An introduction to low dose radiation therapy for shoulder osteoarthritis.

Osteoarthritis (OA) is a painful, degenerative disease that affects the tissues of the joint spaces, such as the shoulder. Conventional medical treatment options, such as corticosteroid injections and anti-inflammatory medications, are not always sufficient to alleviate the symptoms from this disease. Low dose radiotherapy is a newer treatment option for patients with shoulder osteoarthritis and has shown positive outcomes. However, the problem is that there is a paucity of literature about treatment planning considerations for this new treatment option. The purpose of this case study was to provide an example of treatment planning techniques and considerations for shoulder osteoarthritis. Treatment techniques for shoulder LDRT, such as treatment field borders, prescribed dose, beam arrangements, appropriate beam energy, and special considerations are discussed.

Robust VMAT treatment planning for extremity soft tissue sarcomas.

Volumetric modulated arc therapy (VMAT) is a frequently employed and guideline-recommended radiotherapy (RT) modality for extremity soft tissue sarcomas (eSTS). Prior studies have demonstrated that significant tumor volume changes during treatment result in loss of target volume coverage with highly conformal techniques such as VMAT, but few solutions exist to these issues aside from adaptive replanning. Here, we describe a related but novel phenomenon in which relatively minor changes in surface volume contour (whether due to daily setup uncertainty, edema of peritumoral tissue, or progression or pseudo-progression of tumor volume itself) can result in unexpected subcutaneous hotspots. This phenomenon is of significant clinical concern given the known association between skin dose and major wound complications during preoperative RT for eSTS. By evaluating daily cone-beam CT (CBCT) images from thirteen eSTS patients treated with VMAT RT, we identify daily surface contour changes (range: 2 mm-15 mm, median: 8 mm) which are frequently below conventional adaptive replanning thresholds. When applied under experimental conditions, these external contour changes did not have major impacts on target volume coverage (range: 30.2%-91.2%, mean: 72.5%) but did result in unexpected hotspots of 125.8% on average (range: 110.0%-142.2%) in the subcutaneous tissues. To mitigate this issue, we develop a methodology for VMAT treatment planning using flash PTV and virtual bolus (VB) to produce robust treatment plans that are more resistant to target volume changes, surface contour changes, and setup uncertainties than conventional planning methods. With this methodology, robust plans were equivalent to standard plans at baseline, but, after incorporation of surface volume changes, both maintained target volume coverage (p < 0.001) and prevented development of subcutaneous hotspots (p < 0.001) better than standard plans. As such, this treatment planning methodology may facilitate development of robust VMAT treatment plans that minimize development of subcutaneous hotspots and preserve target volume coverage in the context of routine volumetric changes during preoperative RT.

Improved planning efficiency in multiple brain lesion SRS VMAT cases using Eclipse scripting.

Though dosimetry has a multitude of treatment modalities, software, and workflows to aid in the treatment planning process, treatment planners are still responsible for several tedious and monotonous tasks that could decrease their planning efficiency. The purpose of this study was to determine if scripting could improve treatment planning efficiency for multiple brain lesion stereotactic radiosurgery (SRS) volumetric arc therapy cases by reducing planning time commitment. A script was developed for multiple brain lesion SRS cases using Eclipse scripting application programming interface with the intention of improving treatment planning efficiency by creating optimization structures and importing prescription and suggested OS dose metrics to the optimizer. Nine treatment planners were each provided with 3 different multiple brain lesion, single-isocenter SRS cases. Each planner created 2 plans for each case. One of these 2 plans used the SRS script, and the other did not. There were 54 treatment plans developed, totaling 27 plan comparisons. Each of the 54 treatment plans were considered clinically acceptable based on the participating institution's plan quality guidelines. Statistical analyses of planning time commitment with and without the SRS script were performed using RStudio. The mean and median planning times with and without the SRS script were compared using a paired T-test and Wilcoxon Signed Rank test, respectively, and effect size was evaluated using Cohen's classification. Using the SRS script resulted in statistically significant reduction in total contouring time (11.3 vs 2.8 minutes, p < 0.001), optimizer preparation time (7.7 vs 2.1 minutes, p < 0.001), and overall planning time (105.1 vs 77.9 minutes, p < 0.001). This study concluded that scripts developed using Eclipse scripting application programming interface offer an opportunity to improve treatment planning efficiency by reducing the planning time commitment for treatment planners.

