radiation dose terms made simple · • concentration of x-rays • energy deposited – associated...

Radiation DoseTerms MadeSimple

9670970 v1

Equivalent and Effective Dose

Background Radiation

In Air Radiation Measurements Dose Comparisons

System Comparison FactsAbsorbed Dose

ALARA Guidelines

Dose Table Summary

Introduction

Introduction

BackgroundRadiation

DoseComparisons

SystemComparison Facts

Equivalent andEffective Dose

In Air RadiationMeasurements

Dose TableSummaryIntroduction Absorbed Dose ALARA Guidelines

BackgroundRadiation

DoseComparisons




Dose TableSummaryIntroduction Absorbed Dose

Radiation Dose

Goal

To provide basic term definitions and

exhibit how radiation effects the patient,

surgeon and staff.

ALARA Guidelines

BackgroundRadiation

DoseComparisons





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.

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Dose Metrics (NEW SI Terms / Old Terms)

- R - rem - rad

- mGy - mSv - Kerma - CTDI - DLP

ALARA Guidelines

The Essential Physics of Medical Imaging (second edition)

BackgroundRadiation

DoseComparisons




Dose TableSummary ALARA GuidelinesIntroduction Absorbed Dose

Dose Factors!!

Patient Dose Influencers

- Amount of exposure - Time Irradiated

- kVp (kilovolt peak) - Power of the X-ray beam (rain force)

- mA (milliamps) - Amount of Radiation - (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

Force

Amount

BackgroundRadiation

DoseComparisons





In Air RadiationMeasurementsRöntgen / AKR units

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Röntgen (R)

• A term named for Wilhelm Conrad Röntgen

• German Physicist

• 1845-1923 (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

ALARA Guidelines

BackgroundRadiation

DoseComparisons





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)

Absorbed Dose

BackgroundRadiation

DoseComparisons





Grays and rads

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Absorbed Dose

• 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

Energy Absorbed in one unit of mass

1 gray (G)

1 rad

1 joule100 ergs

1 g

1 kg

ABSORBED DOSE

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Gy unit (Gray)

• Named after Louis Harold Gray

• British Physicist / Radiologist

• 1905-1965 (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 Dose in matter (Concentration of X-rays)

• 1 Gy = 1 Joule / kilogram

Gy is a measure of Absorbed Dose, based on the (Sv)

ALARA Guidelines

BackgroundRadiation

DoseComparisons





rad unit (Radiation Absorbed Dose)

• Radiation Absorbed Dose

• Outdated term

• Used in some papers even today

• Measures Absorbed Dose 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 DoseAn old measure of Absorbed Dose

BackgroundRadiation

DoseComparisons





Equivalent andEffective DoseSievert, rem

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Equivalent and Effective Dose

• Measurement Sievert (Sv) and rem Tissue weighting factors

• Equivalent Dose – Identifies affect on the organ – Biological Damage Deterministic Effects (organ)

• Effective Dose – Identifies effect on the whole body – Sum of all Equivalent anatomical weighted dose risks (whole body)

• Radiation breaks protein pairs and changes the function of cells

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Damage is irreversible

Radiation may affect each person differently. Thresholds for damageare determined by the pre-disposition of each individual’s tolerance ofradiation. Some individuals will be more susceptible to organ damage,others to whole body.

Tissue or Organ Tissue Weight Factor

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 1.00

Tissue weighting factors

ALARA Guidelines

http://trshare.triumf.ca/~safety/EHS/rpt/rpt_3/img39.gif

BackgroundRadiation

DoseComparisons





Sievert (Sv)

• A term named after Professor Rolf Sievert

• Swedish Physicist

• 1896-1966

• 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


• 1 Sv = 1 Joule /kilogram with Tissue weighting factor

• Tie Effective and Equivalent Dose back to whole body and organ measurements.

