by Dr. Chinmay Dalal MD CCFP
Everything is Risk vs Benefit - Will this imaging aid in the diagnosis AND change management! This is key, we don’t test just to find an answer, only if it will change the management
Absorption of radiation is affected by body habitus
Modern radiology equipment is VERY focused with very little bleeding of radiation outside the targeted area
Review of the terms:
Millisieverts (mSv) - derived unit of ionizing radiation dose in the International System of Units (SI) and is a measure of the health effect of low levels of ionizing radiation on the human body - 1 rad = approx 10 mSv
Background Radiation = including radon, cosmic rays, terrestrial, and internal sources - Annually, about 3 mSv
The International Commission on Radiological Protection (ICRP) estimates a 4 to 5% increased relative risk of fatal cancer after an average person receives a whole-body radiation dose of 1000 mSv
ESSENTIALLY (in very general terms):
1 Chest X-Ray (PA and Lat) = 0.1 mSv of radiation = 12 days of background radiation
This calculation can then be used to discuss with the patient the risk vs benefit of the test and seek informed consent ie. CT Abdo/Pelvis in a patient with abdominal pain NYD ≅ 10 mSv (or 3 years of background radiation or a 0.04% increased relative risk of fatal cancer)
Photo by: Mikael Häggström / CC0, https://commons.wikimedia.org/wiki/File:Normal_posteroanterior_(PA)_chest_radiograph_(X-ray).jpg