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Verifying the accuracy of dose distribution in Gamma Knife unit in presence of inhomogeneities using PAGAT polymer gel dosimeter and MC simulation
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T. Allahverdi Pourfallah   , M. Allahverdi , N. Riyahi Alam , M.R. Ay , M.H. Zahmatkesh |
| , tallahvardi@razi.tums.ac.ir |
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Abstract: (22465 Views) |
| Background: Polymer gel dosimetry is still the
only dosimetry method for direct measuring of threedimensional
dose distributions. MRI Polymer gel
dosimeters are tissue equivalent and can act as a
phantom material. In this study the obtained isodose
maps with PAGAT polymer gel dosimeter were
compared to those calculated with EGSnrs for singleshot
irradiations of 8 and 18 mm collimators of
Gamma Knife (GK) unit in homogeneous and inhomogeneous
phantoms. Materials and Methods: A
custom-built, 16 cm diameter spherical Plexiglas
head phantom was. Inside the phantom, there was
one cubic cutout for insertion of gel phantoms, and
another cutout for inserting the inhomogeneities. The
phantoms were scanned with a Siemens clinical 1.5 T
MRI scanner. The multiple spin-echo sequence with
32 echoes was used for the MRI scans. Results: The
results of measurement and simulation in homogeneous
and inhomogeneous phantoms showed that the
presence of inhomogeneities in head phantom could
cause spatial uncertainty higher than ±2 mm and
dose uncertainty higher than 7%. Conclusion: the
presence of inhomogeneities could cause dose
differences which were not in accordance with
accuracy in treatment with GK radiosurgery. Moreover,
the findings of Monte Carlo calculation revealed
that the applied simulation code (EGSnrc) was a
proper tool for evaluation of 3D dose distribution in
GK unit. Iran. J. Radiat. Res., 2009 7 (1): 49-56 |
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| Keywords: Gamma knife, PAGAT gel dosimeter, EGSnrc, dose distribution. |
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Full-Text [PDF 1394 kb]
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Type of Study: Original Research |
Subject:
Medical Physics
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