Radiation Environment in Medical Facilities

Ionizing radiations (X-rays, gamma rays, electrons, positrons, protons, neutrons, alpha particles and heavy ions) are commonly used in human healthcare programmes. Now, it is difficult to imagine a human healthcare system without ionizing radiation-based imaging and therapeutic procedures. The medical imaging procedures of ionizing radiation use kilovoltage X-rays generated by specialized equipment as well as gamma rays emitted by radioisotopes. X-ray-based or transmission imaging procedures use a variety of imaging systems such as radiography, fluoroscopy and volumetric imaging (computed tomography, CT) systems. Radioisotope-based or emission imaging procedures involve the use of a radiopharmaceutical (e.g. 99mTc- and 18F-based radiopharmaceuticals) as a source of radiation and an image recording system such as gamma camera, single photon emission computed tomography (SPECT) and positron emission tomography (PET). Hybrid imaging systems such as SPECT-CT and PET-CT are also used in medical imaging procedures. The therapeutic application of radiation is broadly classified as radiotherapy and nuclear medicine therapy. Radiotherapy uses either sealed radioactive sources or accelerated particles, whereas nuclear medicine therapy uses unsealed radioisotopes. Radiotherapy involves the treatment either by a radiation generator away from the patient’s body (external beam therapy) or a radioactive source inside the patient’s body (brachytherapy). A variety of external beam therapy systems such as standard and specialized telecobalt machines, standard and specialized medical electron accelerators, proton beam therapy systems, neutron beam therapy systems and ion beam therapy systems are available. Brachytherapy uses a remote operating device for implanting the miniature radioactive sources (e.g. 192Ir, 60Co) at a predefined location inside the patient’s body. This chapter presents a brief description of important medical imaging and therapy systems vis-a-vis the radiation environment associated with these medical facilities.