JPS60207645A - Radiation tomogram apparatus - Google Patents

Abstract

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

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a tomographic imaging apparatus (Co
m [) u t e r T o m o g r
a p hy :hereinafter referred to as C1-device). (Prior art) Conventionally, radiation is projected onto a subject from a number of angular directions, the projections of the radiation are collected, and from these projection data, each part of the subject is determined by computer processing. A CT apparatus that reconstructs an image of the R1'i layer of a subject based on the line absorption component is well known. Figure 1 shows such a CT-1'! i is a structural diagram showing the main parts of the stomach. In FIG. 1, 1 is an X-ray tube used as a radiation source, 2 is an X-ray detector used as a sheet ray detector, etc. Rotate and cover while reversing the rotation direction in rotation 10. Then, while rotating, X-rays are applied to the subject 3 from many angular directions to collect projection data, and these projection data are converted into digital signals and sent to the combination coater 4.
First, the combicoater 4 reconstructs and covers the tomographic image of the subject 3. Collecting these projection data

[ terminates acceleration in the run-up section to the reference angular position Pa (], starts collecting projection data at the reference angular position Po, first collects the first projection data, and then as shown in Figure 2. Rotating at a constant speed and at constant angular intervals to position 1〕o・[)
Collect projection data every time. By the way, in such a Cr device, generally, X-rays are irradiated in synchronization with the commercial power frequency. However, the X-ray tube 1 and the X-ray detector 2 have a reference angle N P
In the conventional method of irradiating XIm at the peak of the power supply voltage immediately after detecting that it has reached o,
As shown in FIG. 3, the angular position Po' at which the beam irradiation starts deviates from the reference angle mPo by Lo in the rotational direction. Furthermore, since the rotation directions of the X-ray tube 1 and the X-ray detector 2 are reversed every time, the deviation between reciprocating rotations is doubled. Such a rotational shift also affects the reconstructed tomographic image of the subject 3, which is undesirable. One way to correct this kind of rotational deviation is to shift the reference angle position detection sensor so that the rotational deviation becomes zero, but if the rotational speed is low or high,
Since there are different types and two types of rotational directions, detecting a total of four reference angle positions would be cumbersome and adjustment and control processing would be complicated, so it is not practical. The present invention has been developed in view of the above points.The purpose of the present invention is to compensate for rotational deviation and improve the reproducibility of the RJi layer image of the subject. Configuration) The present invention achieves this object by rotating a radiation source and a radiation detector around a subject, irradiating radiation in synchronization with the commercial power frequency, and collecting projection data.
The disconnection tomography apparatus is configured to reconstruct a tomographic image of the subject based on the projection data, and the angle at which the projection data collection is started and the reference angle at which the projection data collection is started are determined. The present invention is characterized in that a tomographic image of the subject is reconstructed based on the angular difference information. (Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 4 is a tab diagram showing an embodiment of the present invention, and the same parts as in FIG. In FIG. 4, reference numeral 5 indicates a rotating section including the X-ray shaft 1 and the X-ray detector 2, and 6 indicates a rotation control section that controls the rotational operation of the rotating section 5. (from rotating part 5) droplet data collection device 7
The projection data Sd is inputted to the second viewer 4 via the reference angle detection signal S+ and the rotational azimuth pulse signal 82 are inputted to the rotation control section 6. A rotation control 91 signal 83 is output from the rotation control section 6 to the rotation section 5, and deviation angle information S4 is input to the computer 4. The operation of the apparatus configured as described above will be explained using time charts 1 to 1 in FIG. 5. In addition, in Figure 5 (
, (a) shows the commercial power supply frequency pulse, (b) shows the X-ray control signal, (C) shows the reference angle detection example @S1, and (d) shows the rotational azimuth pulse signal 3z. ing. The reference angle detection signal S1 is sent to the rotation control unit 6 when it is detected that the X-ray tube 1 and the X-ray detector 2 have reached the reference angle position at which to start collecting projection data, that is, starting X-ray irradiation. be done. Rotation direction tel pulse (Fj number 82 is X-ray tube 1
