JPS5949746A - Ct 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 The present invention relates to a translate-rotate type (second generation) OCT apparatus using a fan-shaped X-ray beam.

A conventional CT rack of this kind, as shown in FIG.
Using a detector 2 in which CH detection parts are arranged closely in parallel,
Translation and rotation operations are performed on the measurement area 3 to obtain projection data, and image reconstruction calculations are performed using this data to reconstruct a CT image. In Fig. 1, 4 is the X-ray tube, 4a is its focal point, α is the fan beam angle, A and mouth are the translation inversion position R, Li/i)
Run rate distance.

By the way, in such a second generation OCT device, in order to obtain projection data for the entire measurement area 3, the X-ray tube 4 is
When the detector 2 is at the translation inversion position (the position shown by the solid line), the right end of the X-ray beam 1 is at the translation inversion position (the position shown by the dotted line). The translation distance is set so that each left end completely leaves the measurement area 3. For this reason, as the fan beam angle α increases, the translation distance also increases, which has the disadvantage that translation takes time and the apparatus becomes larger.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a new CT device that can reduce the translation distance, shorten the translation time, and downsize the device. shall be.

The present invention will be described in detail below with reference to FIG. 4 (not shown in FIG. 2). FIG. 2 is a diagram showing an embodiment of the CT apparatus according to the present invention. I2 is an arithmetic unit that receives data from the scanner body 11 and performs data interpolation and image reconstruction calculations, 43 is a TV monitor that displays CT images based on the calculation results, and 14 is an image reconstruction +1q In addition, in FIG. 2, the same reference numerals as in FIG. 1 indicate the same or equivalent parts.

That is, in the present invention, first, as shown in FIG. 2, the translation distance is set within a range that does not completely leave the measurement area 3 at each translation reversal position.

According to this, during translation, data on both ends of the measurement area 3 cannot be actually measured. For example, in Figure 2, if we now translate from the reversal position A to the mouth,
At the start, the right end of the X-ray beam 1 at the reversal position A, here the part detected by the detection parts I CH to 4 CH of the detector 2, has not left the measurement area, so the detection part I C) (~4 CH) The data at the left end of measurement area 3 cannot be measured completely. Figure 3 is a diagram showing this situation.
In the figure, the ○ mark indicates a portion where data is actually traced, and the ∆ mark indicates a portion where data is not actually measured. As can be seen from FIG. 3, in the example shown in FIG.
Data at the left end of measurement area 3 by CH 4 cannot be measured.

However, at this time, in the vicinity of the left end of the measurement area 3, where data was not actually measured by the detection unit l CH~4, CH.

At the time of the next translation, that is, at the time of translation from the reversal position A to A (or from A to the mouth) after the rotation operation performed following the translation from the reversal position A to the mouth, the detection unit ] 2 CH ~ 5 C1 (The data is actually measured by .) The present invention uses interpolation to obtain the data at each end of the measurement area 3 that cannot be measured from the actual measurement data, and calculates the data in the entire R to survey area 3. This is to obtain projection data. Figure 4 is a diagram for explaining an example of the interpolation method in this case.
+ C3 to D3 and D4 are unmeasurable data at the start of translation from the above-mentioned inversion position A to the mouth, A-D are actual measurement data bordering on the unmeasurable data at the start of the same translation, A'-D' respectively indicate the arrangement of data actually measured in the vicinity of the left end of the unmeasurable measurement area 3 in the detection unit 12 CJ (at the time of the next translation. In this FIG. 4, the unmeasurable data (data in the portion marked with Δ), for example, by interpolation from D to D and A' to D'; here, linear interpolation is used.

This interpolation is performed using the RAW data A/A from the scanner body 11.
an arithmetic unit 12 that takes in (D-converted digital data);
It will be held in This calculator 12 obtains data that cannot be measured by interpolation to obtain projection data for the entire measurement area 3, and then reconstructs the image using this projection data. ? ,I do. The result of this performance is transmitted to the TV monitor I3 and displayed as a CT image.

Note that the translation distance in the device of the present invention is 1, 2
Translate inversion position A as shown in the figure.

At the mouth, the X-ray beam 1 on each side of the measurement area 3 performs image reconstruction! It is conceivable to slightly leave the 4-head area 14 and set it to 7 or higher punch strength.

In the embodiment described above, linear interpolation was used to interpolate the unmeasurable data, but other methods such as quadratic interpolation and divine interpolation can also be used.

As described above, the present invention reduces the translation distance, so that the time required for translation/slate can be shortened, and the apparatus can be made more compact. Moreover, in this case, the data that could not be measured due to the reduction of the translation distance was obtained by interpolation from the actual measurement data to obtain projection data in the entire measurement area, and image reconstruction was performed using this data. This has the effect of minimizing the adverse effects on CT images due to rate distance reduction.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a conventional device, FIG. 2 is a diagram showing an embodiment of a CT device according to the present invention, and FIGS.
Each figure is a diagram for explaining the operation of the apparatus of the present invention. l...X-ray beam, 2...detector, 3...measurement area, 4...X-ray tube, 12...computer, 13...T
V monitor, i. Mouth: Translate inversion position, L: Translate distance. Patent Applicant Hitachi Medico Co., Ltd. Agent Patent Attorney Masami Akimoto Figure 1 Figure 2 1 Figure 3 12 ( 11 ( 0

Claims (1)

[Claims] In a translate-rotate CT rack using a fan-shaped X-ray beam, at the translate reversal position,
The translation distance is set within a range in which the X-ray beam on the measurement area side does not completely leave the measurement area, and the data at both ends of the measurement area that cannot be measured is interpolated from approximate actual measurement data. A CT rack apparatus characterized by comprising calculation means for obtaining projection data in the entire measurement area by calculating the data and performing image reconstruction calculations using the projection data.