several professional associations in USA. Thirteen of them jointly started the Image Gently web page which provides valuable information on the topic. An article in the Science & Technology section of the Hindu a muti-edition daily carries my article on the topic.
K.S.Parthasarathy
Date:06/03/2008 URL: http://www.thehindu.com/thehindu/seta/2008/03/06/stories/2008030650071500.htm
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Image gently, bring down CT dose to kids
Last July, 13 U.S. associations including the American Association of Physicists in Medicine (AAPM), the Society for Paediatric Radiology (SPR), the American College of Radiology (ACR) and the American Society of Radiologic Technologists (ASRT) founded the Alliance for Radiation Safety in Paediatric Imaging.
Collective effort
They launched the Image Gently campaign as a collective effort to bring down radiation doses to children. Its objective is to ensure that medical protocols for imaging children keep pace with technology advances (medicalphysicsweb, February 1, 2008).
Specialists became aware of the safety significance of paediatric CT examinations when the American Journal of Roentgenology (AJR) expressed serious concern on unnecessary radiation doses to children (AJR, February, 2001). On November 2, 2001, the US Food and Drug Administration (FDA) issued a Public Health Notification on the topic.
In December 2001, the Atomic Energy Regulatory Board brought the USFDA advisory to the notice of the managements of CT Units in India.
Image acquisition
The growth of CT use in children has been driven primarily by the decrease in the time needed to perform a scan — now less than 1 second — largely eliminating the need for anaesthesia to prevent the child from moving during image acquisition (The New England Journal of Medicine, NEJM, November 29, 2007). The children get exposed to radiation doses higher than necessary because many technologists use the same x-ray exposure factors for Computed Tomography (CT) examinations of children as those used for adults. Children are more sensitive to radiation than adults, as their tissues are developing.
U.S. figures
Nearly seven million CT procedures are carried out annually in the U.S. among children of all ages, with 33 per cent on children under 10 years of age. Surveys at 71 CT Units in India revealed that on an average 8.9 per cent of CT procedures are on children; paediatric protocols are not used in 32 of these installations. These centres are exposing children to unjustifiably high radiation doses.
CT examination is beneficial, when it is medically needed. But there is a need to reduce dosage.
Tube current
Researchers from the All India Institute of Medical Sciences, Delhi demonstrated that the doses to children can be halved without reducing clinical benefits simply by lowering the tube current (Clinical Radiology 2005).
David Brenner, Eric J. Hall from Columbia University argued that there is direct evidence from epidemiological studies that the organ doses corresponding to a common CT study result in an increased risk of cancer. (The NEJM, 2007). “The evidence is reasonably convincing for adults and very convincing for children,” they asserted.
Dr Marilyn J. Goske, who chairs the Alliance for Radiation Safety in Paediatric Imaging, conceded that there may be disagreement within the medical community about the accuracy of the risk models.
Indisputable fact
“These arguments will not be settled in the near term. However one fact is indisputable; we must continue our efforts to do a better job of reducing radiation dose to children if and when they need a CT scan”, she wrote in an editorial (The AJR, February 2008)
Child-sizing a must
Goske suggested that the technologists must reduce or “child-size” the amount of radiation used; scan only when necessary; scan only the indicated region and scan only once; multiphase scanning is usually not necessary in children.
Everyone handling a CT Unit must read http://www.pedrad.org/associations/5364/ig, the Image Gently web page. Medical literature contains protocols to reduce radiation doses; many of these are scanner specific and not transferable to other units (Image Gently, 2007).
CT centres in India, in consultation with manufacturers may develop appropriate protocols using the “Paediatric CT Protocol Guidance” published at the Image Gently website. Those who do not, must not carry out CT examinations of children.
K.S. PARTHASARATHY
FORMER SECRETARY, AERB
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