Transcript Radiation and Computed Tomography in Children

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
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.
Outline
 Overview
 Risks of radiation in children
 Initiatives to reduce radiation exposure in
children
Outline
 Overview
 Risks of radiation in children
 Initiatives to reduce radiation exposure in
children
Question
What is the relative radiation dose of a CT
compared to a chest x-ray (CXR)?
a. CT = CXR
b. CT = 1-10 CXR
c. CT = 10-100 CXR
d. CT = 100-250 CXR
e. CT ≥ 500 CXR
Lee et al Radiology April 2004
Question
What is the relative radiation dose of a CT
compared to a chest x-ray (CXR)?
a. CT = CXR
b. CT = 1-10 CXR
c. CT = 10-100 CXR
d. CT = 100-250 CXR
e. CT ≥ 500 CXR
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, 328:578-580
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
Pierce and Preston, Radiat Res, 2000
Advent of CT
 1974 – 1st CT scans
performed
 CT has evolved into an
invaluable diagnostic
tool
 2010 – > 6000 scanners
in use
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
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
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
Too good to be true?
 Despite the many benefits of CT, the
radiation exposure associated with this
modality has come under increasing
scrutiny
Dose Contribution of CT
CT
15%
All other
imaging
modalities
85%
% of Imaging Studies
Utilizing Ionizing Radiation
All other
imaging
modalities
30%
CT
70%
% of Total Radiation Dose
from Medical Imaging
Comparison of Effective Radiation
Doses from X-ray and CT
Imaging Study
Chest X-ray
Effective Dose
(mSv)
0.02
Equivalent number
of chest x-rays
1
Head CT
4
200
Abdominal CT
5
250
Chest CT
3
150
Adapted from Brody, et al, Pediatrics 2007
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
Outline
 Overview
 Risks of radiation in children
 Initiatives to reduce radiation exposure in
children
AJR Feb 2001
AJR February 2001
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
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
Hall Pediatric Radiology Apr 2002 pg 226
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
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
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
A Risk Comparison
Activity
Risk
Driving 7,500 miles
1:1000 (accident risk)
Motorcycling for 1,000 miles
1:1000 (accident risk)
Abdominal CT scan
1:1000 (risk of radiationinduced cancer)
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
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
Emerging Human Cohorts
 Chernobyl
 Airline personnel
 Nuclear industry workers
 Radiation therapy patients
 2011 Japanese tsunami/earthquake
Outline
 Overview
 Risks of radiation in children
 Initiatives to reduce radiation exposure in
children
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
ALARA
 ALARA
 for the radiologist
 for the clinician
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
Alternative Imaging Modalities:
Ultrasound
 Advantages
 No radiation
 Inexpensive
 Disadvantages
 Operator-dependent
 Impaired diagnostic efficacy in the obese
and in retrocecal appendix
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
Alternative Imaging Modalities:
MRI
 Improvement in MRI technology needed
 Barriers to routine use of MRI in children
 Cost
 Availability
 Need for sedation
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
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
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
What about when the diagnosis is
uncertain?
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
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
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
BUT….
 ….aren’t most
institutions
following these
practices already?
A century of progress…
1896
2011
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
 www.imagegently.org
 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
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
Questions?