Dr Sajeev Thomas
Christian Institute of Health Sciences and Research, Dimapur
It has been a shock for Ayang, a radiographer working in the busy radiology clinic of the city hospital to notice the woman who just completed the Pelvic Computed Tomography (CT) radiological examination is pregnant. She was in a hurry to complete her duty cycle and the patient was positioned by her health assistant, while she was busy with entering the patient details in the computer, therefore, she could not notice the pregnancy before the exposure. There are chances for unintended radiation exposures to fetuses due to carelessness and lack of safety precautions especially in developing countries. There is no safe level of radiation defined for pregnant women who are not occupational radiation workers. Therefore, it is important to have certain precautions to be taken by professionals and radiology clinics before the radiation exposures of women of their reproductive age.
One of the important precautions is called the’10-day rule’ that is to avoid any radiological examinations in the first 10 days after the onset of the menstruation. Although it was originally proposed for 14 days, it was reduced to 10 days due to the variability of the menstrual cycle. Later it was replaced by a 28-day rule until a period is missed. Therefore, some of the clinics use the 10-day rule for examinations that potentially deliver a high dose to the lower abdomen and pelvis such as CT examinations and barium enema, and 28 -day rule for other examinations. According to international guidelines, there is no need to terminate the pregnancy for fetal doses of less than 100 mGy from the radiation safety aspects. However, appropriate decisions to be made for doses 100-500 mGy in each circumstance. It is complicated based on ethical, religious, moral, and governmental rules in each country. There is a high possibility for fetal damages for doses more than 500 mGy. It is rare the fetal dose goes beyond such higher levels to advise for the termination of pregnancy. The effect of exposure from radiation to the fetus depends on the time of exposure and the date of conception and the absorbed dose. For radiation exposures above 100 mGy days < 25 weeks, the central nervous system will be more sensitive to radiation (8-15 weeks) may lead to a decrease in IQ to mental retardation. However, the chances of receiving such larger doses from a diagnostic procedure are minimal. If such a high dose of exposure is suspected, it should be measured or estimated only by a qualified medical physicist or radiation safety expert. This expertise is not available with Radiologists, radiation oncologists, cardiologists or any other health care professionals. However, the service of medical physicists/radiation safety experts is available with limited hospitals in developing countries. There is minimal risk for pregnant patients to undergo CT or X-ray examination for areas away from the fetus such as for thorax or head for diagnostic purposes. The risk for not making a diagnosis is more than the risk to the fetus from the radiation exposure. There are methods and techniques to perform cardiac catheterization for pregnant patients with minimal risk to the fetus. However, the absence of the expertise of a qualified medical physicist and dosimetric equipment are the key challenges to many of the hospitals in India.
The author is a senior medical physics specialist and clinical scientist certified by the health and care professions council, United Kingdom and a licensed radiation safety expert under the Atomic Energy Regulatory Board, Government of India.
