Safety practices and opportunities for improvement in brachytherapy: A patient safety practices survey of the American Brachytherapy Society membership.

PURPOSE: Safe delivery of brachytherapy and establishing a safety culture are critical in high-quality brachytherapy. The American Brachytherapy Society (ABS) Quality and Safety Committee surveyed members regarding brachytherapy services offered, safety practices during treatment, quality assurance procedures, and needs to develop safety and training materials. METHODS AND MATERIALS: A 22-item survey was sent to ABS membership in early 2019 to physicians, physicists, therapists, nurses, and administrators. Participation was voluntary. Responses were summarized with descriptive statistics and relative frequency distributions. RESULTS: There were 103 unique responses. Approximately one in three was attending physicians and one in three attending physicists. Most were in practice >10 years. A total of 94% and 50% performed gynecologic and prostate brachytherapy, respectively. Ninety-one percent performed two-identification patient verification before treatment. Eighty-six percent performed a time-out. Ninety-five percent had an incident reporting or learning system, but only 71% regularly reviewed incidents. Half reviewed safety practices within the last year. Twenty percent reported they were somewhat or not satisfied with department safety culture, but 92% of respondents were interested in improving safety culture. Most reported time, communication, and staffing as barriers to improving safety. Most respondents desired safety-oriented webinars, self-assessment modules, learning modules, or checklists endorsed by the ABS to improve safety practice. CONCLUSIONS: Most but not all practices use standards and quality assurance procedures in line with society recommendations. There is a need to heighten safety culture at many departments and to shift resources (e.g., time or staffing) to improve safety practice. There is a desire for society guidance to improve brachytherapy safety practices. This is the first survey to assess safety practice patterns among a national sample of radiation oncologists with expertise in brachytherapy.

Clinical transition to model-based dose calculation algorithm: A retrospective analysis of high-dose-rate tandem and ring brachytherapy of the cervix.

PURPOSE: To retrospectively compare clinical dosimetry of CT-based tandem-ring treatment plans using a model-based dose calculation algorithm (MBDCA) with the standard TG-43-based dose formalism. METHODS AND MATERIALS: A cohort of 10 cervical cancer cohorts treated using the tandem and ring high-dose-rate applicators were evaluated. The original treatment plans were created using the department CT-based volume optimization clinical standards. All plans originally calculated with TG-43 dose calculation formalism were recalculated using the MBDCA algorithm. The gross target volume and organs at risk (OARs) were contoured on each data set along with significant heterogeneities like air in cavity and high-density plastic tandem and ring components. The patient tissue was modeled as homogenous liquid water. D90, D95, and D100 for gross target volume, D0.1cm3, D1.0cm3, and D2.0cm3 for bladder, rectum, and sigmoid were extracted from dose-volume histograms for TG-43 and MBDCA calculated plans. Mean absolute difference ± 2σ in the above metrics was calculated for each plan. RESULTS: Using the manual applicator contouring method, MBDCA plans (n = 10) showed 2.1 ± 1.1% reduction in dose to Point A average, 2.6 ± 0.9% reduction in Target D90 dose, and 2.1 ± 0.3% dose reduction to OARs. Results from plans using vendor supplied solid applicator models (n = 5) showed 2.2 ± 1.10% reduction in dose to Point A average, 2.7 ± 0.2% reduction in Target D90 dose, and 2.7 ± 1.0% dose reduction on average to OARs. CONCLUSION: For unshielded plastic gynecologic applicators, minimal dosimetric changes (<5%) were found using MBDCA relative to standard TG-43. Use of solid applicator model is more efficient than manual applicator contouring and also yielded similar MBDCA dosimetric results. Currently, TG-186 dose calculations should be reported along TG-43 until we obtain studies with larger cohorts to fully realize the potential of MBDCA dosimetry.

A quality assurance method with submillimeter accuracy for stereotactic linear accelerators.

The Stereotactic Alignment for Linear Accelerator (S. A. Linac) system is developed to conveniently improve the alignment accuracy of a conventional linac equipped with stereotactic cones. From the Winston-Lutz test, the SAlinac system performs three-dimensional (3D) reconstruction of the quality assurance (QA) ball coordinates with respect to the radiation isocenter, and combines this information with digital images of the laser target to determine the absolute position of the room lasers. A handheld device provides near-real-time repositioning advice to enable the user to align the QA ball and room lasers to within 0.25 mm of the centroid of the radiation isocenter. The results of 37 Winston-Lutz tests over 68 days showed that the median 3D QA ball alignment error was 0.09 mm, and 97% of the time the 3D error was ≤ 0.25 mm. All 3D isocentric errors in the study were 0.3 mm or less. The median x and y laser alignment coordinate error was 0.09 mm, and 94% of the time the x and y laser error was ≤ 0.25 mm. A phantom test showed that the system can make submillimeter end-to-end accuracy achievable, making a conventional linac a "Submillimeter Knife".

