JPH04253848A - X-ray ct apparatus - Google Patents

Abstract

PURPOSE:To obtain a scanogram image capable of withstanding diagnosis by minimizing adverse effect which may be caused when a part of an object overlaps a pass to a reference channel in the photographing of the scanogram image. CONSTITUTION:Average reference correction data (standard correction data) for the photographing of scanogram is stored into a memory beforehand in terms of photographing conditions. A correction data storage memory and a reference correction control means are provided and when any correction data obtained during the photographing of a scanogram image becomes wrong, the average correction data corresponding to photographing conditions in the current operation is read out of the memory to perform a reference correction.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides an X
Regarding X-ray CT equipment, especially when an inconvenience occurs in the reference correction, the X-ray CT device can minimize the adverse effects.
This relates to the T device.

0002

[Prior Art] An X-ray tube-X-ray detector system of a CT scanner is configured to take X-rays while moving the subject relative to the subject in the body axis direction at a predetermined slice thickness. In order to perform reference correction during scanogram imaging to obtain an X-ray image, the multi-element X-ray detector (
Hereinafter, it will simply be referred to as a detector. ) There is an X-ray CT device with reference channels at both ends.

[0003] Here, the reference correction is mainly performed for the purpose of normalizing the measurement data and correcting errors in the measurement data due to temporal fluctuations in X-ray intensity at each imaging time in scanogram imaging. be exposed. Of these, the latter correction of X-ray intensity fluctuation is performed using the following equation (1). log(XD)-log(XR)
(1) Here, XD represents the X-ray input value of the data channel of the detector, and XR represents the X-ray input value of the reference channel of the detector.

0004

[Problems to be Solved by the Invention] The above-mentioned prior art has the following problems. That is, in the above equation (1), it is assumed that nothing other than air exists in the path between the X-ray tube and the reference channel of the detector, and therefore, this is required at the time of imaging.

However, during actual shooting, for example, if the setting of the subject is incorrect or the subject is too large, a part of the subject may end up on the path to the reference channel during some partial image shooting (views). It may also take a while.

[0006] In such a case, the XR value becomes inappropriate and the reference correction result becomes an incorrect value, and the partial image photographed under this condition becomes a dark, sunken image that is not suitable for diagnosis. There was a problem.

[0007]An object of the present invention is to minimize the negative effects even if a part of the object crosses the path to the reference channel, and to obtain a scanogram image that can withstand diagnosis. An object of the present invention is to provide an X-ray CT device.

[0008]

[Means for Solving the Problems] The above object is to perform scanogram image capture in an X-ray CT apparatus having reference channels at both ends of a multi-element detector of the CT scanner in order to perform reference correction in scanogram image capture. Standard reference channel data (standard correction data) for each imaging condition, mainly slice thickness,
If the pre-stored correction data storage memory for each tube voltage and the correction data obtained during scanogram image shooting are inappropriate (if the reference channel is covered by the subject), the relevant correction data will be displayed. This is achieved by providing reference correction control means for reading standard correction data corresponding to the photographing conditions at the time of photographing from the correction data storage memory and performing reference correction.

[0009]

[Operation] The correction data storage memory contains slice thickness,
Standard correction data obtained by actually performing scanogram measurements for various combinations of tube voltages is recorded in advance. When the correction data obtained during actual scanogram image shooting is inappropriate (when a problem occurs in which the reference channel is covered by the subject), the reference correction control means controls the slice thickness and tube voltage at the time of the shooting. Standard correction data corresponding to the combination is read out from the correction data storage memory and subjected to reference correction.

[0010] As a result, even if a part of the object may cross the path to the reference channel, the adverse effects of this can be minimized, and a scanogram image that can withstand diagnosis can be obtained.

[0011] Here, whether or not the correction data obtained when actually capturing a scanogram image is inappropriate is automatically determined by comparing the correction data obtained when capturing each partial image. Alternatively, the scannogram image that has been taken may be displayed and the judgment can be made visually. It can be determined that the data was inappropriate.) In any case, the reference correction control means is operated based on the judgment result, and the correction data of the corresponding path is replaced with the correction data recorded in the correction data storage memory to perform reference correction. .

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an X-ray CT apparatus according to the present invention. In FIG. 1, 1 is a CT scanner comprising an X-ray tube 1a and a detector 1b placed opposite to it, and 2 is a data collection unit into which measurement data from the detector 1b is input. It is a circuit.

3 is an arithmetic/control circuit that performs image processing operations using the data from the data acquisition circuit 2, various correction data, and other various data, or controls various parts of the CT apparatus. do. In the case of scanning a scanogram image, this arithmetic/control circuit 3 operates when the correction data obtained at the time of scanning a scanogram image is inappropriate, that is, when the reference channel of the detector 1b is connected to a subject (not shown). It also serves as a reference correction control means for reading out standard correction data corresponding to the photographing conditions at the time of photographing from a correction data storage memory to be described later and performing reference correction in the event that an inconvenience occurs.

