Delayed convergence of iterative reconstruction in dopamine transporter SPECT with multiple-pinhole collimators

Area of Science:

• Nuclear Medicine
• Radiopharmacology
• Medical Imaging

Background:

• Multiple-pinhole (MPH) collimators enhance brain SPECT resolution-sensitivity tradeoff.
• MPH SPECT with [123I]FP-CIT shows increased noise at the periphery, potentially slowing iterative reconstruction convergence.
• This study investigates the impact of reconstruction iterations on [123I]FP-CIT MPH SPECT.

Purpose of the Study:

• To evaluate the effect of varying effective reconstruction iterations on [123I]FP-CIT SPECT using MPH collimators.
• To determine the optimal number of iterations for balancing image quality and diagnostic performance.

Main Methods:

• Retrospective analysis of 671 patients' MPH SPECT data reconstructed with 3D Tera-Tomo Monte Carlo algorithm (12-300 iterations).
• Assessed diagnostic performance using putaminal specific binding ratio (SBR) and visual Likert 6-score evaluation by 7 readers.
• Statistical analysis included Gaussian mixture models and repeated measures ANOVA.

Main Results:

• Iterative reconstruction converged slower in reference regions than in the striatum.
• Higher iterations improved spatial resolution with acceptable noise increase.
• Putaminal SBR discriminative power peaked at 300 iterations; however, reader confidence and agreement slightly decreased.

Conclusions:

• 300 iterations represent a compromise between resolution, diagnostic power, and noise/variability in [123I]FP-CIT MPH SPECT.
• Reader training is crucial to maintain stability when interpreting images reconstructed with high iteration counts.