Ishtiaq Hussain Bercha MSC, Presenter: Nothing to Disclose

Anobel Maghsoodpour PhD, Abstract Co-Author: Nothing to Disclose

Gary S Keyes, Abstract Co-Author: Nothing to Disclose

Robert A. Kaufman MD, Abstract Co-Author: Nothing to Disclose

To study radiation response characteristics of state of the art plastic coated MOSFET radiation detectors using multi slice CT.

We used five MOSFETs (Model TN-1002RD-H, Best Medical Canada) with a reader and wireless communication to a laptop computer, a GE Light Speed VCT-64 scanner, Radcal 9095 dosimeter with a 0.6 cc ionization chamber and kVp sensor and a 10 cm acrylic phantom with acrylic rods. Each MOSFET was inserted into a custom drilled hole in the acrylic rod separately and positioned  at isocenter inside the acrylic phantom for characterization.  MOSFET energy/kVp dependence, linearity of response, and response at low exposures with the CT X-ray tube in rotate mode were studied. Angular dependency of MOSFET response was studied at 120 kVp with tube parked at various angles in 45 degree increments. An exposure of approximately 1000 mR was delivered to each MOSFET at 80, 100, 120 & 140 kVp. Approximately 220 mR was delivered at 80 kVp to study response/reproducibility at low exposures. Exposures were determined using 0.6 cc ionization chamber placed inside the phantom, positioned at isocenter with CT tube in rotate mode as well as parked at various angles in 45 degree increments.

We observed a 15% decrease in MOSFET response with increasing effective energy of the incident beam between 80 kVp and 140 kVp. All MOSFETs demonstrated excellent linearity at all energies selected (R² = 0.99). The average sensitivity  for the 5 MOSFETs (at 120 kVp) using CT tube in rotate mode was 28 ± 0.7 mV/R. Maximum variation in 5 MOSFET responses as a function of irradiation angle, averaged over each angle, was about 3%, with no statistically significant angular dependence observed. These results are comparable to the data obtained with conventional MOSFETs (unpublished data). At low exposures of about 220 mR, the 5 MOSFETs demonstrated good reproducibility with a coefficient of variation of 0.08.  

The new plastic reinforced MOSFETs demonstrate good radiation response characteristics. The plastic coating does not impact MOSFET radiation response at diagnostic CT energies while providing an enhanced protective layer against mechanical damage during use inside anthropomorphic phantoms for organ dosimetry.

Advance organ radiation dosimetry for clinical scan protocol optimization using anthropomorphic phantoms in multi-slice CT imagers.

Bercha, I, Maghsoodpour, A, Keyes, G, Kaufman, R, Characterization of Next Generation Plastic Reinforced MOSFET (Metal Oxide Semiconductor Field Effect Transistor) Radiation Detectors under Scatter Conditions Using CT Radiation Beam Delivery System.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8003802.html