Commissioning of the world's first compact pencil‐beam scanning proton therapy system

Pidikiti, Rajesh; Patel, Bhaumik Narendrabhai; Maynard, Matthew; Dugas, Joseph P.; Syh, J; Sahoo, Narayan; Wu, H; Rosen, L

doi:10.1002/acm2.12225

Cited by 71 publications

(58 citation statements)

References 14 publications

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“…Sizes of proton spots in air could vary from 3 to 12 mm. [24][25][26] To improve imaging resolution consistently to accommodate different energies and various proton delivery platforms, a collimator was introduced in our design. The purpose of the collimator was to control proton spot size in air.…”

Section: A Spot Sizementioning

confidence: 99%

A novel design of proton computed tomography detected by multiple‐layer ionization chamber with strip chambers: A feasibility study with Monte Carlo simulation

et al. 2019

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Purpose Uncertainty in proton range can be reduced by proton computed tomography (CT). A novel design of proton CT using a multiple‐layer ionization chamber with two strip ionization chambers on the surface is proposed to simplify the imaging acquisition and reconstruction. Methods Two strip ionization chambers facing the proton source were coupled into a multiple‐layer ionization chamber (MLIC). The strip chambers measured locations and lateral profiles of incident proton beamlets after exiting the imaging object, while the integral of depth dose measured in the MLIC was translated into the residual energy of the beamlet. The simulation was performed at five levels of imaging dose to demonstrate the feasibility and performance expectations of our design. The energy of the proton beamlet was set to 150 ± 0.6 MeV. A collimator with a round slit of 1 cm in diameter was placed in the central beam axis upstream from steering magnets. Proton stopping power ratio (SPR) was reconstructed through inverse radon transform on sinograms generated with proton beamlets scanning through an imaging phantom from a half‐circle gantry rotation. The imaging phantom was 10 cm in diameter. The base was made of water‐equivalent material holding 13‐tissue equivalent inserts constructed according to ICRP 1975 (Task Group on Reference Man. “Report of the Task Group on Reference Man: A Report”, Pergamon Press 23, 1975). All inserts were 1 cm in diameter with materials ranging from lung to cortical bone. Percentage discrepancies were reported by comparing to the ground truths. The imaging dose and quality were also evaluated. Results The maximum deviation in reconstructed proton SPR from the ground truths was reported to be 1.02% in one of the 13 inserts when the number of protons per beamlet passing through the slit dropped to 103. Imaging dose was correlated linearly to incident protons and was determined to be 0.54 cGy if 5 × 102 protons per beamlet were used. Imaging quality was acceptable for planning purpose and held consistently through all levels of imaging dose. Spatial resolution was measured as five line pairs per cm consistently in all simulations varying in imaging dose. Conclusions Proton CT using a multiple‐layer ionization chamber with two strip ionization chambers on the surface simplifies data acquisition while achieving excellent accuracy in proton SPR and acceptable spatial resolution. The imaging dose is lower compared to kV CBCT, making it potentially a great tool for localization and plan adaption in proton therapy.

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Section: A Spot Sizementioning

confidence: 99%

A novel design of proton computed tomography detected by multiple‐layer ionization chamber with strip chambers: A feasibility study with Monte Carlo simulation

et al. 2019

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“…Following the methodology recommended by TRS 398 report, the absolute dose output of each nominal monogenic beam was obtained at 15 mm depth in water aligned to the ISO using an ADCL calibrated PPC05 Markus parallel‐plate chamber (IBA Dosimetry). In addition, the known dosimetric output accuracy issues in PCS 3,4 were corrected with AcurosPT calculations for different test fields 7 . To convert the measurements in the transmission beam region to radiation doses, 1.002 k Q factor was used along with 1.1 RBE offset factor, which were then imported to an Eclipse v15.6 (Varian, Palo Alto, CA) for modeling the PCS and NUPO algorithms.…”

Section: Methodsmentioning

confidence: 99%

“…Here, the low‐energy (85 to 70 MeV) dose outputs were slightly adjusted by using 0.995–0.990 for k Q variations 10 . The final IDD outputs particularly for AcurosPT were fine‐tuned for an optimal overall accuracy, based on the measurements of the calibrated ionization chamber two‐dimensional (2D) array on different testing field sizes and various patient plan‐specific QAs 3,4 . In this commissioning, AcurosPT algorithm was exclusively utilized for final planning dose computations.…”

Section: Methodsmentioning

confidence: 99%

“…The principle beam dosimetric components of the commissioning typically comprised of integrated depth dose curves (IDDs), absolute dose calibration for given MUs (or dose output), in‐air beam spot size or profiles 3–6 . Other essential elements are virtual source position relative to ISO, beam spot accuracy and dose uniformity, field size factors (or halo effect of spot profile), MU linearity, mechanical accuracy, OBI and CBCT quality and accuracy, CT stoichiometric calibration, WET measurement for the range shifters, table support and inserts, as well as immobilization and physics accessories 7–9 .…”

Section: Introductionmentioning

confidence: 99%

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Beam characteristics of the first clinical 360° rotational single gantry room scanning pencil beam proton treatment system and comparisons against a multi‐room system

