Download Dosimetry Consideration in Radiotherapy

Dosimetry Consideration in
Radiotherapy
Sou-Tung Chiu-Tsao, PhD, DABR, FAAPM
Quality MediPhys LLC
Denville, NJ, USA
Radiation Dosimetry Workshop
University of Malaya Medical Center
Kuala Lumpur, Malaysia
March 28, 2014
Safe and Accurate Delivery of
Radiotherapy
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Dose
Dose Fractionation or Dose Rate
Anatomical Location(s)
Target Delineation (Contours on Image Slices)
Optimized Dose Distribution in the Target
Minimized Dose to Normal Tissue/Organ(s)
Dose Volume Histogram
Dosimetry Consideration in
Radiotherapy - Broad Sense
Dosimetry Measurement in Phantom
 Dosimetry Verification Measurement
 Dosimetry Calculation
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Imaged-Based Treatment Planning Calculation
Image-Guided Treatment Delivery
Dosimetry Consideration in
Radiotherapy - Measurement
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Dosimetry Measurement in Phantom
Homogeneous Phantom
 Heterogeneous Phantom
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Dosimetry Verification Measurement
In Homogeneous Phantom Before Treatment
 In Heterogeneous Phantom Before Treatment
 In Vivo During Treatment
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Dosimetry Consideration in
Radiotherapy - Calculation
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Dosimetry Calculation –
Image-Based Treatment Planning Calculation
Imaging of Patient Anatomy
 Target Delineation on Image Slices
 Homogeneous Water
 Heterogeneity Corrections
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Patient Anatomy Heterogeneity (Internal)
 Tissue-Air Interface (Skin Surface)
 Patient Support Device Heterogeneity (External)
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Radiation Therapy
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External Beam Therapy
Brachytherapy
Commissioning a Radiotherapy Unit or Modality
(External Beam or Brachy Source)
Commissioning a Treatment Planning System (TPS)
Periodic Calibration (Daily, Monthly or Annual)
Routine Treatment Planning Calculation
External Beam Modality
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Kilovoltage X-Ray Beam
Photon Beam
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SRS, SRT, SBRT
IMRT, VMAT
Electron Beam
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Including Total Body Irradiation (TBI)
Including Total Skin Electron Irradiation (TSEI)
Particle Beam (Proton, Carbon Ion, etc)
Commissioning an External Beam
Radiotherapy Unit or Modality
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Beam Data Acquisition
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Treatment Planning System (TPS)
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Ion Chamber, Diode, Film in Phantom
Beam Data Entry, Modeling, Testing
Verification of TPS Calculation
Point Dosimetry (0D)
 Linear Dosimetry (1D)
 Planar Dosimetry (2D)
 Volume Dosimetry (3D)
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External Beam Treatment of an
Individual Patient/Disease
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Simulation (Planar X-Ray Images, CT, PET, MRI)
Target Delineation, Contours on Image Slices
TPS Calculation
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Heterogeneity correction
Patient Specific Quality Assurance
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Portal Imaging (Film, CR, EPID)
Image Guidance (Planar Images, CBCT, CT On-Rail, MRI)
Verification of Dose Delivery Before Treatment
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Dosimetry In Phantom
Verification of Dose Delivery During Treatment
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Dosimetry In Vivo
Intensity Modulated Radiation
Therapy (IMRT)
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Fixed Gantry Angle
Constant Output Rate
Multileaf Collimator (MLC)
Leaves Move During the
Treatment
Non-Uniform Beam Intensity
Technique
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Sliding Window
Step and Shoot
Volumetric Modulated Arc Therapy
(VMAT)
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Arc Delivery of IMRT
MLC Leaf Motion
Gantry Rotation
Output Rate Variation
Treatment couch
Webb and McQuaid, Phys. Med. Biol. 2009; 54: 4345-4360.
