(d)
Question #5
The gold-198 isotope is used in the treatment of brain, prostate, and ovarian cancer. Au-198 has a
half-life of 2.69 d . If a hospital needs to have 15 mg of on hand for treatments on a

certain day, they must calculate how much of the isotope they need to start with. Since Au-198 has a half-life of 2.69 days, every 2.69 days, the amount of the isotope reduces by half. To maintain a supply of 15 mg after a certain number of days, hospitals typically use the formula to determine the initial quantity needed.

This isotope is not just a numbers game; it’s also a medical marvel. The real-world application of Au-198 in brachytherapy, a form of internal radiation treatment, showcases its effectiveness in shrinking tumors. It’s placed directly into or near a tumor, allowing targeted radiation to kill cancerous cells while minimizing exposure to surrounding healthy tissue— a shining example of how physics and medicine can unite to tackle serious health issues!