Disability and Health Journal 8 (2015) 642e645 www.disabilityandhealthjnl.com
Brief Report
Retrospective study of cumulative diagnostic radiation exposure during childhood in patients with spina bifida Gregory Smookler, M.D.a,b,c, and Alexis Deavenport-Saman, Dr.P.H., M.C.H.E.S.a,b,c,* a
Children’s Hospital Los Angeles, Department of Pediatrics, Los Angeles, CA, USA b USC Keck School of Medicine, Los Angeles, CA, USA c USC Center for Excellence in Developmental Disabilities, Los Angeles, CA, USA
Abstract Background: The Biological Effects of Ionizing Radiation Committee of the National Academy of Sciences in 2005 and other expert panels have warned that risk of cancer increases with higher doses of radiation. Children with spina bifida and hydrocephalus have far greater exposure to radiation than the average person, starting almost directly after birth and continuing throughout their lifetimes. Objective: The purpose of this study was to estimate the amount of ionizing radiation that patients with spina bifida and hydrocephalus are exposed to during childhood from diagnostic imaging. Methods: Thirty patients, ages 18 years or older, with spina bifida and hydrocephalus were randomly selected from a spina bifida clinic and their radiology records were reviewed. Descriptive analyses were conducted. The total radiation exposure was then calculated for the study group, and the mean effective dose per patient was determined. Results: In the study group, during their first 18 years, each patient had a mean of 55.1 studies and a median of 45 radiologic studies, a mean of 9.6 brain CT scans, and a mean cumulative effective dose of 81.9 mSv (2.6 mSv/patient/year over 18 years) and a median cumulative effective dose of 77.2 mSV of accumulated radiation exposure (4.5 mSv/patient/year over 18 years). Conclusions: Clinicians should recognize that increased radiation exposure puts patients with spina bifida and hydrocephalus at higher risk for cancer. The population of children and adults with spina bifida and hydrocephalus should be surveyed for incidence of cancer. Ó 2015 Elsevier Inc. All rights reserved. Keywords: Spina bifida; Hydrocephalus; Childhood; Cancer; Cumulative effective radiation dose
Diagnostic imaging using ionizing radiation is a crucial tool in the management of patients with spina bifida, starting almost directly from the time they are born. During their childhood, a patient with spina bifida will have multiple CT scans of the brain to assess for associated ArnoldChiari II malformation and hydrocephalus, and to evaluate the functioning of their ventriculoperitoneal shunt. They will also have an assessment of their neurogenic bladder with urodynamic studies and possible vessiculouretreral reflux via voiding cystourethrograms. Their skeleton will be X-rayed for orthopedic issues such as spinal curvature problems and hip sub-luxation. Hence, the patient with Statements of funding or conflicts of interest: We have no funding information or conflict-of-interest disclosures to report. Meeting abstracts: Smookler G. Review of cumulative diagnostic radiation exposure during childhood in patients with spina bifida. Cerebrospinal Fluid Res. 2009;6:S36. * Corresponding author. Children’s Hospital Los Angeles, Department of Pediatrics, 4650 Sunset Boulevard, #76, Los Angeles, CA 90027, USA. Fax: þ1 323 361 4429. E-mail address: [email protected] (A. Deavenport-Saman). 1936-6574/$ - see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.dhjo.2015.04.002
spina bifida will have a much greater exposure to radiation than the average person during their childhood.1 The generally increasing usage of radiologic imaging,2,3 particularly CT scanning,4 and its possible risks in children5,6 and adults7 have been a concern for some time. In response to concerns, radiologists have been trying to adjust their techniques8 in order to use the safest and most appropriate doses of radiation when imaging children.9e11 It has long been recognized that children are especially vulnerable due to increased sensitivity of growing tissues, possible long latency periods, and smaller cross-sectional areas exposed to radiation, than adults.12 Studies examining the frequency13 and risks of radiation exposure from computerized tomography in children have shown an increased incidence of cancer.14e18 Pearce et al published the first large-scale study in Lancet demonstrating evidence of increased risk of cancer in children from medical imaging; this study showed significant increases in leukemia incidence in children with cumulative bone marrow doses of at least 30 mSv, and significant brain tumor incidence in children with brain
G. Smookler and A. Deavenport-Saman / Disability and Health Journal 8 (2015) 642e645 16
doses of at least 50 mSv. Aalst et al found that the mean cumulative effective dose for a child with spinal dysraphism, was 23 mSv, with a range from 0.1 to 103 mSv.19 Holmedal et al noted that the mean effective dose among children with spinal dysraphism that had CT scans was 3.2 mSV for children below 6 months of age, and 1.2 mSV for children above 6 months of age; the effective dose per CT scan differed by a factor of 64.20 Brambilla et al conducted a systematic review indicating that the annual cumulative effective dose for patients with cerebrospinal fluid shunts and was less than 3 mSV per year.21 There is limited data, however, about the total amount of ionizing radiation that children with spina bifida and hydrocephalus are exposed to during childhood. Thus, the purpose of this study was to estimate the amount of ionizing radiation that patients with spina bifida and hydrocephalus are exposed to in their first 18 years of life from diagnostic imaging.