VMAT/IMRT Prostate
VMAT
IMRT
30 50 70 90 100 105 %
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Evolving rapidly
MU ~ 300
Less treatment time
Output rate varies with angle
Rotating gantry
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Single arc, Multiple arc
Partial arc, Split arc
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Established
MU ~ 600
More treatment time
Output rate remains fixed
Fixed gantry angle for each
field
Immobilization/Support Devices
Van Prooijen, J. Appl.Clin. Med. Phys. 2010;11(2):128-139.
VMAT
Beams
delivered
through
treatment
couch and
Immobilization
devices
Webb and McQuaid, Phys. Med. Biol. 2009; 54: 4345-4360.
Dosimetry Calculation
Issue of Concern
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Heterogeneity Corrections
Patient Anatomy Heterogeneity (Internal)
 Tissue-Air Interface (Skin Surface)
 Patient Support Device Heterogeneity (External)
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Dose Attenuation at Depth (Target)
 Dose Elevation at Skin and Buildup Region
 Bolus Materials
 Support and Immobilization Devices
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Small Field Dose Calculation
Grade-4 Skin Necrosis
Hoppe, Int. J. Rad. Onc. Biol. Phys. 2008; 72: 1283-1286.
Treatment Plan Comparison
Account for couch and
immobilization device
1 cm bolus
Hoppe, Int. J. Rad. Onc. Biol. Phys. 2008; 72: 1283-1286.
Account for Patient Support Devices
in TPS Calculation
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Apply the heterogeneity correction for treatment
couch and immobilization devices into the TPS
Njeh, J. Appl. Clin. Med. Phys. 2009; 10(3): 16-27.
Gerig, Med. Phys. 2010; 37: 322-328.
Smith, Med. Phys. 2010; 37: 3595- 3606.
Van Prooijen, J. Appl. Clin. Med. Phys. 2010; 11(2): 128-139.
Olch, AAPM TG-176 Report in Preparation.
Brachytherapy Modalities
Photon Source Beta Source
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Ra-226
Sr-90
Co-60
Y-90
Cs-137
Ru/Rh-106
Ir-192
P-32
Yb-169
Cs-131
I-125
Pd-103
50 kVp X-Ray Source
Application method
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Intracavitary
Interstitial
Combined
Intraluminal
Intravascular
Intraoperative
Skin Surface
Eye
Commissioning a New
Brachytherapy Modality
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Dosimetric Parameters of the Brachytherapy Source
Entered into Treatment Planning System (e.g. Those
Recommended by the AAPM TG43 and HEBD)
Verification of the TPS Calculation
For Some Test Cases of Known Geometry
Applicator
 Anatomy
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At a Few Reference Points
Target
 Critical Normal Organ(s)
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Brachytherapy Treatment of an
Individual Patient/Disease
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Orthogonal Films and/or CT/MRI Scan Images
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Target Delineation (for Image-Guided Treatment)
TPS Calculation
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Applicator Position Relative to Anatomy
Homogeneous Water (Current State of Art)
Heterogeneity Correction (Limited Usage)
Patient Specific Quality Assurance
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Verification of Source Position(s) Before Treatment
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Catheter(s)/Needle(s)
Tandem and Ovoids
Verification of Dose Delivery During Treatment
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Dosimetry In Vivo
Heterogeneous Calculation
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Semianalytic Pathlength Correction
Monte Carlo Simulation Calculation
Grid-Based Boltzman Transport Equation
Solver (GBBS) Calculation
Collapsed Cone Method
Dosimeter Used in Measurement
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Active Dosimeter - Real Time Reading
Passive Dosimeter - Reading after Completion of Irradiation
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Considerations of Dosimeter Selection
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Active or Passive
Dosimetry in 0D, 1D, 2D, 3D
Sensitivity, Response per Unit Dose
Size and Shape
Dose Gradient
Dose Rate
In Phantom or In Vivo
Energy Response and Angular Response
Active Dosimeter
Real Time Reading
Dosimeter
 Ion chamber
 Diode
 MOSFET
 Diamond
 PSD
 Silicon Strip
 MAPS
 EPID
0D
0D
0D
0D
0D
1D
2D
2D
Condition
 In Phantom
 In Phantom, In Vivo
 In Phantom, In Vivo
 In Phantom
 In Phantom, In Vivo
 In Phantom
 In Vivo
 In Vivo
Ion Chamber
0.6 cc
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Radiation Induced Ionization
Shape, Volume (Size), Sensitivity
Point Dosimeter (0D)
Types
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Thimble Chamber
Parallel-Plate Chamber
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0.35 cc
Extrapolation Chamber
Fixed Plate Spacing
Spherical Chamber
Well (Re-entrant) Chamber
Electrometer and Bias Voltage
DeWerd, AAPM Summer School 2009, Ch. 6.
