Evaluation of scatter and 2 attenuation correction methods using a originally designed 3D striatal phantom with 3D printer for quantitative brain SPECT

Objectives Scatter correction (SC) and attenuation correction (AC) are important factors in quantitative SPECT. In this study, we evaluated with and w/o SC and AC methods for quantitative brain SPECT.

Methods SPECT imaging of an originally designed 3D striatal (ST) phantom covered with artificial female skull was performed using a triple-head camera with and w/o scatter and 2 AC methods. This phantom was originally designed for ¹²³I SPECT dopamine transporter studies and was manufactured for an anatomically accurate model of ST using 3D printer based on the T1 weighted brain MRI data. It has isolated bilateral caudate nucleus (CN), putamen (PU) and brain shell cavity (background:BG). Each compartment was filled with ¹²³I to obtain different ratios of ST (CN+PU) to BG : right CN; 4.3, right PU; 4.3, left CN; 3.0, left PU; 1.0 to BG; 1.0, respectively, which were considered to be mild Parkinson disease (PD) in right (RT) and severe PD in left (LT) sides. Triple energy window (TEW) method was used as SC. SPECT images were reconstructed with three conditions:(1) w/o SC and AC, (2) with SC and filtered back projection (FBP) with Chang's AC, (3) with SC and FBP with AC using an CT image (CTAC). SPECT and CT images were registered using fusion-software. Fused CT based bilateral 3D ROIs were set in ST. SPECT-measured ratios of ST-to-BG counts were determined with and w/o SC and 2 AC and were then compared with the true ratios in RT and LT sides, respectively.

Results W/o SC and AC, measured ST-to-BG ratios were underestimated by 28.3%(RT) and 39.8%(LT) due to effects of scatter and attenuation. SC and FBP with Chang's AC underestimated the ratios by 9.0%(RT) and 9.4%(LT) due to skull attenuation showing a significant improvement. SC and FBP with CTAC, the ratios were nearly identical to true ratios in RT and LT sides.

Conclusions SC and CTAC significantly improves the ST-to BG ratios.