Method Design and setting This was an observational retrospective cohort study examining the cumulative effective dose of radiation of children with spina bifida and hydrocephalus, starting in 2009. The spina bifida program is located within an urban, tertiary care children’s hospital and is one of the largest centers in the world (with almost 500 patients).
643
Data collection The radiologic records of each of the 30 subjects were reviewed and the total number of imaging studies involving ionizing radiation (CT of the brain, voiding cystourethrogram, chest X-ray, abdominal X-ray, limb X-ray, spine X-ray, and CT of the abdomen/pelvis) were noted. Measurement and outcomes Using standard values22 for the amount of radiation involved in each study, each recorded study was converted into a radiation dose, e.g. one CT of the head has a range of 2e4 milliSieverts (mSV). The milliSievert is the effective dose based on the radio-sensitivity of each exposed organ of radiation in partial irradiations. While some research studies examining more recent data may report the dose length product of each individual examination, the data collected in this study was from an 18-year period from 1991 to 2009; technology has changed over time and some of the records did not have information documented about effective dose and the number of studies. Thus, we used the standard values to calculate the effective dose per study per patient, which tends to be a more conservative estimate. The cumulative effective dose was then determined by adding up all of the individual doses over the 18-year period. The cumulative effective dose per patient was then averaged among the 30 subjects, determining the mean cumulative effective dose of ionizing radiation during childhood for a patient with spina bifida and hydrocephalus. The study was approved by the hospital Institutional Review Board. Analysis
Sample There were 452 patients in the spina bifida clinic. Of these, 66 patients were over 18 years or above and 30 were randomly selected to retrospectively review their radiographic histories. Starting in 2009, patients were randomly selected to examine their radiation exposure periods during their first 18 years of life. Patient charts were randomly selected until the projected sample size was reached. Inclusion criteria were that patients were 18 years of age or above, had spina bifida (myelomeningocele) and hydrocephalus, and had been receiving their care at the spina bifida program since at least one year of age. Exclusion criteria were that they were less than 18 years of age, and had any other significant chronic illness not related to spina bifida and hydrocephalus (e.g. cystic fibrosis, cancer, congenital heart disease, chronic lung disease). To address potential sources of bias, we excluded chronic illnesses not related to spina bifida and hydrocephalus, such as cancer, as we wanted to quantify radiation dose only as it related to their spina bifida. Therefore, if they had any other radiation exposure, it wouldn’t have been related to their spina bifida and hydrocephalus.
Descriptive analyses were conducted. The mean (standard deviation [SD]) and median (interquartile range [IR]) number of radiologic studies were calculated to estimate the number of studies that patients with spina bifida and hydrocephalus have in their first 18 years of life. The mean (SD) and median (IR) cumulative effective radiation dose per child over the first 18 years of life to estimate the amount of ionizing radiation that patients with spina bifida and hydrocephalus are exposed to in their first 18 years of life from diagnostic imaging.
Results The majority of the patients, or over 80%, were of Hispanic descent. Of the patients who were excluded from the study, there were no patients with spina bifida and hydrocephalus who had cancer. Exposure to radiation was from the following diagnostic tests: CT scans of the brain, voiding cystourethrograms (VCUGs), chest X-ray, abdominal X-rays, spine X-rays, Limb X-rays, and CT scans of the abdomen or pelvis. In the study group, during their first 18 years, each patient had a mean of 55.1 (standard
644
G. Smookler and A. Deavenport-Saman / Disability and Health Journal 8 (2015) 642e645
Table 1 Mean and median number of radiologic studies over the first 18 years of life CT VCUG CXR
Mean (SD) number of studies Median (IR) number of studies
ABD
LIMB
SPINE
CT ABD/PEL
(n 5 29)
(n 5 30)
(n 5 10)
(n 5 15)
(n 5 16)
(n 5 21)
(n 5 7)
9.6 (5.3) 8 (6e11)
11.6 (5.4) 12 (8e16)
10.7 (12.8) 6 (3.5e13)
6.2 (5.5) 4 (2e10)
8.1 (3.9) 8 (4e11)
6.2 (0.33) 4 (2e9.5)
2.7 (1.7) 3 (1e3)
CT e Computerized tomography; VCUG e voiding cystourethrogram, CXR e Chest X-ray; ABD e Abdominal X-ray; LIMB e Limb X-ray; SPINE e Spine X-ray; CT ABD/PEL e CT of the abdomen/pelvis; IR e Inter-quartile range.
deviation [SD] 11.5) radiologic studies, with the most studies in the following areas: 11.6 (5.6) VCUGs, 10.7 (12.8) chest X-rays, 9.6 (5.3) CT scans of the brain, and 8.1 (3.9) limb X-rays (Table 1). The medians and interquartile ranges are also presented in Table 1, as the distribution of radiation exposures are frequently right-skewed and the mean is often higher than the median. There were 1.8 studies per patient per year for 18 years. They were exposed to 81.9 mSv (2.6 mSv per patient per year over 18 years) of cumulative radiation exposure. Patients who had CT scans were exposed to an a mean cumulative effective dose of 19.9 mSV (11.2) of radiation, patients with VCUGs were exposed to 18.4 mSV (8.6) of radiation, patients with spinal X-rays were exposed to 11.5 mSV (8.8) of radiation, and patients with CT scans of the abdomen or pelvis were exposed to 27.1 mSV (17) of radiation (Table 2).
