Purpose: To describe and validate the dose calculation algorithm of an independent second-dose check software for spot scanning proton delivery systems with full width at half maximum between 5 and 14 mm and with a negligible spray component. Methods: The analytical dose engine of our independent second-dose check software employs an altered pencil beam algorithm with 3 lateral Gaussian components. It was commissioned using Geant4 and validated by comparison to point dose measurements at several depths within spread-out Bragg peaks of varying ranges, modulations, and field sizes. Water equivalent distance was used to compensate for inhomogeneous geometry. Twelve patients representing different disease sites were selected for validation. Dose calculation results in water were compared to a fast Monte Carlo code and ionization chamber array measurements using dose planes and dose profiles as well as 2-dimensional–3-dimensional and 3-dimensional–3-dimensional γ-index analysis. Results in patient geometry were compared to Monte Carlo simulation using dose–volume histogram indices, 3-dimensional–3-dimensional γ-index analysis, and inpatient dose profiles. Results: Dose engine model parameters were tuned to achieve 1.5% agreement with measured point doses. The in-water γ-index passing rates for the 12 patients using 3%/2 mm criteria were 99.5% ± 0.5% compared to Monte Carlo. The average inpatient γ-index analysis passing rate compared to Monte Carlo was 95.8% ± 2.9%. The average difference in mean dose to the clinical target volume between the dose engine and Monte Carlo was −0.4% ± 1.0%. For a typical plan, dose calculation time was 2 minutes on an inexpensive workstation. Conclusions: Following our commissioning process, the analytical dose engine was validated for all treatment sites except for the lung or for calculating dose–volume histogram indices involving point doses or critical structures immediately distal to target volumes. Monte Carlo simulations are recommended for these scenarios.

Proton beam therapy (PBT) is a state-of-the-art radiotherapy treatment approach that uses focused proton beams for tumor ablation. A key advantage of this approach over conventional photon radiotherapy (XRT) is the unique dose deposition characteristic of protons, which results in superior healthy tissue sparing. This results in fewer unwanted side effects and improved outcomes for patients. Currently available dosimeters are intrinsic, complex, and expensive and are not routinely used to determine the dose delivered to the tumor. Here, we report a hydrogel-based plasmonic nanosensor for detecting clinical doses used in conventional and hyperfractionated proton beam radiotherapy. In this nanosensor, gold ions, encapsulated in a hydrogel, are reduced to gold nanoparticles following irradiation with proton beams. Formation of gold nanoparticles renders a color change to the originally colorless hydrogel. The intensity of the color can be used to calibrate the hydrogel nanosensor in order to quantify different radiation doses employed during proton treatment. The potential of this nanosensor for clinical translation was demonstrated using an anthropomorphic phantom mimicking a clinical radiotherapy session. The simplicity of fabrication, detection range in the fractionated radiotherapy regime, and ease of detection with translational potential makes this a first-in-kind plasmonic colorimetric nanosensor for applications in clinical proton beam therapy.

Introduction: The range shifter (RS) is used to treat shallow tumors for a proton pencil beam scanning system (PBS). Adding RS certainly complicates the commissioning of the treatment planning system (TPS) because the spot sizes are significantly enlarged with RS. In this work, we present an efficient method to configure a commercial TPS for a PBS system with a fixed RS. Methods: By combining a spiral delivery with customized control points, we were able to significantly improve measurement efficiency and obtain 250 field size factors (FSF) within three hours. The measured FSFs were used to characterize the proton fluence and fit the parameters for the double-Gaussian fluence model used in the TPS. Extensive validation was performed using FSFs measured in air and in water, absolute doses of spread-out Bragg peak (SOBP) fields, and the dose measurements carried out for patient-specific quality assurance (QA). Results: The measured in-air FSFs agreed with the model's prediction within 3% for all 250 FSFs, and within 2 for 94% of the FSFs. The agreement between model's prediction and measurement was within 2% for the in-air and in-water FSFs and the absolute doses for SOBP beams. The patient-specific QA of 113 fields showed an excellent gamma passing rates (96.95 ± 2.51%) for the absolute dose comparisons with gamma criteria of 2 mm and 2%. Conclusion: The excellent agreement between the model's prediction and measurements proved the efficiency and accuracy of the proposed method of using FSFs to characterize the proton fluence and configure the TPS for a PBS system with fixed RS.

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Purpose: It is now commonplace to handle treatments of hyperthyroidism using iodine‐131 as an outpatient procedure due to lower costs and less stringent federal regulations. The Nuclear Regulatory Commission has currently updated release guidelines for these procedures, but there is still a large uncertainty in the dose to the public. Current guidelines to minimize dose to the public require patients to remain isolated after treatment. The purpose of this study was to use a low‐cost common device, such as a cell phone, to estimate exposure emitted from a patient to the general public. Methods: Measurements were performed using an Apple iPhone 3GS and a Cs‐137 irradiator. The charge‐coupled device (CCD) camera on the phone was irradiated to exposure rates ranging from 0.1 mR/hr to 100 mR/hr and 30‐sec videos were taken during irradiation with the camera lens covered by electrical tape. Interactions were detected as white pixels on a black background in each video. Both single threshold (ST) and colony counting (CC) methods were performed using MATLAB®. Calibration curves were determined by comparing the total pixel intensity output from each method to the known exposure rate. Results: The calibration curve showed a linear relationship above 5 mR/hr for both analysis techniques. The number of events counted per unit exposure rate within the linear region was 19.5 ± 0.7 events/mR and 8.9 ± 0.4 events/mR for the ST and CC methods respectively. Conclusion: Two algorithms were developed and show a linear relationship between photons detected by a CCD camera and low exposure rates, in the range of 5 mR/hr to 100‐mR/hr. Future work aims to refine this model by investigating the dose‐rate and energy dependencies of the camera response. This algorithm allows for quantitative monitoring of exposure from patients treated with iodine‐131 using a simple device outside of the hospital.