Implementation of MLC-based techniques for kidney protection as isolated organs during radiotherapy of abdominal malignancies

Introduction: Radiotherapy is one of the therapeutic options for malignancies associated with the abdominal cavity. However, the delivered dose must be limited to the kidneys' custom shielding blocks. This study aimed to propose a method in which kidney shielding blocks can be replaced with multi-leaf collimators (MLCs). Materials & Methods: In the initial phase, both kidneys were protected, and the open field area was irradiated. However, the region between each kidney and the lateral abdominal wall was inevitably shielded. Therefore, in subsequent phases, the dose to the shielded region was necessarily compensated. This process was analyzed by treatment planning and Kodak EDR2 film dosimetry. The dosimetric film results, read with MATLAB, were compared with TPS data, showing a mean difference of less than 5%, indicating acceptable agreement between the two methods. Results: The MLC-based shielding method demonstrated a noticeable reduction in treatment time compared to the time required for custom block fabrication and patient setup. The use of MLCs resulted in only a 3.86% increase in MU, which was not clinically significant. The mean dose to both kidneys in the MLC and cerrobend block methods remained within the renal tolerance limits. Furthermore, the consistency of average V10, V15, and V20 data for the left and right kidneys supported the agreement between the cerrobend block and MLC methods. Conclusion: MLC application to the island organ as a shield is suggested, especially in AP/PA WAR. But sufficient accuracy in field matching is needed.