4 is a display device for displaying a scanogram image, CT image, etc. obtained by the calculation and control circuit 3; 5 is a display device for supplying various data and commands to the calculation and control circuit 3; This is a console that operates each part.

6 is the slice thickness according to the imaging conditions;
For each combination of tube voltage, standard reference channel data (standard correction data) for scanogram image capture is provided.
For example, the correction data (R11, R12, R13, R21, R2
2, R23) Storage memory. Here, the standard correction data is obtained by actually performing scanogram measurements for various combinations of slice thickness and tube voltage with no object in the path to the reference channel of detector 1b (with only air present). reference channel data
data is used. The slice thickness obtained in this way,
Correction data for various combinations of tube voltages are recorded in the correction data storage memory 6 in advance.

Next, the operation will be explained. Since there is no particular difference in the normal scanogram image capturing operation from that of the conventional apparatus, the reference correction operation in the scanogram image capturing will be explained here.

FIG. 3 is a diagram showing an example of the channel configuration of the detector 1b. In FIG. 3, R1 and R2 are reference channels (hereinafter, X-ray data of the reference channels are also shown), D1 to Dn is each data channel (hereinafter, X-ray data of the data channel is also shown)
shows. As can be seen from FIG. 3, the reference channels R1 and R2 are located at both ends of the detector 1b.

Reference correction when taking a scanogram image using an X-ray CT apparatus having such a detector 1b is as follows.
This is performed by the arithmetic/control circuit 3 as follows. In the usual method, first, the average of the reference channel X-ray data R1 and R2 at the time of scanning the scanogram image is taken ((R1
+R2)/2), which is taken as reference correction data R. This correction data R is subtracted from the X-ray data D1 to Dn of each data channel (D1-R, D2-R
,...Dn-R), data of each data channel (CD1
, CD2,...CDn) (see Figure 4),
Reference correction is performed. After the reference correction, each data (CD1, CD2, . . . CDn) is further subjected to other corrections and displayed as a scanogram image on the display device 4.

Here, the X-ray data R1 and R2 input to the reference channel are transmitted through the X-ray tube 1 as described above.
It is required that no object exists in the path from a to the detector 1b. If even a part of the subject falls into the path, the reference correction will be inappropriate and that part of the scanogram image will be darkened.

Therefore, for example, when the operator discovers such an abnormality in the image when displaying the scanogram, the arithmetic/control circuit 3 (reference correction control means) is activated. As a result, the calculation/control circuit 3 stores the slice thickness at the time of scanning the scanogram image from the correction data storage memory 6.
Read standard correction data corresponding to the combination of tube voltages, replace the standard correction data with the reference correction data R, perform reference correction in the same manner as described above, and perform other corrections to create a scanogram image. Create and display device 4
to be displayed.

[0021] As a result, even if a part of the object may also cross the path to the reference channel, the adverse effects of this can be minimized, and a scanogram image that can withstand diagnosis can be obtained.

[0022]

As explained above, according to the present invention, standard reference channel data (standard correction data) for scanning scanogram images is stored in advance in memory for each shooting condition, If a part of the subject also crosses the path to the reference channel during image shooting, and the obtained correction data is incorrect, the standard correction data that corresponds to the shooting conditions at the time of image shooting. Since the information is read out from the memory and subjected to reference correction, it is possible to minimize the adverse effects caused by the above-mentioned inconvenience, and it is possible to obtain a scanogram image that can withstand diagnosis.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the device of the present invention.

FIG. 2 is a diagram showing an example of a standard correction data table recorded in a correction data storage memory of the same device.

FIG. 3 is a diagram showing an example of a channel configuration of a detector of the same device.

FIG. 4 is a diagram showing X-ray data of a data channel when reference correction is performed in the same apparatus as above, in correspondence with the data channels.

[Explanation of symbols]

1 CT scanner 1a X-ray tube 1b Multi-element X-ray detector 2 Data acquisition circuit 3 Arithmetic/control circuit (reference correction control means) 4 Display device 5 Operation console 6 Correction data storage memory

Claims (1)

[Claims] Claim 1: X-rays are taken while the subject is moved relative to the X-ray tube-detector system of a CT scanner at a predetermined slice thickness in the body axis direction, and a single X-ray is produced that is continuous in the subject body axis direction. In order to perform reference correction in scanogram image capturing to obtain an image, in an X-ray CT apparatus that has reference channels on both ends of the multi-element detector of the CT scanner, standard reference channel data for scanogram image capturing is used. The correction data storage memory stores data (standard correction data) for each shooting condition in advance, and when the correction data obtained at the time of scanning a scanogram image is inappropriate, An X-ray CT apparatus characterized by comprising reference correction control means for reading out corresponding standard correction data from the correction data storage memory and performing reference correction.