1. Radiation and Computed Tomography in Children…
Is there still a cause for ALARAm?
Nikhil B. Shah, M.D.
Assistant Professor of Pediatrics
Division of Pediatric Emergency Medicine
Weill Cornell Medical Center
Thank you and good morning. I am sure that many of you are aware of the fact that this issue in PEM has received a lot of media attention recently.
Its important because everyday we, as clinicians, are expected to make decisions that impact upon the lives of our patients. In making these decisions, it is hoped that we weigh the benefits of the particular test or intervention against any potential risks. So what I’d like to talk to you about today are the radiation risks associated with pediatric CT and how awareness of these risks should impact on our ordering practices.

2. Disclosure
I have no potential, apparent, or real conflict of interest to disclose and DO NOT INTEND to discuss off-label or investigational use of products or services.

3. Outline Overview Risks of radiation in children
Initiatives to reduce radiation exposure in children

4. Outline Overview Risks of radiation in children
Initiatives to reduce radiation exposure in children

5. Question
What is the relative radiation dose of a CT compared to a chest x-ray (CXR)?
CT = CXR
CT = 1-10 CXR
CT = CXR
CT = CXR
CT ≥ 500 CXR

7. Lee et al Radiology April 2004

8. Question
What is the relative radiation dose of a CT compared to a chest x-ray (CXR)?
CT = CXR
CT = 1-10 CXR
CT = CXR
CT = CXR
CT ≥ 500 CXR

9. Why is this issue important?
Diagnostic imaging in the pediatric emergency department is increasing
Up to 1/3 of studies may not contribute to patient management
The primary concern is the radiation risk of unnecessary diagnostic imaging
Picano E, BMJ 2004, 328:

10. Why is this issue important?
Unnecessary imaging:
Adds to the costs of medical care
Puts the child at risk of discovering an “incidentaloma”
Subjects the child to unnecessary radiation which increases the lifetime risk for fatal cancers
An incidentaloma is an unexpected finding that requires additional evaluation but is eventually found to be irrelevant to the management of the patient.
It usually results in further investigations and sometimes other interventions that usually end up demonstrating that the finding is of no clinical significance.

11. Pierce and Preston, Radiat Res, 2000

12. Advent of CT 1974 – 1st CT scans performed
CT has evolved into an invaluable diagnostic tool
2010 – > 6000 scanners in use
CT has revolutionized medicine because it allows doctors to see diseases that, in the past, could often only be found at surgery or at autopsy
Currently over 6000 scanners are in use

13. Impact of CT 700% increase in CT use over past decade
CT use continues to increase; growth rate 10% per year
Brenner, et al, NEJM 2007

14. Impact of CT More than 70 million CT scans performed annually in US
11% in children (~10 million)
Relatively young technology whose risks are not yet fully quantified
That was then, this is now…
Parentsand patientsalike have come to expect CT when they come to the ER.

15. Why the recent upsurge in CT utilization?
Increased availability
Advances in CT technology (ie, helical CT and MDCT)
Faster scanning - sometimes < 1 second
Decreased need for sedation

16. Too good to be true?
Despite the many benefits of CT, the radiation exposure associated with this modality has come under increasing scrutiny

17. Dose Contribution of CT
% of Imaging Studies Utilizing Ionizing Radiation
% of Total Radiation Dose from Medical Imaging

18. Comparison of Effective Radiation Doses from X-ray and CT
Imaging Study
Effective Dose (mSv)
Equivalent number of chest x-rays
Chest X-ray
0.02 1
Head CT 4
200
Abdominal CT 5
250
Chest CT 3
150
In considering the effective dose of radiation it is helpful to compare the effective dose for different radiologic studies. For example, the radiation from a single abdominal CT is nearly 250 times that of a plain chest radiograph
Adapted from Brody, et al, Pediatrics 2007

19. Societally-Relevant Low Dose Radiation Exposures
Source
Estimated effective dose (mSv)
Natural background radiation
3 mSv/yr
Airline passenger (cross country)
0.04 mSv
Radiation worker exposure limit
20 mSv/yr
Single screening mammogram
3 mSv
Radiological bomb (20 block radius)
3-30 mSV
Chest X-ray (2 views)
0.1 mSv
Head CT
4 mSv
Chest CT
3 mSV
Abdominal CT
5 mSV

20. Outline Overview Risks of radiation in children
Initiatives to reduce radiation exposure in children

21. AJR Feb 2001
Much of the recent attention regarding radiation risks from CT in children stemmed from a series of articles published in the American Journal ofRoentgenology in 2001.

22. One of the sentinel articles on this topic by Brenner, et al sought to assess lifetime cancer mortality risks for different organs attributable to radiation from pediatric CT performed at different ages.
They basically multiplied age-dependent lifetime cancer mortality risks (per unit dose) by estimated age-dependent doses produced by various CT examinations.
AJR February 2001

23. Brenner, et al 2001
Most institutions do not adjust dose settings for children
Recommended dose reduction in pediatric CT
Lifetime cancer mortality risk attributable to CT is considerably higher in children
Estimated 1:500 radiation-induced cancer deaths
The 1:500 estimate is based on 600K abdominal and head CTs/yr in US on children < 15 years old

24. Unique Considerations in Children
Rapidly dividing cells more sensitive to the effects of radiation
10-fold increase in neoplastic potential compared to equivalent dose in an adult
Particularly true for thyroid, breast, and gonadal tissue
Longer lifetime during which malignant transformation may occur
Rapidly dividing cells are more sensitive to the effects of radiation
10-fold increase in neoplastic potential compared to equivalent dose in an adult
Particularly true for thyroid, breast, and gonadal tissue
Longer lifetime during which malignant transformation may occur

