Rapid two-dimensional dose measurement in brachytherapy using plastic scintillator sheet

linearity, signal-to-noise ratio, and energy response characteristics

Harold Perera, Jeffrey F. Williamson, Suzanne P. Monthofer, Walter R. Binns, Joseph Klarmann, Gary L. Fuller, John Wong

Research output: Contribution to journalArticle

Abstract

Because of the large dose gradients encountered near brachytherapy sources, an efficient, accurate, low-atomic number areal detector, which can record dose at many points simultaneously, is highly desirable. We have developed a prototype of such a system using thin plates of plastic scintillator as detectors. A micro-channel plate (MCP) image intensifier was used to amplify the optical scintillation images produced by radioactive 125I and 137Cs sources in water placed 0.5-5.7 cm distance from the detector. A charge-coupled device (CCD) digital camera was used to acquire 2-D light-intensity distributions from the image intensifier output window. For both isotopes, a small area (2 × 3 mm2) PVT detector yields a CCD net count rate that is linear with respect to absorbed dose rate within ± 3% out to 5.7 cm distance. Acquisition times range from 1.5-400 sec with a reproducibility of 0.5-5.5%. If a large-area (6 × 20 em2) PVT detector is used, a four-fold increase in count rate and large deviations from linearity are observed, indicating that neighboring pixels contribute light to the signal through diffusion and scattering in PVT and water. A detailed noise analysis demonstrates that the image intensifier reduces acquisition time 10000-fold, reduces noise relative to signal 200-fold, and reduces amplifier gain noise as well.

Original languageEnglish (US)
Pages (from-to)1059-1069
Number of pages11
JournalInternational Journal of Radiation Oncology, Biology, Physics
Volume23
Issue number5
DOIs
StatePublished - 1992
Externally publishedYes

Fingerprint

Brachytherapy
Signal-To-Noise Ratio
scintillation counters
Plastics
linearity
Noise
signal to noise ratios
plastics
image intensifiers
dosage
detectors
Light
Equipment and Supplies
Water
charge coupled devices
acquisition
Isotopes
energy
microchannel plates
digital cameras

Keywords

  • Brachytherapy
  • Dosimetry
  • Monte Carlo simulation
  • Plastic scintillator detectors

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation

Cite this

Rapid two-dimensional dose measurement in brachytherapy using plastic scintillator sheet : linearity, signal-to-noise ratio, and energy response characteristics. / Perera, Harold; Williamson, Jeffrey F.; Monthofer, Suzanne P.; Binns, Walter R.; Klarmann, Joseph; Fuller, Gary L.; Wong, John.

In: International Journal of Radiation Oncology, Biology, Physics, Vol. 23, No. 5, 1992, p. 1059-1069.

Research output: Contribution to journalArticle

Perera, Harold ; Williamson, Jeffrey F. ; Monthofer, Suzanne P. ; Binns, Walter R. ; Klarmann, Joseph ; Fuller, Gary L. ; Wong, John. / Rapid two-dimensional dose measurement in brachytherapy using plastic scintillator sheet : linearity, signal-to-noise ratio, and energy response characteristics. In: International Journal of Radiation Oncology, Biology, Physics. 1992 ; Vol. 23, No. 5. pp. 1059-1069.
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abstract = "Because of the large dose gradients encountered near brachytherapy sources, an efficient, accurate, low-atomic number areal detector, which can record dose at many points simultaneously, is highly desirable. We have developed a prototype of such a system using thin plates of plastic scintillator as detectors. A micro-channel plate (MCP) image intensifier was used to amplify the optical scintillation images produced by radioactive 125I and 137Cs sources in water placed 0.5-5.7 cm distance from the detector. A charge-coupled device (CCD) digital camera was used to acquire 2-D light-intensity distributions from the image intensifier output window. For both isotopes, a small area (2 × 3 mm2) PVT detector yields a CCD net count rate that is linear with respect to absorbed dose rate within ± 3{\%} out to 5.7 cm distance. Acquisition times range from 1.5-400 sec with a reproducibility of 0.5-5.5{\%}. If a large-area (6 × 20 em2) PVT detector is used, a four-fold increase in count rate and large deviations from linearity are observed, indicating that neighboring pixels contribute light to the signal through diffusion and scattering in PVT and water. A detailed noise analysis demonstrates that the image intensifier reduces acquisition time 10000-fold, reduces noise relative to signal 200-fold, and reduces amplifier gain noise as well.",
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