A.08.1 Liquid Based and Micro-Brachytherapy Sources

Objective

• Develop a NIST traceable standard for liquid-based brachytherapy sources, and micro-brachytherapy sources, and transfer this standard to the ADCLs.

Actions

• Adopt the “brachytherapy” model for calibration, assay and dosimetry of liquid-based and micro-brachytherapy sources rather than the “nuclear medicine” model.

• Establish a system for calibration of dose calibrators by the ADCLs for liquid-base and micro-brachytherapy sources.

• Advance the quantitative, image-based dosimetry for liquid-based brachytherapy and micro-brachytherapy and conduct a consensus building workshop to cover this topic.

• Study the conversion from “contained activity” to “emitted radiation” standards for liquid-based and micro-brachytherapy.

Requirements

• A minimum of 2 person-years per year over the next three year time period is required to launch into these objectives. Some partnerships between NIST and industry are warranted in this area.

Background

Liquid based and micro-brachytherapy sources are coming into wider use for therapy applications. Recently, NIST developed a “nuclear medicine” standard based upon a contained activity measurement. However, such an activity measurement is not sufficiently precise for use in radiation therapy. A preferred standard would consist of a statement of the emitted radiation from the source.

A critical need in this area is a technique to transfer the calibration from the assay of a sample of an unsealed radioactive source, to the calibration of the unsealed source in the environment used for treatment. In some cases, the unsealed source is introduced by a catheter into a balloon, which is implanted into the target tissue. The effect of the balloon, as well as the specific geometry of the unsealed source, must be addressed.