BEIR VII Implications of the Report for the Future of Medical Imaging G. Donald Frey, Ph.D. Department of Radiology Medical University of South Carolina.

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