Verification of the PAGAT polymer gel dosimeter by photon beams using magnetic resonance imaging
B. Azadbakht , M.H. Zahmatkesh , K. Hadad , S. Bagheri
, mheair@yahoo.com
Abstract: (15638 Views)
Background: In this work investigation of the
normoxic PAGAT polymer gel dosimeter such as
sensitivity, the R2-dose response with post time and
the percentage depth dose (PDD) of PAGAT polymer
gel dosimeter have been undertaken. Materials
and Methods: Using MRI, the formulation to give
the maximum change in the transverse relaxation
rate R2 was determined to be 4.5% N,N'-methylenbis-
acrylamide ©(bis), 4.5% acrylamid(AA), 5%
gelatin, 5 mM tetrakis (hydroxymethyl)phosphonium
chloride (THPC), 0.01 mM hydroquinone (HQ) and
86% HPLC (Water). Irradiation of vials was
performed using photon beams by Co-60 therapy
unit and an Electa linear accelerator. Gel dosimeters
were imaged in a Siemens Symphony 1.5 Tesla
clinical MRI scanner using a head coil. Gel
dosimeters were irradiated 1 day post-manufacture,
and imaged 1 day post irradiation. Results: The R2-
dose response was linear up to 30 Gy. The response
of the PAGAT gel is very similar in the lower dose
region and the R2-dose response for doses less than
2 Gy is not exact. The R2-dose response of the
PAGAT polymer gel dosimeters varies between 10 to
30 Gy with R2-dose sensitivities of 0.0905, 0.1037,
0.1023, 0.0907 and 0.123 S-1Gy-1 when imaged at
1, 8, 15, 29 and 38 days post-irradiation
respectively. The percentage depth dose (PDD) of
PAGAT gel dosimeter was determined and at depth
of 21cm, the percentage depth dose for 1.25, 4, 6
and 18 MV photons were determined to be, 48%,
52%, 57.3% and 59.73% respectively. Conclusion:
Calibration curve of the PAGAT polymer gel
dosimeter, were found to be linear between 2-10 Gy
and 10-30 Gy with different slopes of the R2-dose
sensitivity also showed stability with post time
imaging after 38 days. In this study, the percentage
depth dose (PDD) of the PAGAT gel dosimeter was
measured. It can be concluded that in case of higher
energy of photon beams, higher doses can be
delivered to deep-seated tumors.
Keywords: Polymer gels , PAGAT gel , magnetic resonance imaging (MRI).
Full-Text [PDF 334 kb]
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Type of Study: Original Research |
Subject:
Radiation Biology
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