25. Hall Pediatric Radiology Apr 2002 pg 226
Most important is age at exposure. Females have greater risk because of breast and thyroid cancer.
Hall Pediatric Radiology Apr 2002 pg 226

26. If we know all this, why is this an issue?
CT scans are generally not tailored to the smaller size of children
Therefore, children receive a higher radiation dose per unit of tissue compared to an adult for a given study CT

27. The numbers
1 in 500 to 1:1000 children who have had a CT scan will develop a radiation-induced fatal cancer in their lifetime
This correlates to a 0.35% increase over the expected baseline lifetime risk for cancer
Does not account for non-fatal cancer

28. Radiation and Public Health
Radiation risk to the individual is small
Risk to the population as a whole is considerable given the sheer number of CTs
30% will have more than one scan
Dose is cumulative
Dose is cumulative - i.e., multiple scans will result in a greater lifetime cancer risk for the individual

29. A Risk Comparison Activity Risk Driving 7,500 miles
1:1000 (accident risk)
Motorcycling for 1,000 miles
Abdominal CT scan
1:1000 (risk of radiation-induced cancer)
Approx risk in pediatric age group 1:1000 of radiation induced (fatal) cancer at current CT doses. For adults, up to 1:10,000

30. Radiation and Public Health
NCRP reports an increase in effective dose per individual in the US
3.6 mSv in early 1980s to 6.2 mSv in 2006
Indiscriminate use of CT has the potential to become a public health problem
NCRP = National Council on Radiation Protection and Measurement

31. Radiation and Public Health
DHHS (2005) -Diagnostic medical radiation added to list of known human carcinogens
2005 BEIR VII report - Diagnostic radiation substantially increases cancer risks
Ongoing – Large NCI cohort study evaluating cancer incidence in children who have had CT

32. Emerging Human Cohorts
Chernobyl
Airline personnel
Nuclear industry workers
Radiation therapy patients
2011 Japanese tsunami/earthquake

33. Outline Overview Risks of radiation in children
Initiatives to reduce radiation exposure in children

34. ALARA ‘As Low As Reasonably Achievable’
Reducing the amount of radiation a child is exposed to while maintaining efficiency and reliability of the diagnostic modality
Doses could be reduced by > 30-50% to obtain essentially the same information
Various authors have suggested that pediatric CT exposures could be reduced by 30-50% or more relative to adult exposures to obtain essentially the same information.

35. ALARA
ALARA
for the radiologist
for the clinician

36. ALARA: for the radiologist
Develop weight-based protocols
Improve shielding
Focused/limited-view studies when feasible
Discourage repeat CT studies
Consider alternative non-radiation modalities such as MRI or ultrasound
Shah & Platt Curr Opin Pediatr 2008

37. Alternative Imaging Modalities: Ultrasound
Advantages
No radiation
Inexpensive
Disadvantages
Operator-dependent
Impaired diagnostic efficacy in the obese and in retrocecal appendix

38. Alternative Imaging Modalities: MRI
Sparse current literature
One report found MRI accurately identified 100% of acute appendicitis in 20 patients
MRI may be a valuable imaging technique particularly in children and pregnancy

39. Alternative Imaging Modalities: MRI
Improvement in MRI technology needed
Barriers to routine use of MRI in children
Cost
Availability
Need for sedation
Improvement in MRI technology needed
To enable more rapid sequences
Accommodate minor motion artifact
To reduce need for sedation
Cost, availability, and need for sedation remain current barriers to routine use of MRI in children

40. Rapid Brain MRI Short shunt/hydrocephalus protocol
Useful to look at ventricles, but can also see midline shifts or mass effect
Entails sagittal, coronal & axial SSFSE and diffusion weighted sequences
Very rapid – approximately 3 minutes
SSFSEs (single shot fast spin echo)

41. AFARA ? for the Clinician
AFARA – “As Few As Reasonably Achievable” ?
10-30% of all CT scans may be ‘unnecessary’
Limiting the number of CTs to only those that are clinically indicated
Adopting a selective imaging strategy
No such thing as AFARA but there should be!

42. So how do we know which patients to scan?
Identify patients at high- or low-risk for a particular outcome of interest using:
Clinical decision rules
Scoring systems
Clinical practice guidelines

43. What about when the diagnosis is uncertain?

44. AFARA: for the clinician
Role of the pediatric care provider is paramount
Responsible for ordering & providing indications and justifications for CT exams
Principle source of information about imaging studies, including potential risks

45. AFARA: for the clinician
Educating clinicians about judicious CT use may have the most impact in reducing radiation exposure in children
Educating patients about risks, benefits and radiation doses for CT scans

46. AFARA: for the clinician
Explore alternative options and consider true need for a study
Role of pediatric radiologist cannot be overemphasized in this decision-making

47. BUT….
….aren’t most institutions following these practices already?

48. A century of progress…
1896
2011

49. Current Barriers to Selective CT Utilization in the ED
Unique demands of ED setting often justify prompt and accurate diagnosis
Represents a challenge to all clinicians who care for children
Increased potential for litigation
May tilt perceived risk-benefit balance towards overuse of CT in children

50. Alliance for Radiation Safety in Pediatric Imaging in 2007
Alliance for Radiation Safety in Pediatric Imaging in 2007
Goal is to raise awareness of the opportunities to lower radiation dose in the imaging of children  
Medical education handouts for practitioners and patients.

51. Summary
When medically indicated, the benefits of CT far outweigh the individual risks
Recent evidence underscores the importance of judicious utilization of CT
Public awareness & education are essential
Clinicians and radiologists should present a unified team, who together advocate safe practice in children

52. Questions?