(Sv) Measure of BiologicalDamage In Effective orEquivalent Dose Affects Genetics

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Rem Unit

• Roentgen Equivalent Man

• Old dated measure of Effective Dose

• Did not use the metric system conversion (SI Units)


• 1 rem = 0.01 Sv

• 1000 rem exposure is fatal

• Still used for film badge measures today

Old Measure of Biological Damage InEffective or Equivalent Dose! Affects Genetics

ALARA Guidelines

BackgroundRadiation

DoseComparisons





CTDI(Computer TomographyDose Index)

• Special Dose Quantity for CT

• “Index” means “Estimation”

• Considers both Primary Beam and Scatter

• Uses data from One Slice

• Weighted average measurement of dose in a phantom

• Measured in mGys

• Inconsistent measure with high variability

Estimation of Absorbed Dosein CT scans! Energy Absorbed

DOSIMETER

∫ DOSE

W= CTDI

W

ScatteredRadiation

PrimaryRadiation

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Dose Length Product

• Another Special Dose Quantity for CT

• Product of CTDI

• “Estimate” variable measure

• Used to compare various CT procedures

• Measured in Gy-cm

Estimates Total RadiationDose to Patient

CTDI

Dose Length Product

(CTDIvol x Scan Length)

Dose Table Summary

BackgroundRadiation

DoseComparisons





The Essential Physics of Medical Imaging (second edition)

BackgroundRadiation

DoseComparisons





Dose Table Summary

Metric New (SI) Scientific Units

Metric Old What is measured

Air-Kerma AKR kinetic energy released in matter

R (X-ray) Measures amount of radiation in Air

Sievert – msv Rem kinetic energy released in matter

Effective or Equivalent Dose (Affects genetic material (DNA) tissue weighting factor)

Gray – mGy rad Radiation Absorbed Dose measured in ergs

Absorbed Dose Energy Disposed in Tissue

CTDIvol Computer Tomography Dose Index Measures primary beam and scatter in mGy

DLP Dose Length Product Measured in mGy cm CTDIvol X Length of Irradiated Volume

Radiation Sources

BackgroundRadiation

DoseComparisons





Solar

Medical

Dietary Intake Consumer Products

Radon

Other

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Every Day Radiation Sources

Natural Background Radiation – 81%

• Cosmic (Space and sun)

• Terrestrial (Earth sources)

• Radon

Man-made Radiation – 19%

• Nuclear weapons / power plants

• Fossil fuel

• Medicine

• Occupational

• Consumer products (phones)

Background Radiation is a good reference for radiographic procedures!

NaturalBackgroundradiation

81%

19%

Man-maderadiation

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Effective Dose( mSv )

Equivalence in Natural Background Radiation at Sea Level (2.9 mSv/yr)

Abdominal Region - CT of abdomen - O-arm® system spin of abdomen

6.65.6

2 years 2 months1 year 6 months

Chest Region - CT of chest - O-arm® system chest

4.683.92

1 year 5 months1 year 1 month

Head Region - CT of head - O-arm® system spin of head

0.810.65

3 months2.5 months

Comparisons of Radiographic Studies

Comparison of representative CT and Radiograph procedures to Natural Background Radiation (source ACR/ RSNA 2008)

Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-arm® system.

Dose Comparisons

BackgroundRadiation

DoseComparisons




Dose TableSummaryIntroduction Absorbed D ose ALARA Guidelines

BackgroundRadiation

DoseComparisons





Relative doses from radiation sources in millisievert doses

Single procedure Single procedure

Chestx-ray

Mammogram

Airplane Flight100k miles

annual

2 mSv

.02 mSv

annual

Natural Background Radiation Living at

Sea Level

2.9 mSvSingle procedure

O-arm® system Spin of Abdomen

5.6 mSv

.30 mSv

annual

Natural Background Radiation Living

in Denver

4.1 mSv

annual

DiagnosticRadiology

.50 mSv

annual

Radon in Average Home

2 mSvSingle procedure

CT ofAbdomen

6.6 mSv

*Representational values depicted

ALARA Guidelines

Division of Environmental Health Office of Radiation Protection. (2010). Background Radiation Natural versus Man-Made. Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-arm® system.

BackgroundRadiation

DoseComparisons





Dose Gauge

CTScan

22 mammograms

19 mammograms

2.3 times US averageradiation at Sea Level

1.9 times US averageradiation at Sea Level

= =

= = O-arm®system

Scan

ALARA Guidelines

BackgroundRadiation

DoseComparisons





O- arm® System to C-arm Dose Comparison

=

ALARA Guidelines

Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-arm® System. O-arm® Imaging System , Version 3.1(), page 9 second table

Standard 3D ProtocolAbdomen

Large Patient

Regular Fluoroscopy: 56 secondsBoost Fluoroscopy: 19 seconds

BackgroundRadiation

DoseComparisons





Image Quality and Dose!

• 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.

