Liquid Based and Micro-Brachytherapy Sources

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Objective for MPD A.8.1

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

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.

Action Items:

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

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

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

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

Resource Requirements:

1 – 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.