JP2003126078A - X-ray ct unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT unit which does not cause abnormal imaging even if there is any distortion in geometrical measurement system that has been accompanied by the application of two-dimensional multiseriate detectors. SOLUTION: In this X-ray CT unit, after X-rays applied from an X-ray producer 30 and transmitted through an subject 60 are detected by a scanner 20, the measured signals are sent to a image processor 40 to go through a prescribed image processing and then the processed images are displayed on a image display 80 by an image displaying unit 50 to be used in diagnosis and the like. The scanner 20 is provided with two-dimensional multiseriate detectors, having two-dimensional structure, so as to detect such transmitted X-rays. The image displaying unit 50 corrects unreasonable CT fluctuations or abnormal artifacts appearing on the display, by reading, based on the measured data, the change in X-ray exposure due to distortion in geometrical measurement system of the detectors, and by creating a corrective function to normalize the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus for obtaining a tomographic image of a subject by using X-rays, and more particularly, a two-dimensional multi-row detector having a two-dimensional structure as an X-ray detector. And an X-ray CT apparatus having

[0002]

2. Description of the Related Art An X-ray CT which utilizes a transmitted X-ray to obtain a tomographic image of an object such as a patient for diagnosis.
The device is already widely used. In recent years, in such an X-ray CT apparatus, in a scanner, transmission X
As a detector for detecting a line, a so-called two-dimensional multi-row detector having a two-dimensional structure has been widely adopted.

X-ray CT having such a two-dimensional multi-row detector
An example of the flow of measurement by the device according to the related art will be described with reference to the attached FIG.

As shown in FIG. 9, first, X-ray CT
In the apparatus, after performing preliminary measurement for preparing the X-ray tube (normally, it is performed only once after the power is turned on), an air measurement procedure is performed, for example, at intervals of about 2 hours, and then the object (object ) Is measured. That is, in the X-ray CT apparatus, an air measurement procedure (air calibration) is performed in order to measure the data that is the X-ray dose for irradiating the object before actually measuring the object. The data measured here is once stored in the storage device of the X-ray CT apparatus, and is used as the X-ray dose applied to the object when the object is actually measured thereafter.

After that, a measurement procedure for obtaining a tomographic image of the object, which is the main purpose of using the X-ray CT apparatus, is performed. As is apparent from the above, at this time, the detector is the object. Only the X-ray dose after passing through will be measured.

This will be described more specifically by using mathematical expressions. Calculations for obtaining projection data (integrated value of absorption coefficient) are shown as follows: I ₀ is the measurement result in the air measurement procedure (that is, the X-ray dose irradiated on the object), I is the X-ray dose after passing through the object, Then, X at any point x on the X linear path
When the linear absorption coefficient is μ (x), the X-ray dose I after passing through the object is expressed as follows.

[Equation 1]

Alternatively, in order to obtain the projection data, the relation shown by the following formula is established.

[Equation 2] Note that, here, "Log" is basically a natural logarithm, however, it may be a common logarithm. Also, "e
"xp" is an exponential function, and the integral term therein is the projection data to be obtained.

This projection data can be obtained, for example, from the attached FIG.
An object existing in the middle of the X-ray path as shown in (
It is the result of integration of the X-ray absorption coefficient of the measured object), which is the value of the Radon transform result of the original object. actually,
The data set of (I ₀ , I) is a large amount of data obtained by collecting the data having the length of the number of detection elements (the number of channels) of the X-ray CT apparatus by the number of measurement samples (the number of views) per one rotation. That is, projection data is obtained from the data set (I ₀ , I) by the above calculation formula in all X-ray measurement paths.

Further, in the image reconstructing section, the value of the Radon transform result is subjected to, for example, inverse Radon transform using filtered back projection as a representative means, and the X-ray absorption coefficient distribution of the original information is obtained. If air is to be measured (the object to be measured is air), if it is estimated that the effects of dust and dirt in the air can be ignored, μ (x)
Is 0, I = I ₀ , and the projection data of air becomes 0.

That is, in the conventional X-ray CT apparatus, the projection data has been acquired from the intensity of the X-ray measured as described above. In particular, an X-ray CT apparatus having a so-called two-dimensional multi-row detector, which is a detector having a two-dimensional structure that has been widely adopted in recent years, can measure a plurality of rows by one measurement. This makes it possible to irradiate X-rays in a wider irradiation range of X-rays, and at the same time, to perform measurement with a narrower detector width in the row direction (slice direction).

