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The thermal characteristics of different diodes on in vivo patient dosimetry
Author(s) -
Welsh Keith T.,
Reinstein L. E.
Publication year - 2001
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1367862
Subject(s) - diode , dosimetry , materials science , bolus (digestion) , temperature measurement , atmospheric temperature range , calibration , nuclear medicine , skin temperature , biomedical engineering , optics , optoelectronics , medicine , surgery , mathematics , statistics , physics , quantum mechanics , meteorology
Diode sensitivity variations with temperature (SVWT) have been reported to vary from small negative values up to 0.6% per °C. Thus it is possible for diode calibration factors established at room temperature (∼20 °C) to yield errors in the range of −1% to +9% when diodes are placed on a patient's skin (∼30 °C) for in vivo entrance dose measurements. In this study we simulated several skin temperatures using a temperature‐controlled aluminum surface in contact with a section of Bolus. The internal temperatures of several diodes with different buildup thickness were monitored as a function of time when placed in contact with the heated bolus. Our results indicate that for different combinations of room temperature (18 °C–23 °C) and patient skin temperature (28 °C–34 °C) diodes reached 90% of their equilibrium temperature within 3–5 min. In addition, the range of typical skin temperatures was determined by measurements performed on a number of actual patients under clinical conditions. Based on the results of our experiments a protocol was developed to minimize the temperature based errors for in vivo dosimetry.