Validation of clinical acceptability of deep-learning-based automated segmentation of organs-at-risk for head-and-neck radiotherapy treatment planning.

Introduction: Organ-at-risk segmentation for head and neck cancer radiation therapy is a complex and time-consuming process (requiring up to 42 individual structure, and may delay start of treatment or even limit access to function-preserving care. Feasibility of using a deep learning (DL) based autosegmentation model to reduce contouring time without compromising contour accuracy is assessed through a blinded randomized trial of radiation oncologists (ROs) using retrospective, de-identified patient data. Methods: Two head and neck expert ROs used dedicated time to create gold standard (GS) contours on computed tomography (CT) images. 445 CTs were used to train a custom 3D U-Net DL model covering 42 organs-at-risk, with an additional 20 CTs were held out for the randomized trial. For each held-out patient dataset, one of the eight participant ROs was randomly allocated to review and revise the contours produced by the DL model, while another reviewed contours produced by a medical dosimetry assistant (MDA), both blinded to their origin. Time required for MDAs and ROs to contour was recorded, and the unrevised DL contours, as well as the RO-revised contours by the MDAs and DL model were compared to the GS for that patient. Results: Mean time for initial MDA contouring was 2.3 hours (range 1.6-3.8 hours) and RO-revision took 1.1 hours (range, 0.4-4.4 hours), compared to 0.7 hours (range 0.1-2.0 hours) for the RO-revisions to DL contours. Total time reduced by 76% (95%-Confidence Interval: 65%-88%) and RO-revision time reduced by 35% (95%-CI,-39%-91%). All geometric and dosimetric metrics computed, agreement with GS was equivalent or significantly greater (p<0.05) for RO-revised DL contours compared to the RO-revised MDA contours, including volumetric Dice similarity coefficient (VDSC), surface DSC, added path length, and the 95%-Hausdorff distance. 32 OARs (76%) had mean VDSC greater than 0.8 for the RO-revised DL contours, compared to 20 (48%) for RO-revised MDA contours, and 34 (81%) for the unrevised DL OARs. Conclusion: DL autosegmentation demonstrated significant time-savings for organ-at-risk contouring while improving agreement with the institutional GS, indicating comparable accuracy of DL model. Integration into the clinical practice with a prospective evaluation is currently underway.

A case study of radiotherapy treatment for Dupuytren's contracture and Ledderhose disease.

Dupuytren's contracture (DC) and Ledderhose disease (LD) are benign conditions of the fascia in the hands and feet respectively, which result in contracture of the digits. Radiation therapy has been proven effective in treating early-stage DC and LD; however, the problem is that there is a paucity of literature regarding radiation therapy treatment set-up for Dupuytren's and Ledderhose patients. The purpose of this case study was to demonstrate treatment set-up considerations of 6 and 9 MeV for DC and LD cases in radiotherapy (RT). Two patients were selected from the same cancer center, each diagnosed with DC and LD. Treatment plans were established utilizing a clinical set-up, electron dose tables, bolus, and target volumes delineated by the radiation oncologist. For each patient, the radiation oncologist prescribed 2 treatment courses of 300 cGy in 5 fractions per treatment site. The radiation oncologist determined the desired depth of treatment, through the palpation of the nodules, and used electron depth dose tables to determine the energy, isodose lines, and bolus thickness necessary to treat the lesions to the appropriate depth. Doses delivered were verified with metal oxide semiconductor field effect transistors (MOS-FET) in vivo on the first day of treatment for each course. In this case study, researchers demonstrated clinical set-up for 2 patients treated for both DC and LD. The clinical set-up considerations resulted in successful treatment delivery with minor, but acceptable, variations during treatment.

The effect of common dental fixtures on treatment planning and delivery for head and neck intensity modulated proton therapy.

