Performance Study of the Dynamic Multi-leaf Collimator System (DMLC-120)

Background Our research focused on the design of the Dynamic Multi-Leaf Collimator (DMLC-120), which can be installed on the medical linear accelerator (KylinRay-MELAC). This innovative device, consisting of 60 leaf pairs, aims to significantly enhance the precision of radiation therapy. Purpose To address the challenge of high leakage rates observed in traditional arc-end multi-leaf collimators upon leaf closure, we introduced a novel design that combines arc and flat end-face structures. This study evaluates the performance of this composite design, intending to establish a new standard for clinical dose modeling and planning systems, thereby improving the accuracy of radiotherapy delivery. Methods Before assessing performance, we conducted beam commissioning. Following established guidelines, we utilized an Electronic Portal Imaging Device (EPID) for assessing leaf positioning accuracy and reproducibility. The investigation of beam transmission, leakage, and the tongue and groove effect was facilitated through the use of EBT3 radiotherapy verification films and analysis with an EPSON EXPRESSION 12000XL scanner. Output factors, percent depth dose (PDD), and beam profiles were accurately determined using an IBA phantom equipped with an ionization chamber. Results The composite end-face structure demonstrated exceptional performance, with leaf position accuracy and reproducibility deviations at 0.3 mm and 0.11 mm, respectively. Leakage through the leaves averaged at 0.98%, with a penumbra of 6.6 mm for a 10×10 cm2 field, indicating a significant improvement over traditional designs. Conclusions The innovative composite end-face structure for the arc-end MLC significantly mitigates the issue of high leakage rates during leaves closure. Our research demonstrated that all MLC performance levels were within the acceptable range based on the protocols, which were well below the specified tolerance limits, supporting highly accurate radiotherapy delivery.