Anatomy-based inverse planning simulated annealing optimization in high-dose-rate prostate brachytherapy: significant dosimetric advantage over other optimization techniques.

PURPOSE: To perform an independent validation of an anatomy-based inverse planning simulated annealing (IPSA) algorithm in obtaining superior target coverage and reducing the dose to the organs at risk. METHOD AND MATERIALS: In a recent prostate high-dose-rate brachytherapy protocol study by the Radiation Therapy Oncology Group (0321), our institution treated 20 patients between June 1, 2005 and November 30, 2006. These patients had received a high-dose-rate boost dose of 19 Gy to the prostate, in addition to an external beam radiotherapy dose of 45 Gy with intensity-modulated radiotherapy. Three-dimensional dosimetry was obtained for the following optimization schemes in the Plato Brachytherapy Planning System, version 14.3.2, using the same dose constraints for all the patients treated during this period: anatomy-based IPSA optimization, geometric optimization, and dose point optimization. Dose-volume histograms were generated for the planning target volume and organs at risk for each optimization method, from which the volume receiving at least 75% of the dose (V(75%)) for the rectum and bladder, volume receiving at least 125% of the dose (V(125%)) for the urethra, and total volume receiving the reference dose (V(100%)) and volume receiving 150% of the dose (V(150%)) for the planning target volume were determined. The dose homogeneity index and conformal index for the planning target volume for each optimization technique were compared. RESULTS: Despite suboptimal needle position in some implants, the IPSA algorithm was able to comply with the tight Radiation Therapy Oncology Group dose constraints for 90% of the patients in this study. In contrast, the compliance was only 30% for dose point optimization and only 5% for geometric optimization. CONCLUSIONS: Anatomy-based IPSA optimization proved to be the superior technique and also the fastest for reducing the dose to the organs at risk without compromising the target coverage.

Initial comparison of inverse optimization, modified peripheral technique, and geometric optimization as real-time intraoperative computer planning options for permanent seed implantation of the prostate.

PURPOSE: Comparison of inverse optimization (IO) to modified peripheral (MP) and geometric optimization (GO) intraoperative computer planning options for permanent seed implantation (PSI) of the prostate. METHODS AND MATERIALS: One hundred ten patients underwent PSI with iodine-125. Three computer planning options were compared including MP loading, GO, and IO. Preimplant dose goals (prescribed dose [PD] of 144 Gy) and normal tissue constraints were determined at the outset by the participating physicians before intraoperative computer planning. A single computer planning system was used for this comparison. Postimplant dosimetry was performed at 4-5 weeks and compared for V(100) and D(90), urethral V(150), and rectal V(110) of the PD. Acute urinary morbidity was evaluated and compared. RESULTS: All three options achieved a similar preimplant median V(100) (97%). The median number of needles and seeds implanted was greater with GO (29, 75) compared to MP (16, 66) and IO (17, 66) (p<0.0001 and p=0.0024, respectively). Postimplant dosimetry showed that IO achieved a higher percentage with V(100) >95% of the PD in multivariate analysis (p=0.04) and a lower percentage postimplant D(90) <140 Gy (7%) than for MP/GO (26%) (p = 0.01). IO predicted for lower urethral dose (p=0.0169), despite a higher median D(90) (169 Gy) than either MP (159 Gy) or GO (151 Gy) (p = 0.0025). The median percentage V(150) urethra for IO was 8% vs. 16% for MP and 23% for GO (p = 0.0005). With a median followup time of 6 months, acute Grade 2 urinary symptoms were higher with GO (81%) vs. MP (36%) and IO (53%) (p = 0.0019). CONCLUSIONS: Dosimetric outcomes for IO compare favorably to either MP or GO when performed in real time for PSI. In contrast to GO, IO and MP demonstrated excellent correlation between the intraoperative and postoperative plans while using fewer total and interior placed needles and seeds. IO appears feasible as an alternative intraoperative planning solution for PSI.