PURPOSE: Proton treatment plan perturbation by common dental fixtures such as amalgams (Am) and porcelain-fused-to-metal (PFM) crowns has, to date, been uncharacterized. Previous studies have been conducted to determine the physical effect of these materials within the beam path for single spots, but their effects on complex treatment plans and clinical anatomy have not yet been quantified. The present manuscript aims to study the effect of Am and PFM fixtures on proton treatment planning in a clinical setting. METHODS: An anthropomorphic phantom with removable tongue, maxilla, and mandible modules was simulated on a clinical computed tomography (CT) scanner. Spare maxilla modules were modified to include either a 1.5 mm depth central groove occlusal amalgam (Am) or a porcelain-fused-to-metal (PFM) crown, implanted on the first right molar. Modified tongue modules were 3D printed to accommodate several axial or sagittal oriented pieces of EBT-3 film. Clinically representative spot-scanning proton plans were generated in Eclipse v.15.6 using the proton convolution superposition (PCS) algorithm v.15.6.06 using a multi-field optimization (MFO) technique with the goal of delivering a uniform 54 Gy dose to a clinical target volume (CTV) typical of a base-of-tongue (BoT) treatment. A typical geometric beam arrangement of two anterior oblique (AO) beams and a posterior beam was employed. Plans optimized without any material overrides were delivered to the phantom A) without implants; B) with Am fixture; or C) with PFM crown. Plans were also reoptimized and delivered with inclusion of material overrides to equate relative stopping power of the fixture with that of a previously measured result. RESULTS: Plans exhibit slightly greater dose weight towards AO beams. The optimizer accounted for inclusion of fixture overrides by increasing beam weights to the beam closest to the implant. Film measurements exhibited cold spots directly within the beam path through the fixture in plans with and without overridden materials. Cold spots were somewhat mitigated in plans including overridden materials in the structure set but were not entirely eliminated. Cold spots associated with Am and PFM fixtures were quantified at 17% and 14% for plans without overrides, respectively, and 11% and 9% with using Monte Carlo simulation. Compared with film measurements and Monte Carlo simulation, the treatment planning system underestimates the dose shadowing effect in plans including material overrides. CONCLUSIONS: Dental fixtures create a dose shadowing effect directly in line with the beam path through the material. This cold spot is partially mitigated by overriding the material to measured relative stopping powers. Due to uncertainties in modeling perturbation through the fixture, the magnitude of the cold spot is underestimated using the institutional TPS when compared to measurement and MC simulation.

Perceptions of burnout in medical dosimetry within a postpandemic work environment.

According to the World Health Organization, burnout is described as having a negative attitude regarding one's work and being exhausted. Previous studies have shown that occupational burnout exists amongst medical dosimetrists, however, the incidence of medical dosimetrist burnout before and after a pandemic warrant continued research. Medical dosimetrists could be experiencing increased burnout in the workplace postpandemic due to staffing shortages and increased remote planning, which may reduce work performance. The researchers utilized a survey to answer research questions regarding whether staffing shortages or remote planning influenced perceived occupational burnout among medical dosimetrists in a post COVID-19 pandemic environment. The survey was intended to assess levels of emotional exhaustion (EE), depersonalization (DP) and personal accomplishment (PA). It was distributed electronically to 2591 certified medical dosimetrists in the United States through the American Association of Medical Dosimetrists (AAMD) membership database. A total of 160 responses were recorded, resulting in a response rate of 6% (160/2591). The results of this study indicated that increased staffing shortages have a direct relationship with increased burnout incidence. Increased remote work appears to be inversely related to the incidence of burnout among medical dosimetrists.

A survey of medical dosimetrists' perceptions of efficiency and consistency of auto-contouring software.

Although auto-contouring methods were created to reduce the workload for the radiation oncology team, concern lies in whether auto-contouring can improve efficiency regarding generated contours of a treatment plan. Researchers have measured differences between auto-contouring algorithms and manual contour methods specific to the contouring of organs at risk (OAR). The problem lies in the paucity of literature specific to perceptions of auto-contouring and the impact on workflow efficiency. The purpose of this study was to measure medical dosimetrists' perceptions of how auto-contouring software impacts the treatment planning process. To measure perceptions, researchers surveyed medical dosimetrists about their perspectives on consistency and efficiency of auto-contouring during treatment planning. A (Qualtrics, Provo, UT) survey was created based on the 2 research questions in this study. The survey was distributed through email to 2598 full members of the American Association of Medical Dosimetrists (AAMD) who were certified by the MDCB; mostly medical dosimetrists but also included a small group of medical physicists. The email open rate was 39% (1024/2598) but the response rate for those who read the email was only 8.4% (86/1024). Of the survey respondents, 67% (59/86) used auto-contouring software; thus, eligible to complete the remainder of the survey. Majority of participants agreed that auto-contouring software decreases time spent contouring per patient; however, most agreed that manual contouring is more efficient. Therefore, it was inferred that a combination of both auto and manual contouring have an impact on workload efficiency.

