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BEIR VIIBEIR VIIImplications of the Report Implications of the Report for the Future of Medical for the Future of Medical
ImagingImaging
G. Donald Frey, Ph.D.Department of Radiology
Medical University of South Carolina
BEIR VII-Key Results
• The report supports the LNT model.
• The radiations risk values are “similar” to previous reports and other groups like UNSCEAR and ICRP.
• The uncertainties have been reduced for lower dose.
Radiation Dose from Medical Imaging
“The Historical View”• The radiation dose from medical imaging
was low and a small fraction of the dose from natural sources.
• Imaging was viewed as being done only when clearly needed so it was well justified.
• The data on radiation effects was seen as uncertain at doses that would overlap the range of common medical procedures.
DoseDose
Ris
kR
isk
DoseDose
Ris
kR
isk
MedicalImaging
DoseDose
Ris
kR
isk
MedicalImaging
DoseDose
Ris
kR
isk
MedicalImaging
Recently - Doses from Imaging Have Increased
DoseDose
Ris
kR
isk
MedicalImaging
BEIR VII - The Degree of Uncertainty Has Decreased
BEIR VII Suggests
• We need to pay more attention to the justification of medical imaging.
• Practitioners should be well informed about The medical aspects of the procedure so that it
can be justified, The radiation risks from the procedure, and The medical physics aspects of the procedure
so it can be optimized.
BEIR VII Suggests
• We need to pay more attention to ALARA to insure that properly justified procedures are properly done Optimization of the dose-image quality
tradeoff Robust quality assurance techniques to
insure high quality images
Recent DevelopmentsIn Imaging
• Great increases in the number of imaging studies
• Increased use of higher dose techniques Computed Tomography Fluoroscopy
-20%
0%
20%
40%
60%
80%
100%
120%
140%
Conventional Mammography CT Nuclear Imaging
Change in the Number of Imaging ProceduresChange in the Number of Imaging Procedures
1993-19991993-1999
Maitino et al Radiology 2003;227:113-117
0
5
10
15
20
25
2003 2004
Rat
e p
er 1
000
sub
scri
ber
s
Radiologists
Non-Radiologists
Levin JACR 2006;3:90-95
+13%
+29%
Rate Changes 2003-2004
Dose and Collective Dose
• CT accounts for 15% of procedures
• CT accounts for 75% of the total effective dose
Wiest et al Sem in US, CT & MRI 2002, 23;402-410
US Exposures
Medical
15%
Consume
r
2%
Natural
83%
Other
0.28%
NCRP 93
17%
34%
48%
1%
Natural
Radon
Medical
Consumer
Huda-Frey Estimate2.8 mSv
Levin JACR 2006;3:90-95
0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
Podiatry
Chiropractic
Family Practise
Pulmonary Medicine
General Practise
Orthopedic Surgery
Radiology
Un
ac
ce
pta
ble
Im
ag
es
Unacceptable Image Quality: Pennsylvania Blue Shield Study
How Well is Imaging Done?How Well is Imaging Done?
Are Practitioners Are Practitioners Knowledgeable About Knowledgeable About Radiation Dose and Radiation Dose and
Dose Effects?Dose Effects?
0%
10%
20%
30%
40%
50%
60%
CR>CT CT x1-x10
CR
CT x10-
x100 CR
CT x100-
x250 CR
CT > 500
CR
Patients
Radio logis ts
ER Phys ic ians
Changes in the Medical Imaging Environment
• The uncertainties about radiation effects have decreased.
• The number of imaging procedures have increased.
• The increase has been highest in the high dose studies (CT).
• It is not obvious that all studies are well justified.
How Are These Issues Addressed?
• Federal Law & Regulation
• Federal Payment Structure
• State Law & Regulation
• Professional Societies
• Business and Insurance
• Public
Professional Societies
• The AAPM and ACR have undertaken a number of initiatives to address these problems Accreditation programs Task Group Reports
• CTDI Values• DR Exposure Index
Professional Society –Regulatory Partnership
• Cooperation between the regulatory community and professional societies can work to reduce the effects of these many problems.
