X-ray diagnostic apparatus

Claim 2

An X-ray diagnostic apparatus of the type in which the transmitted X-ray image data, produced by an X-ray detector as the result of irradiating an object under examination with X-rays, is digitized and visually displayed, said apparatus comprising: X-ray shield means having an X-ray shield section with a predetermined pattern which may be placed in and retract from an X-ray projeciton area; means for computing a scattered X-ray component using the X-ray transmission data containing the image data collected from said X-ray shield section when said X-ray shield means is placed in the X-ray projection area; and compensating means for subtracting the scattered X-ray component as computed and produced by said scattered X-ray computing means from the X-ray transmission data produced under a condition that said X-ray shield means is not placed in the X-ray projection area, thereby to produce only the primary X-ray component.

Claim 4

The apparatus according to claim 1, characterized in that said X-ray shield section in said X-ray shield means is so configured as to generate X-ray transmission image data containing X-ray data from said X-ray shield section, which is necessary for computing the scattered X-ray component according to a given model of scattered X-ray intensity, and said scattered X-ray computing means is constructed so as to allow the computation of the scattered X-ray component according to said model of scattered X-ray intensity.

Claim 5

The apparatus according to claim 1, characterized in that said X-ray shield section is an acryl plate having a lead plate with a predetermined pattern bonded thereto.

Claim 6

The apparatus according to claim 2, characterized in that said X-ray shield section in said X-ray shield means is configured so as to shield X-rays in a portion of the near center the X-ray projection area, and said scattered X-ray computing means includes a first memory which directly receives through first and second switching means X-ray transmission image data containing the X-ray shield data on the shield of X-rays in a portion of the center near the X-ray projection area under the condition that said X-ray shield means is placed in the X-ray projection area, and scattered X-ray,intensity computing means for computing scattered X-rays by averaging the X-ray transmission image data corresponding to the number of picture elements produced from said first memory, and said compensating means for substracting the scattered X-ray component obtained by said scattered X-ray intensity computing means from said X-ray transmission image data under the condition that said X-ray shield means is not placed in the X-ray projection area and applies the result of the subtraction into said first memory through said first and second switching means.

Claim 7

The apparatus according to claim 3, characterized in that said X-ray shield section in said X-ray shield means is configured so as to shield X-rays along at least either of an X axis and a Y axis in said X-ray projection area, and said scattered X-ray intensity computing means includes a second memory for temporarily storing the X-ray transmission image data containing X-ray shield section data on at least one of the X and Y axes, normalizing means for normalizing the X-ray transmission image data by a reference position data of said X-ray shield section, a third memory for storing predetermined function data necessary for computing said scattered X-ray component and normalized data of said function data, parameter determining means for determining a predetermined parameter to provide an optimal approximation on the basis of the normalized data from said normalizing means and the normalized data output from said third memory, first constant determining means for determining a predetermined constant necessary for computing the scattered X-ray component on the basis of the parameter data output from said parameter determing means, second constant determining means for determining a predetermined constant necessary for computing the scattered X-ray component on the basis of the predetermined constant output from said first constant determining means and the X-ray transmission image data containing the X-ray shield data read out from said second memory and the function data from said third memory, and scattered X-ray intensity computing and storing means for computing and storing an intensity of the scattered X-rays at a proper position in said X-ray shield section on the basis of the parameter data output from said parameter determining means, and the predetermined constant output from said second constant determining means.

Claim 8

The apparatus according to claim 5, characterized in that said lead plate is configured like a chip.

Claim 9

The apparatus according to claim 5, characterized in that the output signal from said subtracting means is applied to said memory through a logarithm converting section for converting the output signal of said subtracting means into a natural logarithmic value.

Claim 10

The apparatus according to claim 6, characterized in that said X and Y axes for defining the configuration of said X-ray shield section lie passing through the center in the X-ray projection area in the X and Y axial directions.

Claim 11

The apparatus according to claim 6, characterized in that said scattered X-ray intensity-computing means further includes high frequency cutting off means for cutting off a high frequency component in the X -ray transmission image data substantially containing said X-ray shield data.

Claim 12

The apparatus according to claim 6, characterized in that said reference position data used to effect the normalization in said normalizing means is the center position data in said X-ray shield section.

Claim 13

The apparatus according to claim 6, charac; terized in that said lead is configured like a cross.

Claim 14

The apparatus according to claim 6, characterized in that the acryl plate constituting said X-ray shield means is selectively placed on a phantom.

Claim 15

The apparatus according to claim 10, characterized in that said high-frequency cutting off means is a low-pass filtering means.

Claim 16

The apparatus according to claim 1, characterized in that said X-ray transmission image data is obtained through a grid for previously suppressing scattered X-ray component.