Our study showed that burnout rates are moderate in members of the radiation oncology team, with dosimetrists and physicists displaying the highest levels of burnout. In order to better estimate professional burnout, larger studies should be conducted to determine causes of burnout. Furthermore, wellness programs should be encouraged and incentivized to help reduce burnout and improve workplace morale, occupational fulfillment, and effective patient care.

Brachytherapy is widely used for the treatment of choroidal melanoma and has recently been explored for the treatment of wet age-related macular degeneration. We propose the use of low dose radiation via episcleral brachytherapy in refractory cases of central serous chorioretinopathy (CSCR). The pathogenesis of CSCR involves dilatation and hyperpermeability of large choroidal vessels. Low dose radiation can induce intimal proliferation in large choroidal vessels and decrease their hyperpermeability. Concerns about the use of brachytherapy in CSCR include damage to the choriocapillaris or the retinal vessels. This can be addressed with the use of a specialized device through which a very precise and appropriate dose can be delivered. The dose of the radiation delivered decreases exponentially at a depth of approximately 0.5-1.5 mm from the devise-sclera interface. Considering an increased choroidal thickness in cases of CSCR, delivery of a safe dose can be assured.

Purpose/Objective(s) This study investigates the dosimetry achieved in VMAT/IMRT-planned lattice radiotherapy (LRT) for bulky, palliative head and neck tumors. LRT allows for the delivery of higher radiation doses without dramatically increasing toxicity by using high-dose spheres within the tumor while directing high dose away from OAR's. Our objective was to analyze LRT using 3 dose levels as a boost for palliative treatment of bulky head and neck tumors. The clinical goal of LRT boost would be to increase the effectiveness of treatment while minimizing the burden of care for patients requiring a quick palliation of symptoms associated with bulky tumors. Materials/Methods Six bulky palliative head and neck cases were used for this study. A 3D lattice of 0.75 cm spheres spaced 0.85 cm apart was applied to the planning scan and restricted to the area inside the lattice inward contour (GTV was contracted by 0.5 mm). Each case was planned with three different dose prescriptions (15 Gy, 20 Gy and 25 Gy in a single fraction) to the lattice of spheres. In addition, a standard IMRT plan was also created to deliver a uniform 20 Gy in 5 fractions to a defined PTV. The margins (CTV + PTV expansions) used were between 0.5 to 1 cm. A total of 7 plans were created for each case, which included the three single fraction doses, the five fractions of standard treatment, and a combination of the single and five fraction plans. Results The average planned tumor volume was 209.77 mL (range 137.80 – 411.01). The number of spheres used in the LRT plan ranged from 13 to 41. The median maximum dose (Dmax) and dose statistics achieved are listed in Table 1. The median ipsilateral carotid dose was high for the 25 Gy (single fraction) plan, so our results suggest that a neoadjuvant LRT boost with of a single fraction of 20 Gy would likely be safe. Conclusion Lattice radiotherapy is a viable treatment option for bulky head and neck cases treated with palliative intent. We were able to achieve acceptable dosimetric plans in both the 15 and 20 Gy boosts (single fraction) followed by 20 Gy in 5 fractions, a combination that would be expected to provide more favorable tumor control and symptom relief than traditional palliative regimens of 20-30 Gy. A clinical application with prospective dose escalation trial is under consideration.

This study was designed to demonstrate the safety and feasibility of episcleral brachytherapy (ESB) for the treatment of anti-vascular endothelial growth factor (anti-VEGF) resistant neovascular age-related macular degeneration (nAMD) in a 6-subject cohort adjunct to anti-VEGF therapy. Six eyes of six subjects with anti-VEGF resistant nAMD (persistent fluid or hemorrhage despite frequent anti-VEGF treatment) were treated with ESB between May 2018 and July 2018 as part of a larger early feasibility trial. Baseline and follow-up exams with multi-modal imaging were conducted. In this analysis, six eyes were included. The mean age was 74.7 years; 33

Monte Carlo (MC) is known to be the most accurate dose calculation method. However, MC suffers from high computational cost as a large number of particles have to be simulated to achieve the desired statistical uncertainty. Enhancing computational power by parallelizing the simulation with multiple GPU threads reduces the time required to reach the desired uncertainty in MC simulation. In this article, we present DOSXYZgpu, a GPU implementation of EGSnrc code which is written in CUDA Fortran as an algorithm. This article relies on a well validated and popular code among medical physicists, EGSnrc/DOSXYZnrc. In order to transport particles between two consecutive interactions, we developed an algorithm to handle several thousands of histories per warp. DOSXYZgpu implementation is evaluated with the original sequential EGSnrc/DOSXYZnrc. Maximum speedup of 205 times is achieved while the statistical uncertainty of the simulation is preserved. The $t$ -test statistical analysis indicates that for more than 95% of the voxels there is no significant difference between the results obtained from the GPU and the CPU.

