JP3604491B2 - Gamma camera device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gamma camera device that measures the spatial distribution of radiation, and more particularly to a gamma camera device that can change spatial resolution (also called positional resolution) and sensitivity without replacing a collimator.
[0002]
[Prior art]
FIG. 2 shows a schematic structure of a conventional gamma camera device. According to the figure, a conventional gamma camera device includes a lead collimator 101 provided with a plurality of honeycomb-shaped parallel holes 101a perpendicular to a radiation incident surface, and a sodium iodide disposed on a rear surface thereof. A scintillator 103 (phosphor) such as (NaI), a light guide 105 for guiding the light emitted by the scintillator 103 by the radiation particles, and a plurality of photomultiplier tubes 107 for detecting the light guided by the light guide. A position calculation circuit 109 for calculating the light emission position of the scintillator from the output of each photomultiplier tube 107; and a radiation shield 111, which measures the spatial distribution of gamma-ray emitting nuclides (RI) distributed in the subject 113. It had been.
[0003]
It is known that the spatial resolution R and the sensitivity G of the gamma camera change when the height a of the collimator used here changes, and the relationship is expressed by the following equation.
[0004]
R = d * (a + b + c) / a (1)
G = [d * d / (a * (d + t))] ² (2)
here,
R: spatial resolution G: sensitivity a: collimator height b: distance from the source to the collimator surface (radiation incident surface) c: distance from the bottom of the collimator to the detector (effective light emitting surface) d: the height of the collimator .
[0005]
Thus, it can be seen that both the spatial resolution and the sensitivity of the gamma camera change depending on the height of the collimator. In other words, the spatial resolution and sensitivity can be adjusted by the height of the collimator.
[0006]
By utilizing this principle, a conventional gamma camera device prepares multiple types of collimators having different heights and hole diameters in advance, and replaces the collimator according to the purpose of the inspection to change the spatial resolution and sensitivity of the gamma camera. Had been adjusted.
[0007]
For example, in a myocardial scintigram, in a first pass test immediately after a bolus injection of a drug labeled with a radioisotope from a vein, it is necessary to observe the temporal movement of the myocardium by a labeled substance passing through the heart at a high speed. A high counting rate is required even if the resolution is low, and in the myocardial SPECT examination thereafter, a high spatial resolution is required even if the counting rate is low in order to observe the viability of the myocardium.
[0008]
[Problems to be solved by the invention]
However, since the collimator is usually made of lead having high radiation shielding ability, the collimator is very heavy, and replacement of the collimator is a labor intensive operation, and lowers the operation rate of the gamma camera device.
[0009]
Further, there is a problem that a storage place for accommodating a large number of such collimators having a large mass must be secured adjacent to the gamma camera device.
[0010]
Also, in the myocardial scintigram, even if an attempt is made to collect two test data of a first pass test and a myocardial SPECT test by one injection of a radiopharmaceutical, the collimator characteristics required between the two tests are different. One had to give up, and in order to obtain both test results, it was necessary to carry out separate tests.
[0011]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a gamma camera device capable of adjusting spatial resolution and sensitivity without replacing a collimator. .
[0012]
Another object of the present invention is to provide a gamma camera device capable of collecting two test data of a first pass test and a myocardial SPECT test by one injection of a radiopharmaceutical, thereby reducing the radiation exposure dose of the subject. It is to be.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
That is, the invention according to claim 1 includes a collimator made of a radiation shielding material provided with a plurality of holes having openings on a radiation incident surface, and a plurality of radiation detectors respectively inserted into the plurality of holes of the collimator. And a detector moving means for arbitrarily varying the depth from the radiation incident surface to the radiation detection surface of the radiation detector.
[0014]
According to a second aspect of the present invention, in the gamma camera device according to the first aspect, the radiation detector is a semiconductor detector.
[0015]
According to a third aspect of the present invention, in the gamma camera device according to the first or second aspect, the detector moving means simultaneously changes the depth of at least two radiation detectors of the plurality of radiation detectors. It is a gist that it can be done.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view of a main part showing an embodiment of a gamma camera device according to the present invention.
[0017]
A collimator 3 using a radiation shielding material such as lead is fitted in a gamma camera frame 1 supported by an arm (not shown). A plurality of holes 3b having the same diameter are provided at regular intervals perpendicular to the radiation incident surface 3a of the collimator 3.
[0018]
The diameter of the hole 3b of the collimator 3 is not particularly limited, but may be, for example, 1 mm to 5 mm. Similarly, the thickness of the collimator wall can be 0.1 mm to 2 mm.
[0019]
In each hole 3b of the collimator 3, one semiconductor radiation detector 5 (hereinafter, referred to as a detector) using cadmium telluride (CdTe) is housed one by one. These detectors 5 are semiconductor radiation detectors of a type in which incident radiation generates pairs of electrons and holes in a semiconductor, and this is extracted as an electric current to the outside. To the connecting plate 9. The radiation detection signal from the detector 5 is connected to a signal processing circuit 13 mounted on the connection plate 9 by a signal cable 11 inserted inside the connection shaft 7.
[0020]
Further, below the collimator 3, a detector moving means 21 including a step motor 15, a screw / nut mechanism 17, and a guide shaft 19 is provided.
[0021]
The gamma camera frame 1 is provided with four guide shafts 19 at four corners thereof for sliding the connecting plate 9 perpendicular to the radiation incident surface 3a.
