Dosimetric comparison between model 9011 and 6711 sources in prostate implants

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Brachytherapy utilizes radioactive seeds for localized cancer treatment.
• Iodine-125 ((125)I) is a common isotope for prostate brachytherapy.
• Accurate dosimetry is crucial for effective treatment and minimizing side effects.

Purpose of the Study:

• To compare the dosimetric coverage of the 9011 iodine-125 ((125)I) source against the 6711 source in prostate implants.
• To evaluate potential errors in dose calculation when using the incorrect source data.

Main Methods:

• Postimplant dosimetry was performed on 18 prostate cancer patients (2 with 9011, 16 with 6711 sources).
• Implants were recalculated using the alternative source data within a commercial planning system.
• Dosimetric parameters (D100, D90, V200, V150, V100, V50, V20) were compared for prostate, bladder, rectum, and urethra.

Main Results:

• The 6711 source data overestimated coverage by 6.4% at D100 and 6.6% at D90 compared to actual 9011 data.
• Discrepancies up to 67% were observed at higher dose levels (V100, V150, V200), with average reductions of 2.7%, 14.6%, and 14.9% respectively.
• Significant differences were also noted in bladder, rectal, and urethral coverage.

Conclusions:

• There are clear dosimetric differences between the 9011 and 6711 iodine-125 ((125)I) sources.
• Utilizing 6711 source data for 9011 implants results in significant dose calculation errors.
• The 9011 source offers comparable dosimetric quality to the 6711 source when used correctly; 6711 data should not substitute for 9011 data.