Robust plan optimization using edge-enhanced intensity for intrafraction organ deformation in prostate...

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-Guided Therapy

Background:

• Prostate intensity-modulated radiation therapy (IMRT) faces challenges with intrafraction organ deformation.
• Accurate dose delivery requires accounting for organ motion during treatment.
• Current methods like planning target volume (PTV) margins may lead to suboptimal dose distributions.

Purpose of the Study:

• To evaluate an edge-enhanced (EE) intensity method for prostate IMRT.
• To compare the EE approach with the conventional PTV margin (PM) approach in the presence of intrafraction organ deformation.
• To assess dosimetric outcomes and treatment efficiency.

Main Methods:

• Utilized data from 37 patients undergoing step-and-shoot IMRT for prostate cancer.
• Assessed organ deformation over the treatment course, assuming setup errors were corrected by image guidance.
• Calculated stochastic doses within the clinical target volume (CTV) considering organ deformation probability.
• Optimized dose distribution using the EE approach with higher dose constraints for underdose regions.
• Compared EE approach with the PM approach, which adds a margin to the CTV.

Main Results:

• The EE approach resulted in significantly lower total monitor units, number of segments, and conformity index compared to the PM approach.
• Dose coverage to the CTV was maintained with the EE approach despite organ deformation.
• Significantly reduced doses to the rectum and bladder were observed with the EE approach.

Conclusions:

• The EE approach is superior to the PM approach for prostate IMRT when managing intrafraction organ deformation.
• EE method offers improved treatment efficiency and organ sparing.
• This method enhances the precision of radiation delivery in the face of internal organ motion.