Immobilization systems and their corresponding set-up errors influence the clinical target volume to the planning target volume (CTV-PTV) margins, which is critical for hypofractionated prostate stereotactic body radiotherapy (SBRT). This preliminary study evaluates intrafraction prostate displacement for two immobilization systems (A and B). Six consecutive patients having localized prostate cancer and implanted prostate marker seeds were studied. Planar X-ray images were acquired pre- and post-treatment to find the intrafraction prostate displacement. The average absolute displacements (lateral, longitudinal, vertical) were 0.9 ± 0.4 mm, 1.7 ± 0.1 mm, 1.3 ± 0.3 mm (system A), and 0.5 ± 0.2 mm, 0.6 ± 0.1 mm, 0.8 ± 0.3 mm (system B), with average three-dimensional displacements of 2.6 ± 0.2 mm (system A) and 1.3 ± 0.2 mm (system B). The computed CTV-PTV margins (lateral, longitudinal, vertical) were 2.5 mm, 2.5 mm, 3.6 mm and 1.4 mm, 1.6 mm, 2.4 mm for systems A and B, respectively. This suggests that the immobilization system influences intrafraction prostate displacement and, therefore, the margins applied. However, the margins found for both systems are comparable to the margins used for hypofractionated prostate SBRT.

The traditional approach to craniospinal irradiation (CSI) involves a prone position and a moving gap junction between the cranial and the spinal field and in between two spinal fields. Patient comfort is improved by treatment in the supine position with the same multifield technique, although the challenge remains in the verification of the gap in between fields. We have thus worked on a robust planning optimization technique for irradiation of the craniospinal axis that provides treatment plans that are superior across the brain-spine and the spine-spine field junctions to those constructed using either conventional field matching techniques, intensity modulation, or unoptimized volumetric modulated arc therapy (VMAT). Patients are simulated supine and a VMAT plan generated consisting of coplanar VMAT arcs for the cranial and spinal fields. The robust technique applies position uncertainties of 7.5mm in the superior-inferior directions independently for all beams in the plan to account for uncertainties in patient position across the two field junctions. The treatment planning system robust optimization computes scenario doses and minimizes the worst objective value over all scenarios. The robust variables used were the minimum PTV doses set equal to the Rx dose. The resulting isodose distribution, including target coverage and normal tissue sparing is computed. In particular, the variation of dose across the field junctions for each of the treatment fields is emphasized and compared to that obtained from 3DCRT. Robust planning resulted in markedly improved PTV coverage with a minimum dose of 98% compared to 3DCRT which frequently has areas that may receive zero dose within the junctions. Normal tissue doses are reduced e.g. lens 30%; and kidney 10%. Notably, the robust technique results in field dose gradients that are slowly varying across the junctions. The gradients are complementary such that moving from the superior to the inferior direction across a junction, the decreasing dose gradient of the superior fields is matched by the increasing dose gradient of the inferior fields such that the sum is nearly constant over a distance of nearly 7.5mm. The clinical importance of this property of the robust plan is that interfractional setup differences of up to 7.5mm will not significantly compromise the plan, while intrafractional movements between treatment beams result in significantly less dose inhomogeneities than with 3DCRT. CSI in the supine position improves patient comfort and the complexity of the treatment set up, both of particular importance when treating pediatric populations requiring anesthesia. Robust planning allows for improved CSI since the planning target volume uniformly receives the prescription dose, normal tissues are spared, and the doses at the field junctions are maintained at a constant level over relatively large (7.5mm) length of the spinal cord, thus preventing inadvertent overdose in case of intrafraction patient shifts.

