PEDIATRICIAN Spring 2003 - AAP-CA

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Weighing the Radiation Risks of CT Scans Nikta Forghani, M.D., Ronald A. Cohen, M.D., and Myles B. Abbott, M.D. Computed tomographic (CT) scanning is a valuable imaging modality on which pediatricians increasingly rely. However, pediatricians may not realize that CT scans expose children to high amounts of ionizing radiation that may have detrimental long-term consequences. Recent data from studies of survivors exposed to low-dose radiation from the atomic bombs in Hiroshima and Nagasaki 1 , and the increased risk of leukemia in children who have two or more radiologic procedures 2 , suggest that pediatricians should be more circumspect when ordering CT scans. More than two million CT scans are done on children each year in the United States. 3 The use of CT imaging in both adults and children has increased by 700% over the past ten years 3 , although it has been estimated that 40% of CT scans performed on children are unnecessary. 4 This increase is in large part due to the fact that CT imaging has been more widely recognized as a superior imaging modality for many clinical problems. While CT imaging has enormous diagnostic benefit, its widespread use is a source of potential harm, especially to pediatric patients. The National Research Council’s Factors and Procedures Yearly exposure at sea level 3 Living in Denver (high altitude) 6 Transcontinental flight 0.25 Committee on the Biological Effects of Ionizing Radiation on Children has determined that children under 10 years of age are several times more sensitive to ionizing radiation than middle-aged adults. 5 In addition, since children have a longer life span, their potential longterm risk of radiation damage is increased. Furthermore, some of the new advances in CT technology make the scans faster and more accurate (and therefore more appealing in the context of pediatric radiology), but may come with a price of higher ionizing radiation exposure. To appreciate the amount of radiation in a CT scan, it may be helpful to compare CT radiation with both a standard chest X- ray and the background radiation to which we are all exposed in the environment. The exposure from an abdominal CT scan is 5 to 10 millisieverts (mSv) 1 , which is 250 to 500 times greater radiation than a standard chest radiograph (which is .02 mSv). The amount of background radiation varies in different locations, but the average background radiation in the United States (excluding medical sources) is about 3 mSv per year. The table shows the Table: Representative Values of Effective Radiation Doses Associated with Various Environmental Factors and Medical Procedures 7, 8 Chest X-ray 0.02 – 0.05 Skull X-ray Abdominal X-ray Intravenous pyelogram Upper gastrointestinal series Barium Enema Head CT Chest CT Abdominal CT Ultrasonography 0 Magnetic Resonance Imaging 0 Effective dose in mSv 0.1– 0.2 0.5 – 1.5 2.5 – 5.0 3.0 3.0 – 7.0 2.0 – 4.0 5.0 – 15.0 5.0 – 15.0 approximate amount of radiation associated with various environmental factors, medical procedures involving ionizing radiation, and medical procedures that do not expose patients to radiation. Much of the current concern about the effects of ionizing radiation on children stems from recently published research about cancer risk in atomic bomb survivors. Today, more than 50 years after their initial exposure, individuals have been identified who received radiation doses that are similar to doses achieved with modern CT scans (8-30 mSv). The research shows that these individuals have a small but statistically significant increased mortality risk from cancer. Pediatricians and pediatric radiologists ought to work collaboratively to determine the best imaging technique for each patient. When non-radiation modalities (ultrasonography or MRI) are as diagnostic as CT for the child’s condition, they should be preferred. However, CT scans are often the most appropriate imaging modality. When CT is used, there are ways to reduce the exposure to radiation: • Reduce CT settings, which can be done without significantly compromising image quality. In one recent trial, ionizing radiation exposure in children was reduced by 75% while quality was maintained. 6 • Utilize more focused or limited CT scans to minimize the extent of radiation exposure. For example, when trying to identify a hepatic abnormality, CT can focus on the liver rather than the entire abdomen and pelvis. • Perform only the minimum number of CT scans necessary for the diagnosis. There are very few circumstances when multiple CT scans are necessary. • Be judicious in repeating CT scans to follow a pathologic process. Consider other imaging modalities to follow the process. REFERENCES: 1. Pierce DA, Preston DL. Radiation-related cancer risks at low doses among atomic bomb survivors. Radiation Research. 2000; 154:178-186. 2. Infante-Rivard C, Mathonnet G, Sinnett D. Risk of childhood leukemia associated with CONTINUED ON PAGE 28 CALIFORNIA PEDIATRICIAN — SPRING 2003/ 7
