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Med Dosim. 1998 Summer;23(2):95-7.

Energy dependence of a new solid state diode for low energy photon beam dosimetry.

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Division of Radiation Oncology, University of Iowa Hospitals & Clinics, Iowa City 52242, USA.


Any newly introduced radiation dosimeters must be evaluated for clinical use. This paper reports an evaluation of the energy response of a newly fabricated solid state diode for low-energy photon beam dosimetry. The diode, which has minimal buildup, is one of five models designed for in vivo patient dosimetry. Measurements were made using this diode for x-ray beams with kilovoltage potential from 20 to 100 kVp from a superficial x-ray treatment unit. In addition, measurements were also made using calibrated ion chamber designed for low-energy x-ray beams. A cone size of 20 x 20 cm was used and measurements were taken with diode and ion chamber placed at 35 cm from the source. The energy response was determined by taking the ratio of the diode measurement to the ion chamber measurement. The results show that the response of this new diode increases as the quality of the x-ray beam increases at low energy range; however, the percent difference of the detector response between the 70 kVp and 100 kVp x-ray beam is less than 1%, suggesting that this detector can be used as a dosimetry tool for the typical superficial x-ray treatments.

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