[0011]

An example of the X-ray intensity distribution in the column direction in the X-ray CT apparatus having the above-mentioned two-dimensional multi-row detector is shown in FIG. 11 attached. That is, normally, FIG.
As shown in FIG. 1 (A), when all rows (in this example, detectors in the first to fourth rows) are irradiated with X-rays having almost the same intensity distribution (completely uniform X-ray irradiation). As shown in FIG. 11B, for example, due to practical circumstances regarding X-ray generation and the diaphragm, the X-ray distribution becomes a strong X-ray distribution at the central part of the detector and its peripheral part. When the distribution is weak (when the X-ray dose is a little small on both ends),
Either distribution is used.

Further, as described above, in the X-ray CT apparatus having the above-mentioned two-dimensional multi-row detector, the width (slice width) per one row is made considerably narrow, whereby the width in the row direction is increased. It is possible to perform measurement with high ability to decompose measurement data.

Generally, in the measurement in the normal state (ideal state) of the X-ray CT apparatus, as shown in FIG.
The measurement geometry of the X-ray CT apparatus is adjusted so that the perpendicular line drawn from the focal point of the X-ray tube comes to the center point of the entire detector array used for measurement. In particular, if the number of measurement columns is an even number, as shown in FIG. 12A, at the boundary between the two columns located at the center point, on the other hand, if the number of measurement columns is an odd number, then FIG.
As shown in FIG. 2 (B), the perpendicular line drawn from the X-ray tube comes to the center of one row of the center points.

X having a two-dimensional multi-row detector as described above
In the case of a line CT device, the width of each detector row for measurement is considerably narrowed. For example, some detectors are designed to have a width of about 1 mm or a width narrower than that. . In addition, after a long time has passed since the adjustment of the measurement geometry of the measurement sequence (for example, at the time of shipping the product), the X-ray focal point shift, the minute distortion of the rotating portion of the measurement geometry, etc. occur, This causes a slight deviation in the measurement geometry system.

Further, in such an apparatus, the interior of the X-ray tube expands due to heat even when continuously measuring for a long time,
This expansion also causes a deviation in the measurement geometry system. Then, the deviation of the measurement geometry system due to these causes has a bad influence on the measurement data obtained in each measurement row, in particular, as the width of the measurement row of the two-dimensional multi-row detector becomes narrower. In other words, the width of each row is narrowed in order to increase the resolution of the measurement in the row direction in the X-ray CT apparatus, but conversely, the measurement geometry is too sensitive to the deviation of the irradiation range of the X-ray beam. This has constituted an academic system, and this has become a major technical issue toward high performance in an X-ray CT apparatus using a two-dimensional multi-row detector.

A phenomenon that occurs when the above problems are not overcome, that is, a measurement when a deviation of the measurement geometry system occurs, will be described below with reference to FIG. As shown in FIG. 13 (A), the data (focal position) in the air measurement procedure did not deviate, but after continuous use for a long time, for example, due to expansion inside the X-ray tube due to heat, As shown in FIG. 13 (B), an example is shown in which the measurement geometrical system is misaligned.

By the way, the intensity I ₀ of the X-rays applied to the object measured in the air measurement procedure is once stored in the storage device of the X-ray CT apparatus, and passed through the object in the subsequent measurement. The intensity I of the subsequent X-ray is measured, and the value corresponding to Radon conversion is calculated by the above equation (Equation 2). Here, for simplicity, the value when air is measured is I
And

When there is no deviation in the measurement geometry system, I ₀ = I and the projection data becomes ₀ except for the influence of detection noise caused by the number of X-ray photons. However, as shown in FIG. 12, when the measurement geometry of the X-ray CT apparatus is deviated, the projection data does not become 0 even if the air is measured. In particular, when the X-ray is intensified due to such a deviation of the measurement geometry system, the projection data becomes an extremely negative value due to its calculation principle, and the X-ray becomes stronger due to the passage of the object. Will be shown. However, such a phenomenon cannot occur in reality, and the reliability of the Radon conversion data itself is greatly lost.

Further, as a serious damage caused by such a deviation of the measurement geometry system, the CT value of the measured object varies from its original value, and further, the measurement data of air is also deviated. If so, X-ray irradiation that is different from the X-ray distribution that should be originally measured is performed, so that image quality deterioration and S / N ratio deterioration may occur.

Therefore, in the present invention, in view of the above-mentioned problems in the prior art, the balance between the data in the air measurement procedure and the data in the actual object measurement caused by the deviation of the measurement geometry of the X-ray CT apparatus is normalized. It is an object of the present invention to provide an X-ray CT apparatus capable of improving an unreasonable CT value fluctuation and an abnormal artifact appearing on an image by obtaining the correct projection data by converting the data into an image.

