Facilitating Multi-Center Consistency in PET/CT Assessment: Transferability and Harmonization of 3D-Printed Phantom Inserts
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Abstract
Objective
Three-dimensional (3D) printing has been used to build cost effective & realistic phantoms in medical imaging but their adaptability across facilities remains under-explored. Verification of the applicability of standardization protocols and quantitative metrics of positron emission tomography (PET) to printed phantoms has been sparse. This study aims to evaluate the harmonization and transferability of one such 3D printed phantom design across two facilities.
Approach
Cubic phantom inserts (40 mm) featuring spherical targets (0, 10, 15, and 20 mm), of a previously proven design, were fabricated at two different facilities using fused deposition modeling (FDM) printers and positioned within a cylinder of a Jaszczak phantom, filled with radiotracer and soap/water solution. At both facilities, acquisitions (Day 0,8) were performed on 5-ring Discovery MI and 32 cm OMNI Legend systems. Quantitative metrics, including CT Hounsfield units (HU), PET recovery coefficients (RC) and PET target-to-background ratios (TBR) were statistically analysed (rank sum tests) to assess the influence of facility, scanner model, and acquisition day.
Main Results
CT images revealed minor differences across facilities and scanners, with notable HU improvement (in emulating water) upon prolonged cube immersion, from about −12 HU to about −6 HU. PET image quality was visually good with respect to phantom feature representation. Average TBR Max (mean±std. dev.) were 1.56 ± 0.03 (expected 2.0), 2.35 ± 0.05 (expected 2.5), and 3.10 ± 0.05 (expected 3.33). RC Max and RC Mean ranged from 0.69 – 1.11 and 0.56 - 0.89. No statistical differences were found for TBR Max , RC Mean , or RC Max (p ≥ 0.07 for Mann Whitney; p ≥ 0.57 for Friedman) and Bland-Altman mean bias < 10%, though Wilcoxon post-hoc tests identified a few outliers.
Significance
Our study demonstrates that a simple digitally shared design file allows for easily reproducible 3D-printed phantoms of varying radiotracer contrasts, with consistency in PET quantitative metrics
