Consequences of optimization in PDR brachytherapy--is a routine geometrical optimization recommendable?

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• Pulsed dose rate (PDR) brachytherapy utilizes a stepping source for precise radiation delivery.
• Interstitial implants and surface molds are common brachytherapy techniques.
• Optimization of dose distribution is crucial for effective cancer treatment and minimizing side effects.

Purpose of the Study:

• To investigate the benefits and drawbacks of geometrical optimization in PDR brachytherapy.
• To compare geometrically optimized PDR dose distributions with non-optimized ones.
• To evaluate optimization effects on both interstitial volume implants and surface molds.

Main Methods:

• Analysis of dose distributions in 25 patients treated with interstitial breast implants.
• Evaluation of isodose curves, reference volume, and dose-volume histograms.
• Investigation of geometrical optimization's effect on surface molds for chest wall relapses, analyzing reference surface, dose profiles, and depth-dose curves.

Main Results:

• Geometrical volume optimization improved dose uniformity and reduced underdosage at implant edges in most cases.
• The reference volume for interstitial implants was generally increased by optimization.
• Surface mold optimization enhanced reference surface and skin surface dose homogeneity.

Conclusions:

• Geometrical optimization significantly alters PDR brachytherapy dose distributions, predominantly favorably.
• While beneficial, careful monitoring is needed to avoid overdosage in specific regions.
• Optimization is essential for achieving homogeneous dose distributions in surface mold treatments.