Nowadays radiotracer has become an indispensable and sophisticated diagnostic tool in medicine and radiotherapy purposes.
The most common radioactivity isotope used in radioactive tracer is technetium (99Tc). Tumors in the brain are located by injecting intravenously 99Tc and then scanning the head with suitable scanners.
131I and most recently 132I and 123I are used to study malfunctioning thyroid glands. Kidney function is also studied using compound containing 131I. 33P is used in DNA sequencing. Tritium (3H) is frequently used as a tracer in biochemical studies. 14C has been used extensively to trace the progress of organic molecule through metabolic pathways.
A most recent development is positron emission tomography (PET), which is a more precise and accurate technique for locating tumors in the body. A positron emitting radionuclide (e.g., 13N, 15O, 18F, etc.) is injected to the patient, and it accumulates in the target tissue. As it emits positron which promptly combines with nearby electrons, it results in the simultaneous emission of two γ-rays in opposite directions. These γ-rays are detected by a PET camera and give precise indication of their origin, that is, depth also. This technique is also used in cardiac and brain imaging.
Compound X-ray tomography or CT scans. The radioactive tracer produces gamma rays or single photons that a gamma camera detects. Emissions come from different angles, and a computer uses them to produce an image. CT scan targets specific area of the body, like the neck or chest, or a specific organ, like the thyroid.