Prophylactic cranial irradiation (PCI) is used to decrease the probability of developing brain metastases in patients with small cell lung cancer and has been linked to deleterious cognitive effects. Although no well-established imaging markers for these effects exist, previous studies have shown that structural and metabolic changes in the brain can be detected with MRI and PET. This study used an image processing technique called texture analysis to explore whether global changes in brain glucose metabolism could be characterized in PET images. Methods: 18F-FDG PET images of the brain from patients with small cell lung cancer, obtained before and after the administration of PCI, were processed using texture analysis. Texture features were compared between the pre- and post-PCI images. Results: Multiple texture features demonstrated statistically significant differences before and after PCI when texture analysis was applied to the brain parenchyma as a whole. Regional differences were also seen but were not statistically significant. Conclusion: Global changes in brain glucose metabolism occur after PCI and are detectable using advanced image processing techniques. These changes may reflect radiation-induced damage and thus may provide a novel method for studying radiation-induced cognitive impairment.

We studied the dosimetry of single-isocenter treatment plans generated to treat a solitary intracranial lesion using linac-based stereotactic radiosurgery (SRS). A common metric for evaluating SRS plan quality is the volume of normal brain tissue irradiated by a dose of at least 12 Gy (V12), which is important because multiple studies have shown a strong correlation between V12 and incidence of radiation necrosis. Unrealistic expectations for values of V12 can lead to wasted planning time. We present a model that estimates V12 without having to construct a full treatment plan. This model was derived by retrospectively analyzing 50 SRS treatment plans, each clinically approved for delivery using circular collimator cone arc therapy (CAT). Each case was re-planned for delivery via dynamic conformal arc therapy (DCAT), and then scaling arguments were used to extend dosimetric data to account for different prescription dose (PD) values (15, 18, 21, or 24 Gy). We determined a phenomenological expression for the total volume receiving at least 12 Gy (TV12) as a function of both planning target volume (PTV) and PD: are fit parameters, and a separate set of values is determined for each plan type. In addition, we generated a sequence of plots to clarify how the relationship between conformity index (CI) and TV12 depends on plan type (CAT vs DCAT), PTV, and PD. These results can be used to suggest realistic plan parameters and planning goals before the start of treatment planning. In the absence of access to more sophisticated pre-planning tools, this model can be locally generated and implemented at relatively low cost with respect to time, money, and expertise.

Most commercially available single channel HDR vaginal cylinder applicators for the VariSource afterloader do not provide adequate dose coverage near the apex (close to the patient cervix) of the device due to the self-shielding effect and the location of the most distal dwell position of the HDR source. To improve the dose coverage, this study utilizes 3D printed vaginal cylinder applicators having distal dwell positions much closer to the apexes. The 24mm and 30mm diameter vaginal cylinders were created in FreeCAD and printed with 3D system CubePro 3D printer (0.2mm resolution). The design of the cylinders facilitates use of a standard HDR catheter (1.9 mm diameter) which includes a half moon nylon button at the distal end. This allows the most distal dwell position in a 3D printed cylinder to be only 3mm from the apex (regardless the cylinder diameter), as compared to the 7mm and 9mm distances from the apex for 23mm and 30mm commercial cylinders with, respectively. In-house template plans from our planning software (with uniform dose to a depth of 5mm from surface of each cylinder) were delivered using commercial vaginal cylinders, then the same plans were delivered using 3D printed counterparts. Gafchromic films that were cut to fit the mid-line shape of the cylinders were exposed during each delivery. The film dosimetry clearly reveals inadequate dose coverage at the apex of commercial vaginal cylinders where the dose at the 5mm prescription depth is 40% and 30% less than the prescription dose for the 23mm and 30mm cylinders, respectively. The 3D printed cylinders demonstrate an overdose at the apex of 3D printed cylinders, which was expected due to the proximity of the most distal dwell position. To avoid overdosing using 3D printed cylinders, new optimized plans were created and delivered for 24mm and 30mm diameter cylinders. Film dosimetry of the new plans show uniform dose coverage around the entire 3D printed cylinders. The 3D printed vaginal cylinders with distal dwell positions closer to the apex, combined with optimized treatment plans, alleviate under dosing at the apex and provide a much more uniform dose distribution compared to commercial cylinders.