And when the X-ray detector 2 rotates by a certain angle, one pulse is sent to the rotation control unit (8.
It is assumed that when the ray tube 1 and the X-ray detector 2 rotate 360 degrees, 2880 pulses of the power potential pulse signal 2) S2 are sent out per rotation. That is, in the case of this example, 0.125[
By rotating, one rotational azimuth pulse signal S2 is sent out. The rotation control unit 6 calculates the angle difference between detecting the reference angle detection signal S1 and actually starting the collection of the first projection data by using the rotational azimuth pulse signal @S? generated during that time. The measurement result is sent to the computer 4 as deviation angle information S4. That is, the rotation control unit 6 counts the number n of pulses of the rotational azimuth pulse signal 82 that is generated between the time when the reference angle detection example @S1 is detected and the subsequent rising edge of the X-ray control signal, and calculates the deviation angle. Measure the amount. In this embodiment, the resolution of the deviation angle amount is 0.125 mm as described above. This resolution is 115 times the X-ray irradiation interval angle when rotating at low speed, and 1/10 of the X-ray irradiation interval angle when rotating at high speed. The X-ray irradiation angle is corrected each time based on the deviation angle information S4 entered, and 1 fl of the subject 3 is assumed to have been collected at the corrected angle.
Performs reconstruction processing of the i-layer image. Here, set the reference angle to eo.
, resolution of deviation angle amount is θa, X-ray irradiation interval angle is Δ0
Then, the first XPA illumination angle θ1 is θ, θQ
+rl・ea, and the second X-ray illumination angle e2 is θ 2 − θ
(, ten n ・ θ a − t Δ θ, and the third
The X-ray radiation angle e3 for the second time is θ3-00+")・θa+2
・Δθ. In addition, while correcting such an angular difference n・ea,
There are two methods for performing the image composition processing of the lli layer image: a method of adding correction to projection data, and a method of adding correction in back projection processing. As an example of a conventional method, correction is performed by linear interpolation according to the angle In・ea from adjacent projection data, and the basic
- There is a method of creating projection data in which the first [1] X-ray irradiation is performed at the angle θ0. The first X-ray irradiation angle that caused the angle difference of r)・ea is Ol, the projection data at this time is P(ei), and the projection data obtained by supplementary one is [](θi l
' ), then P(ei') is P (θ 1 ' ) = P (θ 0 doo (i-
1>-ΔO)=((Δθ-n-ea) ・P((El
i)-t r) ・θ a-P(θ i-1) )
/Δθ. An example of the latter method is a method in which the parameters of the X-ray irradiation angle are changed by the angular difference n-ea when performing back projection calculations on projection data. In the above embodiment, an example in which X-rays are used as the radiation is explained, but the IC is not limited to this, and other radiation may be used. (Effects of the Invention) As explained above, according to the present invention, with a simple configuration,
To improve the reproduction of the IIi layer image of the subject by correcting the rotational deviation of the CT device that collects projection data in synchronization with the commercial power frequency and reconstructs the tomographic image of the subject. Can be done. Moreover, this can significantly improve the efficiency and deterioration of diagnostic analysis that involves position specification when a plurality of tomographic images are taken on the same tomographic plane or at regular intervals.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing the main parts of the CT device, Figures 2 and 3
1 is an explanatory diagram of the operation of FIG. 1, FIG. 4 is a block diagram showing an embodiment of the present invention, and FIG. 5 is a time chart for explaining the operation of FIG. 1... Radiation source (X-ray tube) 2... Radiation detector <xm detector) 3... Subject 4... Computer 5... Rotating section 6... Rotation control section 7. ...Data acquisition device patent applicant Yokogawa Medical Systems Co., Ltd. Figure 1 η

Claims (1)

[Claims] Radiation is irradiated in synchronization with the commercial power frequency while rotating the radiation source and the 11i line detector around the subject, collecting projection data, and reconstructing a tomographic image of the subject based on the projection data. In the radiation tomography apparatus configured to perform the following, the difference between the angle at which projection data collection is started and the reference angle at which projection data collection is started is determined, and the angle difference information is used to calculate the difference between the angle at which projection data collection is started and the reference angle at which projection data collection is started. A radiographic tomographic nine-image apparatus characterized by reconstructing tomographic images.