Radioactivity Study Guide

Radiation therapy is a cancer treatment that utilises high-energy radiation to shrink tumours and eliminate cancer cells. The way this radiation is delivered to the tumour can vary significantly, broadly categorised into external and internal methods. External beam radiation therapy (EBRT) uses a machine outside the body to direct radiation beams at the tumour. This is a common approach for many types of cancer. Internal radiation therapy, also known as brachytherapy, involves placing a radioactive source directly inside or very close to the tumour. This can be temporary, where the source is removed after a certain time, or permanent, where small radioactive 'seeds' are left in the body. Both methods aim to maximise damage to cancerous cells while minimising harm to surrounding healthy tissues, but they achieve this through different means and have distinct advantages and disadvantages regarding dosage delivery, precision, and potential side effects.

Isotopes used in Positron Emission Tomography (PET) scanners, such as Fluorine-18 (an isotope of fluorine with a half-life of approximately 110 minutes), must be produced very close to the clinics or hospitals where they will be used. This necessity arises primarily because these isotopes have relatively short half-lives. A short half-life means that the radioactive material decays rapidly, losing its radioactivity quickly. If the isotopes were produced far away, a significant portion of their radioactivity would be lost during transportation, making them less effective or even unusable by the time they reach the patient. The diagnostic images produced by PET scanners rely on detecting the radiation emitted by these isotopes within the patient's body. Therefore, maintaining sufficient radioactivity is crucial for obtaining clear and accurate diagnostic information. Local production minimises transit time, ensuring a higher dose of the active isotope is available for medical procedures.