Discussion Children with spina bifida and hydrocephalus have had increased exposure to ionizing radiation from medical imaging. Children are particularly vulnerable due to the exposure to smaller cross-sectional areas, possible long latency periods, and increased sensitivity of growing tissues.4,12,23 A study in 200110 showed that 30% of Americans have had 3 CT scans, 7% have had 5, and 4% have had 9. Assuming the typical doses used in 2001, the researchers suggested that 2e3 head CT’s could triple the risk of brain cancer and that 5e10 could triple the risk of leukemia.14 Our study showed that children with spina bifida and hydrocephalus had a mean of 9.6 CT scans over eighteen years, more than 96% of the total population has in their entire lifetime.
Gaskill and Martin showed that their spina bifida patients had a mean of 3.6 CT scans of the brain during their lifetime.1 The average patient with spina bifida and hydrocephalus has more CTs of the brain than the majority of the total population has had all CT scans in their lifetime, and patients are averaging almost 3 times the number of head CTs than there were 10 years ago. Radiologists (mostly led by pediatric radiologists) have been implementing guidelines for optimizing techniques to make medical radiation as safe as possible through programs such as Image Wisely24 and Image Gently.10,25 Neurosurgeons are also taking steps to reduce the placement of VP shunts, and to use MRI modalities26 to evaluate shunt functioning. Recent research into the long-term effects of therapeutic exposures in pediatric cancer patients have shown that radiation can also impact the endocrine and pulmonary systems, plus increase the risk of solid tumors.27 During the study follow-up period of a large-scale study, Pearce et al demonstrated increased risk of cancer in children who received CT scans: 74 of 178,604 patients were diagnosed with leukemia and 135 of 176,587 patients were diagnosed with brain tumors.16 Matthews et al assessed the cancer risk in children and adolescents after exposure to low dose ionizing radiation from CT scans. The incidence rate ratio significantly increased for various types of solid tumors in the brain, urinary tract, female genital area, thyroid, digestive organs, and soft tissue, as well as for myelodysplasia and leukemia.15 CT scanning and other radiologic procedures continue to be highly valuable and often lifesaving diagnostic tools. However, risks from radiation from diagnostic imaging studies are small but real. We need to continue efforts to justify and optimize every dose of ionizing radiation. It is important for clinicians to understand the magnitude of exposure to diagnostic radiation in
Table 2 Mean and median cumulative effective radiation dose per child over the first 18 years of life CT VCUG CXR ABD
Mean (SD) cumulative effective radiation dosea Median cumulative (IR) effective radiation dose
LIMB
SPINE
CT ABD/PEL
(n 5 29)
(n 5 30)
(n 5 10)
(n 5 15)
(n 5 16)
(n 5 20)
(n 5 7)
19.9 (11.2)
18.4 (8.6)
0.6 (0.8)
3.9 (3.9)
0.5 (0.3)
11.5 (8.8)
27.1 (17)
16.8 (12.6e23.1)
19.2 (12.8e25.6)
0.4 (0.2e0.8)
2.8 (1.4e7)
0.5 (0.2e0.7)
7.5 (3.6e17.6)
30 (10e30)
CT e Computerized tomography; VCUG e voiding cystourethrogram, CXR e Chest X-ray; ABD e Abdominal X-ray; LIMB e Limb X-ray; SPINE e Spine X-ray; CT ABD/PEL e CT of the Abdomen/Pelvis; IR e Inter-quartile range. a Cumulative effective radiation dose was measured in milliSieverts (mSv).
