Implanted dosimeters identify radiation overdoses during IMRT for prostate cancer

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Image-guided radiotherapy is standard for prostate cancer.
• Daily dose verification is often lacking despite methods for motion management.

Purpose of the Study:

• To report clinical experience using implantable dosimeters for dose verification in prostate intensity-modulated radiotherapy (IMRT).
• To quantify and adjust the actual delivered dose during IMRT.

Main Methods:

• 20 prostate cancer patients received IMRT with cone-beam CT image guidance.
• Implantable metal-oxide-semiconductor field-effect transistor dosimeters were used for in vivo dose verification.
• Discrepancies >6% or ≥10% triggered investigations and potential replanning.

Main Results:

• Dose measurements >6% higher than predicted occurred in 3 of 20 patients.
• Anatomic changes, not alignment, caused discrepancies.
• Repeat CT simulation and IMRT replanning resolved dose issues in all affected patients.

Conclusions:

• Implanted in vivo dosimetry can reveal dose discrepancies in prostate IMRT.
• Careful planning and delivery are crucial, considering potential anatomic changes.
• This method emphasizes the importance of verifying delivered dose in IMRT.