PRESAGE A Promising New Material for 3D Dosimetry

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PRESAGE - A Promising New Material for 3D
Dosimetry

• Pengyi Guo1, John Adamovics2, Mark Oldham1
• 1 Department of Radiation Oncology,
• Duke University Medical Center, Durham, NC
• 2 Heuris Pharma LLC, Skillman, NJ
• Contact p.guo_at_duke.edu

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Purpose

• Investigate the potential of a new 3D dosimeter
• Characterize the dosimetric properties
• Tissue equivalence
• Spectral absorption response to dose
• Linearity of dose response
• Dose rate dependency
• Reproducibility
• Stability

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PRESAGETM

• A solid 3D dosimeter Polyurethane matrix leuco
  dye
• Advantages
• 3D, dose response insensitive to lab environment,
  machineable plastic, variable sensitivity,
  radiochromic response, convenient and practical.

Un-irradiated
photon
electron
Presage irradiated with matched photon and
electron (lower dose) pencil beams.
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Tissue Equivalence
CT scans of cuvettes
Different formulations of PRESAGE can have
different CT numbers.
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Method and Material

• Optical cuvettes (1x1x4.5cm3) filled with
  PRESAGETM
• Cuvette pairs irradiated in a water-bath
  (figure1) with 6MeV and 6MV beams with different
  dose, and dose rates
• The spectral absorption and depth optical-density
  were measured with spectrophotometer and linear
  cuvette scanner (figure2)
• Pre- and post- irradiation measurements were made
  to determine radiation induced changes

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Irradiation experiment
Cuvette of PRESAGETM
100cm SSD
Beam
Bottom
Water
Fig 1.
Experiment setup for irradiation of PRESAGETM
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New method of characterizing a 3D dosimetry
material efficient, cost effective The linear
cuvette scan
Linear

travel
Laser
Photodiode

Cuvette


Full dose response (0-100) delivered along
depth of single cuvette !
Fig 2.
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Results
Spectral absorption response to radiation
Max OD change occurs at about 630nm
PRESAGETM of low radiation sensitivity
PRESAGETM of high radiation sensitivity
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Spectral absorption response to radiation
Stable within 2 days of irradiation
Negligible Dependency on dose rate
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Depth dose response
Linearity
Linearity with RMS error 2
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Dose rate dependency
Negligible dependency on dose rate
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Reproducibility
Reproducibility (3 deviation)
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Stability
Normalized OD change is stable 5 days post
irradiation while absolute OD change is stable
within 2 days post irradiation.
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Conclusions

• PRESAGETM characteristics
• Stable dosimeter insensitive to oxygen or lab
  environment
• Radiochromic dose response is light-absorbing
  color change with peak at 630nm. Response is
  highly stable post irradiation (lt2 days)
• Dose response is linear (RMS error 2),
  reproducible (3), negligible dose rate
  dependency.
• Presage CT number can be varied 80-500 HU.
• Presage appears a highly promising material for
  3D dosimetery
• Still need to study large volume response