Medical Devices Radiation Safety Cari Borrás, D.Sc., FACR, FAAPM Visiting Professor DOIN -DEN / UFPE DOIN-DEN Recife, Pernambuco, Brazil Co-Chair, IUPESM Health Technology Task Group 1
Radiological equipment has changed a bit since the early days...
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CT DR
PET/CT
3
First Co -60 Co-60 Unit (1951)
Cs-137 Teletherapy (1960’s)
External Beam Therapy Linac with IGRT (200s)
Orthovoltage X-Ray (1990’s)
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Manchester Manchester Applicator Applicator
Ra Ra Needles Needles 1929 1929
1950 1950 -1960 1960
Brachytherapy Cs-137
LDR LDR 1970 1970 -1980 1980
Ir-192 Miniature X-Ray Tube
HDR HDR 1990 1990
Electronic Electronic Brachytherapy Brachytherapy 2000 2000 55
R. Mackie 2009
Global Annual Number of Radiological Exams and Treatments per 1,000 People Practice X Rays Nuclear Medicine
1997- 2007 562
420
(1,607)
(1,230)
5.1 (19)
Radiotherapy
5.6 (19)
0.8 (2.4)
( Data for HCL I )
1991 - 1996
1.0 (1.9) UNSCEAR 2008
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Annual per Caput Effective Dose (mSv) for theUnited States Population
Medical: 3.0
1980
UNSCEAR2008
2006 8
Radiation Risks
▲ ▲
External Internal
Contamination Pathways l
Absorption
l
Inhalation
l
Ingestion 9
Deterministic Effects Radiation effects for which generally a threshold level of dose exists above which the severity of the effect is greater for a higher dose.
Stochastic Effects Radiation effects, generally occurring without a threshold level of dose, whose probability is proportional to the dose and whose severity is independent of the dose. 10
Effects of Cell Death Probability of Death 100%
Dose (mGy) D
Co-60 Radiotherapy Overexposure Panama 2000-2001 11
Whole body response : adult
Acute irradiation syndrome 1-10 Gy
•Whole body clinic of a partial-body irradiation
10-50 Gy
Survival time
> 50 Gy
BMS (bone marrow)
GIS (gastro intestinal)
Chronic irradiation syndrome
Lethal dose 50 / 30
•Mechanism: Neurovegetative disorder •Similar to a sick feeling
CNS (central nervous system)
Dose
•Quite frequent in fractionated radiotherapy 12
Skin Injuries
Interventional Radiology Over -Exposure, USA 1991 Over-Exposure, 13
Effects in the Eye ▲ ▲ ▲ ▲ ▲ ▲
Eye lens is highly radiosensitive. Coagulation of proteins occur with doses greater than 2 Gy. There are 2 basic effects:
Effect
Sv single brief exposure
Sv/year for many years
Detectable opacities
0.5-2.0
> 0.1
Visual impairment (cataract)
5.0
> 0.15
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Deterministic Effects Radiation effects for which generally a threshold level of dose exists above which the severity of the effect is greater for a higher dose.
Stochastic Effects Radiation effects, generally occurring without a threshold level of dose, whose probability is proportional to the dose and whose severity is independent of the dose. Cancer
Heritable Effects 15
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Genetic (Heritable) Effects (Mutations) Fruit Fly Experiments
10
Frequency (%)
5
0
10
20 30 40 Absorbed dose (Gy)
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Genetic Effects ▲
Ionizing radiation is known to cause hereditary mutations in many plants and animals BUT
▲
Intensive studies of 70,000 offspring of the atomic bomb survivors have failed to identify an increase in congenital anomalies, cancer, chromosome aberrations in circulating lymphocytes or mutational blood protein changes.
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ICRP Detriment -Adjusted Nominal Risk Detriment-Adjusted Coefficient for Cancer and Heritable Effects (ICRP 103, 2007) (10--22 Sv--11 – Percent per Sievert) Exposed Population
Cancer Induction
Heritable Effects
Whole
5.5
0.2
Adult
4.1
0.1 19
2000
2000
Unintended
Exposure s
Radiation Therapy Publications 2008
ICRP 112, 201020 2010
Problem
Co-60Miscalibrations
Country
Year
Patients Overdosed
USA
1974-1976
426
Germany
1986-1987
86
UK
1988
207
Costa Rica
1996
114
1985-1987
3
1990
27
Hardware / Software Linear Accelerators
Canada & USA Spain Poland
2001
5
TreatmentPl anning
USA
1987-1988
33
Panama
2000
28 21
ICRP 2010
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621 Radiotherapy Mistakes (NYT)* New York State, 2001 - 2008 Nr. Patients Cause of overexposure 133 Beam-shaping devices error 284 Wrong target 50 Wrong patient 1 Faulty calculation 2 Lack of tests after machine repair * The information presented is that reported in the New York Times (NYT) by Walt Bogdanich in January 2010. No independent verification for accuracy has been performed.
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2 Radiotherapy Mistakes (NYT)* New York City, 2005 (Patients died in 2007) Cancer Site Cause of overexposure
Comments / Consequences 3 of 5 fractions given. Severe Multileaf collimator for morbidity. Physicist checks RX IMRT did not work. Dose given : 7 times prescribed Tongue Open field instead. Hospital and Varian sued (Varian) Varian modifies software 27 of 28 fractions given. Breast Wedge not in the beam. Morbidity appears at the end. Dose given: 3.5 times prescribed 24
Radiotherapy Mistakes (NYT)* Other USA States State Year Florida 2005 Louisiana 2005 Texas 2004 Ohio 2006
Nr. Patients
Cancer Site
Cause of overexposure
Overdose (%)
Linac miscalibration
50
1 Prostate
Wrong CT scan for TPS
100 (38 fractions)
1 Prostate
EBT + Brachy : No dose prescription, no post-implant calcs
?
1 Breast
Incorrect magnification factor
100
77 Brain
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Radiotherapy Mistakes Veterans Affairs Hospitals Location Year Philadelphia Pennsylvania 2002 - 2008
East Orange New Jersey 2006
Nr. Patients
97
Cancer Site
Cause of overexposure
Prostate
Incorrect placement of I-125 seeds No dosimetry
Prostate 56 Head & Neck 36 overirradiated Lung 20 had “errors” Breast 2 Others
No staff training in IMRT No experience No QC, QA 26
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C. Borrás 29 V ALFIM 2010
