Comparison of SPECT and ectomography for evaluating myocardial perfusion with technetium-99m-sestamibi

This study compared myocardial perfusion scintigraphy performed with ectomography to corresponding SPECT studies.

In a comparative study between SPECT and ectomography, 19 patients with suspected coronary artery disease were imaged under similar conditions. A two-day protocol using 99mTc-sestamibi was followed. In SPECT, 32 projection images were acquired by rotating the gamma camera detector through 180 degrees, from 45 degrees left posterior oblique to 45 degrees right anterior oblique. Short-axis view sections and polar tomograms were reconstructed. In ectomography, a 30 degrees slant-hole collimator was rotated through 360 degrees in front of a stationary detector to obtain 64 projection images with different projection directions. The gamma camera was orientated perpendicular to the long axis of the left ventricle; the orientation was determined from the SPECT examination. Short-axis section images through the projected conical volume were reconstructed using a two-dimensional filtered back projection technique. In a blind test, the relative diagnostic value and image quality of the two methods were evaluated by three independent observers assessing short-axis view sections and polar tomograms. An objective evaluation based on relative values in the polar tomograms was also performed. The interpretations were evaluated with analysis of variance.

After injection during exercise, there was no significant difference between SPECT and ectomography. After injection at rest, visualization of the left ventricle was superior (p < 0.05) and influence of external activity was less (p < 0.005) in ectomography. The activity level within a perfusion defect was significantly lower (p < 0.05) and its extension significantly larger (p < 0.05) in ectomography than in SPECT. There was no difference between the diagnosis based on SPECT or ectomography.

In myocardial perfusion imaging with 99mTc-sestamibi, ectomography provides information similar to that obtained with SPECT and can, therefore, be used clinically for evaluation of myocardial perfusion when the gamma camera is postitioned perpendicular to the long axis of the left ventricle.