[0021]

In the present invention, in order to achieve the above object, first, a scanner for projecting an X-ray from an X-ray generator onto a subject to detect the transmitted X-ray, and the scanner. An X-ray CT apparatus comprising: an image display unit that performs predetermined image processing on the measurement signal detected by the image display unit; and an overall control unit that controls the operation of the scanner and the image display unit, The scanner uses the transmission X
The image display unit has a two-dimensional multi-row detector for detecting a line, and the image display unit shifts the irradiation range of the X-ray beam caused by a geometrical measurement factor in the two-dimensional multi-row detector. The present invention provides an X-ray CT apparatus including means for correcting the data of the X-ray intensity applied to the subject by the above method.

According to the present invention, the correction means is
In order to correct the X-ray intensity data, a measurement data correction function is generated based on the X-ray intensity data detected in the air measurement procedure, or the X-ray intensity detection of the reference detector in the two-dimensional multi-row detector is performed. The data of the X-ray intensity applied to the subject is corrected based on the data.

In addition, according to the present invention, the correction means includes a state in which the focal points of the detector and the X-ray generator in the two-dimensional multi-row detector are twisted, and in the two-dimensional multi-row detector. The deviation of the irradiation range of the X-ray beam caused by at least one of the defocused states of the X-ray generator with respect to the detector row direction is corrected.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, an X-ray CT apparatus for measuring data by a two-dimensional multi-row detector and generating a two-dimensional image showing cross-sectional information of a plurality of rows by one measurement, that is, an X-ray CT apparatus having a two-dimensional multi-row detector. An example of the configuration of the line CT apparatus is shown in the attached FIG. The external structure of the two-dimensional multi-row detector used in this X-ray CT apparatus is shown in FIG. 2 attached.

That is, in the X-ray CT apparatus whose schematic configuration is shown in FIG. 1, the overall control CPU 1 for controlling the entire apparatus
0 controls the control unit of the scanner 20, the control unit of the X-ray generator 30, the image processing unit 40, and the image display unit 50. Note that each of these units is provided with a dedicated controller for performing its own detailed control, and the overall control CPU 10 basically gives only control commands to the controllers of these units. It is a thing. Further, reference numeral 60 in the figure denotes, for example, a subject (object) such as a patient, 70 denotes an A / D converter for converting the detection signal from the scanner 20 into a digital signal, and
Reference numeral 80 denotes an image display which displays an image on its screen according to the image signal from the image display section 50. The image processing section 40 is composed of a pre-processing section 41 and a post-processing section 42.

With the recent technological development, X-ray CT
In the apparatus, a detector 100 having a two-dimensional structure (two-dimensional multi-row) as shown in the attached FIG. 2 is used. The two-dimensional multi-row detector 100 is a detector that measures X-rays generated from one X-ray focus by a measurement surface curved in the channel direction as shown in the figure. Then, in the row direction, each row of the detectors 13 measures the X-rays that have reached the detectors through the object existing in the three-dimensional space connecting from the focal point of the X-ray tube to itself. It will be.

In the X-ray CT apparatus having the two-dimensional multi-row detector having such a configuration, first, when the measurement of the X-ray CT apparatus is started, the overall control CPU 10 outputs a scanner start request to the control unit of the scanner 20. On the other hand, on the other hand, the detector and the data acquisition system part of the scanner 20 prepare for data acquisition. That is, when the scanner 20 rotates at a constant rotation speed and the data acquisition system and the X-ray generator 30 are in a measurable state, the overall control CPU 10 causes the X-ray generator 30 to operate.
An X-ray generation command is output to. Further, at the same timing as the generation of X-rays, the data acquisition execution for the measurement system and the transfer command for the image reconstruction unit of the acquired data are output.

As a result, the image reconstructing unit of the image processing unit 40 performs the image reconstructing operation according to the inverse Radon transform theory including the respective correction operations, based on the acquired data.
Then, the result of the image reconstruction thus obtained is transferred to the image display unit and displayed. The measurement data and the image reconstruction result are also stored in the internal storage device of the X-ray CT apparatus.

Generally, in the image reconstruction calculation of the X-ray CT apparatus, the acquired data is first converted into data (common name: projection data) converted into an integrated value of the X-ray absorption coefficient, and the conversion result is For example, a process corresponding to the inverse Radon transform using a filtered back projection as a typical process is performed to obtain a cross-sectional image.