Chemotherapy followed by prophylactic cranial irradiation (PCI) is associated with increased survival in patients with small cell lung cancer but is associated with fatigue and cognitive impairment. This retrospective study evaluated regional differences in 18F-FDG uptake by the brain before and after PCI. The null hypothesis was that direct toxic effects on the brain from PCI and chemotherapy are symmetric; thus, asymmetric deviations may reflect functional changes due to therapy. Methods: Electronic medical records from 2013 to 2016 were reviewed for patients with small cell lung cancer, MRI of brain negative for metastasis, and 18F-FDG PET/CT scans before and after PCI. As the standard of care, patients received first-line chemotherapy or chemoradiation to the thorax followed by PCI. The 18F-FDG PET/CT scans nearest the PCI were selected. Sixteen patients met these initial criteria. Commercially available PET software was used to register and subtract the PET scans before and after PCI to obtain difference maps. Occipital and cerebellar regions were excluded from the final statistical analysis given the known high variability and misregistration. The χ2 test was used to analyze the data. Results: Two patients had 18F-FDG uptake differences only in the occipital and cerebellar regions. The software registration failed on 1 patient’s scans. Therefore, 13 patients were included in the final analysis. Nine of 13 patients demonstrated significant unilateral changes in only 1 region of the brain, and 3 of 13 showed significant changes unilaterally in 2 regions. The χ2 test revealed a significant unilateral regional difference on a patient level (χ2 = 6.24, P = 0.025). The most commonly affected brain region was the frontal lobe. Conclusion: Significantly more patients had unilateral than bilateral regional differences (both increases and decreases) in 18F-FDG uptake in the brain before and after PCI. This finding suggests that differences in unilateral distribution are related to functional changes, since direct toxicity alone from PCI and chemotherapy would be symmetric. The frontal region was the most commonly affected, suggesting a potential contributing etiology for cognitive impairment and decreased executive function after therapy.

PURPOSE: The aim of the study was to identify potential failure modes (FMs) having a high risk and to improve our current quality management (QM) program in Collaborative Ocular Melanoma Study (COMS) ocular brachytherapy by undertaking a failure modes and effects analysis (FMEA) and a fault tree analysis (FTA). METHODS AND MATERIALS: Process mapping and FMEA were performed for COMS ocular brachytherapy. For all FMs identified in FMEA, risk priority numbers (RPNs) were determined by assigning and multiplying occurrence, severity, and lack of detectability values, each ranging from 1 to 10. FTA was performed for the major process that had the highest ranked FM. RESULTS: Twelve major processes, 121 sub-process steps, 188 potential FMs, and 209 possible causes were identified. For 188 FMs, RPN scores ranged from 1.0 to 236.1. The plaque assembly process had the highest ranked FM. The majority of FMs were attributable to human failure (85.6%), and medical physicist related failures were the most numerous (58.9% of all causes). After FMEA, additional QM methods were included for the top 10 FMs and 6 FMs with severity values > 9.0. As a result, for these 16 FMs and the 5 major processes involved, quality control steps were increased from 8 (50%) to 15 (93.8%), and major processes having quality assurance steps were increased from 2 to 4. CONCLUSIONS: To reduce high risk in current clinical practice, we proposed QM methods. They mainly include a check or verification of procedures/steps and the use of checklists for both ophthalmology and radiation oncology staff, and intraoperative ultrasound-guided plaque positioning for ophthalmology staff. (C) 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

PURPOSE:To identify policy and system related weaknesses in treatment planning and plan check work-flows.METHODS:The authors' web deployed plan check automation solution, PlanCheck, which works with all major planning and record and verify systems (demonstrated here for mosaiq only), allows them to compute violation rates for a large number of plan checks across many facilities without requiring the manual data entry involved with incident filings. Workflows and failure modes are heavily influenced by the type of record and verify system used. Rather than tackle multiple record and verify systems at once, the authors restricted the present survey to mosaiq facilities. Violations were investigated by sending inquiries to physicists running the program.RESULTS:Frequent violations included inadequate tracking in the record and verify system of total and prescription doses. Infrequent violations included incorrect setting of patient orientation in the record and verify system. Peaks in the distribution, over facilities, of violation frequencies pointed to suboptimal policies at some of these facilities. Correspondence with physicists often revealed incomplete knowledge of settings at their facility necessary to perform thorough plan checks.CONCLUSIONS:The survey leads to the identification of specific and important policy and system deficiencies that include: suboptimal timing of initial plan checks, lack of communication or agreement on conventions surrounding prescription definitions, and lack of automation in the transfer of some parameters.

