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UK audit of the interoperability of ordered-subset expectation-maximisation reconstruction algorithms
Matthew J Memmott1, Gregory James2, Frances Morgan3
1Nuclear Medicine Department, Manchester University NHS Foundation Trust, Manchester.
Nuclear Medicine Communications
|January 7, 2026
Summary
This study audited ordered-subset expectation-maximisation (OSEM) algorithms for quantitative single-photon emission computed tomography (SPECT). Results showed good agreement between platforms, though users should derive specific factors for their acquisition and reconstruction combinations.
Area of Science:
- Medical Imaging
- Nuclear Medicine
- Computational Phantoms
Background:
- Filtered back projection (FBP) was previously audited for quantitative single-photon emission computed tomography (SPECT).
- Current guidelines favor iterative reconstruction methods like ordered-subset expectation-maximisation (OSEM).
- This study audits OSEM algorithms in clinical use.
Purpose of the Study:
- To audit ordered-subset expectation-maximisation (OSEM) algorithms for quantitative single-photon emission computed tomography (SPECT).
- To evaluate the performance of OSEM reconstruction platforms using standardized phantom data.
Main Methods:
- A computational phantom was used to assess sphere diameter, position, activity concentration, uniformity, and resolution.
- Recovery in photopenic areas and small lesions near active structures was evaluated.
- SPECT projections from three manufacturers were reconstructed using six commercial platforms.
Main Results:
- Excellent agreement was observed among platforms using similar OSEM reconstruction methods.
- One platform's results varied due to its inability to perform true 'pencil-beam' OSEM.
- Differences in reconstruction varied with manufacturer data, with wide-beam reconstruction showing the most variation.
Conclusions:
- Reconstruction platforms show generally small differences when processing data from different manufacturers.
- Wide-beam reconstruction methods exhibited the largest variations.
- Users of quantitative SPECT should determine specific calibration factors for their unique acquisition and reconstruction setups.
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