Comprehensive I-125 multi-seed comparison for prostate brachytherapy: dosimetry and visibility analysis

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Brachytherapy utilizes radioactive seeds for localized cancer treatment.
• Variations in seed design and dosimetry among manufacturers can influence treatment outcomes.

Purpose of the Study:

• To compare the dosimetric properties and imaging visibility of different Iodine-125 (I-125) seed types from various manufacturers.
• To evaluate the impact of these seed variations on treatment planning for prostate and rectal brachytherapy.

Main Methods:

• Five I-125 seed models (Oncoseed, Echoseed, Intersource, Isoseed, Selectseed) were analyzed for point dose at varying angles.
• Patient treatment plans were used to assess dosimetry effects on implant indices (Vp100, Vp200, Dp90, Vr100, Vr69).
• Seed visibility was tested using prostate phantoms under X-ray, fluoroscopy, CT, and MRI.

Main Results:

• Significant dosimetric differences were observed, particularly at close distances, with Selectseed and Isoseed showing lower doses.
• Treatment planning indices like Vp150, Vp200, and D90 showed statistically significant changes between seed types.
• Seed visibility varied across imaging modalities: Intersource was least visible on fluoroscopy/X-ray, while Isoseed and Selectseed were most visible.

Conclusions:

• Dosimetric variations between I-125 seeds necessitate careful consideration during treatment planning.
• Adjustments to treatment plans may be required when changing seed types to meet dose distribution goals.
• Imaging visibility differs across modalities, impacting seed localization during brachytherapy procedures.