Among these processes, in the former process, that is, the process of converting the acquired data into projection data,
Using the property based on the theory of input and output of X-rays, the ratio between the intensity of X-rays radiated on the object and the intensity of X-rays after passing through the object is obtained, and logarithmic conversion is performed to absorb the X-rays. Acquire data corresponding to the integral value of the coefficient.

The data after passing through the object naturally have different values depending on the shape and material of the object. However, the data before passing through the object does not depend on the type of the object, and If the measurement conditions are the same, it is always constant.

Therefore, in the X-ray CT apparatus, only air is first measured (air calibration) in the state where there is no object, and the result is stored in the internal storage device, and the result is transmitted through the object. It is used as the intensity of the previous X-ray. That is, when measuring each object with the X-ray CT apparatus, the projection data can be calculated based on the above-described principle of the input / output relationship of the X-rays, only with the data with the object.

Then, in the X-ray CT apparatus according to the present invention,
X measured in each row based on the measured X-ray dose in a detector called a reference detector of a two-dimensional multi-row detector
The basic principle is to normalize the dose. That is, in the present invention, the balance between the data in the air measurement procedure generated by the deviation of these measurement geometrical systems and the data in the actual object measurement is normalized to obtain correct projection data, which appears on the image. Unreasonable C
It is intended to improve T value fluctuations and abnormal artifacts.

More specifically, the present invention shows two embodiments below, but basically, a weighting function called a measurement data correction curve is defined, and the data is subjected to detector bias correction processing. It is to multiply the data of.

The "detector bias correction process" is a process for obtaining the X-ray dose actually detected by the detector. Further, normally, the data output is not 0 even if X-rays are not generated, and a certain value is measured due to the circumstances of the data conversion system from the detector to the image processing unit.
Here, this value is called "detector bias".

Further, when the X-ray is irradiated, a value indicating the detected X-ray dose is output in a state of being added to the value (detector bias). Therefore, the original X-ray dose is obtained by subtracting the value output when the X-ray is not irradiated, and the value is set as the detected X-ray dose. Specifically, this subtraction is the detector bias correction processing.

The data after this detector bias correction processing (X-ray intensity distribution irradiated during the air measurement procedure) has a shape as shown in FIG. Here, the horizontal axis represents the detector number indicating the position in each row of the X-ray detector of the two-dimensional multi-row detector, and the vertical axis represents the X-ray intensity at that position. That is, normally, as shown in FIG. 3, each row is irradiated with X-rays in a bilaterally symmetrical distribution around the scanner rotation center. In particular, after the above-described detector bias correction processing, the values at the reference detectors on both sides (the values at both ends in the figure) must be substantially equal to each other.

On the other hand, although the reference detector may measure air, these values may change greatly. In such a case, the deviation of the measurement geometry system is estimated. The Rukoto. For example, as shown in FIG. 4, the X-ray generation system (for example, the focus of the X-ray generator) is twisted with respect to the surface (slice surface) to be measured in each row of the detector. is there. In addition, this FIG.
FIG. 4 is a view of a situation in which there is a displacement of an X-ray irradiation position due to a twist in a two-dimensional multi-row detector, viewed from above, and a chain line in the drawing indicates the center line of the range where X-rays should be originally irradiated. In addition, the dotted lines in the figure respectively indicate the center lines (twisted for geometrical reasons) of the range in which the X-rays are actually irradiated.

On the other hand, in the two-dimensional multi-row detector, for example, as shown in FIG. 5 attached, the detected values of the reference detector in each row are different in both the channel direction and the left-right direction of the detector. Although there is almost no such data, however, when the vertical line drawn from the focal point of the X-ray tube is used as the center point, the measurement data of the reference detectors in the row that should be symmetrical in the front-back direction from this center point may be significantly different. It In this case, the measurement geometry system (focus) is displaced in the column direction (see FIG. 11 above). In this case, since the left-right symmetry is not lost in each column, there is no large difference in the values of the left reference detector and the right reference detector. However, the difference between the columns having a symmetric relationship is large. Also in this figure, the alternate long and short dash line in the figure indicates the center line of the range where the X-rays should be originally irradiated, while the dotted line in the figure indicates the center line of the range where the X-rays are actually irradiated (in the column direction). Is deviated to).

The loss of data reliability due to the beam shift, which is to be solved by the present invention, is particularly caused when a higher resolution in the column direction is to be realized in the two-dimensional multi-row detector, or further. This is a technical issue that always arises when considering multiple rows. However, when the number of measurement columns is an odd number, this method cannot be applied because there is no other symmetrical column in the center column.

