Cerebral Imaging Using 68GA DTPA and the U.C.S.F. Multiwire Proportional Chamber Positron Camera

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Abstract
A multiwire proportional chamber positron camera consisting of four 48 × 48 cm2 detectors linked to a small digital computer has been designed, constructed, and characterized. Initial clinical application to brain imaging using 68Ga DTPA in 10 patients with brain tumors is described. Tomographic image reconstruction is accomplished by an algorithm determining the intersection of the annihilation photon paths in planes of interest. Final image processing utilizes uniformity correction, simple thresholding, and smoothing. The positron brain images were compared to conventional scintillation brain scans and x-ray computerized axial tomograms (CAT) in each case. The positron studies have shown significant mitigation of confusing superficial activity resulting from craniotomy in comparison to conventional brain scans. Central necrosis of lesions observed in the positron images, but not in the conventional scans, has been confirmed in CAT. Modifications of the camera are being implemented to improve image quality, and these changes combined with the tomography inherent in the positron scans are anticipated to result in images superior in information content to conventional brain scans.

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