December 18, 2014
Updated: December 18, 2014 01:42 IST
VULNERABLE: Special care must be taken to avoid high doses to children while using CT scans. Photo: M. Periasamy
Children less than 10 years of age are much more radiation sensitive than middle-aged adults as they have more rapidly dividing cells
The use of ionising radiation in medicine saves lives. However, physicians must take care in using this double-edged sword. They must be especially careful when they carry out medical X-ray procedures on children. This is particularly important during procedures such as CT scans which deliver high radiation doses.
They must avoid unnecessary medical X-ray exposure. More so, when the patient is a child as it is at relatively greater risk than adults are. They must justify every radiation procedure.
From the publication No 121 titled “Radiological protection in paediatric diagnostic and interventional radiology,” from the International Commission on Radiological Protection (ICRP), the latest issue of the AERB Newsletter (Vol 27,No 1, 2014), listed the following nine radiological practices as unjustified:
Skull radiograph in an infant or child with epilepsy; skull radiograph in an infant or child with headaches; sinus radiograph in an infant or child under 6 years of age; suspected of having sinusitis; cervical spine radiograph in an infant or child with torticollis without trauma; radiographs of the opposite side for comparison in limb injury; scaphoid radiographs in children under 6 years of age; nasal bone radiographs in children under 3 years of age; routine daily chest examination in intensive care units and radiological examinations requested purely for medico-legal purposes.
Children have more rapidly dividing cells than adults. They have longer life expectancy. The US National Research Council’s Committee on Biological Effects of ionising Radiation has noted that children less than 10 years of age are several times more radiation sensitive than middle-aged adults.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in its report titled “Effects of radiation exposure of children” states that the radiation doses received by children and adults from the same source of ionising radiation can have differing impacts, and therefore, should be considered separately in order to predict risk following exposure more accurately for children (UNSCEAR, October 24, 2013).
The Committee reviewed 23 different cancer types. For over 25 per cent of these cancer types including leukaemia and thyroid, brain and breast cancer, children are found to be more sensitive than adults. Cancer risk is not always immediate but extends later into life. Some of the cancers are highly relevant to assess the radiological consequences of nuclear accidents and some medical procedures. The need to implement paediatric protocols for diagnostic radiation procedures is obvious.
Recently, physicians in U.S. and Canada decided to select appropriate protocols in paediatric nuclear medicine. Health effects depend on many physical factors. For instance, for internal exposure to radiation, there are differences in the doses received by children and adults from exposure to the same distribution of radioactive material.
As infants and children have smaller body diameters, and their organs are less shielded by overlying tissues, the doses to their internal organs are higher than that to an adult for the same exposure. Metabolism and physiology vary with age; this also affects the concentrations of radio-nuclides in different organs and thus the dose to those organs for a given intake.
Infants and children can receive significantly higher doses than adults in medical exposure if the technicians do not adjust the technical settings appropriately. When a CT scan is carried out on a child with the same technique factors that are typically used for an adult, the child receives significantly higher dose than the adult. Regrettably, this happens very often.
While carrying out an AERB-funded safety research project, researchers from the Christian Medical College (CMC) Vellore noted that of the 71 CT Units surveyed, 32 did not use paediatric protocols. They also observed that 8.9 per cent of CT scans are on children. Evidently, substantial numbers of CT equipment expose children to needlessly high radiation doses.
The same researchers, who studied 127 CT scan units, found that there is a wider variability of doses with protocols varying in each centre. For instance, for a routine abdomen study, the doses ranged from 1.6 mSv to 20.6 mSv, for thorax it ranged from 1.9 mSv to 24.9 mSv. For certain other examinations, they found that the maximum dose was very high.
The website of the Alliance for Radiation Safety in Pediatric Imaging (www.imagegently.org) is a rich resource of information for all, including parents.
In spite of many deficiencies, physicians must not refuse a clinically required X-ray examination as the potential risk from such exposure will be relatively small compared to its direct benefit. They must keep abreast with the recommendations of competent professional agencies such the WHO and the ICRP on acceptable referral criteria for diagnostic radiation procedures. Professional associations must standardise the radiation procedures. AERB which is mandated to protect patients must extend all assistance to such associations.
Former Secretary, AERB