Surface-guided analysis of breast shape changes during postoperative radiotherapy by using a functional map framework

Area of Science:

• Medical Physics
• Radiotherapy
• Medical Imaging

Background:

• Breast shape and volume changes during radiotherapy are poorly understood.
• These changes impact treatment effectiveness and patient-specific adaptive planning.
• Accurate characterization of inter-fractional breast deformation is needed.

Purpose of the Study:

• Develop a geometric approach to analyze inter-fractional breast deformation during radiotherapy.
• Utilize 3D surface scans acquired during treatment sessions.
• Enable patient-specific adaptive radiotherapy planning.

Main Methods:

• Collected 3D surface scans of 22 patients undergoing radiotherapy post-lumpectomy.
• Adapted functional map framework for nonrigid correspondence computation.
• Performed intrinsic and extrinsic analyses of breast surface shapes for deformation patterns, displacements, and volume changes.

Main Results:

• Identified deformations in contralateral breast and armpit areas, with positioning shifts.
• Average displacements in the treated breast were 1-2 mm, increasing by the 25th session.
• Observed up to 10% volume change, with most cases between 2-5% over treatment.

Conclusions:

• A novel geometric approach effectively analyzes breast shape changes using surface data.
• The functional map framework facilitates specialized breast shape matching and variability analysis.
• The method reveals significant individual breast changes, supporting quantitative and qualitative deformation analysis for adaptive radiotherapy.