Dosimetric Impact of Air Pockets in the Vaginal Cuff Brachytherapy Using Model-based Dose Calculation Algorithm.

Background: Endometrial cancer is the most common disease of the female reproductive system. Vaginal cuff brachytherapy (VCB) has intrinsic advantages compared to external beam therapy when treated with radiation. A single-channel cylinder is a standard applicator in VCB. The present study aims to estimate a change in the dose to vaginal mucosa due to air pockets between the cylinder and vaginal mucosa by calculating with the Acuros BV algorithm and comparing it to the Task Group 43 (TG-43) algorithm. Materials and Methods: Patients who presented with air packets were included retrospectively. For each patient, three plans were created: the first plan used TG-43, the second plan used dose recalculation with Acuros BV, and the third plan was generated by re-optimization by Acuros BV. On the same axial computed tomography image, the point doses at the cylinder's surface and the displaced mucosa were recorded and the ratios were then estimated. Results: The average volume of air pockets was 0.08 cc (range of 0.01-0.3 cc), and 84% of air pockets displaced the vaginal mucosa by ≥0.2 cm. The average ratios of dose were 0.77 ± 0.09 (1 standard deviation [SD]) and 0.78 ± 0.09 (1 SD) for TG-43 and Acuros BV algorithms, respectively. Due to the air pocket, mucosa received a reduced dose by an average of 22.72% and an average of 23.29% for TG-43 and Acuros BV, respectively. The maximum displacement of mucosa and the ratio of doses were negatively correlated for both. In the Optimized Acuros BV plan, total dwell time increased by 1.8% but no considerable change in the dose ratios. Conclusion: The calculated dose of mucous membrane forced out of the cylinder surface by air pockets by the Acuros BV algorithm was nonsignificantly different from TG-43. Therefore, even in the presence of air pockets, the TG-43 algorithm for calculating the VCB dose is appropriate.

A green physical approach to compatibilize a bio-based poly (lactic acid)/lignin blend for better mechanical, thermal and degradation properties.

The poly (lactic acid) (PLA) and lignin (LG) are promising candidates to develop green plastic. However, the blending of lignin with PLA leads to incompatible blend with poor mechanical and thermal properties. Hence, in the present work, a green and simple approach was employed to make PLA/LG compatible blend with high lignin percentage (5 and 20%). The E-beam irradiated lignins having different absorbed dosages were blended with two different percentages 5 and 20 with PLA in the presence of 3 phr triallyl isocyanurate (TAIC). FTIR and DSC studies have confirmed the formation of PLA-TAIC-Lignin crosslinked structures which act as an interface between the dispersed lignin phase and PLA matrix and hence improved their compatibility in the resulting blend. The compatibility of resulting blends was further validated by the morphology study, Glass transition temperature (Tg) behavior of PLA/LG blends and by observing the significant improvement in the mechanical, thermal and hydrolytic degradation properties.