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children with spina bifida in order to exercise prudence when ordering radiologic studies.23 Clinicians caring for children and adults with spina bifida should be cognizant that their patients have significant risk factors for the development of malignancies, especially those known to be related to radiation exposure such as leukemia and lymphoma. This will help clinicians to provide timely screening for early detection for these conditions. While radiologic studies were examined from one of the largest spina bifida programs in the U.S., with close to 500 patients, data were from one hospital, so the number of studies and amount of radiation exposure may be an underestimate. In addition, given changes in clinical practice and technology over an eighteen-year period, the standard values were used to calculate the effective dose per study per patient, which tends to be a more conservative estimate than the dose length product. Given the descriptive nature of the study, there was no comparison group. Clinicians need to recognize that increased radiation exposure puts patients with spina bifida and hydrocephalus at greater risk for cancer. The population of children and adults with spina bifida and hydrocephalus should be surveyed for incidence of cancer. Radiologists should be utilized as expert consultants to provide optimal imaging modalities. As awareness of this issue grows, future researchers should follow-up on changes in practice. References 1. Gaskill SJ, Marlin AE. Radiation exposure in the myelomenigocele population. Pediatr Neurosurg. 1998;28:63e66. 2. Smith-Bindman R, Miglioretti DL, Johnson E, et al. Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems, 1996e2010. J Am Med Assoc. 2012;307:2400e2409. 3. Dorfman AL, Fazel R, Einstein AJ, et al. Use of medical imaging procedures with ionizing radiation in children. Arch Pediatr Adolesc Med. 2011;165:459e463. 4. Brenner DJ, Hall EJ. Computed tomography-An increasing source of radiation exposure. N Engl J Med. 2007;357:2277e2284. 5. Brody AS. Radiation risk from diagnostic imaging. Pediatr Ann. 2002;10:643e647. 6. Brody AS, Frush DP, Huda W, Brent RL; American Academy of Pediatrics Section on Radiology. Radiation risks to children from computed tomography. Pediatrics. 2007;120:677e682. 7. Sodickson A, Baeyens PF, Andriole KP, et al. Recurrent CT, cumulative radiation exposure, and associated radiation-induced cancer risks from CT of adults. Radiology. 2009;251:175e184. 8. Patterson A, Frush DP, Donnely LF. Helical CT of the body: are settings adjusted for pediatric patients? Am J Roentgenol. 2001;176: 297e301. 9. The Society for Pediatric Radiology. ‘‘Child-size’’ Radiation Dose for Pediatric CT Exams Included in NQF 2009 Safe Practices for Better Healthcare. [Internet] [cited 2014 Sep 15]. Available from: www. pedrad.org/; 2009.
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10. Strauss KJ, Goske MJ, Bulas D, et al. Image gently: ten steps you can take to optimize image quality and lower CT dose for pediatric patients. Am J Roentgenol. 2010;194:864e873. 11. Antypas EJ, Sokhandon F, Farah M, et al. A comprehensive approach to CT radiation dose reduction: one institution’s experience. Am J Roentgenol. 2011;197:935e940. 12. The National Cancer Institute. Radiation Risks and Pediatric Computed Tomography (CT): A Guide for Health Care Providers. [Internet] [cited 2014 Sep 15]. Available from: http://www.cancer. gov/cancertopics/causes/radiation/radiation-risks-pediatric-CT; 2012 June 7. 13. Townsend BA, Callahan MJ, Zurakowski D, Taylor GA. Has pediatric CT at children’s hospitals reached its Peak? Am J Roentgenol. 2010;194:1194e1196. 14. Brenner DJ, Elliston C, Hall E, Berdon W. Estimated risks of radiation-induced fatal cancer from pediatric CT. Am J Roentgenol. 2001;176:289e296. 15. Matthews JD, Forsythe AV, Brady Z, et al. Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians. BMJ. 2013;346: 1e18. 16. Pearce MS, Salotti JA, Little MP, et al. Radiation exposure from CT scans in childhood and subsequent risk of leukemia and brain tumors: a retrospective cohort study. Lancet. 2012;380:499e505. 17. Einstein AJ. Beyond the bombs: cancer risks of low-dose medical radiation. Lancet. 2012;380:455e457. 18. Goske M, Applegate K, Frush D, Schulman MH, Morrison G. CT scans in childhood and risk of leukaemia and brain tumours. Lancet. 2012;380:1737e1738. 19. Aalst J, Jeukens CR, Vles JS, et al. Diagnostic radiation exposure in children with spinal dysraphism: an estimation of the cumulative effective dose in a cohort of 135 children from The Netherlands. Arch Dis Child. 2013;98:680e685. 20. Holmedal LJ, Friberg EG, Børretzen I, Olerud H, Laegreid L, Rosendahl K. Radiation doses to children with shunt-treated hydrocephalus. Pediatr Radiol. 2007;37:1209e1215. 21. Brambilla M, De Mauri A, Lizio D, et al. Cumulative radiation dose estimates from medical imaging in paediatric patients with nononcologic chronic illnesses. A systematic review. Phys Med. 2014;30:403e412. 22. Health Physics Society. Radiation Exposure from Medical Diagnostic Imaging Procedures: Health Physics Society Fact Sheet. [Internet] [cited 2014 Sep 15]. Available from: http://hps.org/documents/ meddiagimaging.pdf; 2010 Jan. 23. Smookler G. Review of cumulative diagnostic radiation exposure during childhood in patients with spina bifida. Cerebrospinal Fluid Res. 2009;6:S36. 24. Image Wisely. Radiation Safety in Adult Medical Imaging. [Internet] [cited 2014 Sep 15]. Available from: http://www.imagewisely.org/; 2014. 25. Image Gently. The Alliance for Radiation Safety in Pediatric Imaging. [Internet] [cited 2014 Sep 15]. Available from: http://www. imagegently.org/; 2014. 26. Koral K, Blackburn T, Bailey AA, Koral KM, Anderson J. Strengthening the argument for rapid brain MR imaging: estimation of reduction in lifetime attributable risk of developing fatal cancer in children with shunted hydrocephalus by instituting a rapid brain MR imaging protocol in lieu of Head CT. AJNR Am J Neuroradiol. 2012;33: 1851e1854. 27. Bhatia S. Long-term complications of therapeutic exposures in childhood: lessons learned from childhood cancer survivors. Pediatrics. 2012;130:1141e1143.
