Chapter 35 – Health Physics RTMR 284 – Winter 2013

Health Physics The term health physics was coined during the early days of the Manhattan Project (development of the atomic bomb). Health Physics is concerned with providing occupational radiation protection and minimizing radiation dose to public. National Academy of Sciences identified the 20 greatest scientific and technical accomplishments of the 20th century: Medical Imaging was 14th ! Radiation is more than dangerous, deadly, or harmful, but used it small doses able to diagnose problems early and help fight cancers with therapy.

Cardinal Principles of Rad Protection TIME DISTANCE SHIELDING

ALARA As Low As Reasonably Achievable Exposure Time = Exposure rate (Gya/hr) * Exposure time (min) !!! remember to keep units the same -># min / 60 (min/hr) Distance….The more you have the less exposure you will receive Inverse Square Law! Int 1/Int 2 = (Dist 2)2 / (Dist 1)2 Shielding…..The amount of a protective barrier reduces radiation intensity can be estimated with the HVL (half value layer) or the TVL (tenth value layer) 1TVL=3.3HVL

Effective Dose / Whole Body Equivalent Dose The Equivalent whole-body dose! When only part of the body is exposed during radiography the risk of a stochastic radiation response is not proportional to the tissue does, but rather the effective dose (E). Effective dose is the weighted average dose to each of the tissues: Effective dose = tissue dose * Weighting factor E= € Di * W t We assume occupational effective dose = 10% of the monitor dose

Radiologic Terrorism All Rescue and Medical emergencies should be attended to before radiologic concerns are addressed Being exposed to radiation does not make a person radioactive! Devices used for terrorism: RED – Radiation Exposure Device (sealed) RDD- Radiologic Dispersal Device (bomb) IND- Improvised Nuclear Device (nuc explosion / weapons) Establishment of boundaries are used to contain exposure In the hospital setting a Radiation Safety Officer is in charge of a response plan in case of a high radiation reading Detection Equipment are used to provide early warnings