JPH01124440A - Computer tomographic apparatus - Google Patents

Abstract

PURPOSE:To shorten the time required in the reconstitution of an image, to reduce the effect of tissue having a CT value separated from that of internal tissue and to display a natural image, by interposing an interpolating operation apparatus performing interpolating operation while reading a memory having a non-linear interpolation coefficient stored therein at every interpolating position. CONSTITUTION:Two forward and reward cross tomographic images are stored in the memories 10a, 10b of a frame memory 10. An operation apparatus 12 contains a table memory of an interpolation coefficient and an image display apparatus 14 displays a longitudinal tomographic image after the data between slices are interpolated and calculated from two successive forward and rearward images with respect to a plurality of cross tomographic images. Two slices of image data 1, 2 necessary for forming the data between the slices are transmitted to the operation apparatus 12 which in turn forms the between the slices from the transmitted data. When an interpolation coefficient is obtained by the indication of a position in such a case that the number of steps of a table (the number of the interpolation coefficients holdable to the table) are limited as the expansion of this table utilization, the interpolation coefficient is calculated from twos interpolation coefficients holding said position therebetween by linear interpolation and interpolation data is formed using said interpolation coefficient.

Description

[Detailed description of the invention] (b) Industrial application field The present invention is utilized in the field of medical imaging.

The present invention relates to a computed tomography (CT) apparatus, and particularly to reconstruction of longitudinal tomographic images.

(b) Images obtained by conventional CT apparatuses are usually cross-sectional images perpendicular to the body axis, but cross-sectional images parallel to the body axis may be clinically required. As a way to achieve this,
Measures are taken to extract and reconstruct the relevant pixel information from the preliminary tomographic plane.

In general, in such means for creating data between slices (cross-sections) from data between them, data is conventionally created by linear interpolation.

(c) Problems to be solved by the invention In data obtained by such linear interpolation, pixels with CT values that are far apart, such as bone and tissue, are strongly influenced by bone, so the longitudinal tomography created The statues tend to have more bones and more angular bones.

An object of the present invention is to provide a computerized tomography system that performs non-linear interpolation of data between slices to reconstruct images that reduce the influence of tissues with CT values that deviate significantly from internal tissues such as bones. It is to provide.

(d) Means for solving the problem The above-mentioned purpose is to create a longitudinal tomographic image from a plurality of cross-sectional images obtained from a CT device, by using the corresponding pixel data of each of the previous and subsequent cross-sectional images. This is achieved by inserting an interpolation calculation device that reads out a memory in which nonlinear interpolation coefficients are stored for each interpolation position in order to interpolate the corresponding pixel data between both images.

(e) Change the interpolation coefficient for data between active faults depending on the number of interpolation points or interpolation position between them, and at that time, convert the interpolation coefficient data into a table and store it in memory, and refer to the table during interpolation calculation to speed up the calculation. Perform nonlinear interpolation calculations.

Kube) Example A preferred embodiment of the invention will be explained based on the drawings.

FIG. 3 is a schematic block diagram showing one embodiment of the present invention.

In this figure, 10 is a frame memory, and two cross-layer images, one before and the other, are stored in the memory 10a.

10b. Reference numeral 12 denotes an arithmetic unit, which includes a table memory for interpolation coefficients, which will be described later.
Reference numeral 14 denotes an image display device, in which a longitudinal tomographic image is displayed after interpolating data between two successive images of a plurality of cross-sectional images.

As shown in FIG. 3, two slices of data (image data 1, image data 2) necessary to create inter-slice data are transferred to the arithmetic unit 12.

The arithmetic unit 12 creates inter-slice data from the transferred two slices of data as follows.

(i) As shown in Fig. 4, data of image data l is
Let ll, DI2, . . . , Din and image data 2 data be D21, D22 .

However, in both cases, n indicates the total number of pixels.

(it) I would like to mention one point. Data 1 and Data 2
Suppose that data of position tK is created from the third data of .

Each data of data 1 and data 2 is Dlj, D2j
is given by The created data is assumed to be Dkj.

The interpolation coefficient at that position is obtained by referring to the table shown in FIG. 2, and the coefficient A k-1 or A' k-1 is obtained.

When the coefficient data in this table is graphed as shown in FIG. 1, it is clearly nonlinear.

Therefore, the interpolation calculation formula is given as follows.

Dkj=D1j+Ak-1* (D2
j Dlj), but only when D2j≧Dlj. Or, Dkj=D1j +A' -
1*(D2j-Dlj), provided that D2j<Dlj.

Note that the coefficients A and A' are symmetrical with respect to position.

The data thus obtained by the arithmetic device 12 is transferred to the image display device 14, and the desired longitudinal tomographic image is displayed.

As an extension of the use of this table, when the number of steps in the table (the number of interpolation coefficients that can be held in the table) is limited, when obtaining interpolation coefficients by specifying a position, the interpolation coefficients are used to interpolate data using the interpolation coefficients closest to the position. Instead of creating (, an interpolation coefficient is calculated by linear interpolation from two interpolation coefficients that sandwich that position, and interpolation data is created using the interpolation coefficient.

(g) Effects According to the present invention, coefficients that differ depending on the interpolation position are not calculated by complex calculations, but are stored in the memory as a table and read out as necessary, reducing the time required for image reconstruction.
It is possible to reduce the influence of tissues with CT values that are distant from internal tissues, such as at a distance, and a natural image is displayed.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a nonlinear interpolation coefficient according to the present invention, FIG. 2 is an example of a table display of the coefficient data, FIG. 3 is a schematic block diagram showing an embodiment of the present invention, and FIG. 4 is an interpolation It is an explanatory diagram. 10 is a frame memory, 12 is an arithmetic unit, and 14 is an image display device. Patent applicant: Shimadzu Corporation Representative: Patent attorney: Ike 1) Tei C-Husband: Medium

Claims (1)

[Claims] When creating one longitudinal tomographic image from multiple cross-sectional images obtained from a CT device, in order to interpolate and calculate the corresponding pixel data between both images from the corresponding pixel data of the previous and subsequent cross-sectional images. 1. A computerized tomography apparatus, characterized in that an interpolation calculation device is inserted that reads out a memory in which nonlinear interpolation coefficients are stored for each interpolation position.