Radiation Dosimetry based on RadioFluorogenic CoPolymerization

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Radiation Dosimetrybased on Radio-Fluorogenic
Co-Polymerization
A Potential Fluorescence Method of Gel Dosimetry
John Warman, Thijs de Haas, Lee Luthjens, Marinus
Hom
Radiation and Isotopes for Health
Department Technical University of Delft, The
Netherlands
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Radiation Dosimetrybased on Radio-Fluorogenic
Co-Polymerization
A Fluorescent Method of Gel Dosimetry?
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The Optical Properties of a Radio-Fluorogenic
Medium
Absorption (white light)
0 Gy
60 Gy
Fluorescence (UV light)
60 Gy
40 Gy
0 Gy
20 Gy
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UNDERLYING PRINCIPLE

• Polymerization of a bulk monomer
• is initiated by irradiation
• A non-fluorescent molecule present
• is incorporated into the growing polymer chains
• and becomes fluorescent
• The fluorescence is permanent and
• proportional to the accumulated radiation dose.

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Ethylinic polymerization

• RR R. R.
  FREE RADICAL
• FORMATION
• R. CH2CH2 R-CH2-CH2.
  CHAIN INITIATION
• R-CH2-CH2. CH2CH2 R-CH2-CH2-CH2-CH2.
  CHAIN PROPAGATION
• GENERAL REACTION SCHEME
• R. n(CH2CH2)
  R-(CH2-CH2)n. n gtgt 100

RADIATION
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Ethylinic polymerization

• RR R. R.
  FREE RADICAL
• FORMATION
• R. CH2CH2 R-CH2-CH2.
  CHAIN INITIATION
• R-CH2-CH2. CH2CH2 R-CH2-CH2-CH2-CH2.
  CHAIN PROPAGATION
• GENERAL REACTION SCHEME
• R. n(CH2CH2)
  R-(CH2-CH2)n. n gtgt 100

RADIATION
NOTE THE DOUBLE BOND CHANGES INTO A SINGLE BOND
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Fluorogenic Probe Molecules (example)
Fluoroprobe (FP) Highly Fluorescent
Verhoeven UvA, 1982
MaleimidoFluoroprobe (MFP) Non-Fluorescent
Verhey Verhoeven UvA, 1996
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Fluoroprobe (FP) Highly Fluorescent
Verhoeven UvA, 1982
MaleimidoFluoroprobe (MFP) Non-Fluorescent
Verhey Verhoeven UvA, 1996
On conversion of the maleimido double bond to a
single bond MFP becomes highly fluorescent
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Fluorogenic Effect on Co-Polymerization
MMA
n
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Increase in the fluorescence of a
gamma-irradiated solution of maleimido-pyrene in
methyl-methacrylate
Integration 370-440 nm
Irradiation time _at_ ca 4 Gy/min
Co-60 gamma source 0.2 ml probe volume
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Variable Sensitivity Dependent on Polymerizable
Monomer
DOSE RATE 0.2 Gy/min
t-Butylacrylate
Methylmethacrylate
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Dose dependence up to 1 kiloGray
Deviation ca 5
MPy in Methylmethacrylate
DOSE RATE 4 Gy/min
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Lee Luthjens Thijs de Haas(pensioners at play)
probe solution 0.2 ml
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Radiation Dosimetrybased on Radio-Fluorogenic
Co-Polymerization
A Fluorescent Method of Gel Dosimetry ?
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Possibility of 2-D (film) and 3-D (bulk)
Radio-Fluorogenic Imaging

• Requires a quasi-rigid (gel) matrix
• Potential Applications
• 3-D phantoms for radiation therapy
• Autoradiography
• Material failure diagnostics (e.g. cracks in
  pipelines)
• Dose labels for irradiated food
• Personnel radiation safety monitors
• Accelerator beam diagnostics

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Radiolytically produced gels by acrylate
polymerization
Butyl Acrylate 8 conversion (20 Gy)
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conversion (40 Gy)
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A Reconstituted Radio-Fluorogenic Butylacrylate
Gel

• Preparation procedure in a cylindrical quartz
  cuvette
• irradiate pure butylacrylate in gamma source to
  ca 10 conversion
• vacuum evaporate off the residual monomer
• replace the monomer with an equal volume of
  fluorogenic solution
• allow to stand for several days -gt
  reconstituted, radio-fluorogenic gel
• some procedures require highly anaerobic (glove
  box) conditions

