Motion detection and correction using multi-rotation 180 degrees single-photon emission tomography for thallium myocardial imaging

Patient and organ motion is a potentially limiting factor in gamma camera s ingle-photon emission tomography (SPET) imaging, as highlighted in stress t hallium myocardial SPET,where the heart may exhibit a systematic axial moti on (cardiac creep) following stress. Multi-rotation SPET has previously bee n described as a means of obtaining better raw data for motion detection an d correction. This study describes the validation of a computerised motion detection algorithm applied to multi-rotation SPET, and reports measured mo tions in thallium myocardial stress SPET studies from a single-headed gamma camera. Forty-two patients underwent pharmacological stress (dipyridamole) with leg raising, with injection of 75 MBq thallium-201 and imaging after a 10-min delay to detect or evaluate coronary artery disease. Multi-rotatio n gamma camera SPET was performed with a single-headed gamma camera, with f ive sequential rapid (4.5 min) continuous SPET mode rotations over 180 degr ees. A one-dimensional cross-correlation alignment technique was applied to the projection images to perform motion detection and correction in the ax ial direction prior to combining the five data sets for tomographic reconst ruction. Validation of the cross-correlation alignment analysis was carried out by performing imaging with measured whole-body axial motions in nine s ubjects, and by reproducibility measurements on multi-rotation data sets. T he effect of the applied motion correction was evaluated by calculating mea n differences between image pairs before and after shifting, and the genera l reliability of the automatic motion detection was checked to within one p ixel by visual assessment of 160 image pairs. Validation measurements of th e cross-con-elation technique gave a mean absolute error of 1.5+/-0.4 mm (0 .24+/-0.06pixels) with a maximum error of 3.7 mm (0.6 pixels). In 40 subjec ts undergoing pharmacological stress Tl-201 myocardial SPET imaging, the me an cardiac axial creep movement was calculated as 3.1+/-0.7 mm (0.49+/-0.11 pixels), with 13 out of 40 (32%) having a calculated motion of 1 pixel (6. 3 mm) or more. The automatic image shift was visually judged to be within 1 pixel in all 160 image pair analyses, and the mean pixel value difference between image pairs was reduced following image shifting. It is concluded t hat multi-rotation 180 degrees SPET imaging provides raw data which allow o bjective and accurate motion detection of cardiac motion in thallium stress myocardial imaging, whilst the one-dimensional cross-correlation technique demonstrates adequate accuracy and reliability to be applied as an automat ic motion screening technique on these data.