Shang¹,

Evans²,

Rahman³

et al. 2020

J Applied Clin Med Phys

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Purpose The purpose of this study was to present the proton beam characteristics of the first clinical single‐room ProBeam Compact™ proton therapy system (SRPT) and comparison against multi‐room ProBeam™ system (MRPT). Materials and Methods A newly designed SRPT with proton beam energies ranging from 70 to 220 MeV was commissioned in late 2019. Integrated depth doses (IDDs) were scanned using 81.6 mm diameter Bragg peak chambers and normalized by outputs at 15 mm WET and 1.1 RBE offset, following the methodology of TRS 398. The in‐air beam spot profiles were acquired by a planar scintillation device, respectively, at ISO, upper and down streams, fitted with single Gaussian distribution for beam modeling in Eclipse v15.6. The field size effect was adjusted for the best overall accuracy of clinically relevant field QAs. The halo effects at near surface were quantified by a pinpoint ionization chamber. Its major dosimetric characteristics were compared against MRPT comparable beam dataset. Results Contrast to MRPT, an increased proton straggling in the Bragg peak region was found with widened beam distal falloffs and elevated proximal transmission dose values. Integrated depth doses showed 0.105–0.221 MeV (energy sigma) or 0.30–0.94 mm broader Bragg peak widths (Rb80–Ra80) for 130 MeV or higher energy beams and up to 0.48–0.79 mm extended distal falloffs (Rb20–Rb80). Minor differences were identified in beam spot sizes, spot divergences, proton particles/MU, and field size output effects. High passing scores are reported for independent end‐to‐end dosimetry checks by IROC and for initial 108 field‐specific QAs at 3%/3 mm Gamma index with fields regardless with or without range shifters. Conclusions The author highlighted the dosimetry differences in IDDs mainly caused by the shortened beam transport system of SRPT, for which new acceptance criteria were adapted. This report offers a unique reference for future commissioning, beam modeling, planning, and analysis of QA and clinical studies.

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“…Proton beam characteristic of active scanning PT systems have been reported from few PT centers, equipped with different proton accelerators and beam delivery techniques. [ 4 5 6 ] However, comprehensive proton-beam characteristics, dosimetric data, electromechanical, image quality, and image registration evaluation results from Proteus 235 PT system with dedicated PBS nozzle is lagging in the literature. In this study, we report the performance characteristics of the first gantry of our multi-room PT facility capable of delivering both single-field uniform dose and intensity-modulated proton therapy.…”

Section: Introductionmentioning

confidence: 99%

Characterization and performance evaluation of the first-proton therapy facility in India

et al. 2020

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Purpose: The purpose of this study is to evaluate the performance characteristic of volumetric image-guided dedicated-nozzle pencil beam-scanning proton therapy (PT) system. Materials and Methods: PT system was characterized for electromechanical, image quality, and registration accuracy. Proton beam of 70.2–226.2 MeV was characterized for short- and long-term reproducibility in integrated depth dose; spot profile characteristics at different air gap and gantry angle; positioning accuracy of single and pattern of spot; dose linearity, reproducibility and consistency. All measurements were carried out using various X-ray and proton-beam specific detectors following standard protocols. Results: All electro-mechanical, imaging, and safety parameters performed well within the specified tolerance limit. The image registration errors along three translation and three rotational axes were ≤0.5 mm and ≤0.2° for both point-based and intensity-based auto-registration. Distal range (R 90 ) and distal dose fall-off (DDF) of 70.2–226.2 MeV proton beams were within 1 mm of calculated values based on the international commission on radiation units and measurements 49 and 0.0156× R 90 , respectively. The R 90 and DDF were reproducible within a standard deviation of 0.05 g/cm 2 during the first 8 months. Dose were linear from 18.5 (0.011 MU/spot) to 8405 (5 MU/spot) MU, reproducible within 0.5% in 5 consecutive days and consistent within 0.8% for full rotation. The cGy/MU for 70.2–226.2MeV was consistent within 0.5%. In-air X(Y) spot-sigma at isocenter varies from 2.96 (3.00) mm to 6.68 (6.52) mm for 70.2–226.2 MeV. Maximum variation of spot-sigma with air-gap of ±20 cm was ±0.36 mm (5.28%) and ±0.82 mm (±12.5%) along X- and Y-direction and 3.56% for full rotation. Relative spot positions were accurate within ±0.6 mm. The planned and delivered spot pattern of known complex geometry agreed with (γ%≤1) for 1% @ 1 mm >98% for representative five-proton energies at four gantry angle. Conclusion: The PT-system performed well within the expected accuracy level and consistent over a period of 8 months. The methodology and data presented here may help upcoming modern PT center during their crucial phase of commissioning.

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Commissioning of the world's first compact pencil‐beam scanning proton therapy system

Cited by 71 publications

References 14 publications

A novel design of proton computed tomography detected by multiple‐layer ionization chamber with strip chambers: A feasibility study with Monte Carlo simulation

A novel design of proton computed tomography detected by multiple‐layer ionization chamber with strip chambers: A feasibility study with Monte Carlo simulation

Beam characteristics of the first clinical 360° rotational single gantry room scanning pencil beam proton treatment system and comparisons against a multi‐room system

Characterization and performance evaluation of the first-proton therapy facility in India

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