An accurate method to quantify breathing-induced prostate motion for patients implanted with electromagnetic...

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-guided Therapy

Background:

• Accurate prostate localization is crucial for radiotherapy.
• Breathing-induced prostate motion (BIPM) can introduce treatment uncertainties.
• Electromagnetic transponders offer precise prostate tracking.

Purpose of the Study:

• To validate a novel method for quantifying BIPM using electromagnetic transponders.
• To assess the clinical applicability of this method in radiotherapy patients.
• To determine the impact of BIPM on treatment accuracy in different patient positions.

Main Methods:

• Development and validation of specialized software for analyzing transponder signals.
• Phantom studies using a programmable breathing simulator.
• Application of the software to analyze 1,132 fractions from supine patients and 61 fractions from prone patients.

Main Results:

• The software accurately determined simulated breathing frequencies and amplitudes in phantom studies.
• For supine patients, median BIPM amplitudes were <0.3 mm in all directions (LR, CC, AP).
• For prone patients, BIPM amplitudes ranged up to 1.7 mm, with potential for >3 mm uncertainty.

Conclusions:

• The validated method accurately quantifies BIPM with sub-millimeter precision.
• BIPM is a minor source of uncertainty for supine radiotherapy patients.
• BIPM poses a significant treatment uncertainty for prone radiotherapy patients, potentially exceeding 3 mm.