Universal evaluation of MLC models in treatment planning systems based on a common set of dynamic tests.

PURPOSE: To demonstrate the feasibility of characterising MLCs and MLC models implemented in TPSs using a common set of dynamic beams. MATERIALS AND METHODS: A set of tests containing synchronous (SG) and asynchronous sweeping gaps (aSG) was distributed among twenty-five participating centres. Doses were measured with a Farmer-type ion chamber and computed in TPSs, which provided a dosimetric characterisation of the leaf tip, tongue-and-groove, and MLC transmission of each MLC, as well as an assessment of the MLC model in each TPS. Five MLC types and four TPSs were evaluated, covering the most frequent combinations used in radiotherapy departments. RESULTS: Measured differences within each MLC type were minimal, while large differences were found between MLC models implemented in clinical TPSs. This resulted in some concerning discrepancies, especially for the HD120 and Agility MLCs, for which differences between measured and calculated doses for some MLC-TPS combinations exceeded 10%. These large differences were particularly evident for small gap sizes (5 and 10 mm), as well as for larger gaps in the presence of tongue-and-groove effects. A much better agreement was found for the Millennium120 and Halcyon MLCs, differences being within ± 5% and ± 2.5%, respectively. CONCLUSIONS: The feasibility of using a common set of tests to assess MLC models in TPSs was demonstrated. Measurements within MLC types were very similar, but TPS dose calculations showed large variations. Standardisation of the MLC configuration in TPSs is necessary. The proposed procedure can be readily applied in radiotherapy departments and can be a valuable tool in IMRT and credentialing audits.

A new short daily brachytherapy schedule in postoperative endometrial carcinoma. Preliminary results.

PURPOSE: To evaluate the preliminary results of vaginal-cuff relapses (VCR) and complications of a short brachytherapy (BT) schedule in postoperative endometrial carcinoma. METHODS AND MATERIALS: From September 2011 to December 2014, 102 patients were treated with postoperative BT for endometrial carcinoma. Seventy-four patients received a single 7 Gy dose after external beam irradiation (Group 1), and 28 intermediate-risk patients received three daily fractions of 6 Gy (Group 2). The dose was prescribed at 5 mm from the applicator surface. Toxicity was prospectively evaluated after the objective late effects of normal tissues-subjective, objective, management, analytic scores for vagina and RTOG scores for rectum and bladder. STATISTICS: χ2 and Student's t tests. RESULTS: The mean followup was 28.85 months (9.6-58.5) in Group 1 and 31.19 months (7.7-62.3) in Group 2. No VCR was found during followup. Late toxicity: vagina toxicity was developed in 24.32% of the patients in Group 1 (G1-G2) and in 21.4% in Group 2 (G1-G2 but 1 G3). Rectal toxicity appeared in only 2.7% of patients in Group 1 (G1). Neither Group 1 nor Group 2 presented late bladder toxicity. No differences were found in late toxicity between Groups 1 and 2. CONCLUSIONS: The present short BT schedule was safe in relation to VCR and late toxicity for the followup period studied. These results are similar to those of two larger previous schedules performed in our center in relation to the same point of followup.