Brief Report
Retrospective study of cumulative diagnostic radiation exposure during childhood in patients with spina bifida Gregory Smookler, M.D.a,b,c, and Alexis Deavenport-Saman, Dr.P.H., M.C.H.E.S.a,b,c,* a
Children’s Hospital Los Angeles, Department of Pediatrics, Los Angeles, CA, USA b USC Keck School of Medicine, Los Angeles, CA, USA c USC Center for Excellence in Developmental Disabilities, Los Angeles, CA, USA
Abstract Background: The Biological Effects of Ionizing Radiation Committee of the National Academy of Sciences in 2005 and other expert panels have warned that risk of cancer increases with higher doses of radiation. Children with spina bifida and hydrocephalus have far greater exposure to radiation than the average person, starting almost directly after birth and continuing throughout their lifetimes. Objective: The purpose of this study was to estimate the amount of ionizing radiation that patients with spina bifida and hydrocephalus are exposed to during childhood from diagnostic imaging. Methods: Thirty patients, ages 18 years or older, with spina bifida and hydrocephalus were randomly selected from a spina bifida clinic and their radiology records were reviewed. Descriptive analyses were conducted. The total radiation exposure was then calculated for the study group, and the mean effective dose per patient was determined. Results: In the study group, during their first 18 years, each patient had a mean of 55.1 studies and a median of 45 radiologic studies, a mean of 9.6 brain CT scans, and a mean cumulative effective dose of 81.9 mSv (2.6 mSv/patient/year over 18 years) and a median cumulative effective dose of 77.2 mSV of accumulated radiation exposure (4.5 mSv/patient/year over 18 years). Conclusions: Clinicians should recognize that increased radiation exposure puts patients with spina bifida and hydrocephalus at higher risk for cancer. The population of children and adults with spina bifida and hydrocephalus should be surveyed for incidence of cancer. Ó 2015 Elsevier Inc. All rights reserved. Keywords: Spina bifida; Hydrocephalus; Childhood; Cancer; Cumulative effective radiation dose
Diagnostic imaging using ionizing radiation is a crucial tool in the management of patients with spina bifida, starting almost directly from the time they are born. During their childhood, a patient with spina bifida will have multiple CT scans of the brain to assess for associated ArnoldChiari II malformation and hydrocephalus, and to evaluate the functioning of their ventriculoperitoneal shunt. They will also have an assessment of their neurogenic bladder with urodynamic studies and possible vessiculouretreral reflux via voiding cystourethrograms. Their skeleton will be X-rayed for orthopedic issues such as spinal curvature problems and hip sub-luxation. Hence, the patient with Statements of funding or conflicts of interest: We have no funding information or conflict-of-interest disclosures to report. Meeting abstracts: Smookler G. Review of cumulative diagnostic radiation exposure during childhood in patients with spina bifida. Cerebrospinal Fluid Res. 2009;6:S36. * Corresponding author. Children’s Hospital Los Angeles, Department of Pediatrics, 4650 Sunset Boulevard, #76, Los Angeles, CA 90027, USA. Fax: þ1 323 361 4429. E-mail address: [email protected] (A. Deavenport-Saman). 1936-6574/$ - see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.dhjo.2015.04.002
spina bifida will have a much greater exposure to radiation than the average person during their childhood.1 The generally increasing usage of radiologic imaging,2,3 particularly CT scanning,4 and its possible risks in children5,6 and adults7 have been a concern for some time. In response to concerns, radiologists have been trying to adjust their techniques8 in order to use the safest and most appropriate doses of radiation when imaging children.9e11 It has long been recognized that children are especially vulnerable due to increased sensitivity of growing tissues, possible long latency periods, and smaller cross-sectional areas exposed to radiation, than adults.12 Studies examining the frequency13 and risks of radiation exposure from computerized tomography in children have shown an increased incidence of cancer.14e18 Pearce et al published the first large-scale study in Lancet demonstrating evidence of increased risk of cancer in children from medical imaging; this study showed significant increases in leukemia incidence in children with cumulative bone marrow doses of at least 30 mSv, and significant brain tumor incidence in children with brain
G. Smookler and A. Deavenport-Saman / Disability and Health Journal 8 (2015) 642e645 16
doses of at least 50 mSv. Aalst et al found that the mean cumulative effective dose for a child with spinal dysraphism, was 23 mSv, with a range from 0.1 to 103 mSv.19 Holmedal et al noted that the mean effective dose among children with spinal dysraphism that had CT scans was 3.2 mSV for children below 6 months of age, and 1.2 mSV for children above 6 months of age; the effective dose per CT scan differed by a factor of 64.20 Brambilla et al conducted a systematic review indicating that the annual cumulative effective dose for patients with cerebrospinal fluid shunts and was less than 3 mSV per year.21 There is limited data, however, about the total amount of ionizing radiation that children with spina bifida and hydrocephalus are exposed to during childhood. Thus, the purpose of this study was to estimate the amount of ionizing radiation that patients with spina bifida and hydrocephalus are exposed to in their first 18 years of life from diagnostic imaging.