[0022]
The step motor 15 can rotate forward or backward by a predetermined angle by a pulse signal sent from a gamma camera controller (not shown). The rotation of the step motor 15 is transmitted to the lead screw 23 fixed to the rotation shaft. Forward or reverse rotation of the lead screw 23 is converted into forward or backward movement of a nut 25 screwed to the lead screw 23, and moves the connecting plate 9 fixed to the nut 25 along the guide shaft 19.
[0023]
Since the connecting plate 9 is provided with a plurality of connecting shafts 7 connected to the respective detectors 5, the respective detectors 5 move through the respective collimator holes 3b as the connecting plate 9 moves. It can move in the depth direction.
[0024]
Accordingly, the respective detectors 5 simultaneously move the collimator holes 3b in the direction of their depths in accordance with an instruction from the gamma camera control device, thereby moving the radiation detection surface (not shown) of the detector 5 from the radiation incident surface 3a of the collimator 3. , The effective collimator height h can be changed, and the spatial resolution and sensitivity can be adjusted steplessly.
[0025]
Next, an operation when the gamma camera device according to the present invention is applied to myocardial scintigraphy, which is a typical nuclear medicine examination of the heart, will be described. First, the position of the detector is set to a position close to the radiation incident surface of the collimator, and the gamma camera device is set to a high sensitivity state.
[0026]
Next, a radiopharmaceutical (for example, labeled using ²⁰¹ Tl, ^99m Tc, or the like) to be taken into muscle cells by myocardial activity is injected as a bolus from the vein of the elbow of the subject. Then, first-pass inspection data is collected, and the movement of the myocardium can be known from the continuous morphological change of the heart lumen during the process in which the radiopharmaceutical passes through the right heart system, the lungs, reaches the left heart system, and flows out to the aorta.
[0027]
Next, after the injected radiopharmaceutical is taken up into cells of the myocardium by metabolism or the like, a myocardial SPECT test is performed. At this time, the position of the detector is set to a position far from the radiation incident surface of the collimator, and the gamma camera device is set to a high resolution state. By this myocardial SPECT examination, a blood flow distribution map of the myocardium is obtained, and lesions such as ischemic heart disease and myocardial infarction are depicted as cold areas.
[0028]
As described above, by using the gamma camera device according to the present invention, the resolution and sensitivity of the gamma camera device can be changed by moving the position of the detector inside the collimator hole, and one injection of the radiopharmaceutical can be performed. Only by doing so, the first pass examination and the myocardial SPECT examination can be performed, so that the burden on the patient is greatly reduced.
[0029]
Although the preferred embodiment has been described above, this does not limit the present invention. For example, a collimator in which the holes of the collimator are hexagonally arranged in a hexagonal close-packed manner may be employed, and various forms of detector moving means are conceivable. Further, the detectors may be divided into a plurality of groups and moved for each group of the detectors. Further, as the type of the radiation detector, the radiation detector movably housed in each collimator hole may be a combination of a scintillator and a semiconductor photodetector (phototransistor, photodiode, etc.).
[0030]
【The invention's effect】
As described above, according to the present invention, the radiation detector is inserted into each of the plurality of holes provided in the collimator, and the depth of the radiation detector up to the radiation detection surface is arbitrarily changed to exchange the collimator. There is an effect that it is possible to provide a gamma camera device capable of changing the spatial resolution and sensitivity in a short time without performing.
[0031]
Further, according to the present invention, there is provided a gamma camera device capable of collecting two examination data of a first pass examination and a myocardial SPECT examination by one injection of a radiopharmaceutical, thereby improving examination efficiency, and improving the examination efficiency and the examination physician and examination technician. Therefore, there is an effect that the work load of the subject can be reduced and the radiation exposure dose of the subject can be reduced.
[0032]
Further, according to the present invention, since there is no need to replace a heavy collimator, the burden on the operator can be reduced, and the operating rate of the gamma camera device can be improved.
[0033]
Further, since there is no need for a place for storing a large number of collimators adjacent to the gamma camera device installation place, there is an effect that the space of the examination room can be effectively used.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional perspective view illustrating an embodiment of a gamma camera device according to the present invention.
FIG. 2 is a sectional view of a main part of a conventional gamma camera device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Gamma camera frame, 3 ... Collimator, 5 ... Semiconductor detector, 7 ... Connection shaft, 9 ... Connection plate, 11 ... Signal cable, 13 ... Signal processing circuit, 15 ... Step motor, 17 ... Screw / nut mechanism, 19 ... guide shaft, 21 ... detector moving means, 23 ... lead screw, 25 ... nut.

Claims (3)

A collimator made of a radiation shielding material provided with a plurality of holes having openings on a radiation incident surface,
A plurality of radiation detectors respectively inserted into a plurality of holes of the collimator,
Detector moving means for arbitrarily varying the depth from the radiation incident surface to the radiation detection surface of the radiation detector,
A gamma camera device comprising: The gamma camera device according to claim 1, wherein the radiation detector is a semiconductor detector. 3. The gamma camera device according to claim 1, wherein the detector moving unit is capable of simultaneously changing a depth of at least two radiation detectors of the plurality of radiation detectors.

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