22-5-medical-applications-of-radioactivity-diagnostic-imaging-and-radiation_summary

The section discusses the medical applications of radioactivity in diagnostic imaging and radiation therapy. In diagnostic imaging, the use of radioisotopes allows for the production of images that provide information about the functioning of various body organs, such as blood flow, heart muscle activity, and iodine uptake in the thyroid gland. Examples of radioactive compounds used for this purpose include radioactive iodine, radioactive thallium salt, and radioactive gallium. PET scans, which use emitters, are also discussed for diagnosing brain disorders like Alzheimer's disease. In therapeutic applications, ionizing radiation is used to kill cancer cells since they reproduce rapidly and are more sensitive to radiation than normal cells. The therapeutic ratio, the ratio of abnormal cells killed to normal cells killed, is a key concern in radiotherapy. The section describes various techniques used to concentrate radiation in cancerous tissue, such as geometric techniques and the use of radiopharmaceuticals. The section also explains the biological effects of ionizing radiation on DNA molecules, leading to damage, senescence, programmed cell death, or unregulated cell division in cancer. The relative biological effectiveness (RBE) of different types of ionizing radiation is discussed in relation to the amount of biological damage that can occur from a given dose. Finally, the section introduces the radiation dose unit called the roentgen equivalent man (rem), which is the dose in rads multiplied by the relative biological effectiveness. Immediate and long-term effects of radiation on humans are also briefly described.