Method Design and setting This was an observational retrospective cohort study examining the cumulative effective dose of radiation of children with spina bifida and hydrocephalus, starting in 2009. The spina bifida program is located within an urban, tertiary care children’s hospital and is one of the largest centers in the world (with almost 500 patients).
643
Data collection The radiologic records of each of the 30 subjects were reviewed and the total number of imaging studies involving ionizing radiation (CT of the brain, voiding cystourethrogram, chest X-ray, abdominal X-ray, limb X-ray, spine X-ray, and CT of the abdomen/pelvis) were noted. Measurement and outcomes Using standard values22 for the amount of radiation involved in each study, each recorded study was converted into a radiation dose, e.g. one CT of the head has a range of 2e4 milliSieverts (mSV). The milliSievert is the effective dose based on the radio-sensitivity of each exposed organ of radiation in partial irradiations. While some research studies examining more recent data may report the dose length product of each individual examination, the data collected in this study was from an 18-year period from 1991 to 2009; technology has changed over time and some of the records did not have information documented about effective dose and the number of studies. Thus, we used the standard values to calculate the effective dose per study per patient, which tends to be a more conservative estimate. The cumulative effective dose was then determined by adding up all of the individual doses over the 18-year period. The cumulative effective dose per patient was then averaged among the 30 subjects, determining the mean cumulative effective dose of ionizing radiation during childhood for a patient with spina bifida and hydrocephalus. The study was approved by the hospital Institutional Review Board. Analysis
Sample There were 452 patients in the spina bifida clinic. Of these, 66 patients were over 18 years or above and 30 were randomly selected to retrospectively review their radiographic histories. Starting in 2009, patients were randomly selected to examine their radiation exposure periods during their first 18 years of life. Patient charts were randomly selected until the projected sample size was reached. Inclusion criteria were that patients were 18 years of age or above, had spina bifida (myelomeningocele) and hydrocephalus, and had been receiving their care at the spina bifida program since at least one year of age. Exclusion criteria were that they were less than 18 years of age, and had any other significant chronic illness not related to spina bifida and hydrocephalus (e.g. cystic fibrosis, cancer, congenital heart disease, chronic lung disease). To address potential sources of bias, we excluded chronic illnesses not related to spina bifida and hydrocephalus, such as cancer, as we wanted to quantify radiation dose only as it related to their spina bifida. Therefore, if they had any other radiation exposure, it wouldn’t have been related to their spina bifida and hydrocephalus.
Descriptive analyses were conducted. The mean (standard deviation [SD]) and median (interquartile range [IR]) number of radiologic studies were calculated to estimate the number of studies that patients with spina bifida and hydrocephalus have in their first 18 years of life. The mean (SD) and median (IR) cumulative effective radiation dose per child over the first 18 years of life to estimate the amount of ionizing radiation that patients with spina bifida and hydrocephalus are exposed to in their first 18 years of life from diagnostic imaging.
Results The majority of the patients, or over 80%, were of Hispanic descent. Of the patients who were excluded from the study, there were no patients with spina bifida and hydrocephalus who had cancer. Exposure to radiation was from the following diagnostic tests: CT scans of the brain, voiding cystourethrograms (VCUGs), chest X-ray, abdominal X-rays, spine X-rays, Limb X-rays, and CT scans of the abdomen or pelvis. In the study group, during their first 18 years, each patient had a mean of 55.1 (standard
644
G. Smookler and A. Deavenport-Saman / Disability and Health Journal 8 (2015) 642e645
Table 1 Mean and median number of radiologic studies over the first 18 years of life CT VCUG CXR
Mean (SD) number of studies Median (IR) number of studies
ABD
LIMB
SPINE
CT ABD/PEL
(n 5 29)
(n 5 30)
(n 5 10)
(n 5 15)
(n 5 16)
(n 5 21)
(n 5 7)
9.6 (5.3) 8 (6e11)
11.6 (5.4) 12 (8e16)
10.7 (12.8) 6 (3.5e13)
6.2 (5.5) 4 (2e10)
8.1 (3.9) 8 (4e11)
6.2 (0.33) 4 (2e9.5)
2.7 (1.7) 3 (1e3)
CT e Computerized tomography; VCUG e voiding cystourethrogram, CXR e Chest X-ray; ABD e Abdominal X-ray; LIMB e Limb X-ray; SPINE e Spine X-ray; CT ABD/PEL e CT of the abdomen/pelvis; IR e Inter-quartile range.
deviation [SD] 11.5) radiologic studies, with the most studies in the following areas: 11.6 (5.6) VCUGs, 10.7 (12.8) chest X-rays, 9.6 (5.3) CT scans of the brain, and 8.1 (3.9) limb X-rays (Table 1). The medians and interquartile ranges are also presented in Table 1, as the distribution of radiation exposures are frequently right-skewed and the mean is often higher than the median. There were 1.8 studies per patient per year for 18 years. They were exposed to 81.9 mSv (2.6 mSv per patient per year over 18 years) of cumulative radiation exposure. Patients who had CT scans were exposed to an a mean cumulative effective dose of 19.9 mSV (11.2) of radiation, patients with VCUGs were exposed to 18.4 mSV (8.6) of radiation, patients with spinal X-rays were exposed to 11.5 mSV (8.8) of radiation, and patients with CT scans of the abdomen or pelvis were exposed to 27.1 mSV (17) of radiation (Table 2).