RFCP GEL (5 mm)
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Radiation Facilities
3 Megavolt, nanosecond-pulsed Electron Accelerator
Cobalt-60 gamma-ray sources
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Aluminium Mask for 2D Fluorogenic Imagingof the
Accelerator Electron Beam
6mm thick Al mask 3mm diameter holes
ACCELERATOR EXIT PORT
RFCP GEL CONTAINER
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Fluorogenic Image of the Masked Electron Beam
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Gel Remains Optically Clear after Irradiation
BEFORE
AFTER
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Comparison of Radio-Fluorogenic and
Radio-Chromic Images
15000 Gy
350 Gy
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Image Stability
HOURS AFTER IRRADIATION
0.5
3
90
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Potential Advantages of RFCPfor
Multi-Dimensional Gel Dosimetry

• Highly sensitive fluorescent (nul) method of
  detection
• Relatively cheap detection equipment, cf MR
  methods
• Simple data-reduction algorithms
• Linear dependence on accumulated dose with large
  dynamic range
• Square root dependence on dose rate -gt increased
  sensitivity in low-dose regions
• Large variation in sensitivity
• Tissue equivalent medium
• Biologically relevant underlying free-radical
  chemistry mechanism
• Possibility of real-time, in-situ monitoring

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Fluorescence on Gamma-Irradiation of Solutions of
FP and MFP in Methylmethacrylate
RADIATION EXPOSURE
J.M. Warman et al, J.Phys.Chem. 101(1997)4913.
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Schematic of Apparatus for In-Situ Fluorogenic
Dosimetry
FIBRE SPLITTER
EXCITATION LIGHT SOURCE
VOLTMETER/ DIGITIZER
FLUORESCENCE DETECTION
MULTI-FIBRE OPTICAL CABLE
COMPUTER
FLUOROGENIC MICROPROBE
RADIATION
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Fluorogenic Microprobe
TWO-WAY OPTICAL FIBRE
CAPSULE (PTFE/PE)
overflow
STAINLESS STEEL JACKET
FLUOROGENIC SOLUTION lt 0.2 ml
OPTICALFIBRE CROSS-SECTION
INPUT EXCITATION 360 nm (UV LED)
OUTPUT FLUORESCENCE gt 370 nm
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spectrometer
360 nm LED light source
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Advantages of RFCPfor real-time, in-situ
radiation dosimetry

• Equipment
• Simple, cheap and readily available optical
  equipment ( 10,000)
• Simple computational data reduction algorithms (
  1,000)
• Cheap and easily prepared probe materials (
  100)

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Advantages of RFCPfor real-time, in-situ
radiation dosimetry

• Probe characteristics
• Accurately reproducible probe composition
• Readily variable sensitivity (sub-Gray to
  kilo-Grays)
• Large dynamic range of linear dose dependence
• Permanent/Fixed fluorescent record of accumulated
  dose

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Advantages of RFCPfor real-time, in-situ
radiation dosimetry

• Relevant to radiobiological applications
• Biologically compatible optical fiber technology
• Tissue equivalent probe materials
• Chemical basis of detection (cf radiological
  damage)
• No electrical wiring or applied voltages

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Increase in fluorescence with time after
immersion in the gamma source for 3 different
dose rates
TOTAL DOSE (Gy)
227
DOSE RATE (Gy/min)
3.76
54
0.90
16
0.26
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Optically clear Radio-Fluorogenic gel(60 Gy
total dose)
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Polymerization of Methylmethacrylate to Perpex
heat light high-energy radiation
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Raw DataIn and Out of Cobalt Source with
Different Lead Attenuators/Dose Rates
3.76 Gy/min
IN
0.90 Gy/min
OUT
IN
0.26 Gy/min
OUT
IN
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The Radio-Fluorogenic Effect
Radio-Fluorogenic solution in normal light
Radio-Fluorogenic solution in ultraviolet light
0 Gy
50 Gy
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The Optical Absorption and Emission Properties of
a Radio-Fluorogenic Medium
Absorption
60 Gy
Emission
60 Gy
40 Gy
0 Gy
20 Gy
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Variable Sensitivity Dependent on Polymerizable
Monomer
t-Butyl-Acrylate
Methyl-Methacrylate
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Increase in the fluorescence of an MFP in MMA
solutionon irradiation
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Optically clear Radio-Fluorogenic gel(60 Gy
total dose)
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Probe preparation in a glove-box