P2 green with circles

1

Increased use of Advanced Medical Imaging,
Radiation Exposure, and Cancer Risk
Diana L. Miglioretti, PhD Group Health Research
Institute Rebecca Smith-Bindman, MD University of
California, San Francisco
May 31, 2011 D. Miglioretti, PhD
2
Outline

• Background
• Utilization of medical imaging
• Cancer risk from radiation
• Radiation from medical imaging
• Study of dose from CT at 4 San Francisco Bay Area
  Facilities
• Dose from CT is high and variable
• Study of imaging at 7 integrated healthcare
  systems
• Imaging utilization and radiation exposure
• CT use in children
• Radiation exposure from CT in children
• Leukemia risk
• Discussion Conclusions

3
Benefits of Medical Imaging

• Earlier and more accurate diagnosis of disease
• Earlier treatment
• Improved patient outcomes
• Quick diagnosis (e.g., CT use in ED)
• Less invasive diagnosis
• Accurate prognosis
• Reassurance

4
Harms Associated with Imaging

• Radiation exposure
• Doses of common exams (e.g., CT) in carcinogenic
  range
• Rare - accidental overdose
• False positives Unnecessary follow-up testing,
  anxiety, cost
• Incidental findings Cascade of testing to rule
  out disease
• Overdiagnosis Unnecessary treatment
• Contrast reactions Most minor, some major
• Healthcare costs
• Advanced imaging is expensive

5
2008
CT and MRI use tripled in 10 years
6
Radiation and Cancer Risk
7
Measures of Radiation Exposure

• Effective dose (ED)
• Estimates a patients overall exposure from
  non-uniform radiation like medical imaging
• Accounts for
• amount of radiation from machine
• body part irradiated (sensitivity of organs to
  radiation)
• patients age and possibly gender
• Reflects sensitivity to developing cancer from
  radiation exposure
• Younger children more sensitive to radiation
• Some organs more sensitive to radiation
• Expressed in milliSieverts (mSv)

8
BEIR VII Report

• The U.S. National Academies of Sciences
  Biological Effects of Ionizing Radiation
  Committee (BEIR) conducted a comprehensive review
  of literature on health risks of low dose
  radiation exposure
• Members included leading scientists from a broad
  range of disciplines
• Estimated cancer risk based on dose and age at
  exposure using a variety of studies

9
Japanese Atomic Bomb Survivors

• Life Span Study of the 120,000 survivors of the
  atomic bombings in Hiroshima and Nagasaki Japan
• The median dose of survivors was 40 mSv
• Organ specific radiation doses are linked with
  organ specific cancers for nearly every cancer
• Even at low doses (10 mSv), survivors were at a
  significantly increased risk of developing cancer

10
Medically Irradiated PopulationsMalignant Disease

• Following radiotherapy for malignant disease,
  there is an elevated risk of second cancers
• Second primary malignancies particularly high
  among survivors of childhood cancer
• Among Hodgkins survivors, radiation-induced
  second primary cancers are a leading cause of
  mortality

11
Medically Irradiated PopulationsBenign Disease

• Radiation commonly used 1930-1960 for benign
  conditions
• Tinea capitis
• Enlarged tonsils
• Enlarged thymus
• Breast conditions (i.e., post partum mastitis)
• Increased risks of radiosensitive cancers
• thyroid, salivary gland, central nervous system,
  skin, and breast

12
Medically Irradiated PopulationsRepeated X-rays

• Studies have assessed groups who received
  repeated radiographs
• Scoliosis
• Tuberculosis
• Children with cardiac catheterizations
• All significantly more likely to develop cancer

13
Radiation Workers

• 400,000 radiation workers in the nuclear industry
  
• Average doses of 20 mSv
• Significant association between exposure (5 - 150
  mSv) and cancer mortality
• Ongoing studies of radiology technologists,
  physicians who use radiation suggest increase
  cancer risks

14
Summary of Evidence of Harmful Effects of
Radiation

• A large body of epidemiological and biologic
  evidence links exposure to radiation (even low
  doses) with development of cancer
• The results are highly consistent across studies
• It has not been scientifically demonstrated that
  any cancer risk exists below 100 mSv is untrue
• The A-bomb survivor data provides best dose
  response data
• However, the effect size is consistent across
  studies

15
Radiation Exposure from Medical Imaging
16
Imaging Studies Associated with Radiation

• Nuclear Medicine (25 of cumulative dose)
• Radioactive material is inhaled, injected, or
  swallowed
• Gamma rays are emitted by the nuclei, and
  detected energy is collected and displayed on a
  computer
• X-Rays (75 of cumulative dose)
• X-rays are generated by a machine, pass through
  patient to form pictures on film / computer
  screen
• Radiographs, fluroscopy, angiography,
  interventional procedures 10 of dose
• CT 65 of dose

17
Medical Radiation

• The risks associated with ionizing radiation are
  not new
• Many of the radiology pioneers developed burns
  or died from radiation-induced cancers
• What is new is the dramatic increase in exposures
  to ionizing radiation from CT