Discussion Children with spina bifida and hydrocephalus have had increased exposure to ionizing radiation from medical imaging. Children are particularly vulnerable due to the exposure to smaller cross-sectional areas, possible long latency periods, and increased sensitivity of growing tissues.4,12,23 A study in 200110 showed that 30% of Americans have had 3 CT scans, 7% have had 5, and 4% have had 9. Assuming the typical doses used in 2001, the researchers suggested that 2e3 head CT’s could triple the risk of brain cancer and that 5e10 could triple the risk of leukemia.14 Our study showed that children with spina bifida and hydrocephalus had a mean of 9.6 CT scans over eighteen years, more than 96% of the total population has in their entire lifetime.
Gaskill and Martin showed that their spina bifida patients had a mean of 3.6 CT scans of the brain during their lifetime.1 The average patient with spina bifida and hydrocephalus has more CTs of the brain than the majority of the total population has had all CT scans in their lifetime, and patients are averaging almost 3 times the number of head CTs than there were 10 years ago. Radiologists (mostly led by pediatric radiologists) have been implementing guidelines for optimizing techniques to make medical radiation as safe as possible through programs such as Image Wisely24 and Image Gently.10,25 Neurosurgeons are also taking steps to reduce the placement of VP shunts, and to use MRI modalities26 to evaluate shunt functioning. Recent research into the long-term effects of therapeutic exposures in pediatric cancer patients have shown that radiation can also impact the endocrine and pulmonary systems, plus increase the risk of solid tumors.27 During the study follow-up period of a large-scale study, Pearce et al demonstrated increased risk of cancer in children who received CT scans: 74 of 178,604 patients were diagnosed with leukemia and 135 of 176,587 patients were diagnosed with brain tumors.16 Matthews et al assessed the cancer risk in children and adolescents after exposure to low dose ionizing radiation from CT scans. The incidence rate ratio significantly increased for various types of solid tumors in the brain, urinary tract, female genital area, thyroid, digestive organs, and soft tissue, as well as for myelodysplasia and leukemia.15 CT scanning and other radiologic procedures continue to be highly valuable and often lifesaving diagnostic tools. However, risks from radiation from diagnostic imaging studies are small but real. We need to continue efforts to justify and optimize every dose of ionizing radiation. It is important for clinicians to understand the magnitude of exposure to diagnostic radiation in
Table 2 Mean and median cumulative effective radiation dose per child over the first 18 years of life CT VCUG CXR ABD
Mean (SD) cumulative effective radiation dosea Median cumulative (IR) effective radiation dose
LIMB
SPINE
CT ABD/PEL
(n 5 29)
(n 5 30)
(n 5 10)
(n 5 15)
(n 5 16)
(n 5 20)
(n 5 7)
19.9 (11.2)
18.4 (8.6)
0.6 (0.8)
3.9 (3.9)
0.5 (0.3)
11.5 (8.8)
27.1 (17)
16.8 (12.6e23.1)
19.2 (12.8e25.6)
0.4 (0.2e0.8)
2.8 (1.4e7)
0.5 (0.2e0.7)
7.5 (3.6e17.6)
30 (10e30)
CT e Computerized tomography; VCUG e voiding cystourethrogram, CXR e Chest X-ray; ABD e Abdominal X-ray; LIMB e Limb X-ray; SPINE e Spine X-ray; CT ABD/PEL e CT of the Abdomen/Pelvis; IR e Inter-quartile range. a Cumulative effective radiation dose was measured in milliSieverts (mSv).
G. Smookler and A. Deavenport-Saman / Disability and Health Journal 8 (2015) 642e645
children with spina bifida in order to exercise prudence when ordering radiologic studies.23 Clinicians caring for children and adults with spina bifida should be cognizant that their patients have significant risk factors for the development of malignancies, especially those known to be related to radiation exposure such as leukemia and lymphoma. This will help clinicians to provide timely screening for early detection for these conditions. While radiologic studies were examined from one of the largest spina bifida programs in the U.S., with close to 500 patients, data were from one hospital, so the number of studies and amount of radiation exposure may be an underestimate. In addition, given changes in clinical practice and technology over an eighteen-year period, the standard values were used to calculate the effective dose per study per patient, which tends to be a more conservative estimate than the dose length product. Given the descriptive nature of the study, there was no comparison group. Clinicians need to recognize that increased radiation exposure puts patients with spina bifida and hydrocephalus at greater risk for cancer. The population of children and adults with spina bifida and hydrocephalus should be surveyed for incidence of cancer. Radiologists should be utilized as expert consultants to provide optimal imaging modalities. As awareness of this issue grows, future researchers should follow-up on changes in practice. References 1. Gaskill SJ, Marlin AE. Radiation exposure in the myelomenigocele population. Pediatr Neurosurg. 1998;28:63e66. 2. Smith-Bindman R, Miglioretti DL, Johnson E, et al. Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems, 1996e2010. J Am Med Assoc. 2012;307:2400e2409. 3. Dorfman AL, Fazel R, Einstein AJ, et al. Use of medical imaging procedures with ionizing radiation in children. Arch Pediatr Adolesc Med. 2011;165:459e463. 4. Brenner DJ, Hall EJ. Computed tomography-An increasing source of radiation exposure. N Engl J Med. 2007;357:2277e2284. 5. Brody AS. Radiation risk from diagnostic imaging. Pediatr Ann. 2002;10:643e647. 6. Brody AS, Frush DP, Huda W, Brent RL; American Academy of Pediatrics Section on Radiology. Radiation risks to children from computed tomography. Pediatrics. 2007;120:677e682. 7. Sodickson A, Baeyens PF, Andriole KP, et al. Recurrent CT, cumulative radiation exposure, and associated radiation-induced cancer risks from CT of adults. Radiology. 2009;251:175e184. 8. Patterson A, Frush DP, Donnely LF. Helical CT of the body: are settings adjusted for pediatric patients? Am J Roentgenol. 2001;176: 297e301. 9. The Society for Pediatric Radiology. ‘‘Child-size’’ Radiation Dose for Pediatric CT Exams Included in NQF 2009 Safe Practices for Better Healthcare. [Internet] [cited 2014 Sep 15]. Available from: www. pedrad.org/; 2009.
