CT device capable of synthesizing tomographic images of a region to be examined.

Structure of the Invention In order to achieve the above object, the apparatus of the present invention includes a plurality of radiation detectors arranged approximately in a ring frame shape,
RI injected into the test area placed within this frame
In an emission CT device that detects radiation emitted by each radiation detector and synthesizes a tomographic image of the examined region, the radiation detector is integrated with a dedicated collimator to form a radiation detection unit, and each radiation detection unit is integrated with a dedicated collimator. The unit is characterized in that it is fixed to the holding frame so that it can scan sectors.

By doing so, the device of the present invention can:
Regardless of the sector scanning angle of each radiation detection unit, the entire area of the radiation detector can always be used to receive radiation, allowing injection RI within the area to be examined.
It becomes possible to detect the radiation emitted from the radiation detector with high efficiency by each radiation detector.

Further, in the present invention, a plurality of radiation detectors are arranged approximately in a ring frame shape, and each radiation detector detects the radiation emitted from the RI injected into the test site placed within the frame. In an emission CT device that synthesizes tomographic images of a region to be examined, each radiation detector is integrated with a dedicated collimator to form a radiation detection unit, and each detection unit is capable of sector scanning on a holding ring that is rotated and scanned at a predetermined angle. The radiation receiving center axis is moved in parallel in synchronization with the rotational scanning of the retaining ring for sector scanning.

By doing so, the device of the present invention can:
The object part can be directly linearly scanned, and the signal processing time for the obtained data can be significantly shortened.

Embodiments Next, preferred embodiments of the present invention will be described based on the drawings. Note that the same reference numerals are given to the members corresponding to those of the conventional apparatus shown in FIGS. 1 to 4, and the explanation thereof will be omitted.

FIG. 5 shows a preferred embodiment of the emission CT device of the present invention. In the device of the embodiment, a plurality of radiation detectors 14 are arranged approximately in a ring shape, and RI is injected inside. Place the test site 18 in the ring and inject into the test site 18.
Radiation emitted from the RI is received by a radiation detector 14 via a collimator 10.

As shown in FIG. 6, the radiation detector 14 includes a radiation detection element 22 that receives radiation incident through the collimator 10 and emits light according to the amount of received light.
and a photomultiplier tube 26 that detects the light emission of the radiation detection element 22 and outputs an electric signal according to the amount of light emission from the electronic circuit 24.
A tomographic image of the region to be examined 18 is synthesized by processing electrical signals outputted from the test section 18 in a signal processing circuit (not shown).

The first characteristic feature of the present invention is that a dedicated collimator 10 is integrally attached to each radiation detector 14 to form a radiation detection unit 28, and each radiation detection unit 28 is fixed to a retaining ring 30 so as to be capable of sector scanning. It's what I did.

By doing so, the radiation incident on the radiation detector 14 via the collimator 10 is
Since it is always perpendicular to the light-receiving surface 14a of the radiation detection element 22, the radiation incident through the collimator 10 is always received over the entire area of the radiation detection element 22, no matter what sector scanning angle the radiation detection unit 28 scans. injection of the test site 18
It becomes possible to detect radiation emitted from RI with high efficiency.

As a result, in the emission CT device of the present invention,
It becomes possible to display a tomographic image of the examined part 18 in a short time and with high resolution.

7 and 8 show the mounting structure of the radiation detection unit 28 on the retaining ring 30, and the device of the embodiment has a plurality of vertically elongated unit mounting plates 32 on the retaining ring 30. A radiation detection unit 28 is mounted on each of these unit mounting plates 32 so as to face the center of the retaining ring 30.

Here, the unit mounting plate 32 is
One end thereof is rotatably fixed to a retaining ring 30, and the other end is formed to be capable of sector scanning.

The device of the embodiment thus retains the retaining ring 3.
In order to enable uniform sector scanning of each unit mounting plate 32 installed on the 0, a scanning ring 36 having engaging protrusions 36a formed at equal intervals is rotated to the inner circumferential side of the retaining ring 30 via a bearing 31. The unit mounting plate 32 is installed so as to be scannable, and a vertically elongated engagement slit 34 is formed at the other end of each unit mounting plate 32 to engage with each of the engagement protrusions 36a.

Then, the rotation of the motor 38 provided on the back surface of the retaining ring 30 is transmitted to the scanning ring 36 via a gear 39.
The scanning ring 36 is rotated and scanned at a predetermined scanning angle.

By doing this, if the scanning ring 36 is reciprocatingly rotated and scanned within a predetermined range, the scanning ring 36
As shown in FIG. 9, each radiation detection unit 28-1, 28-
2, 28-3, . . . are mechanically sector-scanned together with the unit mounting plate 32 at a predetermined scanning angle.

In this way, in the emission CT device of this embodiment, each radiation detection unit 28 mounted on the retaining ring 30 is aligned with the virtual center line 100 connecting the center O of the retaining ring 30 and the pivot position a of the unit mounting plate. By performing sector scanning at a predetermined angle around , and subjecting the data obtained from each detection unit 28 to predetermined signal processing, it is possible to synthesize a desired tomographic image of the examined region 18.

Therefore, according to the device of the present invention, since the dedicated collimator is integrally formed in the radiation detector 14, the radiation incident through the collimator 10 is distributed almost over the entire light receiving surface 14a of the radiation detector 14. vertically and injected into the test site 18
It becomes possible to detect radiation emitted from RI with high efficiency and synthesize tomographic images.

FIG. 10 shows an explanatory diagram of data obtained by sector scanning of the radiation detection unit 28, and FIG. 11 shows data obtained after signal processing of the data obtained in this way. It is shown.

