Validation of K-edge I-125 brachytherapy enhancement with silver compounds

Brachytherapy with radioactive seeds implanted within the tumour volume has demonstrated good success rates in treating certain cancers. In an effort to improve the curative rates in cancer patients, ongoing research is being conducted to enhance the amount of radiation dose that is absorbed within the tumour volume while minimizing the dose absorbed by the surrounding nor mal tissue. One method for enhancing tumour dose absorption with I-125 brac hytherapy seeds is to increase the number of photoelectric atomic interacti ons within the tumour volume by introducing small quantities of a silver co mpound, taking advantage of the K-edge effect. Because low-energy electrons and Auger electrons are the primary sources of brachytherapy dose enhancement, acquiring accurate experimental measuremen ts of absorbed dose increases is a major challenge. To circumvent this prob lem, an x-ray fluorescence excitation spectroscopy dosimetry technique supp lemented with clinically accepted dosimetry calculations was developed to e stimate relative absorbed dose increases in a water phantom containing up t o 7.5 mM of silver. Excellent agreement was observed between theoretically derived Monte Carlo dosimetric predictions and experimental measurements. T hese results successfully demonstrated that K-edge enhanced I-125 brachythe rapy is indeed possible with future development of a non-toxic silver chela te.