18
Radiation Exposure of US Public Has Doubled Due
to Medical Imaging
1985 total 3.7 mSv 75 from natural sources 25
imaging
2006 total 6.2 mSv 50 from natural sources 50
imaging
19
Sample Annual Radiation Exposures
Source mSv
Radon 2.0
Living in Denver 0.63
Food 0.40
Sun exposure 0.27
Dental radiographs (series) 0.05
Jet travel (6 hours) 0.03
Airport screening 0.00001

Chest radiographs (PA Lat) 0.06
CT chest 8.0
CT head, chest, abdomen, pelvis 35-100
20
Radiation Doses of Common Imaging Tests
Source mSv
Chest radiographs (PA Lat) 0.06
Mammogram series, film-screen 0.80
IVP 2.5
GU contrast studies 14
Nuclear medicine renal 23
CT head 2.0
CT chest 8.0
CT abdomen pelvis 12.0
Coronary angiogram 4.6 15.8
Nuclear medicine heart 8.9 17.0
21
Radiation Doses from CT High, Variable, and
Potentially Harmful

• Study of four facilities in San Fran Bay Area
• Smith-Bindman et al., Arch Intern Med, 2009
• Adults, median age 59 years
• January 1 May 30, 2008
• Dose from CT 1.5-5 times higher than widely cited
• Higher than needed for medical diagnosis
• Doses highly variable for same test and
  indication
• Vary 15-20 times among facilities
• Even greater variation among patients (even at
  same facility)
• Expect 2-fold variation due to differences in
  body size

22
Effective Dose for Common CT TypesVariation
within Imaged Region
Typically Reported Doses (mSv) Mean Effective Dose (mSv) Equivalent No. of Chest Radiographs Equivalent No. of Mammograms
Head 2 3
Routine head 2 30 5
Suspected stroke 14 199 33
Chest 7
Routine chest 8 118 20
Suspected pulmonary embolism 10 137 23
Coronary angiogram 22 309 51
Abdomen-pelvis 8 10
Routine 15 234 39
Multiphase 31 442 74
Smith-Bindman et al., Arch Intern Med, 2009
23
Effective Dose for Common CT TypesVariation
across Facilities and Patients
Site 1 Site 2 Site 3 Site 4 Range Across Patients
Head
Routine head 3 2 3 2 0.3 6
Suspected stroke 18 15 8 29 4 56
Chest
Routine chest 6 12 11 7 2 24
Suspected PE 8 21 9 9 2 30
Coronary angiogram 21 20 7 39
Abdomen-pelvis
Routine 12 19 20 12 4 45
Multiphase 24 35 45 34 6 90
Smith-Bindman et al., Arch Intern Med, 2009
24
Radiation exposure varies among and within CT
types
Smith-Bindman et al., Arch Intern Med, 2009
25
Radiation exposure varies among and within CT
types
Smith-Bindman et al., Arch Intern Med, 2009
Average exposure among Japanese atomic bomb
survivors
26
Why are doses so high and variable?

• No clear dose targets for CT in US
• No professional or governmental organization
  responsible for collecting and reporting dose
  data
• Few clear standards
• Lack of knowledge about dose levels among
  physicians and technologists
• May be changing
• Technical improvements in CT have ironically led
  to increasingly high doses for more exams

27
Cancer Risks are Not Trivial
Smith-Bindman et al., Arch Intern Med, 2009
28
Cancer Risks are Not Trivial
Smith-Bindman et al., Arch Intern Med, 2009
If 1000 20 year old women undergo a multi-phase
abdomen and pelvis CT, 4 are estimated to develop
cancer from the test (range in estimate 2- 12)
29
Image Utilization
30
Study of Imaging Use

• Retrospective observational study
• 7 integrated healthcare systems
• 1994-2007 adding data through 2010
• 2.5 million members each year

31
Study Sites
32
Increase in CT Use
33
CT use by Age and Year
34
Contributions of Imaging Tests to Rate of Testing
and Radiation Exposure
Imaging Exams per 1000 enrollees N, Imaging Exams per 1000 enrollees N, Imaging Exams per 1000 enrollees N, Imaging Exams per 1000 enrollees N, Total Radiation Exposure per 1000 enrollees mSv, Total Radiation Exposure per 1000 enrollees mSv, Total Radiation Exposure per 1000 enrollees mSv, Total Radiation Exposure per 1000 enrollees mSv,
1994 1994 2007 2007 1994 1994 2007 2007
Angiography Fluroscopy 66 7 66 4 408 35 357 13
CT 47 5 197 12 342 30 1,662 61
MRI 18 2 89 6
Nuclear Medicine 22 2 65 4 136 12 411 15
Radiographs 704 70 880 55 271 23 311 11
Ultrasound 153 15 294 18
35
Annual (Cumulative) Effective Dose
1
Hiroshima Survivors
10
Median
For each patient, each year, we summed radiation
form all imaging examinations and described the
distribution in dose among those with the highest
annual exposure
36
Summary of Results