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10. Strauss KJ, Goske MJ, Bulas D, et al. Image gently: ten steps you can take to optimize image quality and lower CT dose for pediatric patients. Am J Roentgenol. 2010;194:864e873. 11. Antypas EJ, Sokhandon F, Farah M, et al. A comprehensive approach to CT radiation dose reduction: one institution’s experience. Am J Roentgenol. 2011;197:935e940. 12. The National Cancer Institute. Radiation Risks and Pediatric Computed Tomography (CT): A Guide for Health Care Providers. [Internet] [cited 2014 Sep 15]. Available from: http://www.cancer. gov/cancertopics/causes/radiation/radiation-risks-pediatric-CT; 2012 June 7. 13. Townsend BA, Callahan MJ, Zurakowski D, Taylor GA. Has pediatric CT at children’s hospitals reached its Peak? Am J Roentgenol. 2010;194:1194e1196. 14. Brenner DJ, Elliston C, Hall E, Berdon W. Estimated risks of radiation-induced fatal cancer from pediatric CT. Am J Roentgenol. 2001;176:289e296. 15. Matthews JD, Forsythe AV, Brady Z, et al. Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians. BMJ. 2013;346: 1e18. 16. Pearce MS, Salotti JA, Little MP, et al. Radiation exposure from CT scans in childhood and subsequent risk of leukemia and brain tumors: a retrospective cohort study. Lancet. 2012;380:499e505. 17. Einstein AJ. Beyond the bombs: cancer risks of low-dose medical radiation. Lancet. 2012;380:455e457. 18. Goske M, Applegate K, Frush D, Schulman MH, Morrison G. CT scans in childhood and risk of leukaemia and brain tumours. Lancet. 2012;380:1737e1738. 19. Aalst J, Jeukens CR, Vles JS, et al. Diagnostic radiation exposure in children with spinal dysraphism: an estimation of the cumulative effective dose in a cohort of 135 children from The Netherlands. Arch Dis Child. 2013;98:680e685. 20. Holmedal LJ, Friberg EG, Børretzen I, Olerud H, Laegreid L, Rosendahl K. Radiation doses to children with shunt-treated hydrocephalus. Pediatr Radiol. 2007;37:1209e1215. 21. Brambilla M, De Mauri A, Lizio D, et al. Cumulative radiation dose estimates from medical imaging in paediatric patients with nononcologic chronic illnesses. A systematic review. Phys Med. 2014;30:403e412. 22. Health Physics Society. Radiation Exposure from Medical Diagnostic Imaging Procedures: Health Physics Society Fact Sheet. [Internet] [cited 2014 Sep 15]. Available from: http://hps.org/documents/ meddiagimaging.pdf; 2010 Jan. 23. Smookler G. Review of cumulative diagnostic radiation exposure during childhood in patients with spina bifida. Cerebrospinal Fluid Res. 2009;6:S36. 24. Image Wisely. Radiation Safety in Adult Medical Imaging. [Internet] [cited 2014 Sep 15]. Available from: http://www.imagewisely.org/; 2014. 25. Image Gently. The Alliance for Radiation Safety in Pediatric Imaging. [Internet] [cited 2014 Sep 15]. Available from: http://www. imagegently.org/; 2014. 26. Koral K, Blackburn T, Bailey AA, Koral KM, Anderson J. Strengthening the argument for rapid brain MR imaging: estimation of reduction in lifetime attributable risk of developing fatal cancer in children with shunted hydrocephalus by instituting a rapid brain MR imaging protocol in lieu of Head CT. AJNR Am J Neuroradiol. 2012;33: 1851e1854. 27. Bhatia S. Long-term complications of therapeutic exposures in childhood: lessons learned from childhood cancer survivors. Pediatrics. 2012;130:1141e1143.
