lecture 01 overview rp in dr and ir rtc accra 2011
TRANSCRIPT
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IAEAInternational Atomic Energy Agency
RADIATION PROTECTION INDIAGNOSTIC AND
INTERVENTIONAL RADIOLOGY
L 01. Overview of Radiation Protection in Diagnostic & Interventional Radiology
Motivation for the Course
IAEA Training Material on Radiation Protection in Diagnostic and Interventional RadiologyAdapted for Regional Training Course on RP of Patients for Radiographers
Accra, Ghana, 11-15 July 2011
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IAEA Introduction to Radiation Protection in Diagnostic Radiology 2
Introduction
• An overview of medical uses of radiation• Radiation protection issues in diagnostic &
interventional radiology
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Current use of radiation in medicine
Every year, throughout the world, ionizing radiation is used in*:
• 4.000.000.000 diagnostic procedures
• 35.000.000 nuclear medicine procedures
• 8.000.000 radiotherapy treatment courses
- An expanding activity worldwide
- Impacts on large portion of global population
Diagnostic procedure Nuclear medicine procedure Radiotherapy procedure
These bring huge benefit to healthcare
*UNSCEAR 2010
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Increasing use of radiation in medical applications worldwide• More machines, etc
• New technologies and techniques
• New roles
• Increasing complexity in the planning & delivery of the radiation
Single slice CT → Multi-Detector CTFilm → Computed & Digital RadiographyHybrid imaging, PET-CT
Image-guided interventional proceduresVirtual procedures
E.g. Changes in the role of imaging: First “port of call”
A move towards “screening”, in all its guises
E.g. IMRT, IGRT, etc.
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IAEA 5
UNSCEAR UNSCEAR 19931993
GlobalGlobal annual per caput effective dose annual per caput effective dose
Increasing medical exposure
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UNSCEAR UNSCEAR 20002000
GlobalGlobal annual per caput effective dose annual per caput effective dose
Increasing medical exposure
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IAEA 7
UNSCEAR UNSCEAR 20082008
GlobalGlobal annual per caput effective dose annual per caput effective dose
Increasing medical exposure
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NCRP160 NCRP160 20092009
U.S.U.S. annual per caput effective dose annual per caput effective dose
Increasing medical exposure
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Collective dose from medical exposures
Relative contribution – Level I versus USA
Relative contribution to collective dose
0%
10%
20%
30%
40%
50%
60%
CT Nuclear Medicine Interventional ConventionalRad/fluoro
Per
cen
tag
e
USA
Level I
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Context – another reality
However, However, reports continuereports continue to appear on: to appear on:
• Accidental and unintended exposures
• Unnecessary exposures
Advertisement for radiological screening gift certificatesNewspaper report on recent radiotherapy accident
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Is this increasing use of radiation in medicine cause for concern?
How do patient doses compare with other sources of exposure?
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Radiation from Natural Sources
• Normally 1-3 mSv/year
• Global average is estimated to be 2.4 mSv per year (UNSCEAR)
• In areas of high background, > 10 mSv/year
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Patient effective doses
• Depends on the radiological procedure
• E.g. • Radiography
• A few μSv to a few mSv
• CT
• A few mSv to tens of mSv
• Image-guided interventional procedures
• A few mSv to tens of mSv
• Skin doses up to several 1000 mSvNBR, 2.4 mSv
LD50 3000 - 5000 mSv
Whole body dose
X ray exams
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What are some of the RP issues in diagnostic and interventional radiology?
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What are the issues - radiography?
Staff doses are typically very low• < 1 mSv per year
Doses to the patient are typically low • Effective dose – a few μSv to a few mSv• But variation by a factor of 20 more• Many exams lack proper justification and/or optimization
Hospital ADose = X
Hospital CDose = 10X
Hospital BDose = 2X
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Radiography
• Diagnostic reference levels (DRLs)• Very effective tool in optimization
• Concept introduced in the 1990s
• Implementation in Member States is very uneven• How many African countries have
• Established DRLs; and
• Use them in practice?
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In radiographic practice, does it happen?
• Unjustified exposures - Yes
• Wrong patient - Yes
• Wrong body part - Yes
• Lack of optimization - Yes • Lack of calibration – Yes
• Lack of QA – Yes
• DRLs not used - Yes
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Fluoroscopic examinations - diagnostic
• Staff doses are typically low
• Doses to the patient are typically a few mSv
• But variation through lack of optimization
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Image-Guided Interventional Procedures
• Increase in use continues, in some countries doubling every 2 - 4 years
• Who are the patients?• Mostly adults, > 40 years old
• But also children, ~ 5 %
• Doses can be high• Effective doses
• Can exceed 20 mSv
• Peak skin doses• Can exceed several Gy
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Number of procedures per
patient1 2 3 4 5 6 7 >7
Number of patients
1967
940 194 138 41 29 14 9
Nearly 6% of patients had 3 or more interventions
Udine, Italy – Cardiac Interventions Analysis of > 3000 patients
Repeat procedures – not insignificant
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Induced lens opacities
Reference: Vañó E et al, BJR 1998; 71, 728-733
Image-Guided Interventional Procedures
• Staff issues
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Image-Guided Interventional Procedures
• Increasing frequency
• High doses
• Paediatric patients
• Repeat rate not insignificant
• Radiation protection issues for staff
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CT
• Usage increasing• More scanners• Quicker to use• Can do more with them
• Staff doses low at console, but hand doses of concern in CT fluoroscopy
• Patient doses• Effective doses 1 – 10 mSv• But can exceed 20 mSv
• Many patient dose reduction tools now available• But optimization often not happening
Level I - UNSCEAR 2008
43%
6%4%
47% CT
Nuclear Medicine
Interventional
Conventional Rad/f luoro
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CT
• But issues with:• Justification
• Unnecessary exams
• Self-referral
• Pressure through media for “screening”
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CT
• Issues with:• Multiple follow-up examinations
Hospital in Boston - 22 years of CT
Number of CT exams:
33% of patients - 5 or more CT exams
5% - between 22 & 132 CT exams
Cumulative doses:
15 % - greater than 100 mSv
4 % - between 250 & 1375 mSv
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CT
• Issues with children• Increasing number of children
undergoing CT examinations• E.g. in USA (Mettler, 2000)
• 1989 ~ 4 % of all CT scans
• 1993 ~ 6 %
• 2000 ~ 11 %
• Optimization not always implemented
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Deterministic Effects in CT?
Stroke protocol plus angiography caused temporary hair loss in this study
CT dose 2-3 Gy; angiography dose?
Yoshimasa Imanishi et al Eur Radiol (2005) 15:41–46
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Principles of radiation protection
• Justification
• Optimization
• Dose limitation (not for patients)
In Practice:
• Unjustified examinations are ≈ 20-50%
• Optimization can bring down patient doses by about 50%
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IAEA
Radiographers make a difference
Introduction to Radiation Protection in Diagnostic Radiology 29
The radiographer's attention to imaging details, such as chamber positioning, mAs and kVp settings, have helped reduce radiation exposure during lumbar x-ray studies at the Haukipudas Health Center in northwest Finland.
Radiographers reduce radiation exposure in Finland – 2011 ECR
April 18, 2011 – Radiographers have an important role to play in monitoring patient radiation exposure and adjusting x-ray equipment settings when rates rise, according to Finnish researchers.
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Summary
1. Medical uses of radiation are increasing, bringing great benefit
2. But there is a need to reduce unnecessary exposures
3. Radiographers have a key role to play