A comparison of proton stopping power measured with proton CT and x‐ray CT in fresh postmortem porcine structures

DeJongh, Don F.; DeJongh, Ethan A.; Rykalin, V.; DeFillippo, Greg; Pankuch, Mark; Best, Andrew W.; Coutrakon, G.; Duffin, Kirk L.; Karonis, Nicholas T.; Ordoñez, C.E.; Sarosiek, Christina; Schulte, R.; Winans, John R.; Block, Alec M.; Hentz, Courtney; Welsh, James S.

doi:10.1002/mp.15334

Cited by 24 publications

(14 citation statements)

References 31 publications

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“…As it is the first time that fresh tissue RSPs were compared against a reference measurement for pCT/HECT, it is hard to evaluate our results against other groups. Still, DeJongh et al 49 . conducted a relative comparison between the reconstructed RSP values for pCT and SECT using two heterogeneous porcine tissue samples with pCT and SECT.…”

Section: Discussionmentioning

confidence: 99%

Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

et al. 2021

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Purpose: Measurements comparing relative stopping power (RSP) accuracy of state-of -the-art systems representing single-energy and dual-energy computed tomography (SECT/DECT) with proton CT (pCT) and helium CT (HeCT) in biological tissue samples. Methods: We used 16 porcine and bovine samples of various tissue types and water, covering an RSP range from 0.90±0.06 to 1.78 ±0.05. Samples were packed and sealed into 3D-printed cylinders (d = 2 cm, h = 5 cm) and inserted into an in-house designed cylindrical polymethyl methacrylate (PMMA) phantom (d = 10 cm, h = 10 cm). We scanned the phantom in a commercial SECT and DECT (120 kV; 100 and 140 kV/Sn (tin-filtered)); and acquired pCT and HeCT (E ∼ 200 MeV/u, 2 • steps, ∼ 6.2 × 10 6 (p)/∼ 2.3 × 10 6 (He) particles/projection) with a particle imaging prototype. RSP maps were calculated from SECT/DECT using stoichiometric methods and from pCT/HeCT using the DROP-TVS algorithm.We estimated the average RSP of each tissue per modality in cylindrical volumes of interest and compared it to ground truth RSP taken from peak-detection measurements.Results: Throughout all samples, we observe the following root-mean-squared RSP prediction errors ± combined uncertainty from reference measurement and imaging: SECT 3.10±2.88%, DECT 0.75±2.80%, pCT 1.19± 2.81%, and HeCT 0.78±2.81%.The largest mean errors ± combined uncertainty per modality are SECT 8.22 ±2.79% in cortical bone, DECT 1.74±2.00% in back fat, pCT 1.80 ±4.27% in bone marrow, and HeCT 1.37±4.25% in bone marrow. Ring artifacts 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 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 artifacts. Future work will study accuracy of proton treatment plans using RSP maps from investigated imaging modalities.

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Section: Discussionmentioning

confidence: 99%

Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

et al. 2021

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“…Nevertheless, plastic samples provide only a limited basis for comparison due to their poor representation of human tissues [18] and the homogeneity of the samples. deJongh et al [19] conducted a relative comparison between pCT and SECT based RSP reconstruction for fresh postmortem heterogeneous porcine tissue samples. They report acceptable agreement between the two modalities for soft tissue and larger discrepancies in bones.…”

Section: Introductionmentioning

confidence: 99%

The accuracy of helium ion CT based particle therapy range prediction: an experimental study comparing different particle and x-ray CT modalities

