Marzuki, Rahmatfadli
(2019)
Diode Dosimetric
Characterisations And Assessments
For In-Vivo Dosimetry In
Radiotherapy Treatment.
Masters thesis, Universiti Sains Malaysia.
Abstract
Diode is a kind of radiation dosimetry system that has been applied widely in
radiotherapy treatment and very useful for in-vivo dosimetry (IVD). It is duly
important to understand the characteristic of detector before it can be used in clinical
treatment. In this study, characteristics of three (3) diodes IBA EDP-153G model were
analyzed and compared to calibrated ionization chamber. The 6 MV linear
accelerator (Linac) was used with different field sizes (FS), source to surface
distance (SSD), linac monitor unit (MU), tray field (TF) wedge field (WF) and diode
reading behind cerroband. Actual diode thickness, diode reproducibility, perturbation
effect and diode effect with radiation beam angle and temperature were performed.
From the determination of diode dosimetric characteristic, a clinical computerized
treatment planning system (TPS) model Elekta Monaco and calibrated ionization
chamber were used to verify the accuracy of diode reading in different treatment
techniques. In this study, EDP-153G diode was sensitive with angle of incidence,
wedge, SSD and temperature. The measured angle for diode were less than 2 % at
angle ± 41°, ± 37° and ± 72° for diode 1, diode 2 and diode 3 respectively. SSD
correction factors have increased proportionally by increasing the SSD. SSD
correction factor from SSD 75 cm to 140 cm 0.995 to 1.025, 0.975 to 1.046 and
0.989 to 1.021 for diode 1, diode 2 and diode 3 respectively. Wedge correction
factors have increased proportionally by increasing the wedge angle Diode wedge
correction factor resulted in the range of 1.003 to 1.023, 1.009 to 1.033 and 1.011 to
1.056 for diode 1, diode 2 and diode 3 respectively.
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