According to the Paris system, what is the reference dose rate for treatment dose prescription?

The Paris system is a guideline used in brachytherapy for dose prescription and treatment planning. In this system, the reference dose rate for treatment dose prescription is established at 85% of the mean basal dose rate. The mean basal dose rate refers to the average dose delivered by a source at a reference point in a defined geometry without any modifiers or additional factors influencing it, such as tissue heterogeneities or applicator configurations.

This percentage, 85%, is specifically chosen to account for the variations in dose distribution that can occur in real clinical situations, allowing for adequate coverage of the target volume while minimizing the dose to surrounding healthy tissues. The selection of 85% helps ensure that the prescribed dose is clinically relevant and aligns with the therapeutic objectives of achieving tumor control while keeping side effects manageable.

Using this reference point allows radiation oncologists and dosimetrists to standardize their approaches and compare outcomes across different brachytherapy treatments effectively.