De-multiplexing for improved activity recovery and signal-to-noise for a brain-dedicated multi-pinhole SPECT system

• Published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (NSS MIC RTSD) p. 1
• Main Authors: Pells, S., Zeraatkar, N., Kalluri, K. S., Moore, S. C., May, M., Furenlid, L. R., Kuo, P. H., King, M. A.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 04.11.2023
• Subjects: High-resolution imaging; Imaging phantoms; Microwave integrated circuits; Multiplexing; Noise measurement; Semiconductor detectors; Sensitivity
• ISSN: 2577-0829
• DOI: 10.1109/NSSMICRTSD49126.2023.10338609

Pinhole collimation can provide high-resolution imaging but at the cost of a lower sensitivity compared to parallel-hole collimators. Simultaneous imaging through multiple pinholes increases sensitivity but can lead to multiplexing artefacts due to ambiguity in projection images. Here, the impact of multiplexing artefacts on activity recovery and detectability was considered, as well as the utilisation of de-multiplexing to counter this impact. These are important considerations for quantitative imaging in multi-pinhole SPECT.A model of the brain-dedicated AdaptiSPECT-C system and a digital spherical phantom with spherical inserts of diameters 37 to 10~mm was used to assess the impact of multiplexing on activity recovery and detectability. Projection images with and without multiplexing were simulated with equal acquisition time. A de-multiplexing algorithm was applied and the activity recovery and signal-to-noise ratios were determined for two noise levels.Activity recovery was significantly worse for multiplexed compared to non-multiplexed images. However, activity recovery of de-multiplexed images was equivalent to or superior than that of the multiplex-free acquisition for all spherical inserts. De-multiplexing also improved signal-to-noise ratios for both noise levels. In addition, including a multiplex-free frame in the multiplexed acquisition further improved activity recovery for noisy data.