15543 Background: To assess the use of HDR surface applicators as an alternative radiotherapy modality to external radiation (electrons or low-energy x-rays) for the treatment of skin lesions of the head and neck. Skin carcinomas require efficient and accurate delivery of HDR Brachytherapy, which can be precisely reproduced on an outpatient basis. Methods: Patients were treated to various sites, which included lesions of the face and scalp. Thermoplastic casts were fitted with Leipzig Surface Applicators and custom molded to the patient to treat squamous or basal cell carcinomas ≤ 2 cm in diameter. A custom surface mold applicator (Freiburg Flap) was used for lesions up to 4 cm. Planning target volume included the tumor plus a 5 mm margin. Biweekly photographs of the treatment volume were taken for documentation and monitoring of radiation reactions. Treatment was delivered by HDR Brachytherapy (Ir-192), 5 Gy per fraction, twice per week for four weeks to a 5 mm depth. TLD’s were placed at the center of the treated volume under the applicator and at critical structures (i.e. lateral canthus of the ipsilateral eye, auditory canal or gingivolabial sulcus) twice during the course of treatment. Results: Patients’ setup and reproducibility were accurate and treatment time was short which added great convenience for the patients. With the HDR surface applicators, dose distribution was uniform in the surface of the skin and at 5 mm depth in the whole area of the applicator. Differences between the areas of maximum and minimum dose at this depth did not reach values higher than 5% of the prescribed dose. At the edges of the applicators, the dose gradient was sharp, with the detected dose at 5 mm from the applicator being negligible. An exudative radiation reaction was noted in some patients, which reversed with appropriate therapy. Conclusion: High Dose Rate Brachytherapy offers a highly effective treatment of skin carcinomas. Surface applicators, used in conjunction with HDR brachytherapy equipment, make a uniform dose distribution and sharp dose gradient at the edge of the treatment field. Surface applicators are easy and safe to use, and they fit very accurately for each fraction. These applicators have the ability to become the standard treatment for skin carcinomas in the near future. No significant financial relationships to disclose.
Purpose: To evaluate the dosimetric differences in treatment planning between Cesium‐131 and Palladium‐103 in prostate brachytherapy. Introduction: Due to the short half‐life of Cesium‐131 and the energy emitted, when compared to Palladium‐103, planning guidelines must be established. This study focuses on seed count, dose to critical structures and homogenous dose distribution. Materials and Methods: Thirty patients were planned using Varian's Variseed 7.1, both with Palladium‐103 and Cesium‐131 for monotherapy, to a prescribed dose of 125Gy and 115 Gy respectively. The average gland size was 28.48 cc. All volumes were contoured and sources were placed using Palladium‐103 at an activity of 2.0u. Another treatment plan was developed using Cesium‐131 at an activity of 2.0u. All prostatic contours were identical between the two treatment plans for each patient. The following quantities were derived from each plan: total seed count, total needle count, D90, V150, V100, V90, V80, R100, and U10. Results: In the series, there was a decrease of 17.46% planned seeds (70 vs. 59) and 6% planned needles (18 vs. 17) when planning for Cesium‐131 as compared to Palladium‐103. There was a decrease in the V150 of 35.53% (39.31% for Cs131 vs. 60.97% for Pd103), while maintaining an average D90 of 115.46% for Cs131 and 115.29% for Pd103. There was a decrease in the R100 of 44.23% (0.15cc for Cs131 vs. 0.28cc for Pd103). A small decrease in U10 of 1.98% was also noted. Conclusion: Cesium‐131 as an alternative to Palladium‐103 for prostate brachytherapy is favorable in this study as it reduces the overall seeds and needles needed for implants while offering an improved homogeneous dose distribution; reducing the overall dose to the rectum and prostatic urethra. Further studies on these patients are in progress to assess the actual post‐implant dosimetry and morbidity associated with Cesium‐131.
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