Collimation for Imaging the Myocardium. II

Line-source response functions and modulation transfer functions (MTF) were used to compare the spatial resolutions obtained with an Anger camera system and four different nuclides used as myocardial-imaging agents: 99mTc, 123I, 201Tl, and 43K. The measurements were made with a low-energy converging collimator (LECY, a medium-energy converging collimator (MEC), and a pinhole collimator. The MTF values for 99mTc were very similar for all three collimator types, although the LEC collimator gave slightly higher values at hgih spatial frequencies and had 40% greater sensitivity. Iodine-123 was satisfactorily imaged only with the MEC and pinhole collimators, which in turn yielded MTF values comparable to those measured for 99mTc. Thallium-201 produced MTF curves that were similar for the MEC and pinhole collimators; the curve for th LEC collimator was slightly poorer. All three MTF curves for 201 Tl were inferior to those of 99mTc. For imaging with 43K, only the pinhole collimator provided marginally acceptable spatial resolution.