Monte Carlo-based scatter correction for the SMARTZOOM collimator

Martijn M A Dietze,Hugo W A M De Jong,Martina Stella,Britt Kunnen

doi:10.1186/s40658-020-00318-7

Martijn M A Dietze, Hugo W A M De Jong + Show 2 more

Open Access

https://doi.org/10.1186/s40658-020-00318-7

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Abstract

BackgroundMyocardial perfusion imaging is a commonly performed SPECT protocol and hence it would be beneficial if its scan duration could be shortened. For traditional gamma cameras, two developments have separately shown to allow for a shortened scan duration: (i) reconstructing with Monte Carlo-based scatter correction instead of dual-energy window scatter correction and (ii) acquiring projections with the SMARTZOOM collimator instead of a parallel-hole collimator. This study investigates which reduction in scan duration can be achieved when both methods are combined in a single system.ResultsThe SMARTZOOM collimator was implemented in a Monte Carlo-based reconstruction package and the implementation was validated through image quality phantom experiments. The potential for scan duration reduction was evaluated with a phantom configuration that is realistic for myocardial perfusion imaging. The original reconstruction quality was achieved in 76 ± 8% of the original scan duration when switching from dual-energy window scatter correction to Monte Carlo-based scatter correction. The original reconstruction quality was achieved in 56 ± 13% of the original scan duration when switching from the parallel-hole to the SMARTZOOM collimator. After combining both methods in a single system, the original reconstruction quality was achieved in 34 ± 7% of the original scan duration.ConclusionsMonte Carlo-based scatter correction combined with the SMARTZOOM collimator can further decrease the scan duration in myocardial perfusion imaging.

Highlights

Myocardial perfusion imaging is a commonly performed single-photon emission computed tomography (SPECT) protocol and it would be beneficial if its scan duration could be shortened
Acquisition All phantom scans were performed on a dual-head Siemens Symbia T2 SPECT/CT scanner with our current clinical scan protocol for myocardial perfusion imaging
The point spread function of the SMARTZOOM collimator has a spatial variance over the collimator surface: the PSF is largest in the middle of the collimator and smallest in the collimator corners

Summary

Introduction

Myocardial perfusion imaging is a commonly performed SPECT protocol and it would be beneficial if its scan duration could be shortened. The SMARTZOOM collimator has been introduced in clinical practice by Siemens Healthineers (Erlangen, Germany) on IQ-SPECT systems [3, 4] This collimator has a converging (i.e., high sensitivity) inner part with diverging (low sensitivity) outer regions. The diverging parts of the collimator ensure that photons originating from outside of the heart will not produce truncation artifacts in the reconstruction. Since this collimator design provides a higher local sensitivity, it is frequently used to decrease the scan duration [5]. The maximum CNR values were collected for every scan duration and it was determined at which scan durations an equal reconstruction quality was achieved

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