Toward a dynamic real-time intraoperative permanent prostate brachytherapy methodology.

Area of Science:

• Medical Physics
• Oncology
• Radiotherapy

Background:

• Permanent Prostate Brachytherapy (PPB) is a common treatment for localized prostate cancer.
• Accurate dosimetry is crucial for effective treatment and minimizing side effects.
• Traditional dosimetry relies on post-operative imaging, delaying assessment.

Purpose of the Study:

• To evaluate dosimetry and source location accuracy in real-time dynamic PPB using inverse treatment planning.
• To compare intraoperative dosimetry with post-operative CT-based dosimetry.

Main Methods:

• Developed a dynamic PPB algorithm with inverse planning and real-time transrectal ultrasound guidance.
• Monitored dosimetry during seed placement with real-time assessments and adjustments.
• Performed intraoperative dosimetry (OR-D) and compared it with post-operative CT dosimetry (CT-D) at 3 weeks.
• Developed a matrix algorithm to match seed locations between ultrasound and CT data.

Main Results:

• Twenty-six patients underwent dynamic PPB.
• Mean D90 values were similar between OR-D (109%) and CT-D (105%), with no statistically significant difference (p=0.894).
• V100 and V150 analyses also showed insignificant differences between OR-D and CT-D.
• Mean root-mean-square error for seed location matching was 4.6 mm.

Conclusions:

• Real-time dynamic PPB with inverse planning demonstrates good correlation between intraoperative and post-operative dosimetry.
• The developed algorithm shows potential for improving implant dosimetry and documenting dose accurately intraoperatively.
• Further studies are needed to confirm the benefits and potential to eliminate the need for post-implant dosimetry.