PatientThickness

Dose

ALARA Guidelines

http://www.ndt-ed.org/EducationResources/CommunityCollege/RadiationSafety/Graphics/Exposure-Limits.gif

Occupational Dose (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 – http://www.xrayrisk.com/calculator/calculator.php

Total EffectiveDose Equivalent -Whole Body5 Rem (0.05 Sv)

Eye Dose Equivalent15 Rems (0.15 Sv)

Shallow DoseEquivalentWhole-Body 50 Rems (0.50 Sv)

Total OrganDose Equivalent - Any Organ50 Rems (0.50 Sv)

BackgroundRadiation

DoseComparisons





Sample O-arm® SystemPatient Dose 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 Dose Report is automatically sent to the PACS system as part of the patient record.

The Dose Report allows for better patient monitoring and management of radiation dose by providing:

BackgroundRadiation

DoseComparisons





ID kVp mAs CTDI (mGy) DLP (mGy cm) Phantom (cm)3D #1 120.00 93.75 11.91 190.42 Head 163D #2 120.00 195.50 14.08 225.13 Body 32Total 415.55

Mode of Op Exposure Time (sec) Exposure (mGy) DAP (mGy cm2)Fluoro 32.01 13.01 2917.28High Level Fluoro 13.09 3.64 816.37Total 45.11 16.65 3733.65

3D Dose

Fluoro Dose

Dose Report

Generated On 7/6/2010 2:17:36 PMInstitution Name Medtronic MNL Station Name 268Patient Last Name AppleseedPatient First Name JohnPatient Middle Name APatient ID 126465523-AStudy Date 7/06/2010 2:14:09 PMAccession Number Sample Accession NumberStudy Description Sample Test DescriptionPerforming Physician Smith, Jim

For more information, please roll-over any of the Dose Report terms, Fluoro Dose or 3D Dose chart terms

System Comparison Facts

BackgroundRadiation

DoseComparisons





BackgroundRadiation

DoseComparisons





Imaging Space

CT Flat Platebased system

Image Intensifier based system

10cm12cm15cm

O-arm® system

ALARA Guidelines

BackgroundRadiation

DoseComparisons





2D Image Intensifier System 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)

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Flat Plate Based SystemFD 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


ALARA Guidelines

BackgroundRadiation

DoseComparisons





2D Imaging Space

Image Intensifier-based system23cm

Flat Plate-based system 20x20cm

30cm 30cm

40cm 40cm

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Three DimensionalImaging 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


O-arm® system

O-arm® system

II system

II system must be centered perfectly to acquire anatomy of interest. This may result in multiple images being required.

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.

ALARA Guidelines

BackgroundRadiation

DoseComparisons





Flat Plate (FP) BasedSystem 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


O-arm® system

O-arm® system

FP system

FP system must be centered perfectly to acquire anatomy of interest. This may result in multiple images being required.

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.

ALARA Guidelines

ALARA Guidelines

BackgroundRadiation

DoseComparisons





BackgroundRadiation

DoseComparisons





ALARA Guidelines

• 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

Medtronic recommendsusing ALARA

Image Receptor

Grid

Patient

Primary Beam

Photons:

BackgroundRadiation

DoseComparisons





ReferencesDivision of Environmental Health Office of Radiation Protection. (2010). Background Radiation Natural versus Man-Made. Retrieved from http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-htm/fs10bkvsman.htm

FDA U.S. Food and Drug Administration. (2002). Radiation-Emitting Products. Retrieved from http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115317.htm

HPS Health Physics Society. (2009). Radiation Dose Units.Retrieved from http://hps.org/publicinformation/ate/faqs/radiationdoses.html

Kerma. (n.d.). In Wikipedia. Retrieved from http://en.wikipedia.org/wiki/Kerma_(physics)

Los Alamos National Laboratory. (2008-09). Annual Radiation Dose Calculator.Retrieved from http://newnet.lanl.gov/info/dosecalc.asp

Masse, F.X. (2009, November). Dosimetry Report for the Medtronic O-Arm System.O-arm® Imaging System , Version 3.1(), 4, 6.

Rontgen. (n.d.). In Wikipedia. Retrieved from http://en.wikipedia.org/wiki/Wilhelm_R%C3%B6ntgen

U.S. Environmental Protection Agency. (2010). Radiation Publications.Retrieved from http://www.epa.gov/radiation/pubs.html#understanding_radiation

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 2002.

9670970 v1 Radiation Dose Terms Made Simple © Medtronic, Inc. 2011. All Rights Reserved. Developed in USA

radiation dose terms made simple · • concentration of x-rays • energy deposited – associated...

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