Radiation Dose Terms Made Simple v1

Transcription

1 Terms Made Simple v1

2 In Air Absorbed Table

3 In Air Absorbed Table

4 Goal To provide basic term definitions and exhibit how radiation effects the patient, surgeon and staff. In Air Absorbed Table

5 Why do I need to know these terms? To understand what, why and how radiation exposure is measured For patient awareness To recognize terminology used in dose reports Innovating for life. In Air Absorbed Table

6 Metrics (NEW SI Terms / Old Terms) - mgy - msv - Kerma - CTDI - DLP - R - rem - rad The Essential Physics of Medical Imaging (second edition) In Air Absorbed Table

7 Factors!! Force Patient Influencers - Amount of exposure - Time Irradiated - kvp (kilovolt peak) - Power of the X-ray beam (rain force) - ma (milliamps) - Amount of - (rain amount) - Area exposed - Size - Distance from source - Inverse Square Law (>distance better) - Energy (Type) - X-rays, Gamma, Alpha rays - Different Tissues - Tissue tolerances (weighting) - Measurement Air/Tissue Amount In Air Absorbed Table

8 In Air Röntgen / AKR units In Air Absorbed Table

9 Röntgen (R) A term named for Wilhelm Conrad Röntgen German Physicist (77 yrs) Father of Diagnostic Radiology Named - X-rays Wife s hand was first image (R) symbol for Rontgen (out dated measure) but still seen in some articles today R is old measure of exposure in air In Air Absorbed Table

10 AKR Unit (Air-Kerma Rate) Kerma (Kinetic Energy Released per MAss (of air) Measures ionizing radiation in materials (AKR) Used for measuring exposure rates Contained in Dosimetry Reports for CT s Cell phone outputs Kinetic Energy Released per unit MAss (New measure of radiation in air) In Air Absorbed Table

11 Absorbed Grays and rads In Air Absorbed Table

12 1 gray (G) Absorbed Measured in rad or Gray Concentration of X-rays Energy Deposited Associated Locally Whole body Absorbed Energy per unit Mass Rad (100 ergs into 1gram of tissue) Gray (1 Joule into 1 kilogram) Measured in the center of tissue phantoms 100 ergs 1 rad 1 g 1 joule 1 kg Energy Absorbed in one unit of mass ABSORBED DOSE In Air Absorbed Table

13 Gy unit (Gray) Named after Louis Harold Gray British Physicist / Radiologist (60 yrs) Fathered Radiobiology Term (Gy) define in 1975 (SI Unit) Whole body exposure of 5 Grays results in death in 14 days Measures Absorbed in matter (Concentration of X-rays) 1 Gy = 1 Joule / kilogram Gy is a measure of Absorbed, based on the (Sv) In Air Absorbed Table

14 rad unit ( Absorbed ) Absorbed Outdated term Used in some papers even today Measures Absorbed in matter (Concentration of X-rays) Measures absorbed dose in Ergs (Not an SI unit) One rad equal to 10 mgy rad measure of Absorbed An old measure of Absorbed In Air Absorbed Table

15 Sievert, rem In Air Absorbed Table

16 Measurement Sievert (Sv) and rem Tissue weighting factors Equivalent Identifies affect on the organ Biological Damage Deterministic Effects (organ) Identifies effect on the whole body Sum of all Equivalent anatomical weighted dose risks (whole body) breaks protein pairs and changes the function of cells In Air Absorbed Table

17 Damage is irreversible Tissue weighting factors Tissue or Organ Tissue Weight Factor may affect each person differently. Thresholds for damage are determined by the pre-disposition of each individual s tolerance of radiation. Some individuals will be more susceptible to organ damage, others to whole body. Gonads 0.20 Bone Marrow (red) 0.12 Colon 0.12 Lung 0.12 Stomach 0.12 Bladder 0.05 Breast 0.05 Liver 0.05 Esophagus 0.05 Thyroid 0.05 Skin 0.01 Bone Surface 0.01 Remainder 0.05 Total In Air Absorbed Table

18 Sievert (Sv) A term named after Professor Rolf Sievert Swedish Physicist Pioneering role in measuring diagnostic and cancer treatment radiation doses In 1979 the General Conference on Weights and Measures named a dose measure after him Concentration of X-rays 1 Sv = 1 Joule /kilogram with Tissue weighting factor Tie Effective and Equivalent back to whole body and organ measurements. (Sv) Measure of Biological Damage In Effective or Equivalent Affects Genetics In Air Absorbed Table

