Comparison between continuous and discrete sources in the Paris system of implants

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy

Background:

• The Paris system for interstitial brachytherapy traditionally uses iridium wires.
• The feasibility of substituting discrete point sources in afterloading ribbons requires analysis.

Purpose of the Study:

• To analyze the consequences of replacing iridium wires with discrete point sources in brachytherapy.
• To evaluate implant quality for various configurations using point sources.

Main Methods:

• Analysis of single ribbons, single plane implants (0.5-1.0 cm thickness), and biplanar implants (1.5-3.0 cm thickness).
• Evaluation of implant quality using the uniformity index, considering treatment volume and dose homogeneity.
• Assessment of parameters like total activity, treatment volume, and dose rates.

Main Results:

• Changes in implant quality were observed when comparing wires and point sources up to 1.5 cm spacing.
• The uniformity index was used to quantify implant quality.
• Results with 1 cm seed spacing were compatible with wire implants, often showing improved quality.

Conclusions:

• Discrete point sources in afterloading ribbons can be a viable alternative to iridium wires in brachytherapy.
• Optimized seed spacing, such as 1 cm, can enhance the quality of brachytherapy implants.
• The uniformity index provides a comprehensive measure for assessing brachytherapy implant quality.