JPS6321039A - Multiple radiation source ct scanner - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to computed tomography using radiation or the like as a source.
: In the CT method, the present invention relates to a CT scanner that can reduce the time of CT examination by using multiple radiation sources and detectors.

[Conventional technology]

Conventionally, for example, in a first-generation or second-generation CT scanner that performs translation (translational scanning), as described in "Iwai W rCT Scanner" (Corona Publishing), pages 15 to 16, As shown in Figure 2, one radiation source 21 and one detector 22. Alternatively, multiple detectors (
(not shown) are placed with the subject 20 facing each other,
Radiation transmission data 25 (hereinafter abbreviated as transmission data) was collected by performing translational scanning 239 and rotational scanning 24 of these.

[Problem that the invention seeks to solve]

To illustrate the problems of conventional CT scanners, the following radiation sources:
This article describes a first generation CT scanner (see Fig. 2) that has two detectors each.

In the first generation CT scanner, the translational scanning range is 2,
Translational scanning pinch is ΔX, rotation pitch is Δθ (rad)
Then, the total number of samplings P for transmission data collection
teeth.

P=M-N=CQ/Δ0)・(7c/Δ0)=-(1)
However, M and N can each be expressed as the number of translations and nine rotations. Therefore, for example, 12=300mm.

If Δx=1mmt Δfll=1° and radiation counting time per sample point is 1 second, then 300X180X1
= 15 hours of inspection time will be required.

As described above, the long inspection time causes disadvantages such as deterioration of inspection efficiency and increase of inspection cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a CT scanner that can shorten the inspection time of a CT scanner that requires translational scanning compared to conventional CT scanners.

[Means for solving problems]

To achieve the above objectives, the source strength must be increased.

- It is sufficient to shorten the counting time per sample point.

However, when pulse counting is used to measure radiation, in which radiation is counted one by one, the counting rate is suppressed by the dead time of radiation detectors (scintillators, etc.) and measurement circuits, so radiation source intensity is unnecessarily measured. become unable to raise it.

- For example, a NaI (Tll) scintillator is used as a detector,
NIM (Nuclear Instr.
The maximum counting rate when using the Umenta-tion Module) is approximately 10 (28 seconds), and in a measurement system that achieves this counting rate, increasing the intensity of the a source makes it difficult to obtain accurate counts. you won't be able to get it.

Therefore, the present invention provides a CT scanner with translational scanning, in which a plurality of radiation sources and a plurality of detectors are arranged in place of the conventional structure in which one uA source is arranged, thereby shortening the translational distance. Therefore, the inspection time can be shortened.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

A plurality of radiation sources 10 and detectors 11 (four each in the case of the figure) are arranged at constant intervals d in the translational scanning direction 23.

They are arranged one-on-one with each other. Furthermore, radiation @
10 and a collimator 1 having a slit in front of the detector 11 made of a material that blocks radiation, such as lead or tungsten.
2 is a provision. This collimator narrows the radiation beam and determines the spatial resolution of the reconstructed CT image.

The intensity of the radiation source may be determined based on the slit width of the collimator 12, the maximum count rate of the distance detection system between the radiation source 10 and the detector 11, etc.1 For example, NaI (
TQ) When using a scintillator and NIM module,
The source intensity should be set so that a count value of No. 10 (28 seconds) can be obtained.

The number of radiation g10 can also be determined from the inspection time. In the embodiment, it is a CT scanner equipped with a radiation source 10 and a detector 11 on the + side. The distance d between the radiation sources is when the scanning range is 300+a+++.

d=300/10=30 mm, and the + side radiation source is installed on the same translation table. The translational scanning range in this example is 30 mm. Therefore, if the translation pitch is 1 m+a as in the above example, the number of translations will be 30 times.

The number of samplings P' covered by the above solid radiation source and detector arrangement and the detectors using the scanning method is calculated from equation (1) as ff=30mI11. When Δx=1ms+ and Δ0=1°, P=30×180. Therefore, if the measurement time per sample point is 1 second, the inspection time is 1.5 hours, which is 1/10 shorter than the inspection time of a conventional CT scanner with one radiation source and one detector. Can be done.

According to the present invention, since a plurality of radiation sources 10 are used, the influence of scattered radiation from adjacent radiation sources can be considered;
The influence of scattered radiation can be eliminated by increasing the distance d between the sources, narrowing the radiation beam by using a collimator on the source side, increasing the length of the collimator 24 on the detector side, etc.

Countermeasures for these are described in 10. Since the detectors 11 are arranged independently, this can be easily realized.

Furthermore, since a plurality of radiation sources 10 and detectors 24 are used, artifacts (pseudo images) due to variations in sensitivity between channels are likely to appear in the CT reconstructed image. This is known as a sensitivity correction method after the second generation by arranging a multi-channel detector.
By photographing a uniform substance (eg, air, water) in advance, variations between channels can be easily corrected.

Although the above embodiments have been described with respect to a first generation type CT scanner, the same can be said of a second generation type CT scanner in which the detector is multi-channeled and translational scanning is retained.

The inspection time is 1/1 when using n sources and detectors.
It can be shortened to n. In a CT scanner that uses, for example, gamma rays as a radiation source, the gamma ray source itself is small, so it is relatively easy to arrange a plurality of radiation sources.

〔Effect of the invention〕

According to the present invention, the inspection time can be shortened while maintaining the allowable count value of the detector.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a radiation source, a detector arrangement method, and a scanning method according to an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional first generation scanning method. 10... Radiation source, 11... Detector, 12... Collimator, 20... Subject, 23... Translational scanning, 24
... Rotational scanning.

Claims (1)

[Claims] 1. In a CT scanner that uses radiation as a source and performs translational and rotational scanning, the same number of the plurality of radiation sources and detectors are arranged in the translational scanning direction, and A multi-ray source CT scanner, characterized in that the CT inspection time is shortened by performing translational scanning between the two and shortening the distance of the translational scanning.