One can’t imagine healthcare into existence without medical imaging, Prevalent imaging modalities includes X-ray, CT Scan, Nuclear imaging, MRI, Laser, and Ultrasound.
Each of the imaging modalities mentioned above are based on some principle and each one has its pros and cons, but out of them first three are matter of concern because of the harmful radiation involved with them, and that is Ionization radiation (high-energy radiation that can potentially cause damage to local tissues, DNA (Genetic material).
These types of imaging procedures had led to improvements in the diagnosis and treatment of numerous medical conditions. At the same time, these types of exams exposes patients to ionizing radiation, which may elevate a person’s lifetime risk of developing cancer due to damaged DNA that doesn’t got repaired by body’s natural repair mechanism.
NOTE: Ultrasound and MRI are Radiation Safe but X-ray, CT scan and nuclear imaging not: –
- Ultrasound is non-ionizing radiation, so it does not have the same risks as x-rays or other types of ionizing radiation. Even though there are NO known risks of ultrasound imaging, it can produce effects on the body.
- MRI also does not use ionizing radiation. There are no known harmful side-effects associated with temporary exposure to the strong magnetic field used by MRI scanners however one should not carry any metal object such as coin, pen, key etc during MRI scan and also does not have any metal implant in the body such as pacemaker or orthopedic bone fixation metal screws , plates etc. Also Credit/Debit card are prohibited to carry during MRI scan because their content got erased on MRI Exposure.
All though, modern imaging modalities are equipped with all the shielding structures and now a days the infrastructure of the scanning room is build to support and minimize the risk of radiation, But some of the past time hospitals are still using old infrastructure and hence a common man as well as poorly trained health worker who is not aware of the principle of radiation and safety issues involved with it, are more prone to higher doses of radiation and subsequent risks involved.
Quick revision to radiation
Radiation simply is energy generated from a source and is part of Electromagnetic spectrum, It can travel in all direction in vacuum as well as penetrate through matter and hence can travel in media. It can be in form of a wave or as stream of particles. Sources of radiation includes
- Natural – Radioisotopes (ground), Cosmic Rays (Background Radiation).
- Man-made – Medical Radiation Equipment, Consumer products, Radiation Fall-out
but the topic of concern here is man made ionization radiation sources in medical domain such as :
- X-rays -Radiography, CT Scanners
- Radio isotopes for treatment – (Cobalt, Iridium – 192, Cesium -137)
- Radio isotopes for imaging – (Iodine -131, Technetium -99m)
Four Pillars of Radiation Protection:
- TIME:- Minimize the exposure time, The more time you are exposed to radiation, The more is the absorbed dose by your body as well as scatter radiation which can affect others.
- DISTANCE:– The Radiation absorbed follows inverse square law with distance, So little more the distance from source, Significant less is radiation absorbed.
- SHIELDING:- Personal shielding such as lead apron and thyroid shield for those within the room, lead glasses and gloves for surgeons/staff having close continuous exposure, also infrastructure is build with protective concrete walls and lead glasses so as to minimize the scatter and leakage radiation reaching out of the room.
- CONTAMINATION:- Spills of radioactive substance used in Nuclear Imaging should be isolated using forceps provided in emergency kit with all protection into the shielded container by an trained worker followed by decontamination procedures (surfaces, equipment, persons).
By understanding these principles one can be free of fear and be protected from unwanted radiation and hence associated risks.
Two principles of medical radiation protection
Given for radiographer, radiotherapist, as well as for information of general public developed by the International Commission on Radiological Protection: –
- Justification: The imaging procedure should be judged to do more good than harm to the individual patient. Therefore, all examinations using ionizing radiation should be performed only when necessary to answer a medical question, help treat a disease, or guide a procedure. The clinical indication and patient medical history should be carefully considered before referring a patient for any imaging examination.
- Dose Optimization: Medical imaging examinations should use techniques that are adjusted to administer the lowest radiation dose that yields an image quality adequate for diagnosis or intervention (i.e., radiation doses should be “As Low as Reasonably Achievable”). The technique factors used should be chosen based on the clinical indication, patient size, and anatomical area scanned, and the equipment should be properly maintained and tested.
A Note for Pregnant Women:
As per the law of bergonie and tribondeau:- A higher proliferation rate for cells and high growth rate for tissues result in increased radio sensitivity this is the reason why one should shield gonads and try not go for x-ray during first trimester of pregnancy and restricted for rest of time of pregnancy and babies.
Keep Records of your Imaging Scans and Communicate your history to doctor :
You can prevent unnecessary radiation exposure by avoiding unneeded or duplicate CT scans. Keep track of your all imaging scans. If your doctor wants you to have a CT scan, show him your records and previous history and make sure you still need the scan and ask and follow the safety guidelines provided during exam.
References and Further reading:
- Radiation Shielding and Radiological Protection by J. Kenneth Shultis and Richard E. Faw
- http://www.research.northwestern.edu/ors/forms/radiation-safety-handbook.pdf
- http://www.ncsu.edu/ehs/radiation/forms/alara.pdf