19 Rem Unit Roentgen Equivalent Man Old dated measure of Did not use the metric system conversion (SI Units) Concentration of X-rays 1 rem = 0.01 Sv 1000 rem exposure is fatal Still used for film badge measures today Old Measure of Biological Damage In Effective or Equivalent! Affects Genetics In Air Absorbed Table

20 CTDI (Computer Tomography Index) Special Quantity for CT DOSE W = CTDI Index means Estimation Considers both Primary Beam and Scatter Uses data from One Slice W DOSIMETER Weighted average measurement of dose in a phantom Measured in mgys Inconsistent measure with high variability Primary Scattered Estimation of Absorbed in CT scans! Energy Absorbed In Air Absorbed Table

21 CTDI (CTDIvol x Scan Length) Length Product Another Special Quantity for CT Product of CTDI Estimate variable measure Used to compare various CT procedures Measured in Gy-cm Estimates Total to Patient Length Product In Air Absorbed Table

22 Table In Air Absorbed Table

23 Table Metric New (SI) Scientific Units Air-Kerma AKR kinetic energy released in matter Metric Old What is measured R (X-ray) Measures amount of radiation in Air Sievert msv Rem kinetic energy released in matter Gray mgy rad Absorbed measured in ergs Effective or Equivalent (Affects genetic material (DNA) tissue weighting factor) Absorbed Energy Disposed in Tissue CTDIvol Computer Tomography Index Measures primary beam and scatter in mgy DLP Length Product Measured in mgy cm CTDIvol X Length of Irradiated Volume The Essential Physics of Medical Imaging (second edition) In Air Absorbed Table

24 Solar Sources Other Medical Radon Dietary Intake Consumer Products In Air Absorbed Table

25 Every Day Sources Natural 81% Cosmic (Space and sun) Terrestrial (Earth sources) Radon Man-made 19% Nuclear weapons / power plants Fossil fuel Medicine Occupational Consumer products (phones) Natural radiation Man-made radiation 81% 19% is a good reference for radiographic procedures! In Air Absorbed Table

26 of Radiographic Studies Abdominal Region - CT of abdomen - O-arm system spin of abdomen ( msv ) Equivalence in Natural at Sea Level (2.9 msv/yr) 2 years 2 months 1 year 6 months Chest Region - CT of chest - O-arm system chest year 5 months 1 year 1 month Head Region - CT of head - O-arm system spin of head months 2.5 months Comparison of representative CT and Radiograph procedures to Natural (source ACR/ RSNA 2008) Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-arm system. In Air Absorbed Table

27 In Air Absorbed D ose Table

28 Relative doses from radiation sources in millisievert doses Radon in Average Home Airplane Flight 100k miles Natural Living at Sea Level Natural Living in Denver O-arm system Spin of Abdomen CT of Abdomen annual 2 msv annual 2 msv annual 2.9 msv annual 4.1 msv Single procedure 5.6 msv Single procedure 6.6 msv Single procedure.02 msv Chest x-ray Single procedure.30 msv Mammogram annual.50 msv Diagnostic Radiology *Representational values depicted Division of Environmental Health Office of Protection. (2010). Natural versus Man-Made. Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-arm system. In Air Absorbed Table

29 Gauge CT Scan = = 22 mammograms 2.3 times US average radiation at Sea Level O-arm system Scan = = 19 mammograms 1.9 times US average radiation at Sea Level In Air Absorbed Table

30 O- arm to C-arm Comparison Standard 3D Protocol Abdomen Large Patient = Regular Fluoroscopy: 56 seconds Boost Fluoroscopy: 19 seconds Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-arm. O-arm Imaging, Version 3.1(), page 9 second table In Air Absorbed Table

31 Image Quality and! Physicists: MEASURE DOSE NOT IMAGE QUALITY! Surgeons determine Image Quality measure Increased thickness, and dense tissue result in increase dose More corpulent (big) patients receive larger doses than children do. X-ray Rain (More rain more information to a point!) Flat Plate technology and bigger generators provide better image Effects magnified for pediatric patients. Anatomical Density Bones, etc. Patient Thickness In Air Absorbed Table

32 Occupational (Surgeon) OSHA & International Commission on Radiological Protection Limits of 50mSv per year. Torso Limits of 50mSv or 5000 mrems or per year. Extremity Limits of 500 msv or 50,000 mrems per year recommended (10X greater than general public). Eye Limits of 150 msv Risk Calculator based on exposure Eye Equivalent 15 Rems (0.15 Sv) Shallow Equivalent Whole-Body 50 Rems (0.50 Sv) Total Organ Equivalent - Any Organ 50 Rems (0.50 Sv) Total Effective Equivalent - Whole Body 5 Rem (0.05 Sv) In Air Absorbed Table