That is, as shown in FIG. 10, when each radiation detection unit 28 scans sectors at a scanning angle of β on both left and right sides about the virtual center line 100, each detection unit 28 outputs fan beam projection data Pf of the region to be examined 18. (β, φ) is obtained.

Here, this projection data Pf is determined by the sector scanning angle β of the detection unit 28 and the holding ring 30.
given as a function of two angles, the angle φ depending on the mounting position of the detection unit 28 on the
In order to synthesize a tomographic image of the examined region 18 from such sector scanning projection data Pf (β, φ), the projection data Pf (β, φ) is scanned in parallel with a beam as shown in FIG. It is necessary to perform conversion processing into projection data P obtained by linear scanning. The projection data P after this conversion is P(l,
θ').

Here, θ'=φ+β l=R ₁ sin β where R ₁ represents the radius of the retaining ring.

Therefore, in this emission CT device,
If each radiation detection unit 28 can be linearly scanned from the beginning as shown in FIG. 11, there will be no need to convert the data obtained from each detection unit 28 as shown in FIGS. 10 to 11. It is understood that the calculation processing time for constructing a tomographic image from the obtained data can be significantly reduced.

Another feature of the present invention is that the radiation detection unit 28 mounted on the retaining ring 30 is capable of linear scanning, thereby significantly reducing the time required for image processing of the data obtained.

Therefore, in the device of the present invention, the detection unit 2
The holding ring 30 to which 8 is attached is configured to be capable of reciprocating rotational scanning within a predetermined range, and in synchronization with the rotational scanning of the holding ring 30, each radiation detection unit 28 is sector-scanned so that its radiation receiving center axis moves in parallel. There is.

By doing so, according to the present invention,
As shown in FIG. 12, the holding ring 30 is rotated and scanned left and right to the positions 200a and 200b centering on the scanning reference position 200, and at the same time, the unit 2 is synchronized with the rotational scanning of the holding ring 30.
By performing 8 sector scans, each radiation detection unit 28 is mechanically linearly scanned by combining both scans, and each detection unit 28 generates projection data P(l,
θ′) can be obtained directly. As a result, according to the apparatus of the present invention, it is possible to significantly shorten the calculation processing time for data output from each radiation detection unit 28.

FIG. 13 shows the specific structure of such a device, and in the device of the embodiment, the support body 40
A retaining ring 30 is rotatably supported on the top via a bearing 42, and the shaft output of a control motor (not shown) is transmitted to the retaining ring 30 via a gear 44, thereby rotating the retaining ring 30 within a predetermined range. scanning.

Note that when each radiation detection unit 28 is linearly scanned in this way, the distance z between the tip of the detection unit 28 and the examined part 18 changes, and the distance z between the detection unit 28
Place the area to be examined 18 on the preset focal point.
It is also conceivable that it may not be located. In such a case, some kind of guide may be provided on the retaining ring 30 in advance, and the detection units 28 may be configured to move forward or backward relative to the retaining ring 30 in accordance with the scanning position of each detection unit 28.

By doing this, the detection unit 28
The unit 2 detects the distance between the tip of the
8 can be kept almost constant regardless of the linear scanning position, and it becomes possible to further improve the accuracy of the obtained tomographic image.

Effects of the Invention As explained above, according to the present invention, a radiation detector is integrally provided with a dedicated collimator to form a radiation detection unit, and the detection unit scans sectors to detect RI injected into the test site. Therefore, the radiation detector of each detection unit can always efficiently detect the radiation emitted from the injected RI in the examination area over the entire area of the detector, regardless of its scanning angle. As a result, it becomes possible to display a tomographic image of the examined region in a short time and with high resolution.

Furthermore, according to the apparatus of the present invention, each of the radiation detection units can linearly scan the region to be examined and receive the radiation emitted from the injection RI in the region to be examined. Signal processing of the obtained data can be performed extremely easily and in a short time.

[Brief explanation of drawings]

Figures 1 to 4 are explanatory diagrams of a conventional emission CT device, and Figure 5 is an explanatory diagram of an emission CT device according to the present invention.
An explanatory diagram showing a preferred embodiment of the CT device, FIG. 6 is an explanatory diagram of a radiation detection unit used in the device shown in FIG. 5, and FIGS. 7 and 8 are a retaining ring portion of the device shown in FIG. 5. FIG. 9 is an explanatory diagram showing the structure of the apparatus of the present invention, and FIG.
0 and 11 are explanatory diagrams of data obtained by the device of the present invention, FIG. 12 is an explanatory diagram showing linear scanning of another embodiment of the present invention, and FIG. 13 is a diagram showing the holding of the device shown in FIG. 12. It is an explanatory view showing the structure of a frame attachment part. 10... Collimator, 14... Radiation detector,
18... Test site, 28... Radiation detection unit, 30... Retaining ring.

Claims (1)

[Claims] 1. A plurality of radiation detectors are arranged approximately in a ring frame shape, and each radiation detector detects radiation emitted from an RI injected into a test site placed within the frame. In an emission CT device that synthesizes tomographic images of a region to be examined, each radiation detector is integrated with a dedicated collimator to form a radiation detection unit, and each detection unit is fixed to a holding frame so as to be capable of sector scanning. An emission CT device featuring: 2 A plurality of radiation detectors are arranged approximately in a ring frame shape, and each radiation detector detects the radiation emitted from the RI injected into the area to be examined placed within this frame, and the tomography of the area to be examined is detected. In an emission CT device that synthesizes images, each radiation detector is integrated with a dedicated collimator to form a radiation detection unit, and each detection unit is attached to a holding ring that is rotated at a predetermined angle so as to be scanned in sectors. An emission CT device characterized in that sector scanning is performed so that the radiation receiving center axis is moved in parallel in synchronization with the rotational scanning of the emission CT device.