Intensity Modulated Proton Therapy for Bilateral Breast or Chest Wall and Comprehensive Nodal Irradiation for Synchronous Bilateral Breast Cancer: Initial Clinical Experience and Dosimetric Comparison.

Purpose: Synchronous bilateral breast cancer (SBBC) poses distinct challenges for radiation therapy planning. We report our proton therapy experience in treating patients with SBBC. We also provide a dosimetric comparison of intensity modulated proton therapy (IMPT) versus photon therapy. Methods and Materials: Patients with SBBC who received IMPT at our institution were retrospectively analyzed. The clinical target volume (CTV) included the breast or chest wall and comprehensive regional lymph nodes, including axilla, supraclavicular fossa, and the internal mammary chain. Intensity modulated proton therapy and volumetric modulated arc therapy (VMAT) plans were generated with the goal that 90% of the CTV would recieve at least 90% of the prescription dose (D90>=90%). Comparisons between modalities were made using the Wilcoxon signed rank test. Physician-reported acute toxic effects and photography were collected at baseline, end of treatment, and each follow-up visit. Results: Between 2015 and 2018, 11 patients with SBBC were treated with IMPT. The prescription was 50 Gy in 25 fractions. The median CTV D90 was 99.9% for IMPT and 97.6% for VMAT (P = .001). The mean heart dose was 0.7 Gy versus 7.2 Gy (P = .001), the total lung mean dose was 7.8 Gy versus 17.3 Gy (P = .001), and the total lung volume recieving 20 Gy was 13.0% versus 27.4% (P = .001). The most common acute toxic effects were dermatitis (mostly grade 1-2 with 1 case of grade 3) and grade 1 to 2 fatigue. The most common toxic effects at the last-follow up (median, 32 months) were grade 1 skin hyperpigmentation, superficial fibrosis, and extremity lymphedema. No nondermatologic or nonfatigue adverse events of grade >1 were recorded. Conclusions: Bilateral breast and/or chest wall and comprehensive nodal IMPT is technically feasible and associated with low rates of severe acute toxic effects. Treatment with IMPT offered improved target coverage and normal-tissue sparing compared with photon therapy. Long-term follow-up is ongoing to assess efficacy and toxic effects.

Analyzing changes in radiotherapy treatment planning error reporting during the COVID-19 pandemic.

The 2019 coronavirus (COVID-19) pandemic has affected medical physics and radiation oncology departments and the delivery of radiation therapy. Among the changes implemented in response to the onset of the pandemic was a shift to remote treatment planning by health care institutions. The purpose of this study was to determine whether the overall frequency of errors changed after the implementation of remote radiation therapy treatment planning during the COVID-19 pandemic. Reported incidents were obtained from an incident reporting database operated by a multisite cancer care facility in the Northeast. Researchers compared the frequency of reported events in a period prior to the start of the pandemic (March 2019 to February 2020) with a period after the onset of the pandemic (March 2020 to February 2021). No significant increase in reported incidents was detected suggesting the efficiency and safety of remote radiotherapy treatment planning.

A dosimetric comparison of 3D DCAT vs VMAT for palliative and early-stage liver lesions using eclipse TPS.

Volumetric modulated arc therapy (VMAT) and 3D dynamic conformal arc therapy (DCAT) are 2 methods proven useful for the clinical implementation of stereotactic body radiation therapy (SBRT) for lung lesions however, similar comparisons of SBRT liver lesions are lacking. The purpose of this study was to determine if the conformity of dose, irradiated volume, and dose to organs at risk (OAR) are equivalent or improved with the use of DCAT as an alternative treatment method when compared to standard VMAT for SBRT delivery of palliative and early-stage liver lesions. Twenty patients with liver lesions sized 2.0 to 5.0 cm were selected for this study. Plans were created with both DCAT and VMAT techniques for each patient. Metrics evaluated included the mean heart, kidney, large bowel, small bowel, esophagus, and stomach doses, the lung volume receiving 20 Gy (V20), the volume of the normal liver receiving 15 Gy (V15), conformity index (CI), heterogeneity index (HI), and the irradiated volume or volume receiving 25 Gy (V25). The p-values for the mean dose to kidneys, small bowel, esophagus, and the lung V20 were greater than 0.05, and no statistical difference could be determined between DCAT and VMAT. The p-values for the mean heart, large bowel, stomach, and liver V15 were less than 0.05, indicating statistical significance and superiority of VMAT for minimizing dose to these organs, especially V15 of the liver. The DCAT technique produced CI greater than 1.0 for all patients proving superior coverage, while standard VMAT produced significantly improved V25 with p-values less than 0.0001, and consequently higher HI.