1,000 cc
External Beam
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Point (0D) Dosimeter
Brachy Source
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Source Strength Measurement
Source
100 cm
Source
Dosimeter
Electrometer
Electrometer
Phantom
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1D/2D Ion Chamber Array for
1D/2D Dose Measurement
5 cm
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Move Source Vertically to Locate the
Sweet Spot with the Highest Reading
Diode
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Radiation Induced Ionization
Silicon Diode, n- or p-Type
Semiconductor Technology
Size: mm, Point Dosimeter (0D)
Not Tissue Equivalent
High Sensitivity
Electrometer
In Phantom or In Vivo
Response Dependent on
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Dose Rate, Energy
Temperature
Angle
1D/2D Diode Array for 1D/2D
Dose Measurement
Prof. Rosenfeld to Describe Detail in a Separate Lecture.
Zhu, AAPM 2009 Summer School, Ch. 28.
Diamond
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Radiation Induced Ionization
Industrial Diamond
Size: mm, Point Dosimeter (0D)
More Sensitive Than Diode
Water proof
Nearly Tissue Equivalent
Electrometer
In Phantom
Difficult to Manufacture
Expensive
Das, AAPM 2009 Summer School, Ch. 27.
Electrometer
Plastic Scintillation Dosimeter (PSD)
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Radiation Induced Light Emission
Polyvinyltoluene doped with one or more Fluors
Size: mm, Point Dosimeter (0D)
Tissue Equivalent
In Phantom or In Vivo
Optical Fiber Light Guide Cable
Photo Detector: PMT or CCD Camera
Weak Energy Response above 125 keV
Longitudinal Angular Dependence
No Dose Rate Dependence below 2700 MU/min
2D PSD Array for 2D Dose Measurement
Beddar, AAPM 2009 Summer School, Ch. 32.
Metal-Oxide Semiconductor FieldEffect Transistor (MOSFET)
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Radiation Induced Voltage Change
MOSkin
Semiconductor Technology
Size: mm, Point Dosimeter (0D)
Not Tissue Equivalent
In Phantom or In Vivo
Qi, Med Phys 2009; 36: 59-70.
Strong Energy Response
 Active
Angular Response
 Best, TN models
Finite Life Time
 CMRP, MOSkin
1D/2D MOSFET Array for
 Passive
1D/2D Dose Measurement
 Sicel, OneDose
Prof. Rosenfeld to Describe Detail in a Separate Lecture.
MOSFET
•On skin surface
• Intracavitary
Multi-use
Single use
MOSkin
Cygler, MOSFET dosimetry, AAPM Summer School 2009.
MOSFET Devices
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Active
Multiple Use
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Passive
Single Use
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Passive, Implantable
Cygler, AAPM 2009 Summer School, Ch. 29.
2D Array of Dosimeters
Ion chamber
Diode
PSD
Silicon Strip Dosimeter
Dose Magnifying Glass (DMG)
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Radiation Induced Ionization
Semiconductor Technology
Linear Array of p-n Junctions (1D)
High Resolution, 0.2 mm
Not Tissue Equivalent
Data Acquisition System (DAQ)
In Phantom
Response Dependent on
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Dose Rate, Energy
Temperature
Angle
Prof. Rosenfeld to Describe Detail in a Separate Lecture.