Some Suggested Some Suggested ApproachesApproaches
&&Some Current ActivitiesSome Current Activities
Practitioners
• Practitioners who use fluoroscopy or direct CT examinations should be able to demonstrate knowledge of: Radiation effects Radiation risks Basic physics of the modality Image optimization
Practitioners
• Regulation like that used to determine status as an authorized user in Part 35 would be prudent and relevant.
Medical Physicists
• Medical physicists play a key roles in: Radiation protection Image optimization Definition and supervision of quality
assurance
• Many state regulations are based on obsolete roles for diagnostic medical physicists.
Medical Physicists
• Limitations in existing State regulations mean that individuals who act as medical physicists can often lack the knowledge to Properly optimize image quality Design and specify proper quality
assurance programs
Medical Physicists
• Existing State regulations have created a group of “diagnostic physicists” who can only deal with prescriptive regulations
• But cannot Optimize image quality Provide effective quality assurance
programs
Medical Physicists
• State Regulations should require that medical physicists should be able to demonstrate competence.
• The AAPM definition of a qualified medical physicist should form the basis of standards which would be used to define the competence of a medical physicist.
Medical Physicists
• New regulations should concentrate on establishing the competence of medical physicists and then allow medical physicists to exercise their professional judgment in many areas
• Prescriptive regulations cannot keep up with the rapid changes in medical equipment so professional judgment is required
Equipment Regulations
• Difficult because of rapid changes in equipment
• Also regulations have to encompass both new and old equipment
Current Regulation
• Stresses testing of details of equipment performance There is frequently little or no evidence
that specific items in these regulations protect the public in an effective way
They may create a false sense of security
False Sense of Security
• Equipment that meets regulations but produces poor images
• Equipment that meets regulations but is used poorly
• Reliance on CTDI values that significantly underestimate actual patient doses significantly distorts the situation
Issues with Current Regulations
CT as an Example
• Dose testing is highly prescriptive but does not set standards
• Image quality does not set standards
CT as an Example
• Dose Measurement in SSR Use phantom that underestimates the
dose for most most body studies Require measurements for each head,
body or whole body scan Do not set limitations for the measured
values
CT Scanning
• Current SSR require image quality testing.
• However there is no minimum performance that is required.
• There is no definition of the phantom that is used.
How Might Regulation Be Improved?
(CT as an Example)• Dose testing should relate to national
and international standards for reference doses.
• Testing should be done to insure an acceptable level of image quality.
• The image quality should be determined by reference to a national standard.
European Union Guidelines
Examination CTDIw mGy DLP
mGy-cmRoutine Head 60 1,050
Face & Sinus 35 360
Routine Chest 30 650
High Res Chest
35 280
Routine Abdomen
35 780
European Guidelines on quality criteria for CT (EUR 16262EN)
ACR CT Accreditation
Examination CTDIw mGyRoutine Head 60
Adult Abdomen
35
Pediatric Abdomen
25
I Negus – Berreford Hospital, Plymouth, GD
Improved RegulationImage Quality Testing
• National Standard for Performance
• National Phantom
• This is commonly done for mammography and should be adopted for CT.
Image Quality Testing
• ACR accreditation testing
• National standard for performance
Quality Assurance• Regulations cannot keep up with the
rapid changes in imaging equipment.
• Qualified medical physicists should have some latitude in specifying quality assurance programs and image quality as long as the programs relate to a national standard.
Dose Tracking Trends
• The NEXT program has long been the standard for determining radiation dose trends.
• NEXT Data has been of great value in determining trends in use and dose.
NEXT Limitations
• Equipment has become more complex so it is difficult to make meaningful measurement.
• The variety of procedures changes rapidly so NEXT data tends to “lag” current practice.
Electronic Monitoring
• Modern equipment has the ability to collect dose data automatically.
• The medical and regulator communities should support efforts to collect and analyze this data in an automatic fashion.
Summary
• BEIR VII suggests we should be more concerned about high dose medical exposure.
• Recent data suggests that not all medical imaging is well justified or well done.
Summary
• Professional Societies (AAPM, ACR, etc) are aware of these problems
• The Regulatory Community (CRCPD) is also aware of these problems
• A strong partnership between these communities can address these problems in effective ways
Summary
• Regulatory Philosophies should change: Insure that medical practitioners and
medical physicists are well qualified and stay well qualified
Regulations should become more flexible in detail
Regulations should require testing to a national standard