A novel proton-integrating radiography system design using a monolithic scintillator detector: Experimental studies

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Integrated-mode proton radiography leading to water equivalent thickness (WET) maps is an avenue of interest for motion management, patient positioning, and in vivo range verification. Radiographs can be obtained using a pencil beam scanning setup with a large 3D monolithic scintillator coupled with optical cameras. Established reconstruction methods either (1) involve a camera at the distal end of the scintillator, or (2) use a lateral view camera as a range telescope. Both approaches lead to limited image quality. The purpose of this work is to propose a third, novel reconstruction framework that exploits the 2D information provided by two lateral view cameras, to improve image quality achievable using lateral views. The three methods are first compared in a simulated Geant4 Monte Carlo framework using an extended cardiac torso (XCAT) phantom and a slanted edge. The proposed method with 2D lateral views is also compared with the range telescope approach using experimental data acquired with a plastic volumetric scintillator. Scanned phantoms include a Las Vegas (contrast), 9 tissue-substitute inserts (WET accuracy), and a paediatric head phantom. Resolution increases from 0.24 lp/mm (distal) to 0.33 lp/mm (proposed method) on the simulated slanted edge phantom, and the mean absolute error on WET maps of the XCAT phantom is reduced from 3.4 to 2.7 mm with the same methods. Experimental data from the proposed 2D lateral views indicate a 36\% increase in contrast relative to the range telescope method. High WET accuracy is obtained, with a mean absolute error of 0.4 mm over 9 inserts. Results are presented for various pencil beam spacing ranging from 2 to 6 mm. This work illustrates that high quality proton radiographs can be obtained with clinical beam settings and the proposed reconstruction framework with 2D lateral views, with potential applications in adaptive proton therapy.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Integrated-mode proton radiography with 2D lateral projections

Simard,

Robertson,

Fullarton

et al. 2024

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“…Most recently, a detector utilising a monolithic scintillator block imaged from multiple angles with chargecoupled device cameras has been developed to make measurements of proton depth-light curves and spots for QA and proton radiography purposes (Darne et al 2017(Darne et al , 2022. Results with this device have been promising, with range QA measurements shown to be accurate to 0.1mm and the multi-camera setup allowing for precise tracking of beam position in 3D.…”

Section: Ocular Proton Beam Therapy At the Clatterbridge Cancer Centrementioning

confidence: 99%

Spread-out Bragg peak measurements using a compact quality assurance range calorimeter at the Clatterbridge cancer centre

Shaikh,

Escribano-Rodriguez,

Radogna

et al. 2024

Objective: The superior dose conformity provided by proton therapy relative to conventional X-ray radiotherapy necessitates more rigorous Quality Assurance (QA) procedures to ensure optimal patient safety. Practically however, time-constraints prevent comprehensive measurements to be made of the proton range in water: a key parameter in ensuring accurate treatment delivery. Approach: A novel scintillator-based device for fast, accurate water-equivalent proton range QA measurements for ocular proton therapy is presented. Experiments were conducted using a compact detector prototype, the Quality Assurance Range Calorimeter (QuARC), at the Clatterbridge Cancer Centre (CCC) in Wirral, UK for the measurement of pristine and spread-out Bragg peaks (SOBPs). The QuARC uses a series of 14 optically-isolated 100 x 100 x 2.85 mm polystyrene scintillator sheets, read out by a series of photodiodes. The detector system is housed in a custom 3D-printed enclosure mounted directly to the nozzle and a numerical model was used to fit measured depth-light curves and correct for scintillator light quenching. Main Results: Measurements of the pristine 60 MeV proton Bragg curve found the QuARC able to measure proton ranges accurate to 0.2 mm and reduced QA measurement times from several minutes down to a few seconds. A new framework of the quenching model was deployed to successfully fit depth-light curves of SOBPs with similar range accuracy. Significance: The speed, range accuracy and simplicity of the QuARC make the device a promising candidate for ocular proton range QA. Further work to investigate the performance of SOBP fitting at higher energies/greater depths is warranted.

“…However, this technology has defects such as high cost, large detector volume and high requirements for stability of output low flux beams which prevent its clinical application. For the proton-integrating radiography (Cormack and Koehler 1976, Seco and Depauw 2011, Tanaka et al 2016, Park et al 2017, Krah et al 2018, Tanaka et al 2018, Darne et al 2019, Darne et al 2022, two methods are derived, including time-resolved method and energy-resolved method. It only requires a detector to record the proton fluence and energy deposition passing through the object to determine the WEPL values.…”

Section: Introductionmentioning

confidence: 99%

A denoising method based on deep learning for proton radiograph using energy resolved dose function

Sheng,

Ding,

et al. 2024

Objective: Proton radiograph has been broadly applied in proton radiotherapy which is affected by scattered protons which result in the lower spatial resolution of proton radiographs than that of X-ray images. Traditional image denoising method may lead to the change of water equivalent path length (WEPL) resulting in the lower WEPL measurement accuracy. In this study, we proposed a new denoising method of proton radiographs based on energy resolved dose function (ERDF) curves.Approach: Firstly, the corresponding relationship between the distortion of WEPL characteristic curve, and energy and proportion of scattered protons was established. Then, to improve the accuracy of proton radiographs, deep learning technique was used to remove scattered protons and correct deviated WEPL values. Experiments on a calibration phantom to prove the effectiveness and feasibility of this method were performed. In addition, an anthropomorphic head phantom was selected to demonstrate the clinical relevance of this technology and the denoising effect was analyzed.Main results: The curves of WEPL profiles of proton radiographs became smoother and deviated WEPL values were corrected. For the calibration phantom proton radiograph, the average absolute error (MAE) of WEPL values decreased from 2.23 to 1.72, the mean percentage difference of all materials of relative stopping power (RSP) decreased from 1.24 to 0.39, and the average relative WEPL corrected due to the denoising process was 1.06%. In addition, WEPL values correcting were also observed on the proton radiograph for anthropomorphic head phantom due to this denoising process.Significance: The experiments showed that this new method was effective for proton radiograph denoising and had greater advantages than end-to-end image denoising methods, laying the foundation for the implementation of precise proton radiotherapy.