Poster - Thur Eve - 69: Attenuation Correction for 99m Tc-Tetrofosmin Micro SPECT/CT Cardiac Measurements in Rats
Objective: Small animal microSPECT is an important pre‐clinical imaging modality. However, the quantitative accuracy may be somewhat limited by photon loss due to attenuation in the body of the subject. Our goal is investigate the effects of including attenuation correction in the reconstruction of rat SPECT/CT data, and to assess the impact on the quantitative uptake in the myocardium and the uniformity of the distribution of uptake. Method: A rat was injected with ∼2.0 mCi of 99mTc‐tetrofosmin (Myoview) and scanned with a nanoSPECT scanner (BioScan, Washington, DC). Scan parameters were as follows: single, 1.5 mm pinhole, 4 hour scan duration commencing 30 minutes post injection, 48 projections, and circular scan. The rat was also scanned with the built‐in CTscanner (45 keV, cone beam). The CT data were reconstructed using filtered backprojection and rescaled to generate a linear attenuation map for the 140 keV 99mTc photons. The SPECT data were reconstructed using an iterative ordered subsets expectation maximization (OSEM) algorithm. Iterative reconstruction allows photon attenuation to be modelled as part of the reconstruction algorithm, and the reconstruction was done both with and without including attenuation. Results: As expected, inclusion of attenuation correction in the reconstruction increased by about 30% the total observed activity in the heart. However, we found no evidence that ignoring the attenuation correction introduces any significant artefacts in the uniformity of the reconstructed activity map. Conclusions: Including attenuation correction in the reconstruction of 99mTc cardiac images has little impact on the measured distribution of activity in the myocardium.