Patent Number: 043485910
Section: summary

TECHNICAL FIELD This invention relates to utilizing gamma cameras for uptake studies and restricted fields of view and multiple aperture collimator systems therefor. More particularly it relates to gamma cameras of the Anger type as originally disclosed in U.S. Pat. No. 3,011,057 issued to H. O. Anger on Nov. 28, 1961. In these cameras a plurality of light detectors, usually nineteen or more photo multipliers, are located behind a crystal which scintillates, that is, produces pinpoints of light when certain atoms in the crystal are struck by very high energy X-rays called gamma rays emitted from radioactive atoms. The radioactive atoms are taken up by selected organs to be examined and thus images of the organ may be recorded. The signals from the detectors are combined in complex electronic circuitry and the position of each light scintillation is calculated and the intensity of the scintillation is also calculated. This intensity and position is then displayed on a cathode ray tube and may be recorded on photographic film. While the apparatus is detecting the location and intensity of a single scintillation, other scintillations occurring will be disregarded. Thus, many gamma rays or particles reaching a gamma camera are disregarded. BACKGROUND ART Gamma cameras according to the prior art are provided with collimators comprised of several inches of lead, having a plurality of usually parallel channels therethrough, thus limiting the field of view to parallel gamma rays or gamma rays emitted over a very small angular cone. However, in certain instances, according to the prior art, the channels through the lead collimator are conically aligned so that rays emitted from a relatively close point source may be imaged throughout the entire face of the scintillating crystal. This is shown, for example, in U.S. Pat. No. 4,068,126 issued Jan. 10, 1978 to D. T. Wilson. Gamma cameras, as previously stated, are utilized to image organs which have taken up radioactive material. Another very common form of radiographic study used in the prior art is called an uptake. In an uptake, radioactive material is given to the patient and is taken up by a selected organ. The amount of radioactive material taken up may be indicative of a disease process. Thus, at a predetermined time after the patient has taken the radioactive material, according to the prior art, the organ is exposed to a single scintillation detector which merely counts the total number of gamma rays produced. The total number of counts received by the scanner indicates the amount of radioactive uptake. Although gamma cameras are provided with counters, they cannot be practically employed for uptakes since the amount of time required for the uptake study would be very large, due to the fact that the gamma camera cannot count every gamma ray or gamma particle reaching the scintillating material, as previously described. Furthermore, at high count rates the counts registered by a gamma camera are not proportional to the actual counts received. I have discovered that gamma cameras may be very successfully employed for uptake studies, such as thyroid studies, by masking or shielding off the greater portion of the gamma camera and providing the remaining central portion with a generally cylindrical open collimator. Most conveniently this flat field collimator may be provided as an adapter for conical collimators supporting pinholes which are also utilized by gamma cameras. Additional collimators can also be provided according to my invention. For example, another adapter collimator interfitting to the conical pinhole supporting collimator, may be a restricted field lead cylinder having a plurality of parallel channels therethrough. This collimator may be used for small organ gamma studies and due to the great length of the passageways increases the gamma camera's resolution as disclosed in U.S. Pat. No. 4,118,632, issued Oct. 3, 1978 to Heribert Luig. In another embodiment of the invention the adapter may be provided with long channels which diverge from the organ to the scintillation crystal to provide an image magnification. In another alternative embodiment the flat field straight bore collimator may be a separate collimator rather than an adapter for use with a pinhole collimator. OBJECTS OF THE INVENTION It is therefore a principal object of the invention to provide a method and apparatus for utilizing gamma cameras for uptake studies. Another principal object of the invention is to provide methods and apparatus for utilizing gamma cameras for restricted fields of view. Still another principal object of the invention is to provide multiple aperture collimator systems providing the above objects. A still further object of the invention is to provide such multiple aperture collimator systems providing for a pinhole collimator. Yet another object of the invention is to provide such multiple aperture collimator systems providing for small organ studies of enhanced resolution. A yet further object of the invention is to provide such multiple aperture collimator systems providing for enlarged images of small organs. Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the several steps in the relation of one or more such steps with respect to each of the others thereof, which will be exemplified in the methods hereinafter disclosed and articles of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the articles hereinafter described. The scope of the invention will be indicated in the claims.