Radiant energy – Invisible radiant energy responsive electric signalling – With or including a luminophor
Reexamination Certificate
1992-12-29
2001-09-11
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
With or including a luminophor
C250S363040, C250S363050, C250S363100
Reexamination Certificate
active
06288397
ABSTRACT:
FIELD OF THE INVENTION
This invention is concerned with gamma camera systems and more particularly, with such systems using dual detector cameras.
BACKGROUND OF THE INVENTION
The original gamma camera systems used one detector head. Originally, the one detector head was positioned above an organ to be imaged. Subsequently, the one detector head was used for what is known as single photon emission computerized tomography (SPECT) or emission computerized tomography (ECT). SPECT or ECT involve mounting the camera detector head in a gantry enabling it to rotate or orbit about the patient so as to obtain tomographic data and thereby provide tomographic images. Another aspect in the development of the gamma cameras is whole body imaging wherein the gamma camera head is passed over the entire body to obtain a complete image of the patient.
To increase the efficiency of the whole body scans and the tomographic scans, multi-headed cameras have been used. First, dual-headed cameras were used wherein the gamma camera system comprised a pair of camera heads spaced apart and oppositely disposed to enable obtaining images from opposite sides of the patient simultaneously. For example, the dual heads were moved around the patient with one head on each side of the patient.
Recently triple-headed gamma camera systems have been used. In triple-headed gamma camera systems, the heads are mounted to form a triangular shape with the three planes of the heads each separated by 60°.
It would seem that multi-headed cameras would reduce the rotational travel required to obtain imaging data from a 180° orbit or a 360° orbit. It is true that with two oppositely disposed heads, the 360° orbital data can be obtained with a 180° rotation. However, the 180° orbital data cannot be obtained in a scan of 90°. Similarly, with a three-headed camera system, a 360° scan can be accomplished with an orbital movement of a little over 120°. The 180° orbital data, however, also requires a scan of 120°. From scan travel distances required it is seen that the 360° scan times are drastically reduced by multi-head systems. However, when 180° scans are required such as for cardiac studies, there is little or no time saving when using multi-headed cameras. Accordingly, a more efficient camera system is required for cardiac studies.
Another problem with the presently available gamma camera systems is in obtaining images during cardiac exercise studies. In these studies a static image is acquired while the patient pedals on an ergometer, for example. If a single camera head is used for data acquisition during the exercise study, it is oriented in an optimal left anterior oblique position. However, the behavior of the inferior wall of the heart which is of great interest to cardiologists cannot be seen from this orientation. Accordingly, a camera system is required wherein the image of the heart during exercise also includes a good view of the inferior wall of the heart.
Thus, what the present cameras do not provide is a two-headed gamma camera system with the heads oriented relative to each other to enable cardiac ECT studies in a reduced scan time. The arrangement of the two heads in the gamma camera system should assure that there is no minimum radius of rotation. The three-headed systems presently available inherently have a minimum radius of rotation which interferes with some studies, such as in pediatric applications.
Also presently lacking are gamma camera systems that can efficiently image during exercise studies and obtain images of the heart including the inferior wall. The gamma camera system that overcome the above noted deficiencies should also provide increased count rates to enhance first pass studies.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with one preferred aspect of the present invention a gamma camera system is provided having two detectors where the detectors include a scintillating crystal, light detecting means such as photomultipliers hereinafter often referred to as “transducer means” or “camera head” thus, the detector comprises a crystal and photomultipliers for converting scintillations to voltages. The heads are mounted so as to describe an angular shape such as a modified L-shape wherein both legs of the “L” may be of equal size, for example. This type of camera is ideally suited for 180° ECT cardiac studies. The orientation of the two heads enables data acquisition from a 180° arc with a 90° rotational movement. This type of camera is also ideally suited for spot cardiac studies during an exercise mode. Thus, the two detectors arranged in an L-shape are mounted so that the complete heart including the inferior wall can be imaged during the exercise program.
In a broad aspect of the present invention, a unique two-headed gamma camera system for converting gamma radiation emitted from a patient to imaging data is provided, said system comprising:
means for displaying an image based on said imaging data,
said dual detector camera system having a first detector and a second detector,
means for mounting said second detector juxtaposed to said first detector to define an angle therebetween, and
means for utilizing the camera to obtain image data.
It is a feature of the invention that a scan is obtainable by orbiting the heads about the patient for 90° which gives the equivalent of a 180° scan in effectively one-half the time.
Another feature of the present invention, utilizes a single L-shaped collimator to which the two heads are attached.
According to still another feature of the present invention, the cameras system comprises two detectors mounted with a 90° angle therebetween in a single camera.
According to yet another feature of the present invention, the gamma camera detector heads are rectangularly shaped and one side of the rectangle of each of the heads are juxtaposed to each other to form a modified L-shaped camera system. A criterion of the junction being to obtain the shortest possible patient-detector distance for both detectors. This is accomplished by arranging the inner sides of the fields of view to coincide with or be very close to the line of intersection of the detector planes.
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Lim et al, “Triangular SPECT System for 3-D Total Organ Volume Imaging: Design and Preliminary Results”, IEEE Tran. Nucl. Sci, NS-32 (1), Feb. 1985, pp. 741-747.*
IEEE Transactions on Nuclear Science, vol. NS-28, No. 1, Feb. 1981, pp. 69-80, Jaszczak et al, “Physical Conditions Affecting Quantitative Measurements Using Camera-Based Single Photon Emission Computed Tomography (SPECT)”.
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