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A Two-Edged Sword? Radiation-induced cancer risks from pediatric CT David Brenner

A Two-Edged Sword? Radiation-induced cancer risks from pediatric CT David Brenner Columbia University, New York Lecture can be downloaded from www.columbia.edu/~djb3. Pediatric CT: Very different from adult CT – or any other radiological exam. Organ doses much larger than for adults

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A Two-Edged Sword? Radiation-induced cancer risks from pediatric CT David Brenner

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  1. A Two-Edged Sword? Radiation-induced cancer risks from pediatric CTDavid Brenner Columbia University, New York Lecture can be downloaded fromwww.columbia.edu/~djb3

  2. Pediatric CT: Very different from adult CT – or any other radiological exam • Organ doses much larger than for adults • Pediatric CT usage is increasing rapidly, mostly in children who have many years of life in front of them • Children are much more sensitive to radiation-induced cancer than adults 2

  3. For a given mAs, doses from CT are larger for children than for adults Different-energy X rays: Adult Different-energy X rays: Child 3

  4. Pediatric CT Scans1989:~4% of all CT scans 1993:~6%2000: ~11%About 2.7 million CT exams /yrin the US are on children under 15 4

  5. Number of abdominal / pelvic CT scansunder a given age, St. Louis Children’s Hospital 1996-1999 Data courtesy of Dr. W. McAlister 5

  6. CT exams contribute disproportionately to the collective radiation dose to the population:In the US,11%of diagnostic radiological procedures are currently CT examinations….but their contribution to the collective dose from diagnostic radiology is~67%Mettler et al, 2000 6

  7. Multiple CT examinations • 30% of patients who have CT scans • have at least 3 scans • 7% of patients who have CT scans • have at least 5 scans • 4% of patients who have CT scans • have at least 9 scans (Mettler et al 2000) 7

  8. Lifetime risks based on updated (to 1990) A-bomb data 8

  9. Estimating the Risks 1. Estimate the dose to each organ, as a function of age, gender, and type of CT exam 2. Apply estimates of age-, gender-, and organ-specific risks-per-unit dose 3. Sum the risks for all the organs 9

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  12. Organ doses for 200 mAs setting 12

  13. Relevant dose ranges for asingle neonate CT:Abdomen CT (stomach dose)300 mAsè30 mSv100 mAsè 10 mSvHead CT(brain dose)300 mAsè60 mSv100 mAsè 20 mSv 13

  14. Relevant dose range for pediatric CT:6 - 100 mSv (0.006 - 0.1 Sv) “there is direct, statistically significant evidence for risk in the dose range from 0 to 0.1 Sv”Pierce and Preston, 2000 14

  15. Number of solid cancers in A-bomb survivors exposed to doses from 5-100 mSv 15

  16. Lifetime attributable cancer mortality risk, as a function of age at exam, for a single CT examination 16

  17. Head CT- Lifetime cancer mortality risk (percent) Female vs. male 17

  18. Abdominal CT - Lifetime cancer mortality risk (percent)female vs. male 18

  19. Predicted cancer deaths (US) from one year of pediatric head and abdominal CT exams(200 mAs) • 300 from pediatric head CT • 425 from pediatric abdominal CT • ~1,100 from all pediatric CT 19

  20. What are the uncertainties assiciated with these risk estimates: Probably about a factor of 3 in either direction? What are the uncertainties associated with these risk estimates? • About a factor of 3 in either direction 20

  21. Pediatric CT scans: benefits vs. risk Individual Risk Benefits 21

  22. Risks and Benefits • Important to distinguish between individual risks and collective, public-health risks • The individual risks are small, so the benefit / risk ratio for any child will generally be verylarge • But the exposed population (~2.7 million children/yr in the US) is large • Even a very small individual radiation risk, when multiplied by a large (and increasing) number of children, is likely to produce a significant long-term public health concern 22

  23. It is 15 years since the first paper on pediatric CT dose reduction was published… 23

  24. 15 year old boy - lung CT 40 mAs 150 mAs 24

  25. …yet most pediatric CT’s are still being performed with adult settings 25

  26. Two ways to reduce the collective dose (and therefore the risk) from pediatric CT What are the uncertainties assiciated with these risk estimates: Probably about a factor of 3 in either direction? • Reduce the CT exposure settings for children • More selective use of pediatric CT in cases where its benefits are not so clear cut 26

  27. Some situations where the benefits of pediatric CT are not so clear cut: 27

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