Dose Rate Effects from the 1950s through to the Era of FLASH.

Numerous dose rate effects have been described over the past 6-7 decades in the radiation biology and radiation oncology literature depending on the dose rate range being discussed. This review focuses on the impact and understanding of altering dose rates in the context of radiation therapy, but does not discuss dose rate effects as relevant to radiation protection. The review starts with a short historic review of early studies on dose rate effects, considers mechanisms thought to underlie dose rate dependencies, then discusses some current issues in clinical findings with altered dose rates, the importance of dose rate in brachytherapy, and the current timely topic of the use of very high dose rates, so-called FLASH radiotherapy.

A Systematic Comparison of Dose Distributions Delivered in I Plaque Brachytherapy and Proton Radiation Therapy for Ocular Melanoma.

Purpose: To characterize dose distributions with I plaque brachytherapy compared with proton radiation therapy for ocular melanoma for relevant clinical scenarios, based on tumor base diameter (d), apical height (h), and location.

Methods And Materials: Plaque and proton treatment plans were created for 4 groups of cases: (1) REF: 39 instances of reference midsize circular-base tumor (d = 12 mm, h = 5 mm), in locations varying by retinal clock hours and distance to fovea, optic disc, and corneal limbus; (2) SUP: 25 superiorly located; (3) TEMP: 25 temporal; and (4) NAS: 25 nasally located tumors that were a fixed distance from the fovea but varying in d (6-18 mm) and h (3-11 mm). For both modalities, 111 unique scenarios were characterized in terms of the distance to points of interest, doses delivered to fovea, optic disc, optic nerve at 3 mm posterior to the disc (ON@3mm), lens, and retina.

MRI-Based Radiotherapy Planning to Reduce Rectal Dose in Excess of Tolerance.

Materials And Methods: This prospective single-arm study enrolled 15 men treated with IG-IMRT for localized prostate cancer. All participants received a dedicated 3 Tesla MRI examination of the prostate in addition to a pelvic CT examination for treatment planning. Two volumetric modulated arc therapy (VMAT) plans with a prescription dose of 79.

Technical Note: Scintillation markers for real-time visual source tracking during skin high dose rate brachytherapy.

Background: Treatment misadministration during high dose rate (HDR) brachytherapy is mainly caused due to gross errors in incorrect manual entry of catheter length and manual connection of hardware. The probability of these errors increases with increasing complexity of a surface applicator. A simple, real-time visual verification method was developed using a scintillator to enhance quality assurance (QA) measures for HDR surface brachytherapy and thus reduce manual errors and improve patient safety.

Characterization of efficacy and toxicity after high-dose pelvic reirradiation with palliative intent for genitourinary second malignant neoplasms or local recurrences after full-dose radiation therapy in the pelvis: A high-volume cancer center experience.

Purpose: The use of large-field external beam reirradiation (re-RT) after pelvic radiation therapy (RT) for genitourinary (GU) cancers has not been reported. We report the results of such treatment in patients with either symptomatic GU second malignant neoplasms or locally recurrent pelvic tumors after initial RT for whom surgery or further systemic therapy was not an option.

Methods And Materials: The records of 28 consecutive patients with advanced, bulky GU malignancies treated with high-dose, large-field re-RT with palliative intent between 2008 and 2014 were retrospectively reviewed.

Custom-made micro applicators for high-dose-rate brachytherapy treatment of chronic psoriasis.

Purpose: In this study, we present the treatment of the psoriatic nail beds of patients refractory to standard therapies using high-dose-rate (HDR) brachytherapy. The custom-made micro applicators (CMMA) were designed and constructed for radiation dose delivery to small curvy targets with complicated topology. The role of the HDR brachytherapy treatment was to stimulate the T cells for an increased immune response.

The value of systematic contouring of the bowel for treatment plan optimization in image-guided cervical cancer high-dose-rate brachytherapy.

Purpose: To investigate the dose-volume histogram metrics and optimization results of the contoured bowel in cervical cancer brachytherapy.

Methods And Materials: Treatment plans of cervical cancer patients treated with image-guided high dose rate were retrospectively analyzed with institutional review board approval. In addition to the clinical target volume, rectum, bladder, and sigmoid, the bowel was contoured at the time of planning (Group 1) or at the time of this analysis (Group 2).

Outcomes with volume-based dose specification in CT-planned high-dose-rate brachytherapy for stage I-II cervical carcinoma: A 10-year institutional experience.

