Room: Track 2
Purpose: Using end-to-end measurements to compare relative stopping power (RSP) accuracy of state-of-the-art single-energy and dual-energy CT (SECT/DECT) with pre-clinical proton CT (pCT) and helium CT (HeCT) in biological tissue samples.
Methods: We used 17 porcine and bovine samples of various tissue types, including lung, belly fat, back fat, marrow, blood, cheek muscle, loin muscle (x2), leg muscle, brain, kidney (x2), liver (x2), trabecular bone, cortical bone and water. Samples were packed and sealed into 3D-printed cylinders (d=2cm, h=5cm) and inserted into an in-house designed cylindrical PMMA phantom (d=10cm, h=10cm). We scanned the phantom in a commercial SECT and DECT (120kV; 100kV & 140kV/Sn (tin-filtered)); and acquired pCT and HeCT (E=200.38MeV/u, 2° steps, 1.5x107 particles/projection) with a pre-clinical particle imaging prototype. RSP maps were calculated from SECT/DECT using stoichiometric methods (Schneider et al., PMB 41.1, Bourque et al., PMB 59.8) and from pCT/HeCT using the DROP-TVS algorithm (8 iterations). We estimated the average RSP of each tissue per modality in volumes of interest (V=682mm³) and compared it to ground truth RSP taken from peak-detection measurements.
Results: Throughout all samples, we observe the following root-mean-squared RSP errors: SECT 3.21%, DECT 0.89%, pCT 1.39%, HeCT 1.29%. The largest errors per modality are: SECT (8.69±2.41)% in cortical bone, DECT (1.75±3.33)% in back fat, pCT (-2.33±1.01)% in loin, HeCT (-2.77±3.05)% in kidney. Ring artefacts were observed in both pCT and HeCT reconstructions, imposing a systematic shift to predicted RSPs.
Conclusion: Comparing state-of-the-art SECT/DECT technology and a pre-clinical pCT/HeCT prototype, DECT provided the most accurate RSP prediction, closely followed by particle imaging. The novel modalities pCT and HeCT have the potential to further improve on RSP accuracies with work focusing on the origin and correction of ring artefacts. Future work will study the accuracy of proton treatment plans using RSP maps from investigated imaging modalities.
Not Applicable / None Entered.