Validation of SPECT-CT image reconstruction for the Mediso AnyScan SCP scanner in STIR

Single photon emission tomography (SPECT) is widely used in clinical practice for a large number of diagnostic applications. However, different hospitals might use different scanners containing different hardware and software technologies, therefore making reproducibility of results a hard task. The aim of this work is to establish the basis for a tool able to include different clinical scanner models to facilitate inter-comparison of activity measurements across different institutions. We used the open source software for tomographic image reconstruction (STIR) and implemented functionalities to read, process and reconstruct the data from the Mediso AnyScan SCP scanner. In particular, the triple energy window method for scatter estimation, a method to re-scale the CT Hounsfield units in attenuation coefficient units (cm−1), SPECT normalisation functionalities and list mode (LM) functionalities were implemented and tested. 3D printed phantom data, with organ inserts filled with 177Lu, and a 99mTc clinical bone study were reconstructed using the implemented corrections and different anatomically-guided algorithms. The effect of the aforementioned correction was studied using ROI analysis and line profiles, whereas visual comparison was carried out between the reconstructed images with the vendor software and with STIR. Moreover, we demonstrated the feasibility of SPECT image reconstruction using the CT and iterative SPECT image estimates as prior information. Finally, a run time performance study showed that, when using multiple cores, an acceleration of a factor 2.7 is achieved for OSEM and around 2 for the other algorithms which involved more image-based operations. The availability of such tool will make SPECT research applications more accessible and reproducible.