Dynamic modulated brachytherapy (DMBT) for rectal cancer.

Area of Science:

• Radiation Oncology
• Medical Physics
• Brachytherapy Technology

Background:

• Current high-dose-rate brachytherapy (HDR-BT) relies on immobile applicators, limiting dose conformity.
• The dynamic motion of applicators represents an unexplored degree of freedom for optimizing radiation delivery.
• This study introduces dynamic modulated brachytherapy (DMBT) to enhance dose distribution in HDR-BT.

Purpose of the Study:

• To evaluate the dosimetric potential of a novel dynamic modulated brachytherapy (DMBT) system.
• To assess the benefits of applicator motion for rectal cancer treatment using Monte Carlo and treatment planning simulations.
• To compare DMBT with conventional intracavitary mold applicators (ICMA).

Main Methods:

• Developed an in-house DMBT system utilizing a tungsten alloy shielded (192)Ir source capable of dynamic translation and rotation.
• Employed Monte Carlo simulations and planning optimization algorithms to evaluate treatment plans.
• Analyzed 36 clinical treatment plans from 13 rectal cancer patients, comparing DMBT with ICMA for a prescription dose of 10 Gy/fraction.

Main Results:

• DMBT plans demonstrated a >30% decrease in high-dose volume (D5) and a ~40% reduction in dose heterogeneity index compared to ICMA.
• Mean dose and D98 to critical structures were reduced by 40%-60% with DMBT.
• Total treatment time increased from 7.6 to 20.8 minutes for DMBT at the specified source strength and dose.

Conclusions:

• The novel DMBT system shows significant dosimetric advantages over conventional ICMA for HDR-BT (192)Ir technology.
• Dynamic applicator motion offers substantial potential for increasing plan quality in brachytherapy.
• DMBT represents a prospective advancement for improving treatment precision and reducing toxicity in brachytherapy applications.