Case study of a bolus helmet used to maintain optic chiasm and nerve sparing while improving target coverage using IMPT.

The purpose of this study was to examine if the use of a bolus helmet when treating the head with intensity modulated proton therapy (IMPT) will maintain organs at risk (OAR) sparing while improving the clinical target volume (CTV) coverage. A bolus helmet is a device that aims to improve on the traditionally used range shifter in proton therapy by improving dose distribution characteristics. Ten patients were retrospectively selected who had 2 separate treatment planning scans performed, a scan with the bolus helmet and a second scan without. Plans were created using both scans. Dose to organs at risk (OAR) including the left optic nerve, right optic nerve, optic chiasm, and normal brain minus CTV (brain-CTV), as well as CTV coverage were compared between the 2 plans. The use of the bolus helmet displayed lower mean OAR doses as well as higher CTV coverage, suggesting that use of the bolus helmet provides benefit when treating the head with IMPT.

A case study of DIBH to spare abdominal organs at risk for renal cell carcinoma MR-guided radiotherapy.

Historically, respiratory induced motion has made renal radiotherapy difficult due to the potential risk of additional toxicities to the patient due to tumor movement. The use of deep inspiration breath holds (DIBH) in congruence with magnetic resonance guided radiotherapy (MRgRT) may be an effective method to manage tumor and organ at risk (OAR) motion and deliver radiation safer and more effectively. The purpose of this case study was to evaluate the effectiveness of DIBH in sparing radiation dose to colon and small bowel during MRgRT of right sided renal cell carcinoma (RCC). The goals were to reduce radiation dose to colon and small bowel during RCC treatment with these motion management techniques. A retrospective case study of a patient with oligoprogression in the postoperative renal fossa was found to be a candidate for DIBH using MRgRT. Treatment planning called for motion management and real-time imaging in order to safely treat the tumor volume. Results were evaluated by the achievement of specific dosimetric criteria and tolerances and the regression of disease in the renal fossa. The use of real-time imaging and simultaneous motion management proved to be effective tools for the treatment of RCC. This radiation therapy treatment resulted in the elimination of malignancy at the primary site of disease.

Robust optimization used to mitigate setup uncertainties in vulvar patients receiving VMAT.

Many radiation planning techniques have been used to increase dose to the vulvar surface when treating patients with vulvar cancer with volumetric modulated arc therapy. Target volumes near the skin surface, such as vulvar tumors, do not meet the International Commission on Radiation Units and Measurements safety guidelines. Without the needed expansions and setup uncertainties, there are concerns that treated dose to the vulvar surface varies from the planned dose. The purpose of this study was to determine if the robust optimization tool used in volumetric modulated arc therapy planning can reproducibly deliver prescription dose to the vulvar skin surface despite setup uncertainties and reduced safety margins. To further mitigate the possibilities of setup errors and dose variation to the vulvar surface, robust optimization during planning must be considered. For this case study, 5 patients with similar diagnoses and vulvar surface dose requirements were retrospectively replanned using robust optimization. An evaluation structure was created representing the vulvar surface for each patient. This structure was assigned robustness characteristics. After multiple optimizations and planning scenarios, perturbed dose representing dataset shifts were evaluated along the vulvar surface. Every patient met minimal metrics of 100% of vulvar surface volume receiving 95% of the prescription dose. An additional review of 95% of vulvar surface volume receiving 100% of the prescription dose showed similar results. Robust optimization can be used in the planning process to mitigate setup uncertainties.

Intensity-Modulated Proton Therapy (IMPT) Treatment of Angiosarcoma of the Face and Scalp.

