Collaborative Research and Support of Fitzsimmons Army Medical Center Defense Women's Health Research Program Projects. Subtitle: Simultaneous Transmission/Emission Protocol (STEP) for Attenuation Correction of Breast and Diaphragmatic Attenuation Artifacts During SPECT 99mTc-Sestamibi Myocardial Perfusion Scans in Patients without Coronary Artery Disease

Breast and diaphragm attenuation artifacts in SPECT 99mTc Sestamibi (MIBI) myocardial perfusion imaging are the source of decreased specificity of these studies. Same day stress and rest SPECT MIBI imaging, using the commercially available CEQual algorithm (CQL) which docs not correct for attenuation, and a method which corrects for attenuation using simultaneous transmission/emission data from MIBI and a Gadolinium line source (STE), was performed on 58 normal women divided into 3 groups (normal, large breasted, and obese) and tracer distribution within the heart studied. There was no significant difference between groups for either STE or CQL. STE images demonstrated less pixel variability than CQL images. However, there was a significant difference (p 01) in uniformity (homogeneity of tracer distribution) of myocardial distribution in the stress and rest images, with STE demonstrating improved uniformity (approximately 50%) in the anterior, anterolateral, septal, and inferolateral walls and slightly less uniformity in the inferoseptal wall, apex and mid-base. The inferolateral wall in STE images tended to show a reversible stress/rest defect, which may be misinterpreted as ischemia. Decreased tracer in the apex on STE images compared to CQL was seen, and may reflect a more accurate depiction of physiologic apical thinning. Areas of improved STE uniformity were seen in areas considered prone to attenuation artifacts. STE generally results in less variable and more uniform images than non-attenuation corrected images. For STE, care should be exercise when interpreting the apex, where there is a tendency toward less tracer activity than expected, and in the inferolateral wall, where reversible defects were seen. There was no difference in uniformity in STE or CQL images when patients were stratified by breast sine or body habitus. M%e McBiles De%s S%oud M%e McBiles De%s S%oud