A refocussing filter based on Fridman's theorem, applied to Tl-201 myocardial scintigrams

Tl-201 myocardial scans show good infarct detectibility by visual examination and possibly by quantitative analysis of multiprojection scans. At least the first method is improved if the scan is refocussed. However, in order to avoid noise blobs of size comparable to expected infarct sizes, the filter should suppress high frequencies as least as possible. A filter - further referred to as Fridman filter - has been developed which meets above mentioned restrictions, and whose derivation may furthermore add some theoretical background to Iinuma type deconvolution filters as used in scintigraphy. The Fridman filter was applied successfully to about 120 research and clinical thallium studies of the myocardium, each recorded in six projections of 128x128 resolution, zoomed in on the heart. Experience learns that refocussing of the images grants the use of a high-sensitivity collimator instead of a high-resolution one, so as to make ECG-gated studies less time-consuming