Evaluation of Resolution Recovery for Each Collimator in Brain Perfusion Image.

PURPOSE: This study aimed to verify the resolution recovery for each collimator in the brain perfusion image.

METHOD: To verify the effect of the resolution recovery for each collimator, we evaluated via the three-dimensional brain phantom (phantom) and the normal brain perfusion single photon emission computed tomography (SPECT) data. These data were reconstructed using the three-dimensional ordered subset expectation maximization method (3D-OSEM) (Evolution for bone(TM)) that was performed with scatter correction, attenuation correction, and resolution recovery (RR). The performance of resolution recovery was evaluated in the two collimator systems (ELEGP and MEGP) reconstruction condition via the contrast value, mean counts, normalized mean square error (NMSE), and regional brain activity.

RESULT: In the "with resolution recovery (+RR)", the NMSE indicated minimum value with SI (subset×iteration) = 100, cut-off frequency (Fc) = 0.50 cycles/cm. The contrast value in the "+RR" increased 20% for the cortical region and decreased 28% and 6% at ELEGP collimator and MEGP collimator for the central region, as compared to the "without resolution recovery (-RR)". In the phantom study, the error of the brain activity using MEGP collimator at the temporal lobe and sub-lobar decreased 15%, compared with ELEGP collimator in the + RR. In the clinical study, the error of the regional brain activity using MEGP collimator in the "+RR" increased from 3% to 8%, compared with "-RR".

DISCUSSION: The accurate resolution recovery was obtained at SI = 100 and Fc = 0.50 cycles/cm. The contrast value and regional brain activity at the central region decreased due to incomplete resolution recovery by use of ELEGP collimator.