PURPOSE: To successfully plan and treat a patient with diffuse angiosarcoma involving the face and scalp with intensity-modulated proton therapy (IMPT) before surgical resection. MATERIALS AND METHODS: A patient presented to the radiation oncology department for preoperative treatment of an angiosarcoma diffusely involving the face and scalp. A 4-field IMPT technique was used to create a homogeneous dose distribution to the entire target volume while sparing underlying critical structures from toxicity and low-dose spread. A custom Monte Carlo optimizer was necessary to achieve treatment goals. Biological dose was evaluated with a linear energy transfer-based biological enhancement model. Robustness criteria were evaluated per department standard. The patient was successfully planned and treated according to clinical goals. RESULTS: The patient successfully completed the course of IMPT and was able to undergo surgical resection. Pathology indicated no presence of angiosarcoma. CONCLUSION: IMPT using a custom Monte Carlo optimizer is a suitable radiation therapy treatment option for patients with diffuse angiosarcoma of the scalp and face.

The effect of measurement geometry on patient specific QA pass/fail rates for stereotactic body radiation therapy (SBRT) Plans.

Patient quality assurance (QA) is a required part of the treatment care path, and plan failure can lead to increased personnel hours or delay of treatment. The recommendation by the American Association of Physicists in Medicine is that gamma analysis be used to evaluate measured volumetric modulated arc therapy plans. Vendors have developed many different measurement geometries for patient QA devices which could yield varying pass rates when used with the recommended tolerances, normalization, and criterion. For this study, clinically treated stereotactic body radiation therapy plans were used to evaluate differences in gamma dose tolerances and sampled dose distribution complexity for centralized or peripheral measurement geometries on a cylindrical phantom. Random errors were then introduced into a subset of these plans, and the differences in pass rates between the geometries were correlated with differences in the observed mathematical differences. Finally, a single clinically relevant target coverage deviation was introduced to another subset of plans to evaluate whether a particular geometry is measurably better at identifying clinically relevant errors. It was found that centralized geometries resulted in more lenient dose tolerances and less complex sampled dose distributions compared to peripheral geometries. Pass rates were uniformly lower in the peripheral measurement geometry, and the difference in pass rates between the geometries correlated strongly with the difference in dose tolerance and weakly with the difference in the chosen complexity metrics. However, neither of the geometries were sufficiently sensitive enough to detect clinically relevant changes to target coverage when using recommended tolerances and criteria, and no statistically significant difference was found between their pass rates. Given these findings, the authors concluded that stereotactic body radiation therapy plans could fail patient QA when measured in the peripheral geometry but pass in the centralized geometry, with possibly neither having correlation to true clinical deviation.

Incidence of work related musculoskeletal disorders in medical dosimetry.

Musculoskeletal disorders (MSDs) account for almost 70 million physician office visits per year in the United States and are the most common workplace injuries. These are conditions involving the nerves, tendons, muscles, and supporting structures of the body. Previous studies have concluded that computer users are at high risk of developing work-related musculoskeletal disorders (WRMSDs). As computer users, medical dosimetrists are at risk of developing WRMSDs, yet there is a lack of information regarding the incidence of WRMSDs among medical dosimetrists. The purpose of this study was to determine the incidence of WRMSDs and variables of workstation ergonomics that contribute to the increased risk of WRMSDs in medical dosimetrists. A Qualtrics survey was created to support the 3 research questions guiding this study. The survey was distributed to 2,646 full members of the American Association of Medical Dosimetrists (AAMD), which included only certified medical dosimetrists (CMDs), via email. The distribution of email surveys sent through the AAMD email distribution list resulted in 988 emails opened, for a contact rate of 37% (988/2646). One hundred sixty-four responses were recorded yielding a completion rate of 17% (164/988). Fifty-five percent (90/163) of participants responded that they have experienced WRMSDs. Forty-four percent (289/652) of responses indicated WRMSDs have a slight or moderate interference on work. Sixty-two percent (94/152) of participants felt that their workstations were not ergonomically designed; even greater 68% (104/153) did not feel their workstations were designed for their individually needs. Of those respondents 64% (98/152) would like to see further adaptations made to their workspaces.

Multiple case dosimetric evaluation of VMAT scalp irradiation using 3D milled bolus.

