Effect of motion on thallium-201 SPECT studies: a simulation and clinical study

Although patient motion on 201Tl SPECT studies has been reported as a source of artifacts, systematic studies on motion patterns and resultant artifacts are lacking. Accordingly, we simulated 74 motion patterns upon a normal study. The tomograms were assessed for presence of defects: The "motion pixel area index" ranged from 1 to 83; 26 of 30 (87%) simulations with an index > or = 21 had defects, whereas 38 of 44 (86%) simulations with an index < 21 were normal. Defect location was dependent on motion direction; defect intensity was dependent on its magnitude and timing. Review of data acquisition in 164 recent normal patient studies revealed motion in 42 (26%). Motion was generally minimal and caused defects in only seven (4%). Thus, mild motion is unlikely to produce defects. In our laboratory, motion is now an infrequent source of artifacts; severe motion produces recognizable patterns that depend on its direction, magnitude and timing.