Commenced in January 2007
Paper Count: 30174
Characterization of Three Photodetector Types for Computed Tomography Dosimetry
Abstract:In this study three commercial semiconductor devices were characterized in the laboratory for computed tomography dosimetry: one photodiode and two phototransistors. It was evaluated four responses to the irradiation: dose linearity, energy dependence, angular dependence and loss of sensitivity after X ray exposure. The results showed that the three devices have proportional response with the air kerma; the energy dependence displayed for each device suggests that some calibration factors would be applied for each one; the angular dependence showed a similar pattern among the three electronic components. In respect to the fourth parameter analyzed, one phototransistor has the highest sensitivity however it also showed the greatest loss of sensitivity with the accumulated dose. The photodiode was the device with the smaller sensitivity to radiation, on the other hand, the loss of sensitivity after irradiation is negligible. Since high accuracy is a desired feature for a dosimeter, the photodiode can be the most suitable of the three devices for dosimetry in tomography. The phototransistors can also be used for CT dosimetry, however it would be necessary a correction factor due to loss of sensitivity with accumulated dose.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1081573Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1789
 R. L. Dixon, "A new look at CT dose measurements: Beyond CTDI," Medical Physics, vol. 30, pp. 570-578, June 2003.
 K. D. Nakonechny, B. G. Fallone, S. Rathee, "Novel methods of measuring single scan dose profiles and cumulative dose in CT," Medical Physics, vol. 32, pp. 98-109, Jan. 2005.
 L. Herrnsdorf, M. Björk, B. Cederquist, C. G. Mattsson, G. Thungström, C. Fröjdh. "Point dose profile measurements using solid-staate detectors in characterizaion of computed tomography systems," Nuclear Instruments and Methods in Physics Research A, vol. 607, pp. 223-225, March 2009.
 L. Aoyoma, S. Koyama, C. Kawaura, "An in-phantom dosimetry system using pin silicon photodiode radiation sensors for measuring organ doses in X-ray CT and other diagnostic radiology," Medical Physics, vol. 29, pp. 1504-1510, July 2002.
 S. Kim, T. T. Yashizumi, G. Toncheva, D. P. Frush, F-F Yin, "Estimation of absorved doses from pediatric cone-beam CT scans: MOSFET measurements and Monte Carlo simulations," Radiation Protection Dosimetry, vol. 138, pp. 257-263, Nov. 2009.
 L. A. P. Santos, C. M. S. Magalh├úes, J. O. Silva, J. Antonio Filho, E. F. Silva Jr., W. M. A. Santos, "A feasibility study of a phototransistor for the dosimetry of computerized tomography and stereotactic radiosurgery beams," Radiation Measurements, vol. 43, pp. 904-907, Feb. 2008.
 L. A. P. Santos, E. F. Silva Jr., E. Vilela, "Filtered x-ray beam dosimetry from 10-3 to 102 Gy dose range by using phototransistors," Radiation Protection Dosimetry, vol. 101, pp. 145-148, 2002.
 G. Batignani, S. Bettarini, M. Bondioli, M. Boscardin, L. Bosisio, G-F D. Betta et al., "Functional characterization of a high-gain BJT radiation detector," IEEE Transactions on Nuclear Science, vol. 52, no. 5, pp. 1882-1886, Oct. 2005.
 IEC 61267, "Medical diagnostic X-ray equipment - Radiation conditions for use in determination of characteristics," International Electrotechnical Commissiom (IEC). Genève, 2005.
 OP520, OP521, "Silicon Phototransistor in Miniature SMT Package: OP520, OP521," Optek Technology, Issue 1.1, 4 p, 2005.
 BPW34FS, "Silicon PIN Photodiode with daylight filter," Siemens, 4 p, 1997.
 TRS 457, "Dosimetry in Diagnostic Radiology: An International Code of Practice," International Atomic Energy Agency (IAEA). Viena, 2007.