Device for determining the density distribution in an object

• US 4,375,695 A
• Filed: 10/20/1980
• Issued: 03/01/1983
• Est. Priority Date: 11/02/1979
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Harding, Geoffrey, Wagner, Wolfgang
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Grigsby, T. N.
• Application Number:
  US06/198,740
• Time in Patent Office: 862 Days
• Field of Search: 250/445 T, 378/006, 378/010
• US Class Current: 378/6
• CPC Class Codes: A61B 6/06 Diaphragms
• CPC Class Codes: A61B 6/483 involving scattered radiation
• CPC Class Codes: A61B 6/583 using calibration phantoms

Abstract

In a device for determining the density distribution on a straight line by means of a narrow penetrating beam, the measuring accuracy for the center of an object to be examined is increased in that the primary beam is not only displaced perpendicularly to its direction, but is also rotated around a point in this center. To this end, a radiation source and a detector device are mounted on a supporting device which can rotate the path of the primary beam around a central point, preferably the center of the object, around an axis which intersects the path of the primary beam at right angles.

Claims

1. In a device for determining the density distribution in an object which comprises:

radiation source means for generating a narrow primary beam which irradiates the object;

detector means arranged adjacent the primary beam for detecting scattered radiation produced in the object by the primary beam;

diaphragm means arranged between the object and the detector means which function to collimate the scattered radiation so that the detector means measure a set of scattered radiation values from the path of the primary beam in the object; and

drive means for displacing the path of the primary beam through the object;

the improvement wherein the device further comprises;

support means which define a free space around the object and which are rotatable about an axis which intersects the path of the primary beam and is directed transverse thereto;

wherein the drive means function to rotate the support means about the axis; and

wherein the radiation source means and the diaphragm means are mounted on and rotate with the support means.

2. A device as claimed in claim 1, wherein the detector means are mounted on and rotate with the support means.

3. A device as claimed in claim 1, wherein the detector means are stationary and form an arc of a circle which is concentric with the axis.

4. A device as claimed in any one of the preceeding claims 1-3, comprising:

a first plurality of diaphragm means arranged on first side of the primary beam and a second plurality of diaphragm means arranged on a second side of the primary beam which is opposite the first side;

wherein the detector means comprise a plurality of detector elements; and

wherein each of the diaphragm means functions to collimate scattered radiation so that, at each rotational position of the support means, scattered radiation from a given zone of the primary beam passes through each of the diaphragm means to an associated element of the detector means.

5. A device as claimed in claim 4, wherein the radiation source comprises

an x-ray source;

and further comprising;

a first collimator associated with the radiation source, and

an additional radiation detector which is disposed and functions to measure the intensity of x-rays which have passed from the x-ray source through both the first collimator and the object.

6. A device as claimed in claim 5, further comprising:

a second collimator disposed between the radiation source and the object and means for displacing the second collimator perpendicular to the plane of examination,

the second collimator defining two apertures and functioning so that when the second collimator is displaced to a first position a first aperture defines the narrow primary beam and when the second collimator is displaced to a second position the second aperture defines a wide radiation beam which irradiates an entire examination plane in the object.

7. A device as claimed in claim 1, 2 or 3, wherein the radiation source comprises

an x-ray source;

and further comprising;

a first collimator associated with the radiation source; and

an additional radiation detector which is disposed and functions to measure the intensity of x-rays which have passed from the x-ray source through both the first collimator and the object.

8. A device as claimed in claim 7, further comprising:

a second collimator disposed between the radiation source and the object and means for displacing the second collimator perpendicular to the plane of examination,

the second collimator defining two apertures and functioning so that when the second collimator is displaced to a first position a first aperture defines the narrow primary beam and when the second collimator is displaced to a second position the second aperture defines a wide radiation beam which irradiates an entire examination plane in the object.

9. A device as claimed in claim 3, further comprising:

a second collimator disposed between the radiation source and the object and means for displacing the second collimator perpendicular to the plane of examination,

the second collimator defining two apertures and functioning so that when the second collimator is displaced to a first position a first aperture defines the narrow primary beam and when the second collimator is displaced to a second position the second aperture defines a wide radiation beam which irradiates an entire examination plane in the object.