Wong, Med. Phys. 2010; 37: 427-439, Med. Phys. 2011; 38: 1226-1238; 2256-2264.
Monolithic Active Pixel Sensors
(MAPS)
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Radiation Induced Ionization
Semiconductor/ IC Technology
Planar Pixellated Detector (2D)
High Resolution
Data Acquisition System (DAQ)
In Vivo Monitoring
MLC Movement Position
~50 mm precision
During IMRT
Upstream Camera System
Prof. Rosenfeld to Describe Detail in a Separate Lecture.
Page, Nuclear Science, IEEE Transaction; 2014; PP(99): 1-5.
Medipix2
BrachyView
Electronic Portal Imaging
(EPID)
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Radiation Induced Light Emission
Amorphous Silicon
2D Image of Transit Doses
In Vivo
Tx Delivery Verification
Quantitative analysis
Gamma Index Images
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Lung Treatment
Patient Internal Changes of Pleural Effusion from Original
CT to First Treatment
Berry, Int. J. Rad. Onc. Biol. Phys. 2014: 88; 204-209.
Passive Dosimeter
Reading after completion of irradiation
Dosimeter
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TLD
OSLD
RPLGD
MOSFET (OneDose)
Alanine Dosimeter
Radiographic Film
Radiochromic Film
CR Image Plate
Polymer Gel
Fricke Gel
PRESAGE
(Radiochromic Plastic)
Condition
0D
0D
0D
0D
0D
2D
2D
2D
3D
3D
3D
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In Phantom, In Vivo
In Phantom, In Vivo
In Phantom, In Vivo
In Phantom, In Vivo
In Phantom
In Phantom, In Vivo
In Phantom, In Vivo
In Vivo
In Phantom
In Phantom
In Phantom
ThermoLuminescent Dosimeter
(TLD)
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Radiation Induced Color Center Defects
LiF, CaF2 Chip or Powder Doped with Impurities
Size: mm, Point Dosimeter (0D)
Nearly Tissue Equivalent
In Phantom or In Vivo
Readout Device
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Heating Mechanism
Emitted Light Measurement
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Labor Intensive Handling Procedure
Energy Response
Reusable After Annealing
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2D TLD Slab Li3B7012:Cu, Readout w/CCD Camera
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DeWerd, AAPM 2009 summer School, Ch. 24.
Shinsho, Rad. Meas. 2014 Jan online.
Reader
Indexing Disc
50 TLDs
Optically Stimulated Luminescence
Dosimeter (OSLD)
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Radiation Induced Color Center Defects
Al2O3:C Crystal
Size: mm, Point Dosimeter (0D)
Nearly Tissue Equivalent
In Phantom or In Vivo
Readout Device
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Stimulation Light (540 nm Green) Illumination
Emitted Light (420 nm Blue) Measurement
Energy Response
2D OSLD Film, Readout w/Laser Scanner
Jursinic, Med. Phys. 2010; 37: 132-140.
Cygler, AAPM 2009 Summer School, Ch. 25.
Ahmed, Rad. Meas. 2014 (Jan. online)
Radio-Photoluminescence Glass
Dosimeter (RPLGD)
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Radiation Induced Color Center Defects
Silver Activated Phosphate Glass (High Z = 12)
Size: mm, Point Dosimeter (0D)
In Phantom or In Vivo
NOT Tissue Equivalent
Readout Device
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UV Laser Excitation
Emitted Orange Light Measurement
Energy Response (reduced to 1.2 w/compensator filter)
Angular Response (~ 6% variation)
Reusable After Annealing
Araki, Med. Phys. 2003; 30: 1976-1981.
Huang, Adv. Cancer Therapy Nov. 2011.
Alanine
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Radiation Induced Chemical Change
Crystalline Amino Acid Alanine (CH3-CH(NH2)-COOH)
CH3-C•H-COOH Free Radicals Produced
Alanine Crystal in Pellet form
Size: mm, Point Dosimeter (0D)
In Phantom
Tissue Equivalent
Readout Device:
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EPR Spectrometer in Standards Labs
Mailed Dosimeter
Weak Energy Response
McEwen, AAPM 2009 Summer School, Ch 31.
