Collimator Evaluation for TI-2O1 Myocardial Imaging

Three collimators—high-resolution, converging, und pinhole—were eval uated for Tl-201 myocardial imaging. Line spread function, sensitivity meas urements, and phantom and animal studies were used. Features common to all the collimators were: a) better resolution at a closer distance with higher count density, and b) higher infarcìdetection rate in the tangential projection than in the en face view relative to the lesion. Furthermore, an infarcìin the epicardial location was better visualized than one in the endocardial location. In terms of resolution and sensitivity, the high-resolution collimator was found to be satisfactory in most clinical imagings, but for visualization of an infarcì,its size by weight must be over 10—12g. The pinhole collimator could resolve an infarcìas small as 7 g, and use of the pinhole yielded a diagnostic accuracy of over 90%, compared wilh 75—80% for the high-resolution collimator. Although the low sensitivity of the pinhole collimator precludes its routine clinical use, the selected view would increase diagnostic accuracy. The converging collimator performed poorly in terms of lesion detectability, and its routine clinical use is not encouraged. The conclusion drawn here is valid in the system ice have sludied, but the variety of converging collimators must be evaluated further for their specific purposes. J NucÃMed 19: 1067-1073, 1978