Reducing X-ray imaging for proton postmastectomy chest wall patients

Area of Science:

• Medical Physics
• Radiation Oncology
• Imaging Technology

Background:

• Proton postmastectomy radiation therapy (PMRT) traditionally uses daily surface imaging and additional x-ray imaging for patient positioning verification.
• Ensuring accurate patient positioning is critical for effective radiation delivery and minimizing off-target exposure.

Purpose of the Study:

• To evaluate the sufficiency of weekly x-ray imaging combined with daily surface imaging for maintaining patient positioning fidelity in PMRT.
• To compare this approach with the standard daily x-ray confirmation method.

Main Methods:

• Analysis of radiographic corrections and surface imaging setup errors in 28 PMRT patients.
• Study of radiographic translations exceeding 3 mm after surface imaging positioning.
• Comparison of treatment angle surface images with planning CT scans using skin markers instead of bony landmarks.

Main Results:

• Discrepancies between surface and x-ray imaging were more common in patients without breast implants or with large implants.
• One-quarter of patients had radiographic translations >3 mm in the final treatment week.
• Most radiographic corrections did not significantly alter patient position, staying within 3 mm/2° tolerances.
• A patient's implant shift was detected only through x-ray imaging, highlighting its importance.

Conclusions:

• Initial and weekly x-ray acquisition with daily surface imaging is likely sufficient for routine PMRT positioning and monitoring treatment area changes.
• The limitations of surface imaging systems require further investigation, particularly for patients without breast implants or with large implant reconstructions.