High-resolution three-dimensional dosimetry in clinically relevant volumes utilizing optically stimulated luminescence.

Background: The continued development of new radiotherapy techniques requires dosimetry systems that satisfy increasingly rigorous requirements, such as high sensitivity, wide dose range, and high spatial resolution. An emerging requirement is the ability to read out doses in three dimensions (3D) with high precision and spatial resolution. A few dosimetry systems with 3D capabilities are available, but their application in a clinical workflow is limited for various reasons, primarily originating from their chemical nature.

Consistency in contouring of organs at risk by artificial intelligence vs oncologists in head and neck cancer patients.

Background: In the Danish Head and Neck Cancer Group (DAHANCA) 35 trial, patients are selected for proton treatment based on simulated reductions of Normal Tissue Complication Probability (NTCP) for proton compared to photon treatment at the referring departments. After inclusion in the trial, immobilization, scanning, contouring and planning are repeated at the national proton centre. The new contours could result in reduced expected NTCP gain of the proton plan, resulting in a loss of validity in the selection process.

Evaluation of decentralised model-based selection of head and neck cancer patients for a proton treatment study. DAHANCA 35.

Introduction: Proton treatment can potentially spare patients with H&N cancer for substantial treatment-related toxicities. The current study investigated the reproducibility of a decentralised model-based selection of patients for a proton treatment study when the selection plans were compared to the clinical treatment plans performed at the proton centre.

Methods: Sixty-three patients were selected for proton treatment in the six Danish Head and Neck Cancer (DAHANCA) centres.

Technical note: Temporal and thermal stability of optical response for silicone-based 3D radiochromic dosimeters.

Background: Radiochromic silicone-based dosimeters are flexible 3D dosimeters, which at appropriate concentration of leucomalachite green (LMG) and curing agent are dose-rate independent for clinical photon beams. However, their dose response is based on chemical processes that can be influenced by temporal and thermal conditions, impacting measurement stability.

Purpose: The aim of this study was to investigate the temporal stability of the dose response of radiochromic dosimeters for different curing times and post-irradiation storage temperatures.

Towards range-guidance in proton therapy to detect organ motion-induced dose degradations.

Internal organ motion and deformations may cause dose degradations in proton therapy (PT) that are challenging to resolve using conventional image-guidance strategies. This study aimed to investigate the potential ofusing water-equivalent path length (WEPL) calculations to detect dose degradations occurring in PT..

Empirical quenching correction in radiochromic silicone-based three-dimensional dosimetry of spot-scanning proton therapy.

Background And Purpose: Three-dimensional dosimetry of proton therapy (PT) with chemical dosimeters is challenged by signal quenching, which is a lower dose-response in regions with high ionization density due to high linear-energy-transfer (LET) and dose-rate. This study aimed to assess the viability of an empirical correction model for 3D radiochromic silicone-based dosimeters irradiated with spot-scanning PT, by parametrizing its LET and dose-rate dependency.

Materials And Methods: Ten cylindrical radiochromic dosimeters (Ø50 and Ø75 mm) were produced in-house, and irradiated with different spot-scanning proton beam configurations and machine-set dose rates ranging from 56 to 145 Gy/min.

Chemically tuned linear energy transfer dependent quenching in a deformable, radiochromic 3D dosimeter.

Most solid-state detectors, including 3D dosimeters, show lower signal in the Bragg peak than expected, a process termed quenching. The purpose of this study was to investigate how variation in chemical composition of a recently developed radiochromic, silicone-based 3D dosimeter influences the observed quenching in proton beams. The dependency of dose response on linear energy transfer, as calculated through Monte Carlo simulations of the dosimeter, was investigated in 60 MeV proton beams.

Technical Note: Improving proton stopping power ratio determination for a deformable silicone-based 3D dosimeter using dual energy CT.

Purpose: The aim of this study was to investigate whether the stopping power ratio (SPR) of a deformable, silicone-based 3D dosimeter could be determined more accurately using dual energy (DE) CT compared to using conventional methods based on single energy (SE) CT. The use of SECT combined with the stoichiometric calibration method was therefore compared to DECT-based determination.

Methods: The SPR of the dosimeter was estimated based on its Hounsfield units (HUs) in both a SECT image and a DECT image set.

Dosimetric verification of complex radiotherapy with a 3D optically based dosimetry system: dose painting and target tracking.

Background: The increasing complexity of radiotherapy (RT) has motivated research into three-dimensional (3D) dosimetry. In this study we investigate the use of 3D dosimetry with polymerizing gels and optical computed tomography (optical CT) as a verification tool for complex RT: dose painting and target tracking.

Materials And Methods: For the dose painting studies, two dosimeters were irradiated with a seven-field intensity modulated radiotherapy (IMRT) plan with and without dose prescription based on a hypoxia image dataset of a head and neck patient.

Temperature and temporal dependence of the optical response for a radiochromic dosimeter.

Purpose: Both temporal and thermal dependencies of the dose response have been observed in radiochromic dosimeters. As these dependencies may be influenced by the dose level, the present study investigates the temperature dependence during irradiation and the temporal change of the optical response following irradiation of radiochromic dosimeters at a range of doses.

Methods: Cuvette samples of the PRESAGE™ radiochromic dosimeter were irradiated within a dose range of 0-10 Gy at irradiation temperatures within 5-35 °C and postirradiation storage within 6-30 °C.

Temperature dependence of the dose response for a solid-state radiochromic dosimeter during irradiation and storage.

Purpose: The dose response of radiochromic dosimeters is based on radiation-induced chemical reactions and is thus likely to be thermally influenced. In this study we have therefore investigated the temperature dependence of the dose response for such dosimeters, regarding both irradiation and storage conditions.

Methods: Dosimeter samples in cuvettes were irradiated to 5 Gy.

Characterization of the optical properties and stability of Presage™ following irradiation with photons and carbon ions.

Background: The on-going development of both intensity-modulated radiotherapy (IMRT), including the more recent intensity-modulated arc therapy, as well as particle beam therapy, has created a clear need for accurate verification of dose distributions in three dimensions (3D). Presage™ is a new 3D dosimetry material that exhibits a radiochromic response when exposed to ionizing radiation. In this study we have 1) developed an improved optical set-up for measurements of changes in OD of Presage™ point dosimeters, 2) investigated the dose response of Presage™ for photons and carbon ions in the therapy range, 3) investigated the dose response of Presage™ for photons in the kGy range and 4) investigated the fading (i.