A Statistical DOI Estimation Algorithm for a SiPM-Based Clinical SPECT Insert

A prototype clinical brain single-photon emission computed tomography (SPECT) insert has been designed for use in simultaneous SPECT/MRI. The system utilizes novel slit-slat collimators which, like pinhole collimators, suffers from parallax errors due to the large incident angle of photons. A statistical algorithm has been developed to determine the depth-of-interaction (DOI) with a view to improving image performance. The importance of DOI correction was demonstrated using Monte Carlo simulation. This simulation also indicated that four DOI layers (3 x 1.5 mm + 3.5 mm) may be sufficient. The improvement in event localization was demonstrated on a single detector before implementing the algorithm on the full clinical prototype where some limitations in event localization in layers close to the readout plane were observed. Nevertheless, DOI enabled the rejection of poorly localized events with improved resolution in reconstructed line sources.

Automated summary

A prototype clinical brain single-photon emission computed tomography (SPECT) insert has been designed for use in simultaneous SPECT/MRI. The system incorporates novel slit-slat collimators and a statistical algorithm to determine the depth-of-interaction (DOI) for improved image performance. Monte Carlo simulation and experimental results showed the importance of DOI correction and suggested that four DOI layers may be sufficient. However, some limitations in event localization close to the readout plane were observed in the full clinical prototype.