Objective: To determine prognostic factors for progression-free survival (PFS) and overall survival (OS) for stage I-II cervical-cancer patients treated using computed-tomography (CT)-planned high-dose-rate (HDR) intracavitary brachytherapy (BT).

Methods: A total of 150 patients were treated for Stage I-II cervical cancer using CT-planned BT between 4/2004 and 10/2014. Of these, 128 were eligible for inclusion.

Clinical implementation of a novel applicator in high-dose-rate brachytherapy treatment of esophageal cancer.

Purpose: In this study, we present the clinical implementation of a novel transoral balloon centering esophageal applicator (BCEA) and the initial clinical experience in high-dose-rate (HDR) brachytherapy treatment of esophageal cancer, using this applicator.

Material And Methods: Acceptance testing and commissioning of the BCEA were performed prior to clinical use. Full performance testing was conducted including measurements of the dimensions and the catheter diameter, evaluation of the inflatable balloon consistency, visibility of the radio-opaque markers, congruence of the markers, absolute and relative accuracy of the HDR source in the applicator using the radiochromic film and source position simulator, visibility and digitization of the applicator on the computed tomography (CT) images under the clinical conditions, and reproducibility of the offset.

Redesign of process map to increase efficiency: Reducing procedure time in cervical cancer brachytherapy.

Purpose: To increase intraprocedural efficiency in the use of clinical resources and to decrease planning time for cervical cancer brachytherapy treatments through redesign of the procedure's process map.

Methods And Materials: A multidisciplinary team identified all tasks and associated resources involved in cervical cancer brachytherapy in our institution and arranged them in a process map. A redesign of the treatment planning component of the process map was conducted with the goal of minimizing planning time.

Independent brachytherapy plan verification software: improving efficacy and efficiency.

Background And Purpose: To compare the pre-treatment brachytherapy plan verification by a physicist assisted by custom plan verification software (SAV) with those performed manually (MV).

Materials And Methods: All HDR brachytherapy plans used for treatment in 2013, verified using either SAV or MV, were retrospectively reviewed. Error rate (number of errors/number of plans) was measured and verification time calculated.

Vaginal brachytherapy for early stage uterine papillary serous and clear cell endometrial cancer.

Objective: To report clinical outcomes following adjuvant high-dose-rate (HDR) vaginal brachytherapy (VB) for early-stage uterine papillary serous (UPSC) and clear cell (CC) endometrial cancer.

Methods: A retrospective study of Stage I and II papillary serous and clear cell endometrial cancer treated with post-operative HDR VB between October 2005 and May 2012 was performed. A total of 37 patients were identified, 26 with UPSC, 9 with CC and 2 with mixed UPSC/CC.

A phenomenological kV beam model for cone-beam imaging.

A phenomenological kV beam model was developed to address attenuation and scatter in radiographic images for the purpose of cone-beam imaging. Characterization of a kV beam in terms of the minimal number of parameters and calculation of attenuation and scatter in radiographs of scanned objects are the main applications of this model. Model parameters are derived from radiographs of homogeneous solid water phantoms for various depths and field sizes.

Evaluation of MatriXX for IMRT and VMAT dose verifications in peripheral dose regions.

Purpose: MatriXX is a two-dimensional ion chamber array designed for IMRT/VMAT (RapidArc, IMAT, etc.) dose verifications. Its dosimetric properties have been characterized for megavoltage beams in a number of studies; however, to the best of the authors' knowledge, there is still a lack of an investigation into its performance in the peripheral or low dose regions.

An oscillating sweeping gap test for VMAT quality assurance.

The objective of this study was to develop an oscillating sweeping gap test for volumetric modulated arc therapy (VMAT) quality assurance (QA). A novel test was designed and used to simultaneously determine uncertainties associated with linac performance, dose calculation and dosimetric MLC parameters during VMAT delivery. Delivered doses were measured with Matrixx, ionization chamber A12 and EDR2 films, and compared to calculations from the treatment planning system (TPS) Eclipse.

Angular dose dependence of Matrixx TM and its calibration.

One of the applications of MatriXX (IBA Dosimetry) is experimental verification of dose for IMRT, VMAT, and tomotherapy. For cumulative plan verification, dose is delivered for all the treatment gantry angles to a stationary detector. Experimental calibration of MatriXX detector recommended by the manufacturer involves only AP calibration fields and does not address angular dependency of MatriXX.