TOMOGRAPHIC SCINTILLATION CAMERA WITH IMPROVED RESOLUTION

• US 3,752,982 A
• Filed: 02/23/1972
• Issued: 08/14/1973
• Est. Priority Date: 02/23/1972
• Status: Expired due to Term

• Current Assignee: Ronald J. Jaszczak
• Original Assignee: Ronald J. Jaszczak
• Inventors: Jaszczak, Ronald J.
• Primary Examiner(s): Borchelt, Archie R.
• Application Number:
  US05/228,640
• Time in Patent Office: 538 Days
• Field of Search: 250/71.5S,105
• US Class Current: 250/368
• CPC Class Codes: A61B 6/037 Emission tomography
• CPC Class Codes: G01T 1/2985 In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); using external radiation sources A61B6/02

Abstract

An Anger-type scintillation camera employing a rotating slanted channel collimator and associated circuitry to produce a tomographic imaging capability and also employing a scanning radiation filter and associated signal filtering circuitry to improve the resolution of the tomographic imaging. Circuitry at the output of the camera corrects the detector output signal before they are processed by the signal filtering circuitry to eliminate the effect of apparent circular precession of passageways in the radiation filter caused by rotation of the collimator. After signal filtering the effect of apparent circular precession of the radiation filter passageways is reintroduced either by separate circuitry before processing by tomographic camera circuitry or by tomographic camera circuitry adapted to allow for the earlier signal correction. The system may employ the rotating collimator alone or in conjunction with a bed which precesses in a circle.

Claims

1. In a radiation camera for imaging the volume distribution of radionuclides throughout an object under investigation, in combination:

a radiation detector, including a radiation sensitive transducer of the type producing a pair of detector output signals representing plane position coordinates of a quantum of radiation interacting with said transducer, said detector having a redetermined resolution value expressed in terms of full width at half maximum;

a collimator rotatably mounted on said detector adjacent said transducer, said collimator comprising a plurality of channels having a non-normal axial orientation with respect to said transducer;

radiation filter means interposed between said collimator and said object for defining a plurality of mutually spaced radiation passageways to said transducer for radiation quanta emitted from said object;

driving means for rotating said collimator including means for producing a pair of collimator orientation signals, said collimator rotation producing apparent circular precession of said radiation passageways with respect to said transducer;

circuit means at the output of said radiation detector for correcting said detector output signals in accordance with said collimator orientation signals to eliminate the effect of said apparent circular precession of said radiation passageways;

signal filtering means receiving said corrected detector output signals operative to produce a pair of filtered output signals corresponding to coordinates of a central axis of one of said radiation passageways traversed by a quantum of radiation interacting with said transducer;

circuit means receiving said passageway identification signals operative to translate said signals in accordance with a selectively attenuated value of said collimator orientation signals into a visual documentation on said documentation medium associated with a tomographic image of an associated plane through said object; and

scanning means for producing relative scanning between said object and said radiation filter means and a corresponding synchronous relative scanning between said documentation medium and said signal filtering means such that all of said object is exposed to said transducer through said radiation passageways;

the size and separation distance of said radiation passageways being preselected in terms of said full width at half maximum resolution value of said detector to produce a desired value of resolution of the overall apparatus.

2. In a radiation camera for imaging the volume distribution of radionuclides throughout an object under investigation, in combination:

a radiation detector, including a radiation sensitive transducer of the type producing a pair of detector output signals, x and y, representing plane position coordinates of a quantum of radiation interacting with said transducer, said detector having a predetermined resolution value expressed in terms of full width at half maximum;

a collimator rotatably mounted on said detector adjacent said transducer, said collimator comprising a multiplicity of channels with the axis of each channel at an angle phi with respect to a line normal to said transducer;

a radiation filter movably mounted adjacent said collimator at a distance d from said transducer, said filter comprising a flat plate of substantially radiation opaque material having a plurality of apertures therein and having a thickness sufficient to absorb substantially all ionizing quanta emitted from said object toward said transducer except such quanta as pass through said apertures;

driving means for rotating said collimator, including means for producing a pair of collimator orientation signals, cos theta and sin theta , where theta is the time varying rotational coordinate of said collimator;

a pair of summing circuit means receiving said detector output signals, x and y, and said collimator orientation signals, cos theta and sin theta , and producing a pair of corrected detector output signals, x and y according to the equations;

x x + d ctn phi cos theta , y y + d ctn phi sin theta ;

signal filtering means receiving said corrected detector output signals, x and y, operative to produce a pair of corrected filtered output signals, xf and yf, corresponding to coordinates of a central axis of one of said radiation passageways traversed by a quantum of radiation interacting with said transducer;

a pair of difference circuit means receiving said corrected, filtered output signals, xf and yf, and said collimator orientation signals, cos theta and sin theta , and producing a pair of filtered output signals, xf yf, according to the equations;

xf xf - d ctn phi cos theta , yf yf - d CTN phi sin theta ;

tomographic circuit means receiving said filtered output signals, xf and yf, and said collimator orientation signals, cos theta and sin theta , and producing a pair of tomographic filtered output signals, xft and yft, in accordance with tomographic camera principles;

display means including a cathode ray tube for displaying said tomographic filtered output signals; and

scanning means for producing relative scanning between said object and said radiation filter and a corresponding synchronous relative scanning of said signal filtering means;

the size and separation distance of said apertures in said radiation filter being preselected in terms of said full width at half maximum resolution value of said detector to produce a desired value of resolution of the overall apparatus.