Medical Devices Radiation Safety

Transcription

1 Medical Devices Radiation Safety Cari Borrás, D.Sc., FACR, FAAPM Visiting Professor DOIN-DEN DEN / UFPE Recife, Pernambuco, Brazil Co-Chair, Chair, IUPESM Health Technology Task Group 1

2 Radiological equipment has changed a bit since the early days... 2

3 CT DR PET/CT 3

4 First Co-60 Unit (1951) Cs-137 Teletherapy (1960 s) External Beam Therapy Linac with IGRT (200s) Orthovoltage X-Ray X (1990 s) 4

5 Manchester Applicator 1950 Ra - Needles Brachytherapy Cs-137 LDR Ir-192 HDR 1990 Miniature X-Ray Tube Electronic Brachytherapy

6 R. Mackie 2009

7 Global Annual Number of Radiological Exams and Treatments per 1,000 People Practice X Rays Nuclear Medicine Radiotherapy 562 (1,607) 5.1 (19) 0.8 (2.4) 420 (1,230) (19) (1.9) ( Data for HCL I ) UNSCEAR

8 Annual per Caput Effective Dose (msv) for theunited States Population Medical: UNSCEAR2008 8

9 Radiation Risks External Internal Contamination Pathways l Absorption l l Inhalation Ingestion 9

10 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

11 Effects of Cell Death Probability of Death 100% D Dose (mgy) Co-60 Radiotherapy Overexposure Panama

12 Whole body response : adult Acute irradiation syndrome Survival time BMS (bone marrow) 1-10 Gy GIS (gastro intestinal) Gy > 50 Gy CNS (central nervous system) Dose Lethal dose 50 / 30 Chronic irradiation syndrome Whole body clinic of a partial-body irradiation Mechanism: Neurovegetative disorder Similar to a sick feeling Quite frequent in fractionated radiotherapy 12

13 Skin Injuries Interventional Radiology Over-Exposure, USA

14 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 Detectable opacities Visual impairment (cataract) Sv single brief exposure Sv/year for many years > 0.1 >

15 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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17 Genetic (Heritable) Effects (Mutations) Fruit Fly Experiments 10 Frequency (%) Absorbed dose (Gy) 17

18 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. 18

19 ICRP Detriment-Adjusted Nominal Risk Coefficient for Cancer and Heritable Effects (ICRP 103, 2007) (10-2 Sv -1 Percent per Sievert) Exposed Population Cancer Induction Heritable Effects Whole Adult

20 Unintended Exposure s Radiation Therapy Publications 2008 ICRP 112,

21 Problem Co-60Mis 60Mis- calibrations Hardware / Software Linear Accelerators TreatmentPl anning Country Year Patients Overdosed USA Germany UK Costa Rica Canada & USA Spain Poland USA Panama

22 ICRP

23 621 Radiotherapy Mistakes (NYT)* New York State, 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 No independent verification for accuracy has been performed. 23

24 2 Radiotherapy Mistakes (NYT)* New York City, 2005 (Patients died in 2007) Cancer Site Tongue Breast Cause of overexposure Multileaf collimator for IMRT did not work. Open field instead. (Varian) Wedge not in the beam. Comments / Consequences 3 of 5 fractions given. Severe morbidity. Physicist checks RX Dose given : 7 times prescribed Hospital and Varian sued Varian modifies software 27 of 28 fractions given. Morbidity appears at the end. Dose given: 3.5 times prescribed 24

25 State Year Radiotherapy Mistakes (NYT)* Nr. Patients Other USA States Cancer Site Cause of overexposure Overdose (%) Florida Brain Linac miscalibration 50 Louisiana Prostate Wrong CT scan for TPS 100 (38 fractions) Texas Prostate EBT + Brachy : No dose prescription, no post-implant calcs? Ohio Breast Incorrect magnification factor

26 Radiotherapy Mistakes Veterans Affairs Hospitals Location Year Philadelphia Pennsylvania East Orange New Jersey 2006 Nr. Patients Cancer Site 97 Prostate overirradiated 20 had errors Prostate Head & Neck Lung Breast 2 Others Cause of overexposure Incorrect placement of I-125 seeds No dosimetry No staff training in IMRT No experience No QC, QA 26

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29 C. Borrás 29 V ALFIM 2010