Radiant energy – Invisible radiant energy responsive electric signalling – With or including a luminophor
Reexamination Certificate
1998-09-23
2001-08-07
Epps, Georgia (Department: 2873)
Radiant energy
Invisible radiant energy responsive electric signalling
With or including a luminophor
C250S368000, C250S369000
Reexamination Certificate
active
06271525
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved high resolution/small field-of-view gamma camera for use in breast cancer and similar anatomical imaging, and to a method for accurately determining the position of lesions and other imaged abnormalities.
BACKGROUND OF THE INVENTION
X-ray mammography is the primary clinical screening tool for breast cancer. Over 15 million mammograms were performed in 1995 and over 25 million are expected to be performed by 2000. However mammography suffers from a high false positive rate. Currently, biopsies are performed following a positive mammogram to determine whether a suspicious lesion is cancerous or benign. Of the approximately 800,00 biopsies performed in 1995, roughly 600,000 were conducted on benign lesions. In addition to the expense involved, biopsy is a stressful procedure for the patient and the scarring left by the biopsy makes subsequent mammograms more difficult to interpret. Additionally, about 15-25% of all women have breast tissue that results in indeterminate mammograms. Dense tissue and scarring from prior surgery have x-ray densities similar to breast lesions, resulting in low contrast mammograms that are difficult to interpret.
Scintimammography has been shown to be able to complement mammography by imaging the metabolic activity of cancerous lesions while ignoring benign lesions and healthy tissue. In studies conducted over the past five years involving 600 women, in connection with the approval process of the DuPont Merck Pharmaceutical Company imaging agent Miraluma™, it was concluded that scintimammography is useful in differentiating cancerous and benign lesions. However, the studies also concluded that current large field-of-view gamma cameras cannot reliably image breast lesions smaller than 1.2-1.5 cm. In addition, the large size of these cameras limits their use to the lateral (side) views and does not allow for imaging the breast from other desirable viewing angles, and lesions in the chest wall are very difficult to detect.
U.S. Pat. No. 5,753,917 to Engdahl issued May 19, 1998 describes a multilayer gamma ray discrimination device comprising a pair of scintillator layers mounted in front of an array of photomultiplier tubes for purposes of discriminating between two types of gamma rays. The photomultipliers are neither position sensitive, nor are they or their capabilities described as high resolution. Each individual photomultiplier is apparently capable of individual detection, however collectively they possess no positioning capability and for this reason would not provide the resolution necessary to produce the resolution and positioning capability required of cameras of the type described and claimed herein.
Through the use of novel gamma detector technology, the camera of the present invention images at a higher resolution than can be achieved with conventional gamma cameras, allowing smaller tumors to be seen. The smaller physical size of the camera of the present invention allows close imaging in both lateral and cranial-caudal (top) views.
SUMMARY OF THE INVENTION
The improved gamma camera of the present invention, through the use of an array of position sensitive, high resolution photomultiplier devices and a camera configuration that effectively eliminates “dead space”, in combination with enhanced image analysis techniques, provides a system that is capable of detecting and locating tumors which could not be reliably detected or located with conventional large field-of-view cameras, and allows for the obtaining of close imaging in views that were unobtainable with such large field-of-view cameras.
The gamma camera of the present invention comprises essentially and in order from the front outer or gamma ray impinging surface: 1) a collimator, 2) a scintillator layer, 3) a light guide, 4) an array of position sensitive, high resolution photomultiplier tubes, and 5) printed circuit boards or circuitry for receipt of the output of the photomultiplier. In use, an area of the human body suspected of containing a lesion or other abnormality which has been previously injected with a radiotracer is exposed to the gamma camera of the present invention, the information supplied by the high resolution, position sensitive photomultiplier tubes is communicated to: a) a computer where it is processed using advanced image processing techniques and a specific algorithm to calculate the center of gravity of any abnormality observed during imaging, and b) optional image display and telecommunications ports. The make-up of these various layers and elements, their interactions and additional optional elements desirable for the production of a practical diagnostic tool will be described in greater detail hereinafter.
REFERENCES:
patent: 5276615 (1994-01-01), Edmond et al.
patent: 5401969 (1995-03-01), Basler
patent: 5610967 (1997-03-01), Moorman et al.
patent: 5864141 (1999-01-01), Majewski et al.
Majewski Stanislaw
Weisenberger Andrew G.
Wojcik Randolph F.
Epps Georgia
Hanig Richard
Southeastern University Research Assn.
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