NIST, http://www.nist.gov/pml/div682/grp02/smallfield_epr.cfm
Radiographic Film
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Radiation Induced Darkening of AgBr
Emulsion (High Z)
Chemical Processing: Developing/Fixing
High Spatial Resolution, 2D Dosimeter
Sensitive to Room Light,
Need Light Tight Envelope
Kodak Film Models
 XTL, XV, EDR2
Pai, Med. Phys. 2007; 34: 2228-2258 (AAPM TG-69 Report).
Cadman, J. Appl. Clin. Med. Phys. 2005; 6: 74-86.
Radiographic Film
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In Phantom or In Vivo
NOT Tissue Equivalent
Readout Device
 Point Densitometer → 0D (Point) Dose
 2D Scanner/Densitometer → 2D dose
Distribution
Strong Energy Response
Pai, Med. Phys. 2007; 34: 2228-2258 (AAPM TG-69 Report).
Cadman, J. Appl. Clin. Med. Phys. 2005; 6: 74-86.
Radiochromic Film
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Radiation Induced Color Change
Polymer-based Emulsion
Self Developing
High Spatial Resolution, 2D Dosimeter
Insensitive to Room Light
Cut to Any Shape, Size
Ashland Film Models
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HD, MD
EBT, EBT2, EBT3, RTQA
XR-RV, XR-QA
Separate Lecture dedicated to Radiochromic Film Dosimetry
Soares, AAPM 2009 Summer School, Ch. 23.
EBT2, EBT3
EBT
Radiochromic Film
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In Phantom and In Vivo
Nearly Tissue Equivalent
Readout Device
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Point Densitometer
→ 0D (Point) Dose
2D Color Scanner/Imaging Densitometer
→ 2D Dose Distribution
Energy Response Varies with Film Model
Separate Lecture dedicated to Radiochromic Film Dosimetry
Soares, AAPM 2009 Summer School, Ch. 23.
XR-RV2
Computed Radiography (CR)
Image Plate
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Radiation Induced Electron Excitation
Photostimulable Storage Phosphor Plate in Cassette
Readout Device
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Photostimulated Luminescence by Laser Scanner
Luminescence Detected by Photomultiplier Tube
Conversion to Electronic Signal
High Spatial Resolution, 2D Image
Semi-Quantitative Digital Dose Data
Treatment Portal Image
Image (Phosphor) Plate Reusable
Polymer Gel
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Radiation Induced Chemical and Color Changes
Polymer-based Gel
3D Dosimeter
Tissue Equivalent
Gel Types
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In Phantom
Readout Device
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BANG, PAGAT, MAGIC,
NIPAM, VIPAR
MRI, Optical CT, X-Ray CT
Verification of 3D Dose Distribution
Energy Response Varies with Gel Type
Schreiner, AAPM 2009 Summer School, Ch. 30.
Fricke Gel
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Radiation Induced Transformation
Fe2+ (ferrous) → Fe3+ (ferric)
In Phantom
Readout Device
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NMR Spin-Lattice Relaxation Rate
Optical Density (at 224, 303 nm)
Used in Standards Labs
Not Used in the Clinics
McEwen, AAPM 2009 Summer School, Ch 31.
PRESAGE
(Radiochromic Plastic)
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Radiation Induced Color Change
Transparent Solid Polyurethane-Based
3D Dosimeter, in Various Sizes, Shapes
Tissue equivalent
In Phantom
Readout Device
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Optical CT Scanner (OCTOPUS)
Verification of 3D Dose Distribution
Energy Response
Guo, Med. Phys. 2006; 33: 3962-3972.
Conclusion
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Safe and Accurate Delivery of Radiotherapy
Dosimetry Measurement in Phantom
Dosimetry Verification Measurement
Dosimetry Calculation – TPS Calculation
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Heterogeneity Corrections
Dosimeters Used in Measurement