Validation of Optimum ROI Size for 123I-FP-CIT SPECT Imaging Using a 3D Mathematical Cylinder Phantom

Abstract

Objective(s): The partial volume effect (PVE) of single-photon emission computedtomography (SPECT) on corpus striatum imaging is caused by the underestimation ofspecific binding ratio (SBR). A large ROI (region of interest) set using the Southamptonmethod is independent of PVE for SBR. The present study aimed to determinethe optimal ROI size with contrast and SBR for striatum images and validate theSouthampton method using a three-dimensional mathematical cylinder (3D-MAC)phantom.Methods: We used ROIs sizes of 27, 36, 44, 51, 61, 68, and 76 mm for targets withdiameters 40, 20, and 10 mm on reference and processed images reconstructed usingthe 3D-MAC phantom. Contrast values and SBR were compared with the theoreticalvalues to obtain the optimal ROI size.Results: The contrast values in the ROI with diameters of 51 (target: 40 mm indiameter) and 44 (target: 20 mm in diameter) mm matched the theoretical values.However, this value did not correspond with the 10-mm-diameter target. The SBRmatched the theoretical value with an ROI of > 44 mm in the 20-mm-diameter target;but, it was under- and overestimated under any other conditions.Conclusion: These results suggested that an ROI should be 4-2 folds larger thanthe target size without PVE, and that the Southampton method was remarkablyaccurate.

Keywords

• specific binding ratio
• partial volume effect
• Southampton method