JPH0345A - Phantom for ct - Google Patents

Abstract

PURPOSE:To relieve a positioning burden for calibration on a body to be tested the centers of the testing portions of which are changed from each other by providing a plurality of cylinder body parts joined together in a state that central axes are positioned eccentrically to each other. CONSTITUTION:In an X-ray CT, a phantom 17 is used to perform calibration of a detector 9. The phantom 17 comprises a phantom part 17a for a head and a phantom 17b for a trunk, and the phantoms are joined together such that central axes O1 and O2 of the phantoms are positioned eccentrically to each other. A mounting device 19 is mounted on the one end surface of the phantom 17, the mounting device 19 is mounted to a mounting jig 15, and the phantom 17 is disposed to a top plate 11. Through slide of the top plate 11, the phantom 17 is disposed in a photographing space 5, and reference data on the head part of a body P to be tested and the trunk part of the body P to be tested is obtained by the phantom part 17a for a head and the phantom part 17b for a trunk. Since there is no need to vertically move the top plate 11 and effect tilt operation of a frame 1, a scan time is shortened and the burden of an operator is relieved.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a rough phantom for CT used for calibrating a detector included in a CT apparatus, and in particular, to Concerning structural improvements.

(Prior Art) In a CT apparatus, for example, an X-ray CT apparatus, the sensitivity of a detector for detecting X-rays changes over time, so calibration of the sensitivity of the detector is required.

Therefore, in advance, a phantom made mainly of water or the like, which has a constant amount of X-ray absorption, is scanned to obtain reference data about a cross section in the X-ray irradiation direction (hereinafter simply referred to as a cross section), and based on this reference data, the subject is The scanned data is being calibrated.

In this type of calibration, a calibrated tomographic image of the subject is displayed on one display screen by inserting and arranging the subject in the area occupied by the cross section of the phantom in the imaging space (hereinafter referred to as the phantom area). The system is configured to display . Therefore, the larger the phantom area, the easier it is to place the subject in the imaging space, but the larger the cross-sectional area of the phantom, the more
It is desirable that the cross-sectional area of the phantom be as close as possible to the cross-sectional area of the test site of the subject, since the amount of radiation absorption is large and the signal amount S is reduced, leading to a decrease in the S/N ratio of the reference data.

For this reason, when scanning the subject's head, we use a cylindrical head phantom with a diameter that corresponds to the cross-sectional area of the head, and when scanning the torso, we use a cylindrical head phantom that has a diameter that corresponds to the area of the torso. A phantom for the torso is used. Furthermore, a combined phantom in which these head and body phantoms are superimposed with their respective central axes aligned has also been put into practical use.

Using this combined phantom, phantom regions ffj, for the head and torso (hereinafter referred to as head phantom region and torso phantom region, respectively) are obtained in the head and torso regions, respectively, and these respective phantom regions are If the subject's head and torso are continuously scanned within the scanner, the scanning time can be shortened.

(Problem to be Solved by the Invention) However, when photographing the head, it is often desired to perform the photograph with the well-known 0M line aligned in the vertical direction. When continuously scanning the torso with steps,
If the above-mentioned combined phantoms whose central axes coincide are used, a situation may occur where the head does not fit within the head phantom area when the torso is placed in the imaging space so that it falls within the torso phantom area, and each phantom area In order to place the head and torso inside, it becomes necessary to move the top of the bed on which the subject is placed up and down, or to tilt the pedestal.
This caused a burden on the operator.

The present invention has been made in consideration of the problems of the prior art, and aims to provide a rough antom for CT that can reduce the burden of hlU1 alignment for calibration for objects in which the center of each examination part changes. purpose.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the rough antom for CT according to the present invention includes a plurality of cylindrical body parts that are joined together with their central axes eccentric to each other. The gist is that.

(Function) According to the above-described configuration, the following effects are achieved. That is, for example, when imaging a head whose 0M line is vertically aligned and a torso whose central axis differs from that of the head, these images can be used for multiple examination parts whose central axes change from each other. If calibration is performed using a phantom in which the center axes of multiple cylindrical bodies are eccentric to correspond to the changing center axes, the subject can be slid without moving the top plate up and down or tilting the pedestal. Since each test site enters the phantom region with just one step, the burden of positioning for calibration with respect to the object can be reduced.

(Embodiment) An embodiment of the rough antom for CT according to the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a CT scan in which the phantom according to the present invention is used.
, for example, shows a schematic configuration of an X-ray CT.