Adolescent Idiopathic Scoliosis While it is normal for the spine to have curvatures in the lateral plane (lordosis in the lumbar and cervical regions and kyphosis in the thoracic region), the spine is normally straight when viewed from the frontal plane. Scoliosis is a lateral curvature of the spine, and is always abnormal. The term scoliosis is derived from the Greek term ‘scolio’ (curved or bent). There are many causes of scoliosis but the most common is adolescent idiopathic scoliosis (AIS), which accounts for a great majority of cases. This is a structural (stiff) curve with rotation of the spine that occurs at or near the onset of puberty without an established cause. A variety of possible etiological factors have been implicated, including hormones, genetic predisposition, muscular imbalance and neurologic abnormalities. However, no direct link between these factors and the development of scoliosis have been established in this population. The diagnosis of AIS is suspected by the presence of asymmetry on the Adams forward bend test. However, some children may have muscular asymmetry without a true scoliosis. In addition, care should be taken to account for any leg-length discrepancy (LLD) as this can also produce asymmetry of the spine and a lateral curvature. If scoliosis is suspected, a standing postero-anterior (PA) radiograph should be obtained. A curve of 10 degrees or greater confirms the diagnosis of scoliosis. The prevalence in the adolescent population (10 to 16 yrs) is approximately 2 to 3%. The female: male ratio for smaller curves is almost equal, whereas the female:male ratio for larger curves is 3.6:1. The history should include any family history of scoliosis or other back problems, prior lower extremity fracture, any neurologic complaints (including bowel and bladder function) as well as any history of back pain. Pain is not normally associated with AIS, whereas painful scoliosis may be the result of a herniated disk or tumor. A careful physical examination should include an evaluation for LLD and inspection of the back and skin for any abnormal skin markings, dimples or hairy patches that may indicate an underlying spinal cord abnormality. The entire body should be inspected for the presence of cafe au lait spots or other manifestations of neurofibromatosis. Finally, a detailed neurologic examination including upper and lower extremity motor Robert M. Bernstein, M.D. strength, sensation, and reflexes should be undertaken. Abdominal reflexes (stroking each side of the umbilicus gently with a blunt object should result in equal movement of the umbilicus toward the stimulated side) should also be checked as asymmetry of this reflex may indicate intra-spinal pathology. Pain, asymmetry of abdominal reflexes, or any abnormal neurologic finding may indicate an underlying spinal cord abnormality and should be investigated. The incidence of spinal cord abnormality (syrinx or chiari malformation) is extremely low in AIS, and in general, only a plain radiograph (PA) need be obtained. PA radiographs are preferred over anteroposterior radiographs because the radiation exposure of the breast is minimized. Curves measuring less than 10 0 should be considered a normal variant and do not require further evaluation. In addition, it should be kept in mind that labeling the child with a diagnosis of scoliosis may have implications with respect to future insurability. The majority of children with AIS will never require active treatment (less than 10%). The natural history is related to a number of factors: the age (maturity) of the patient, the location of the curve, the curve pattern, and the size of the curve. Younger patients have more potential growth and thus have a greater risk of curve progression. Curves in the thoracic region are stabilized by the ribs and thus are less likely to progress than lumbar and thoraco-lumbar curves. Double curves are more likely to progress than single curves, and larger curves are more likely to progress than smaller ones. Once the patient reaches skeletal maturity, curve progression