US 4,065,397 AGranted

Planigraphic X-ray apparatus for the preparation of tomographic images

AssigneeSiemens Aktiengesellschaft

InventorsErnst-Peter Ruhrnschopf, Gerhard Linke

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Abstract

A planigraphic X-ray apparatus for the preparation of transverse tomographic or planigraphic images of an exposure object, which consists of an X-ray measuring arrangement including an X-ray source generating a polyenergetic X-ray beam penetrating through the exposure object, with a radiation receiver which determines the radiation intensity of the X-radiation as a reference value prior to its ingress into the object, and a further radiation receiver which determines the radiation intensity behind the object in the direction of the radiation as attenuated values, through scanning of the projected X-ray beam at sequential equidistant points, a comparator element which forms a measured magnitude from the two values, as well as a drive arrangement for the measuring arrangement, consisting of a pivot mounting for producing rotational movements of the X-ray measuring arrangement through small equidistant angular amounts about a rotational axis generally coincident with the symmetrical longitudinal axis of the exposure object in an alternating sequence with each respective scan and, a measured value converter for the transformation of the measured values into a tomographic image wherein a function stage applies a proximation function to the results obtained with polyenergetic X-ray energy so as to convert the results to values suitable for processing based on the assumption of monoenergetic radiation.

Claims2

Dependent claims

In a planigraphic X-ray apparatus for the preparation of tomographic images of an exposure object;

including an X-ray measuring arrangement having an X-ray source generating an X-ray beam penetrating the exposure object, the cross-sectional expanse of said beam perpendicular to the planigraphic plane being equal to the plane thickness;
a first radiation receiver for determining the radiation intensity of the X-radiation as a reference value preceding its ingress into the object;
a second radiation receiver for determining the radiation intensity behind the object in the direction of the radiation as attenuated values through scanning of the projected X-ray beam at sequential equidistant points;
a comparator for forming a measured magnitude from the reference and attenuated values;
a drive means for the measuring arrangement including a pivot mounting for producing rotational movement of the X-ray measuring arrangement through small equidistant angular amounts about a rotational axis generally coincident with the symmetrical longitudinal axis of the exposure object in alternating sequence with respectively each scan;
and a measured value converter for transforming the measured values into a tomographic image the improvement comprising:
a function stage for forming, from the logarithm of the measured value y defined by the X-ray intensity I.sub.0 in the ray direction preceding the exposure object and the X-ray intensity I behind the exposure object as the quotient, a correction factor C pursuant to the proximating function ##STR3## with counting values, dependent upon a selectable normalized radiation spectrum, of y.sub.1, A.sub.0 ;
B.sub.0 ;
and B.sub.2, said and counting values, at an X-ray tube voltage of 100 kV and a normalization spectral line at 51 keV, are y.sub.1 = 4.45;
A.sub.0 = -0.035;
A.sub.1 = 0.0039;
B.sub.0 = -0.04;
B.sub.1 = -0.0126;
and B.sub.2 = 0.00075;
and a multiplication stage receiving said correction factor C for the multiplicative influencing of the measured value.

12 more elements

In a planigraphic X-ray apparatus for the preparation of tomographic images of an exposure object;

including an X-ray measuring arrangement having an X-ray source generating an X-ray beam penetrating the exposure object, the cross-sectional expanse of said beam perpendicular to the planigraphic plane being generally equal to the plane thickness;
a first radiation receiver for determining the radiation intensity of the X-radiation as a reference value preceding its ingress into the object;
a second radiation receiver for determining the radiation intensity behind the object in the direction of the radiation as attenuated values through scanning of the projected X-ray beam at sequential equidistant points;
a comparator for forming a measured magnitude from the reference and attenuated values;
a drive means for the measuring arrangement including a pivot mounting for producing rotational movement of the X-ray measuring arrangement through small equidistant angular amounts of a rotational axis generally coincident with the symmetrical longitudinal axis of the exposure object in alternating sequence with respectively each scan;
and a measured value converter for transforming the measured values into a tomographic image, the improvement comprising:
a function stage for forming, from the measured value y defined as a function of the quotient of the X-ray intensity I.sub.0 in the ray direction preceding the exposure object and the X-ray intensity I behind the exposure object, a correction factor C pursuant to a proximating function which serves to normalize the output of the measured value converter so as to essentially conform the values which would be obtained for monoenergetic X-ray energy level, said proximating function corresponding to a curve extending substantially through points y = 0, C = 1.0;
y =y.sub.1, C = 1.0;
and which reaches a peak value of C intermediate y = O and y = y.sub.1, and which progressively decreases in value of C as a function of y for values of y between y = y.sub.1 and y = 10, said function stage forming a multiplicative correction factor C for correction of the measured values, the correction factor C corresponding to a proximating function such that C is equal to one at y equal zero and at y equals about 4.45, and such that the value of C corresponds to a curve which progressively increses and substantially passes through the coordinates y = 0, C =1.0;
y = 1.0, C = 1.11;
y = 2.0, C = 1.13, between y = 0 and y = 2.0;
and progressively decreases and substantially corresponds to a curve through points having the proximate coordinates y = 3.0, C = 1.10;
y = 4.0, C = 1.03, y = 5.0, C = 0.95;
y = 6.0;
C = 0.86;
y = 7.0, C = 0.77;
y = 8.0, C = 0.67;
and y = 9.0, C = 0.58, between y = 2.0 and y = 9.0.

15 more elements

Dependencies are inferred from the claim text.