As shown in this figure, -XvAcT is equipped with a gantry 1 and a bed device 3. In the pedestal 1, an X-ray tube 7 and a detector 9 are disposed facing each other with an imaging space 5 formed therebetween. This X-ray tube 7 rotates around a center assumed in the imaging space 5, and directs the X-ray toward an X-ray detector 9, which also rotates around the center.
It is designed to emit lines in a fan shape. The signal obtained by the X-ray detector 9 is then amplified, integrated, and digitally converted.

Processing such as image reconstruction is performed, and the content of the processing results is displayed as an image on a monitor such as a CRT (not shown).

Further, a top plate 11 is provided on the upper surface of the bed device 3. The top plate 11 is configured to be slidable along its longitudinal direction, and a mounting jig 15 is attached to the end of the pedestal 1 side to allow attaching and detaching accessories such as the headrest 13.
is installed.

In an X-ray CT having such a configuration, a phantom 17 is used to calibrate the detector 9.

This phantom 17 is as shown in FIG.

It consists of a head phantom part 17a exhibiting a cylindrical body and a body phantom part 17b. And each of these Phantom 17
The diameters of a and 17b are approximately 240 mm, 111 mm, and 400 mm, respectively, depending on the dimensions of an adult's head and body.

Also, the central axis of each of these phantoms is 0.202
are eccentric and combined with each other. The degree of eccentricity is determined by the following: The torso of the subject P is placed horizontally on the top plate 11, and the headrest 13 is placed on the headrest 13, which is inclined so that the 0M line connecting the outer corner of the eyes and the inner corner of the ear is in the vertical direction. The central axis B (two-dot chain line) and the central axis B2 (three-dot chain line) of each of the two heads of the subject are set so that they coincide with the central axis ○1, 0□. The central axis 0. of the phantom portion 17a. is disposed at a position approximately 801111 points above the central axis 02 of the body phantom 17b.

Note that the reference numeral 19 indicated by a broken line in FIG.
7 to the mounting jig 15.

Next, the operation of the above embodiment will be described.

A mounting device 19 is installed on one end surface of the phantom 17, and this mounting device 19 is attached to the mounting jig 15, so that the phantom 17 is disposed on the top plate 11. By sliding this top plate 11, the phantom 17
is inserted into the photographing space 5, and a 5-head phantom section 17a,
The subject P in each part of the torso phantom part 17b!
Obtain reference data for part I and torso part of subject P.

Next, in the mounting jig 15, the phantom 17 and the mounting device W19 are removed and the headrest 13 is mounted, and the subject pg section on which the headrest 13 is placed is tilted so that the 0M line is in the vertical direction. let

Next, the torso of the subject P is placed on the top plate 11 and the head is placed on the headrest 17, and continuous scanning is performed while the top plate 11 is slid.

During this continuous scanning, the head and torso of the subject P can be set using the phantom 17 by simply sliding the top plate 11 without moving the top plate 11 up and down or tilting the pedestal 1. Since the data can be entered into the head phantom region and torso phantom region, all the obtained data can be calibrated. This calibrated data is then subjected to various signal processing and displayed as an image on a monitor.

In this way, since there is no need to move the top plate 11 up and down or to tilt the pedestal 1, the scanning time can be shortened and the burden on the operator can be reduced. Further, the vertical movement mechanism and the tilt 111fit are not required for each of the bed device N3 and the pedestal 1, and by not providing these mechanisms, the cost of the bed device 3 and the pedestal 1 can be reduced.

[Effects of the Invention] As explained in detail above, in the rough phantom for CT according to the present invention, for a plurality of examination sites whose central axes change from each other, the phantom has a plurality of positions corresponding to the changing central axes. If calibration is performed using a phantom whose central axis of the cylindrical body is eccentric, each test region can be brought into the phantom area by simply sliding the subject without moving the top plate up or down or tilting the pedestal. Therefore, the burden of positioning for calibration with respect to the subject can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a CT apparatus using a phantom according to the present invention, and FIG. 2 is a perspective explanatory diagram showing an embodiment of a rough antom for CT. 1... Frame 3... Bed device 7...
X-ray tube 9...detector 11...top plate 17...
... Phantom 17a ... Head phantom part 17b ... Body phantom part

Claims (1)

[Claims] (1) A CT phantom characterized by comprising a plurality of cylindrical bodies that are joined together with their central axes eccentric to each other.