Further, according to the present invention, in the X-ray CT apparatus having the two-dimensional multi-row detector, first, a measurement data correction curve for normalizing and correcting the above-mentioned two types of deviations is defined. In addition, these measurement data correction curves are
One is the correction curve for the case where the detector and the X-ray focus are misaligned in a twisted state (see FIG. 8 above), and the other is the case where the focus is misaligned in the column direction ( 11 is a correction curve (see FIG. 10).

First, the definition of the correction curve in the case where the detector and the X-ray focus are misaligned in a twisted state will be described with reference to the attached FIG.

First, the data after the detector bias correction processing in the reference detector in each column is obtained, and the average value in the scanner angle direction (view direction) is obtained. However, at this time, if the reference detector data largely fluctuates from the surrounding view direction data, it is considered that there are objects on these reference detectors. Excluded from the target. In addition, since a plurality of reference detectors are usually installed (for example, two at the left and right ends), the average value thereof is taken as the left value and the right value. By doing this, the following two data are obtained.

Dl: average value of left reference detector after detector bias correction processing Dr: average value of right reference detector after detector bias correction processing

Therefore, based on these data, a linear function (thick line in the figure) as shown in FIG. 6 is defined. However, at the detector number corresponding to the center of rotation of the scanner, the value of the linear function is 1.0 (reference point) (for example, the value of the portion corresponding to the center point, and if there is no quarter offset, the function value is 1.0) and the above Dl and D
A straight line can be defined by the ratio with r. It should be noted that this is an approximate one that can be corrected by a linear function based on the assumption that the focus shift related to the twist is minute, but when a large shift is to be corrected, the above A non-linear function may be used instead of such a linear function.

The linear function (thick line) shown in FIG. 6 obtained in this way is a measurement data correction curve for the deviation of the focal point of the X-ray tube and the twisting direction of the detector. In addition, in the X-ray CT apparatus of the present invention, at the time of measurement, first, each row of the detector is multiplied by the measurement data correction curve, and thus the data in the twist direction of each row is corrected. If the two-dimensional multi-row detector of the applied X-ray CT apparatus has a condition that this twist direction does not occur, such correction may not be performed.

Next, the measurement data correction curve for the defocus in the column direction will be considered. As described above, even in the two-dimensional multi-row detector, in the measurement of even rows, the measurement center point in the row direction is always the center portion of the two center rows (see FIG. 12A above). ), On the other hand, for the measurement of odd-numbered columns, only one central column is defined, and the central point is the center of that column (see FIG. 12B above). In an X-ray CT apparatus having a two-dimensional multi-row detector, the X-ray generation distribution should ideally be symmetrical in the front-rear direction of the row about the center point in the row direction. is there.

Therefore, when the average values of the reference detectors in the columns having a symmetrical relationship greatly differ for each of them, it is considered that the X-ray focus is deviated by that amount (FIG. 13 (B above). See)). The measurement data correction curve in this case can be defined more easily. Specifically, this measurement data correction curve can be defined by the ratio of the average values of the left and right reference detectors after the detector bias correction processing of columns having a symmetrical relationship.

That is, the measurement data correction curve relating to the deviation in the column direction does not depend on the detector channel number, but only on the measurement column. The definition of the measurement data correction curve regarding the deviation in the column direction is shown in the attached FIGS. 7 and 8. That is, FIG. 7 (A) shows the X-ray intensity distribution in the row A having the two-dimensional multi-row detector, and FIG. 7 (B) shows a row symmetrical with respect to the measurement center point of the row A. The X-ray intensity distribution in B is shown. Then, in FIG. 8A, the measurement data correction curve for column A obtained from the above is also shown in FIG.
(B) shows the measurement data correction curves for column B, respectively.

As described above, in the X-ray CT apparatus having the two-dimensional multi-row detector according to the present invention, the above-mentioned deviation of the measurement geometric system is caused based on the measurement X-ray dose in the reference detector. A correction curve for normalizing these types of deviations is prepared. Then, the measurement data correction curve for correcting the deviation of these measurement geometrical systems is multiplied by the data after the detector bias correction processing that is actually obtained from the two-dimensional multi-row detector at the time of measurement, so that the two-dimensional Correction is made for a shift related to the measurement geometry of the X-ray CT apparatus having a row detector. It should be noted that these corrections can be performed in any measurement by an X-ray CT apparatus having a two-dimensional multi-row detector. Of course, the air measurement procedure can be similarly performed.