slows dramatically or stops. Thoracic curves under 30 0 don’t progress after skeletal maturity. Those curves between 30 0 and 50 0 may progress but do so very slowly. However, thoracic curves between 50 0 and 75 0 have the greatest risk of progression and may do so at up to 1 0 per year. The biggest concern with thoracic curves is the loss of normal thoracic kyphosis. Loss of kyphosis with progression of the curve can result in a decrease in pulmonary function. This loss of function is measurable when the curve reaches 60 0 to 70 0 , but will not be noticeable to the patient until the curve reaches over 100 0 . Lumbar and thoraco-lumbar curves under 30 0 tend not to progress after maturity. Those greater than 30 0 will progress but the extent of progression is difficult to predict. They may result in a significant trunk asymmetry that is cosmetically displeasing to the patient and family. The association between curve magnitude and a decrease in pulmonary function only occurs with thoracic curves and does not apply to lumbar and thoraco-lumbar curves. Treatment may involve simple observation, bracing, or surgery. While exercises and electrical stimulation have been utilized in the past, there is no evidence that these modalities affect curve progression. In addition, recent literature has not shown any benefit from chiropractic manipulation. As the majority of AIS curves are small and thus have a low likelihood of progression, most patients will simply require regular follow-up visits with radiographs to look for curve progression. Bracing is instituted in skeletally immature patients in order to prevent the curve from achieving a magnitude that will continue to progress after maturity. Once the brace is removed, the curve usually returns to its prebrace magnitude. A brace is recommended when progression has been documented in curves under 30 0 , for those curves measuring 30 0 -40 0 on initial presentation, and occasionally for somewhat larger curves. Curves over 50 0 are likely to progress even after maturity and thus are generally not brace candidates. The current surgical treatment for scoliosis is spinal fusion, usually with instrumentation. The primary goal of fusion is to prevent further progression of the curve, and a secondary goal is to improve cosmetic appearance, usually by decreasing the size of the curve using rods, hooks, wires, and/or screws. Reducing the curve size is only important to the patient in how it affects their appearance, and this must be balanced with the risk of neurologic injury. As a general rule, the curve can safely be reduced by about 50% its original size. The indications for surgery vary and are related to curve magnitude, progression, curve pattern, and cosmetic appearance. Once a thoracic curve has reached 50 0 , the risk of progression after skeletal maturity is high and most of these patients should undergo fusion. Curves over 40 0 that progress in spite of bracing are also fusion candidates. The indications for surgery in the lumbar and thoraco-lumbar spine is more controversial. If little trunk imbalance is present, no intervention may be the best approach, as fusing into the lumbar spine significantly affects mobility and may increase the risk of back pain. However, curves that create significant trunk imbalance may be candidates for surgery from a cosmetic standpoint. The choice between posterior spinal fusion, anterior spinal fusion, or both is somewhat surgeon dependant and is also related to the location of the curve, risk factors for non- CONTINUED ON PAGE 26 8 / CALIFORNIA PEDIATRICIAN — SPRING 2003
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Page 3 and 4: TABLE OF CONTENTS continued Distric
Page 5 and 6: in and of itself, but I think you t
Page 7: CMA House of Delegates Report Paul
Page 11 and 12: A Low-Glycemic Index Diet in the Tr
Page 13 and 14: Why California’s MICRA Is Good fo
Page 15 and 16: The Tao of Pediatrics and Chinese M
Page 17 and 18: Chronic Pain in Children: A Multidi
Page 19 and 20: LUNG TRANSPLANTATION CONTINUED FROM
Page 21 and 22: Childcare Health Linkages Program:
Page 23 and 24: Annual Las Vegas Seminars — 25 Ye
Page 25 and 26: Early Hearing Detection and Interve
Page 27 and 28: THE TAO OF PEDIATRICS AND CHINESE M
Page 29 and 30: A LOW-GLYCEMIC INDEX DIET IN THE TR
Page 31 and 32: I write in late March, as American
Page 33 and 34: Nikta Forghani, M.D. Weighing the R
Page 35 and 36: COUNCIL ON CHILD HEALTH CHAPTER 1 B
Page 37: CALENDAR May 14, 2003 Los Angeles P

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