Lucido, John J

Abstract Background Highly modulated radiotherapy delivery demands functional multileaf collimator (MLC) quality assurance (QA) with the ability to measure very low doses during short (<1 s) temporal segments of beam delivery. A radiochromic film with adequate sensitivity in the few‐cGy range is therefore needed. LD‐V1 film was designed for 2–20 cGy measurements in diagnostic kV energy ranges, but its performance for megavoltage (MV) beam qualities has not been well characterized. Purpose To demonstrate the feasibility of LD‐V1 film for low‐dose MV measurements and characterize its signal dependence under conditions relevant for clinical QA. Methods A 6 MV calibration curve was generated using eight dose levels between 0 and 40 cGy and compared with EBT4 film irradiated under identical conditions. Film characteristics evaluated included dose response, scanner and film signal uniformity, scan repeatability, energy dependence, post‐exposure signal evolution, scanning‐orientation dependence, and one‐dimensional (1‐D) profile visualization. Results LD‐V1 demonstrated higher net optical density (OD) and significantly less measurement uncertainty compared to EBT4 at dose levels less than 40 cGy. Significant energy dependence between kV and MV beam qualities was seen. Average net OD differences of 6.3% were seen between landscape and portrait scanning orientations. Post‐irradiation signal growth followed a logarithmic trend, stabilizing at ∼24 h. Scan‐to‐scan variation was <0.1%. Film‐signal uniformity was within 3.9%. 1‐D profiles showed discernible dose fall‐off for doses as low as 10 cGy. Conclusions LD‐V1 demonstrates suitability for low‐dose MV measurements and exhibits improved low‐dose sensitivity relative to EBT4, indicating its potential value for MLC QA in highly dynamic treatment deliveries. Nonetheless, its pronounced energy and scanning‐orientation dependence underscores the need for rigorous and consistent calibration and handling procedures.

AbstractBackgroundThis study was aimed at developing and validating a decision‐making tool predictive of overall survival (OS) for patients receiving stereotactic body radiation therapy (SBRT) for spinal metastases.MethodsThree hundred sixty‐one patients at one institution were used for the training set, and 182 at a second institution were used for external validation. Treatments most commonly involved one or three fractions of spine SBRT. Exclusion criteria included proton therapy and benign histologies.ResultsThe final model consisted of the following variables and scores: Spinal Instability Neoplastic Score (SINS) ≥ 6 (1), time from primary diagnosis < 21 months (1), Eastern Cooperative Oncology Group (ECOG) performance status = 1 (1) or ECOG performance status > 1 (2), and >1 organ system involved (1). Each variable was an independent predictor of OS (p < .001), and each 1‐point increase in the score was associated with a hazard ratio of 2.01 (95% confidence interval [CI], 1.79–2.25; p < .0001). The concordance value was 0.75 (95% CI, 0.71–0.78). The scores were discretized into three groups—favorable (score = 0–1), intermediate (score = 2), and poor survival (score = 3–5)—with 2‐year OS rates of 84% (95% CI, 79%–90%), 46% (95% CI, 36%–59%), and 21% (95% CI, 14%–32%), respectively (p < .0001 for each). In the external validation set (182 patients), the score was also predictive of OS (p < .0001). Increasing SINS<zaq;6> was predictive of decreased OS as a continuous variable (p < .0001).ConclusionsThis novel score is proposed as a decision‐making tool to help to optimize patient selection for spine SBRT. SINS may be an independent predictor of OS.

AbstractPurposeFor total skin electron (TSE) beam radiation therapy, the anterior eye and conjunctiva can be protected with eye shields to prevent keratitis, xerophthalmia, and cataractogenesis. Conventional metal eye shields can reduce patient balance by obscuring vision and thus increasing the risk for falls. We report on the design, fabrication, and clinical use of transparent acrylic eye shields for TSE.MethodsThe primary design goals were a seven‐fold reduction in the dose to the anterior eye and conjunctiva to meet published dose‐recommendations, preservation of vision for the wearer, and biocompatibility for external use. Resembling thick swim goggles, the design features 23 mm thick acrylic lenses that are mounted in a 3‐D printed support structure that conforms to the eye socket and can be worn with a strap. Dose measurements were performed in a simulated Stanford‐technique treatment with an anthropomorphic phantom using Gafchromic EBT filmResultsThe transparent eye shields were manufactured using a 3D‐printer and CNC‐machine. Based on measurements from the simulated treatments for each of the eye shields, the eye shields provided a 12‐fold reduction in dose to the lens. After use in more than 200 fractions, the shields were well tolerated by patients, and there were no reports of any incidents or adverse events.ConclusionTransparent TSE eye shields are able to reduce the dose to the eyes while maintaining vision during treatment at a reasonable cost.