COMPARISON OF SPECT AND ECTOMOGRAPHY FOR EVALUATING MYOCARDIAL PERFUSION WITH TECHNETIUM-99M-SESTAMIBI

This study compared myocardial perfusion scintigraphy performed with e ctomography to corresponding SPECT studies. Methods: In a comparative study between SPECT and ectomography, 19 patients with suspected coron ary artery disease were imaged under similar conditions. A two-day pro tocol using Tc-99m-sestamibi was followed. In SPECT, 32 projection ima ges were acquired by rotating the gamma camera detector through 180 de grees, from 45 degrees left posterior oblique to 45 degrees right ante rior oblique. Short-axis view sections and polar tomograms were recons tructed. In ectomography, a 30 degrees slant-hole collimator was rotat ed through 360 degrees in front of a stationary detector to obtain 64 projection images with different projection directions. The gamma came ra was orientated perpendicular to the long axis of the left ventricle ; the orientation was determined from the SPECT examination. Short-axi s section images through the projected conical volume were reconstruct ed using a two-dimensional filtered back projection technique. In a bl ind test, the relative diagnostic value and image quality of the two m ethods were evaluated by three independent observers assessing short-a xis view sections and polar tomograms. An objective evaluation based o n relative values in the polar tomograms was also performed. The inter pretations were evaluated with analysis of variance. Results: After in jection during exercise, there was no significant difference between S PECT and ectomography. After injection at rest, visualization of the l eft ventricle was superior (p < 0.05) and influence of external activi ty was less (p < 0.005) in ectomography, The activity level within a p erfusion defect was significantly lower (p < 0.05) and its extension s ignificantly larger (p < 0.05) in ectomography than in SPECT. There wa s no difference between the diagnosis based on SPECT or ectomography. Conclusion: In myocardial perfusion imaging with Tc-99m-sestamibi, ect omography provides information similar to that obtained with SPECT and can, therefore, be used clinically for evaluation of myocardial perfu sion when the gamma camera is postitioned perpendicular to the long ax is of the left ventricle.