et al. 2021

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This work provides a quantitative assessment of helium ion CT (HeCT) for particle therapy treatment planning. For the first time, HeCT based range prediction accuracy in a heterogeneous tissue phantom is presented and compared to single-energy x-ray CT (SECT), dual-energy x-ray CT (DECT) and proton CT (pCT). HeCT and pCT scans were acquired using the US pCT collaboration prototype particle CT scanner at the Heidelberg Ion-Beam Therapy Center. SECT and DECT scans were done with a Siemens Somatom Definition Flash and converted to RSP. A Catphan CTP404 module was used to study the RSP accuracy of HeCT. A custom phantom of 20 cm diameter containing several tissue equivalent plastic cubes was used to assess the spatial resolution of HeCT and compare it to DECT. A clinically realistic heterogeneous tissue phantom was constructed using cranial slices from a pig head placed inside a cylindrical phantom (ø150 mm). A proton beam (84.67 mm range) depth-dose measurement was acquired using a stack of GafchromicTM EBT-XD films in a central dosimetry insert in the phantom. CT scans of the phantom were acquired with each modality, and proton depth-dose estimates were simulated based on the reconstructions. The RSP accuracy of HeCT for the plastic phantom was found to be 0.3 ± 0.1%. The spatial resolution for HeCT of the cube phantom was 5.9 ± 0.4 lp cm−1 for central, and 7.6 ± 0.8 lp cm−1 for peripheral cubes, comparable to DECT spatial resolution (7.7 ± 0.3 lp cm−1 and 7.4 ± 0.2 lp cm−1, respectively). For the pig head, HeCT, SECT, DECT and pCT predicted range accuracy was 0.25%, −1.40%, −0.45% and 0.39%, respectively. In this study, HeCT acquired with a prototype system showed potential for particle therapy treatment planning, offering RSP accuracy, spatial resolution, and range prediction accuracy comparable to that achieved with a commercial DECT scanner. Still, technical improvements of HeCT are needed to enable clinical implementation.

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“…To ensure conservatism in annual dose estimates, it is assumed all proton imaging will be acquired in pCT mode, as opposed to pRad mode. The number of protons per tomography has been estimated to be 7.5 × 10 8 based on the 1.5 × 10 7 protons used to acquire a proton tomography of a pig's head, 4 and noting that the noise levels will likely need to be reduced in the clinical setting. The conservative workload calculations also assume that every treatment fraction includes a pCT image acquisition.…”

Section: Methodsmentioning

confidence: 99%

Radiation shielding assessment of high‐energy proton imaging at a proton therapy facility

Penfold

2022

Medical Physics

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Background Proton imaging makes use of high‐energy, low‐intensity proton beams that fully traverse the patient and has been suggested to reduce range uncertainty in proton therapy. Upright patient positioning with proton imaging is being considered for a fixed beam room of a new proton therapy facility currently under construction. Considering that the yield and energy spectrum of secondary radiation from high‐energy proton beams is proton beam energy dependent, an assessment of radiation shielding at the energies required for proton imaging should be performed prior to use. Furthermore, NCRP 144 recommends that pion production be considered for proton energies greater than 300 MeV, which are not typically utilized for proton therapy but may be required for proton imaging. Purpose The purpose of this work was to determine whether proton treatment and imaging with an upright patient positioning system on a fixed beamline were acceptable from a radiation shielding perspective. This is the first report on radiation shielding assessment of proton imaging applications and includes consideration of pion production at the proton beam energy of 330 MeV. Methods The Geant4 Monte Carlo toolkit was used for the radiation shielding assessment. The calculations consisted of the generation of secondary particle phase‐space files by simulating the passage of high‐energy proton beams in two target materials, and subsequent simulation of the secondary particles in the proton therapy facility geometry. Particle fluence was converted to operational and protection radiation safety quantities with a custom python script for assessment of instantaneous and annual doses, respectively. Results The total yields of pions from a 330‐MeV proton beam were many orders of magnitude less than that of neutrons and photons. Three‐dimensional maps of ambient dose rate for a 330‐MeV proton beam showed doses arising from secondary neutrons and photons far exceed those arising from pion production. Incorporating representative annual workloads into the calculation demonstrated that proton imaging doses outside the shielded area were negligible compared to those arising from proton therapy. Conclusions Pion production has a negligible impact on the radiation shielding of proton imaging at 330 MeV relative to neutron and photon production. Radiation shielding designed for proton therapy is adequate for high‐energy proton imaging applications.

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A comparison of proton stopping power measured with proton CT and x‐ray CT in fresh postmortem porcine structures

Cited by 24 publications

References 31 publications

Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

Experimental comparison of photon versus particle computed tomography to predict tissue relative stopping powers

The accuracy of helium ion CT based particle therapy range prediction: an experimental study comparing different particle and x-ray CT modalities

Radiation shielding assessment of high‐energy proton imaging at a proton therapy facility

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