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Sci Tech
Revival of risky medical X-ray practices
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CT scan is a unique tool to diagnose disease and monitor treatment. It may help to determine the extent of the disease but should not be used indiscriminately. CT screening is unlikely to discover serious disease and the potential harm to the individual may be greater than the presumed benefit.
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The effective dose in CT procedure is not much less than the lowest dose received by some of the survivors of the atomic bombs.
JACK SCHUBERT and Ralph E Lapp in their eminently readable book entitled `Radiation — What It Is and How It Affects You' wrote about a medical practice that had, in the fifties, become almost a standard, among many firms like General Motors, Ford and ChryslerThey used to send their executives off to a clinic for a complete annual medical check up. The check up included X-ray screening of the lungs, heart, stomach, upper and lower intestinal tracts, kidneys and other organs. They received a whopping radiation dosage of about 50 roentgen in the bargain! (Roentgen is a unit of radiation exposure; a chest X-ray may involve an exposure of about 0.1r).
On April 26, 2002, the U.S. Food and Drug Administration (USFDA) noted that some medical imaging facilities are now promoting and marketing whole body CT scanning or screening as a preventive or proactive health measure to healthy individuals who have no symptoms or suspicions of disease. FDA asserted that it knows of no scientific study demonstrating that whole body CT screening is effective in detecting any particular disease early enough for the disease to be treated or cured.
According to FDA "Any such presumed benefit of whole body CT screening is uncertain, and such benefit may not be great enough to offset the potential harms such screening could cause. Public health agencies and national medical societies — the American College of Radiology, the American College of Cardiology and the American Heart Association — do not recommend CT screening".
CT is a unique tool to diagnose disease, trauma or abnormality and to plan, guide and monitor treatment. It may help to determine the extent of the disease. But it is not to be used indiscriminately.
Screening of symptom-less patients provides uncertain benefit with potential for some risk. The dose received by a patient during a CT procedure is generally much larger than that from most conventional X-ray procedures.
The effective dose in CT procedure is not much less than the lowest dose received by some of the survivors of the atomic bombs. FDA noted that these survivors have demonstrated a small but increased radiation related excess risk for cancer.
All radiation doses have an associated risk; a small possibility of developing radiation-induced cancer some time later in life. In a medically needed procedure, the benefit to the patient far outweighs the risks.
FDA warns that for a person without symptoms, CT screening is unlikely to discover serious disease and the potential harm to the individual may be greater than the presumed benefit.
The book by Schubert and Lapp quotes a 1956 communication of the National Committee on Radiation Protection, "one of the important sources of radiation exposure is that applied by general practitioners. They have no techniques by which you can really estimate the exposure given in a gastrointestinal tract examination". The British Medical Journal (13th April 2002) published a letter by a consultant radiologist K. Grower Thomas and his colleagues from several other hospitals.
They compiled a simple questionnaire and interviewed 130 doctors of all grades including consultant radiologists. They asked the physicians for an approximate dose of radiation in a chest radiograph. This dose was to be taken as a unit of one to calculate how many units a patient would receive for several types of medical X-ray examinations carried out in a busy radiology department (17 examinations in total).
Believe it or not, only 3/130 scored a pass mark of 50 per cent in spite of a generous marking scheme and no negative marking. "The degree of knowledge was inversely proportional to seniority, with consultants scoring less than junior colleagues. It was clear and worrying that doctors have no real knowledge of radiation doses that their patients receive."
I wrote about the Indian experience in the same issue of BMJ. The Atomic Energy Regulatory Board organised appreciation programmes on X-ray safety for the benefit of radiologists, physicians, medical students and para-medical staff. Invariably, everyone wanted to know the effect of irradiation on the unborn child. We found that many specialists were not equipped to offer advice on the magnitude of radiation doses in different medical X-ray procedures. Responding to a Popular Science article on medical X-ray protection, a few patients approached their radiologists to get some idea about the radiation doses they receive in medical X-ray examinations. Even senior specialists did not know.
In reply to the letters on the topic, Dr. Adrian K. Midgey, a general practitioner from the U.K. reacted. "You cannot make it feasible for all of us to remember the radiation dose in an examination since this is changeable and we have other things to do than replace minimally useful numbers in our memory with new improved and minimally useful numbers".
He is correct up to a point. But if the physician knew about the relative magnitude of the doses in various procedures, it may help to reduce unwanted referrals of symptom-free patients. Let us hope that our corporate hospitals will not use CT indiscriminately for screening.
K.S. Parthasarathy
Atomic Energy Regulatory Board
Mumbai
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