Influence of adipose tissue in myocardial counts using attenuation correction in SPECT/CT imaging: study in phantom

Myocardial perfusion imaging (MIP) with single photon emission computer tomography is one of the most accurate procedures for the detection of coronary artery disease. Tissue attenuation artifacts are a significant limitation of MIP, especially in obese patients. CT-based attenuation correction (AC) is widely used to undermine these artifacts. The objective of this study was to evaluate the influence of an adipose tissue equivalent in the total myocardial counts after AC in SPECT/CT imaging. To accomplish this a Heart Thorax Phantom was filled with 99mTcO 4 -(simulating the uptake of 99mTc-Tetrofosmin in the cardiac walls and liver) for SPECT/CT imaging using an additional layer of 100% lipid fat and a torso phantom. The acquired data was reconstructed with Filtered Back Projection (FBP), iterative algorithms without AC (IRNC) and iterative algorithms with AC (IRAC) for posterior evaluation of total cardiac wall counts (Anterior, Inferior, Lateral and Septal). There was a significant reduction in total mean counts of the lateral and septal walls, with the addition of a layer of fat and the torso phantom, when FBP and IRNC reconstructions were applied (p ≤0,05) which may have been caused by tissue attenuation artifacts. The addition of a layer of fat and of the torso phantom, directly increased the total mean counts of the septal, lateral and inferior walls, when IRAC reconstruction was used (p ≤0,05) suggesting a benefit in the use of AC in larger body habitus. In conclusion the adipose tissue equivalent directly influenced the total myocardium counts when AC methods were applied, and further research is advised.