Adequate dose homogeneity and full prescription dose delivery to the scalp still remains a dosimetric problem during scalp irradiation due to the anatomical shape of the cranium. Confounding variables such as gravity, the irregular and convex shape of the cranium, air gaps between scalp surface and commercial bolus, and potential inconsistencies in a 3D printed bolus can negatively impact the dose delivered to the scalp surface during scalp irradiation. The purpose of this retrospective case study was to implement the use of a 3D milled rigid bolus technique combined with volumetric modulated arc therapy (VMAT) treatment planning and evaluate the dosimetric efficacy in delivering dose to the surface of the scalp. The 8-patient retrospective case study consisted of patients with a scalp lesion treated using a 3D milled bolus, VMAT, 6 megavoltage (MV) photon beams, and aligned for treatment using daily conebeam computed tomography (CT) and 6° of freedom couch positioning. Dose volume histograms (DVHs) were used to evaluate maximum dose delivered to the planning target volumes (PTVs) while the dose homogeneity index (DHI) was calculated and compared to that of an ideal value of 1. The researchers evaluated the minimum dose delivered to the individual PTVs after plan normalization. The researchers found that the 3D milled bolus coupled with volumetric modulated arc therapy increased surface dose homogeneity, while also increasing the percentage of planning target volumes receiving full prescription dose. With statistically significant results, patient specific 3D milled rigid bolus offers a viable bolus option for treatment of superficial scalp lesions when combined with volumetric modulated arc therapy treatment planning. However, a larger sample size used in a scientific research study across multiple institutions would be desirable to validate these case study findings.

Minimizing clearance issues with prone breast patients on Varian linear accelerators through isocenter placement.

The prone position is frequently used for breast irradiation in an effort to minimize dose to normal tissue and reduce skin toxicities. Immobilization required for prone breast irradiation can cause collision issues with the linear accelerator, disrupting treatment and negatively affecting the patient experience. The purpose of this retrospective study was to determine if an isocenter location guideline could be developed to prevent collisions with the prone breast immobilization device and gantry head, while still creating a clinically acceptable treatment plan. Clearance isocenter guidelines were established by measuring clearance between the Civco Horizon breast board and Varian linear accelerator. Fourteen patients with known clearance issues at a single institution were selected for this study and re-planned using clearance isocenter guidelines. Collision plans were compared to clearance plans created within the established clearance threshold through the institutions breast treatment guidelines based on arm II of the Radiation Therapy Oncology Group (RTOG) 1005 recommendations. Researchers in this study demonstrated clinical relevance by establishing that a clearance isocenter location guideline can be developed to prevent collisions with the prone breast immobilization and gantry head, while still creating a clinically acceptable treatment plan.

A case study of evaluating bilateral lung dose for VMAT treatment planning using a partial sagittal arc.

Radiation pneumonitis (RP) is a potential toxic side effect of thoracic radiotherapy. Optimal planning techniques must maintain tumor coverage while limiting dose to normal lung tissue to reduce the risk of patients developing RP. The addition of a noncoplanar arc may be beneficial by increasing treatment angles and providing an ideal dose distribution for tumor coverage while decreasing dose to organs at risk (OAR). The purpose of this research was to compare the effects on the normal bilateral lung tissue receiving 20 Gy, 10 Gy and 5 Gy (V20, V10, V5) and the mean lung dose (MLD) values when medial lung tumors are treated with 3 partial coplanar arcs vs 2 partial coplanar arcs combined with a partial sagittal arc. Researchers hypothesized that a beam arrangement of 2 partial coplanar arcs and 1 partial sagittal arc would reduce V20, V10, V5, and MLD values when compared to a 3 partial coplanar arc plan. In a retrospective study of 5 patients with bulky, medial right lung lesions without nodal involvement, cases were planned with both a noncoplanar and a coplanar arc geometry. Results were evaluated using a two-tailed t-test to determine the statistical significance (p < 0.05) of changes to total lung volume analyzation metrics when a noncoplanar sagittal arc was incorporated compared to the standard lung treatment using only coplanar arcs. Although some patient cases showed minor improvement in the V20, V10, V5, and MLD metrics, the study results were not statistically significant and showed no advantage with the introduction of an anterior sagittal arc over a coplanar beam arrangement.