• A quadrupling in CT
• From 47 to 197/1000 enrollees per year
• 10 annual growth
• Similar increases for other imaging modalities
• Quadrupling in MRI
• Doubling in ultrasounds and nuclear medicine
• No decrease in radiographs
• Annual imaging costs increased three-fold and by
  2007 averaged 300 per person per year.
• Half of costs from CT and MRI
• Preliminary results from 2008-2010 shows rates
  may be starting to plateau or possibly even
  coming down

37
Summary of Results

• In 1994, CT accounted for 5 of imaging and 30
  of radiation exposure
• In 2007, CT accounted for 12 of imaging and 61
  of radiation exposure
• In 2007, 7 of enrollees received an annual
  radiation exposure of 10 mSv or higher

38
Pediatric Imaging
39
Study of Imaging Use

• Retrospective observational study
• 7 integrated healthcare systems
• 1994-2010 (some sites only until 2007)
• Ages 14 years or younger
• 169,000 511,000 children per year

40
Study Sites
41
CT use in Children
42
Body Areas Imaged with CT
1994
2007
43
Radiation Doses from Common CTs

• Data abstracted on 1,266 exams from three sites
• Group Health Cooperative, Washington
• Kaiser Permanente Hawaii
• Kaiser Permanente North West, Oregon
• Sample
• 1994-2008
• - One site collected additional data from
  2009-2010
• Ages lt 1 year 30 years
• Randomly selected CT exams performed on
• Head (brain, face, orbit)
• Abdomen/Pelvis
• Chest
• Spine or Neck
• Abstracted dose values from all CTs on same child
  on same day

44
Calculation of Effective and Bone Marrow Doses
and Leukemia Risk

• Doses calculated by Choonsik Lee PhD,
  Investigator, Radiation Epidemiology Branch, NCI
• Developed improved methods
• Multiple phantom sizes
• Newborn, 1, 5, 10, 15, adult
• Male and female representing 50th percentile body
  size
• Improved phantom anatomy and skeleton dosimetry
  method
• Organ doses estimated from a precalculated dose
  matrix covering whole body with a series of
  continuous axial slices of 1cm thickness.
• Hybrid phantom series coupled with Monte Carlo
  modeling of Siemens sensation 16 were used to
  generate the precalculated dose matrix.
• Machine-specific CTDIw used to convert Siemens
  sensation 16 dose to other machines.
• Estimated RR of death from leukemia 5 years after
  exam, based on bone marrow dose (based on BEIR
  VII)

45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
Relative Risk of Leukemia Death 5 years after CT
Exam
Age Group Number of CTs Min 5th 25th 50th 75th 95th Max 2.0 3.0
lt 1 year 87 1.1 1.2 1.4 1.6 2.0 2.6 3.8 24.0 3.4
1 year 52 1.1 1.1 1.3 1.5 1.8 2.5 2.7 9.6 0
2 4 years 144 1.1 1.1 1.2 1.3 1.5 2.0 2.6 5.6 0
5 9 years 246 1.0 1.0 1.1 1.2 1.3 1.5 2.2 0.8 0
10 14 years 308 1.0 1.0 1.0 1.1 1.1 1.2 1.8 0 0
49
Summary of Pediatric Imaging

• CT use quintupled from 11 to 52 CTs / 1,000
  children per year
• Doses decreased until 2002, then in 2005,
  increased
• May be coming back down
• Doses and cancer risk higher for infants and
  toddlers
• Over 10 of children 4 years or younger received
  an effective dose of 20mSv from one exam
• Many children have repeat testing
• - Among children with 1 CT, the with gt1 CT in
  a year increased from 20 in 1998 to 42 in
  2006-2008
• Many exams resulted in more than a doubling of
  risk of dying from leukemia 5 years after exam
• 1 in 5 children lt1 year
• 1 in 10 children 1 year
• 1 in 20 children 2-4 years

50
Discussion and Conclusions
51
Factors Contributing to Increased Advanced
Medical Imaging Use

• Improvements in technology
• Increased capacity
• Patient demand no perceived disincentive
• Physician demand
• Easy
• Lack of tolerance for ambiguity
• Limited evidence-based guidelines (or any
  guidelines)
• Malpractice concerns leads to defensive imaging
• High profitability self-referral

52
How to Reduce Radiation Exposure

• Reduce the number of studies shared
  responsibility
• Make sure test hasnt already been done
• Need evidence-based guidelines
• Reduce doses per test
• Standard protocols
• Dose reference levels
• Educate physicians and technologists on
  importance of reducing dose
• Educate patients and providers about risks
  benefits of imaging
• Directly assess the risks /benefits of CT to
  inform practice

53
Conclusions

• Medical Imaging is an integral component of
  medical care
• However, there are few evidenced based guidelines
  about when to image, and the default is to
  over-image
• More widespread efforts needed to reduce dose,
  especially in children, by
• Reducing unnecessary exams
• Reducing dose when imaging necessary
• Research is desperately needed to determine when
  to image, and how to do so using lowest possible
  doses

54
(No Transcript)