More specifically, two embodiments have been shown above. Basically, however, in the present invention, a weighting function called a measurement data correction curve is defined, and these correction data are used as the detector bias. The data after the correction processing is multiplied. That is, in the present invention, the balance between the data in the air measurement procedure generated by the deviation of these measurement geometric systems and the data in the object measurement of actual removal is normalized to obtain correct projection data, which appears on the image. It is intended to improve unreasonable CT value fluctuations and abnormal artifacts. However, with respect to the S / N ratio caused by the actually irradiated X-ray dose, a large improvement effect cannot be expected in the present invention.

[0053]

As is clear from the above detailed description, the X-ray CT apparatus according to the present invention has a two-dimensional multi-row detector having a two-dimensional multi-row detector having a two-dimensional structure. X
In a line CT device, even if the resolution is improved or even when continuous long measurement is performed, the adverse effect on the measurement data due to the deviation of the measurement geometry system is eliminated, and CT value fluctuations and artifacts on the image are improved. The excellent effect of enabling high performance in the X-ray CT apparatus is exhibited.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of the configuration of an X-ray CT apparatus having a two-dimensional multi-row detector that is an embodiment of the present invention.

FIG. 2 is a perspective view showing an external configuration of a two-dimensional multi-row detector used in the X-ray CT apparatus.

FIG. 3 is a diagram showing a shape of an X-ray intensity distribution after detector bias correction processing.

FIG. 4 is a top view showing a situation where a two-dimensional multi-row detector has an X-ray irradiation position shift due to a twist.

FIG. 5 is a top view showing a situation in which a measurement geometry system (focus) in the two-dimensional multi-row detector has a shift in the row direction.

FIG. 6 is a diagram showing an example of the definition of a correction curve when the detector and the X-ray focal point are twisted and deviated in the two-dimensional multi-row detector.

FIG. 7 is a diagram showing an X-ray intensity distribution when the measurement geometry system (focal point) is displaced in the column direction in the two-dimensional multi-row detector.

8 is a diagram showing an example of the definition of a correction curve for the X-ray intensity distribution due to the shift of the focal point in the column direction shown in FIG.

FIG. 9: X with two-dimensional multi-row detector in the prior art
It is a figure which shows an example of the flow of measurement of a line CT apparatus.

FIG. 10 is a diagram for explaining the principle of a measurement procedure for obtaining a tomographic image of an object using an X-ray CT apparatus.

FIG. 11 is a diagram showing an example of column-direction X-ray intensity distribution in an X-ray CT apparatus having a two-dimensional multi-row detector.

FIG. 12 is a diagram for explaining a measurement geometry system of a two-dimensional multi-row detector and a focus of an X-ray tube in a normal state of the X-ray CT apparatus.

FIG. 13 is a diagram for explaining measurement when a deviation occurs in the measurement geometry system of the two-dimensional multi-row detector.

[Explanation of symbols]

10 Overall control CPU 20 scanner 30 X-ray generator 40 Image processing unit 50 Image display section 60 object (patient) 70 A / D converter 80 image display 100 two-dimensional multi-row detector

Claims (4)

[Claims] 1. A scanner for projecting X-rays from an X-ray generator onto a subject to detect transmitted X-rays, and an image display for displaying an image by performing predetermined image processing on a measurement signal detected by the scanner. X-ray C including a scanning section and overall control means for controlling the operations of the scanner and the image display section
In the T-apparatus, the scanner has a two-dimensional multi-row detector for detecting the transmitted X-rays, and the image display unit is a geometric unit in the two-dimensional multi-row detector. An X-ray CT apparatus comprising means for correcting the data of the X-ray intensity applied to the subject due to the deviation of the irradiation range of the X-ray beam caused by various measurement factors. 2. The correction means generates a measurement data correction function based on the X-ray intensity data detected in the air measurement procedure in order to correct the X-ray intensity data. X-ray CT system. 3. The correction means corrects the data of the X-ray intensity applied to the subject based on the X-ray intensity detection data of the reference detector in the two-dimensional multi-row detector. The X-ray CT apparatus according to claim 1. 4. The correction means includes a detector in the two-dimensional multi-row detector and a focus of the X-ray generator in a twisted state, and the X in the detector row direction in the two-dimensional multi-row detector. 2. The X-ray CT apparatus according to claim 1, wherein the deviation of the irradiation range of the X-ray beam caused by at least one of the defocused states of the line generator is corrected.