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Diode calibration for dose determination in total body irradiation
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M. Allahverdi   , Gh. Geraily , M. Esfehani , A. Sharafi , A. Shirazi |
| , alahverdi@sina.tums.ac.ir |
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Abstract: (15140 Views) |
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Background: Total Body Irradiation (TBI) is
different from standard radiotherapy in many aspects,
so it is not easy to predict the delivered dose to the
patient under TBI treatment. Diode dosimetry
procedures for surface dose reading can help to
define variations of the actually delivered dose from
the prescribed one. The aim of this study was to
describe the measurements made to calibrate diodes
in order to implement as a dosimeter for TBI tratment.
An algorithm was also proposed based on diode
dosimetry in order to determine the midplane dose.
Materials and Methods: In this study, four p-type
diodes connected to a MULTIDOSE electrometer were
implemented as dosimeter. For diode calibration a
water phantom with dimension of 30×30×32cm3
along with a 0.6 cc Farmer ion chamber were used.
Directional dependence of diodes, the effects of
thickness correction factor and complete backscatter
factor were studied. Three algorithms, arithmetic,
geometric mean and proposed algorithm were used to
investigate midplane dose determination in TBI
condition. Results: It was found by measurements
that the effect of angle incident on diode response
was significant and should have been taken into
account. Variation in thickness correction factor was
found about 0.7%. The accuracy in midplane dose
determination in the arithmetic, geometric mean and
proposed algorithm was about 3.8, 12.5 and 3.3%,
respectively. Conclusion: Diode dosimetry is very
useful as a check of midplane dose delivered to
patients under TBI treatment. When the calibration
and correction factors are carefully determined, high
precision can be obtained. The proposed algorithm by
this study seems to be useful in order to midplane
dose determination in TBI condition. Iran. J. Radiat.
Res., 2008 6 (1): 43-50 |
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| Keywords: Diode calibration, total body irradiation. |
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Full-Text [PDF 431 kb]
(4815 Downloads)
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Type of Study: Original Research |
Subject:
Radiation Biology
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