To Study the Impact of Different Optimization Methods on Intensity-Modulated Radiotherapy and Volumetric-Modulated...

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Metallic hip implants pose challenges in radiotherapy planning due to potential dose deposition and artifact generation.
• Optimizing radiation delivery techniques is crucial to minimize dose to healthy tissues while ensuring adequate tumor coverage in the presence of implants.

Purpose of the Study:

• To evaluate the impact of different optimization strategies on intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) plans for patients with metallic hip implants.
• To compare the effectiveness of restricting radiation beam entry and exit doses towards the metallic implant.

Main Methods:

• A cohort of 16 patients with metallic hip implants was studied.
• Three sets of IMRT and VMAT plans were generated: unrestricted (Base), restricted beam entry (ENT), and restricted entry and exit (EXT+ENT).
• Plan quality was assessed based on target coverage, dose homogeneity, and organ-at-risk sparing.

Main Results:

• Restricting beam entry (IM_ENT) significantly improved planning target volume (PTV) coverage and homogeneity for IMRT compared to unrestricted plans.
• IMRT plans with restricted entry and exit (IM_EXT+ENT) showed significant reductions in bladder, rectum, and bowel doses compared to IM_ENT.
• VMAT plans consistently outperformed IMRT plans across all optimization methods, demonstrating superior volumetric coverage, fewer hotspots, and reduced heterogeneity.

Conclusions:

• Blocking radiation beam entry is recommended for IMRT and VMAT planning in cases involving hip prostheses.
• VMAT techniques provide superior plan quality, including better volumetric coverage and homogeneity, compared to IMRT when treating patients with metallic hip implants.