Calcifications are potential surrogates for prostate localization in image-guided radiotherapy.

Area of Science:

• Radiation Oncology
• Medical Imaging

Background:

• Image-guided radiotherapy (IGRT) is crucial for accurate treatment delivery.
• Fiducial markers are often used for prostate localization, but their implantation is invasive.
• Cone-beam computed tomography (CBCT) enables image guidance during treatment.

Purpose of the Study:

• To assess the feasibility of using prostate calcifications as surrogates for prostate position during CBCT image-guided radiotherapy.
• To determine the stability and reliability of calcifications as internal landmarks.

Main Methods:

• Retrospective analysis of CBCT images from 4 patients to evaluate calcification stability.
• Review of planning CT scans from 131 prostate cancer patients to determine calcification occurrence rate.
• Online registration using prostate calcifications as landmarks in 2 patients, with both standard and low-dose CBCT modes utilized.

Main Results:

• Prostate calcifications demonstrated stability throughout the treatment course.
• The positional difference between calcifications and fiducial markers was within acceptable limits (0.2-0.8 mm).
• Well-defined calcifications were present in 35% of patients, and they were clearly visible on low-dose CBCT scans, enabling precise registration.

Conclusions:

• Prostate calcifications can serve as reliable, non-invasive markers for prostate positioning in image-guided radiotherapy.
• This approach facilitates precise image guidance with a low imaging dose.
• Approximately one-third of prostate cancer patients may benefit from this non-invasive image guidance strategy.