33 Sample O-arm Patient Report Documentation of patient s estimated radiation dose for each procedure Enables trending of dose levels across patients and procedures An explanation of the effect of different system options (collimation, fluoroscopy exposure time, number of spins) on patient dose levels The Report is automatically sent to the PACS system as part of the patient record. Fluoro The Report allows for better patient monitoring and management of radiation dose by providing: Mode of Op Exposure Time (sec) Exposure (mgy) DAP (mgy cm2) Fluoro High Level Fluoro Total D For more information, please roll-over any of the Report terms, Fluoro or 3D chart terms Report Generated On 7/6/2010 2:17:36 PM Institution Name Medtronic MNL Station Name 268 Patient Last Name Appleseed Patient First Name John Patient Middle Name A Patient ID A Study Date 7/06/2010 2:14:09 PM Accession Number Sample Accession Number Study Description Sample Test Description Performing Physician Smith, Jim ID kvp mas CTDI (mgy) DLP (mgy cm) Phantom (cm) 3D # Head 16 3D # Body 32 Total In Air Absorbed Table

34 In Air Absorbed Table

35 Imaging Space CT O-arm system Image Intensifier based system Flat Plate based system 15cm 12cm 10cm In Air Absorbed Table

36 2D Image Intensifier Fluoro O-arm system (3X more image information) 13-inch Image Intensifier II system will require assessments of multiple regions to match O-arm system FOV Multiple regions require more exposure (increases cumulative dose) In Air Absorbed Table

37 Flat Plate Based FD Vario 3D O-arm system (3X more image information) 3 mega pixel vs 1 mega pixel FP FP system will require assessments of multiple regions to match O-arm system FOV Multiple regions require more exposure (increases cumulative dose) In Air Absorbed Table

38 2D Imaging Space 30cm 30cm 40cm 40cm Image Intensifier-based system 23cm Flat Plate-based system 20x20cm In Air Absorbed Table

39 Three Dimensional Imaging Section O-arm system (2.72X greater volume image) O-arm system cylinder presentation II system cube presentation 12cm x 12cm x 12cm cube II system will require assessments of multiple regions to match O-arm system FOV Multiple regions require more exposure (increases cumulative dose) O-arm system II system II system must be centered perfectly to acquire anatomy of interest. This may result in multiple images being required. O-arm system II system II system must be centered perfectly to acquire anatomy of interest. This may result in multiple images being required. 2 x 3D scans are required to equal the O-arm system anatomical information. In Air Absorbed Table

40 Flat Plate (FP) Based FD 3D O-arm system (4.7X greater volume image) O-arm system cylinder presentation FP system cube presentation 10cm x 10cm x 10cm cube FP system will require assessments of multiple regions to match O-arm system FOV Multiple regions require more exposure (increases cumulative dose) O-arm system FP system FP system must be centered perfectly to acquire anatomy of interest. This may result in multiple images being required. O-arm system FP system FP system must be centered perfectly to acquire anatomy of interest. This may result in multiple images being required. 2 x 3D scans are required to equal the O-arm system anatomical information. In Air Absorbed Table

41 In Air Absorbed Table

42 ALAR A Guidelines Primary Beam ALARA- As Low As Reasonably Acceptable Guidance for safe exposure Used in other areas of Medical Imaging Provides first line of defense in reducing dose RT s are taught to use ALARA Reducing collimation reduces overall radiation Patient Photons: Grid Medtronic recommends using ALARA Image Receptor In Air Absorbed Table

43 v1 Terms Made Simple Medtronic, Inc All Rights Reserved. Developed in USA References Division of Environmental Health Office of Protection. (2010). Natural versus Man-Made. Retrieved from FDA U.S. Food and Drug Administration. (2002). -Emitting Products. Retrieved from HPS Health Physics Society. (2009). Units. Retrieved from Kerma. (n.d.). In Wikipedia. Retrieved from Los Alamos National Laboratory. ( ). Annual Calculator. Retrieved from Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-Arm. O-arm Imaging, Version 3.1(), 4, 6. Rontgen. (n.d.). In Wikipedia. Retrieved from U.S. Environmental Protection Agency. (2010). Publications. Retrieved from The Essential Physics of Medical Imaging (second edition) Jerrold T. Bushberg, J. Anthony Seibert, Edwin M. Leidholdt Jr., John M. Boone, Lippincott Williams and Wilkins In Air Absorbed Table