Pre-clinical PET reconstruction algorithm effect on Cu-64 ATSM lesion hypoxia

INTRODUCTION: Application of distinct PET scan reconstruction algorithms can lead to statistically significant differences in measuring lesion functional properties. We look at the influence of two-dimensional filtered backprojection (2D FBP), two-dimensional ordered subset expectation maximization (2D OSEM), three-dimensional ordered subset expectation maximization without 3D maximum a posteriori (3D OSEM) and with (3D OSEM MAP) on lesion hypoxia tracer uptake using a pre-clinical PET scanner.
METHODS: Reconstructed images of a rodent tumour model bearing P22 carcinosarcoma injected with hypoxia tracer Copper-64-Diacetyl-bis(N4-methylthiosemicarbazone) ( i.e. Cu-64 ATSM) were analysed at 10minute intervals till 60minute post injection. Lesion maximum standardized uptake values (SUVmax) and SUVmax/background SUVmean (T/B) were recorded and investigated after application of multiple algorithm and reconstruction parameters to assess their influence on Cu-64 ATSM measurements and associated trends over time.
RESULTS: SUVmax exhibited convergence for OSEM reconstructions while ANOVA results showed a significant difference in SUVmax or T/B between 2D FBP, 2D OSEM, 3D OSEM and 3D OSEM MAP reconstructions across all time frames. SUVmax and T/B were greatest in magnitude for 2D OSEM followed by 3D OSEM MAP, 3D OSEM and then 2D FBP at all time frames respectively. Similarly SUVmax and T/B standard deviations (SD) were lowest for 2D OSEM in comparison with other algorithms.
DISCUSSION AND CONCLUSION: Significantly higher magnitude lesion SUVmax and T/B combined with lower SD were observed using 2D OSEM reconstruction in comparison with 2D FBP, 3D OSEM and 3D OSEM MAP algorithms at all time frames. Results are consistent with other published studies however more specimens are required for full validation.