Purpose:To evaluate the variations in dwell times and doses expected when using an episcleral brachytherapy device for treatment of neovascular agerelated macular degeneration (n‐AMD) based on accurate imaging modalitiesMethods:Data from 40 eyes from 40 subjects with known n‐ AMD acquired through the Distance of Choroid Study (DOCS) conducted at Moorfields Eye Hospital was used to determine the target depth; the distance from the outer scleral surface of the eye, through the choroid, to the apex of the choroidal neovascularization (CNV). Each subject underwent, in triplicate, enhanced‐depth Spectral Domain Optical Coherence Tomography (SD‐OCT), Swept Source Optical Coherence Tomography, (SS‐OCT) and Ocular Ultrasound (O‐US). These data are the most comprehensive and accurate measurements of the dimensions of the CNV and adjacent layers of the eye for this cohort of patients. During treatment of n‐AMD, patients receive a dose of 24Gy to the apex at the target depth. Using the percentage depth dose for a Sr‐90 episcleral brachytherapy device, dwell times and doses to the apex were computed to determine the expected variations.Results:The mean target depth and the 95% confidence interval (CI) determined by combining O‐US with SD‐OCT were 1326 (956,1696)µm and with SS‐OCT were 1332 (970,1693)µm. The calculated corresponding mean dwell times and 95% (CI) were 334 (223,445)s and 335 (226,445)s for SD‐OCT and SS‐OCT determined depths, respectively. The corresponding mean apex dose and 95% (CI) were 24 (35.9,18.0)Gy (SD‐OCT) and 24 (35.6,18.1)Gy (SS‐OCT).Conclusion:For episcleral brachytherapy treatment of n‐AMD, using a patient population average target depth for treatment planning is inadequate, resulting in dose variations of a factor of approximately two over the 95% CI and larger variations for a nontrivial segment of the population. Each patient should have individualized imaging studies to determine the target depth for use in the dwell time calculation.Study was sponsored by Salutaris Medical Devices, Ltd., a subsidiary of Salutaris Medical Devices, Inc. Hamilton and Marsteller are founders of Salutaris Medical Devices, Inc. Drew, McGovern and Vitali are minor equity holders in Salutaris Medical Devices, Inc.

Episcleral plaque brachytherapy is a proven modality for treatment of medium-sized ocular melanoma tumors. Radiation dose calculation for this technique was previously performed using the Task Group 43 point-source system. However, the newer Task Group 129 is now recommending using the line-source system. The purpose of this study is to evaluate the dose differences between the two calculation methods on preservation of vision. Two programs were created using Matlab for line source and point source approximation methods. The comparison was solely based on the doses differences between the two methods ignoring all other factors such as heterogeneous correction, backscatter and shielding effects from the bowl backing, the Silastics insert and the collimator clips. The doses were calculated for 106 patients treated with I-125 Amersham model 6711 and Best Medical model 2301 seeds. Differences between both methods were compared and correlated with preservation of visual acuity. The average percent doses differences were calculated for 57 patients treated with Amersham model 6711 showing 0.39% (±0.77%) at apex, 0.31% (±0.76%) at 5mm point, 1.05% (±0.63%) at sclera, 0.21% (±0.53) at eye center, 0.104%(±0.32%) at contralateral retina, -0.87% (±1.17) at macula , -0.03%(±0.38%) at lens and -1.08%(±0.8%) at optic disk. For the 49 patients treated with Best Medical model 2301, the average percent doses differences were 0.49% (±0.73%) at apex, 0.44% (±0.74%) at 5mm point, 1.31% (±0.63%) at sclera, 0.33% (±0.49) at eye center, 0.33%(±0.30%) at contralateral retina, -2.8% (±1.97) at macula, 2.03%(±0.34%) at lens, and 2.04%(±1.03%) at optic disk. Although, the maximum dose difference was found to be 7% at the macula, there were no significant differences between the doses calculated by point or source methods. Patients with retained visual acuity tended to received lower doses to the macula (p=0.001), and optic disk (p<0.001), regardless of dose calculation method. The doses calculated by point and line source methods showed similar results for both tumor and normal structures. Furthermore, doses differences calculated by the two methods were not associated with any clinically significant benefit or detriment in visual preservation. Future research on doses calculation should take in account the heterogeneous correction, backscatter and shielding effects from the bowl backing, the Silastics inserts and the collimator lips.