Medical Physics Seminar - Monday, November 9, 2009

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Dosimetric Characteristics of Optically Stimulated Luminescent dosimeters, OSLDS,

or

Bringing Coals to Newcastle

Paul A. Jursinic, Ph.D.

Director of Physics

West Michigan Cancer Center

Kalamazoo, Michigan

Optically stimulated luminescent dosimeters, OSLDs, are plastic discs infused with aluminum oxide doped with carbon (Al2O3:C).  These discs are encased in a light tight plastic holder.  Crystals of Al2O3:C when exposed to ionizing radiation store energy that is released as luminescence (420 nm) when the OSLD is illuminated with stimulation light (540 nm).  The intensity of the luminescence depends on the dose absorbed by the OSLD and the intensity of the stimulation light.  OSLDs used in this work were NanoDot dosimeters, which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL).
  
The following are dosimetric properties of the OSLD that were determined: After a single irradiation, repeated readings cause the signal to decrease by 0.05% per reading; the OSLD could be discharged by greater than 99.98% by illumination for 2 hours with a 14 W compact fluorescent lamp; after irradiation there was a transient signal that decayed with a 0.8 min halftime; after the transient signal decay the signal was stable for days; repeated irradiations and readings of an individual OSLD gave a signal with a coefficient of variation of 0.6%; the dose sensitivity of OSLDs from a batch of detectors has a coefficient of variation of 0.9%, response was linear with absorbed dose over a test range of 1 cGy to 300 cGy; above 300 cGy supra-linear behavior occurs; with accumulated dose above 20 Gy device sensitivity and supra-linearity change; there was no dose-per-pulse dependence over a 388 fold range; there was no dependence on radiation energy or mode for 6 and 15 MV x-rays and 6 to 20 MeV electrons; for Ir-192 gamma rays OSLD had 6% higher sensitivity; dose sensitivity was not dependent on the angle of incidence of radiation; the OSLD in its light tight case has an intrinsic buildup of 0.04 g/cm2; dose sensitivity of the OSLD was not dependent on temperature at the time of irradiation in the range of 10 to 40 ºC.  OSLDs have been used successfully in the clinic for in vivo dosimetric measurements for two years.

Location: 1345 Health Sciences Learning Center (HSLC)

Time:  4:00pm-5:00pm

Refreshments will be provided prior to the talk

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