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Evaluation of dosimetric characteristics of a grid block fabricated for Mega-voltage grid therapy purposes
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K. Ghazi-khanlou Sani   , M. Mohammadi , A. Eskandarlo , H. Gholam-hosseinian |
| , ghazi@umsha.ac.ir |
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Abstract: (13545 Views) |
| Background: In conventional radiation therapy,
regarding normal tissue tolerance, the treatment of
bulk tumors is one of the remaining challenges. Grid
Radiation Therapy (GRT) is a technique to deliver high
doses, approximately 15 – 20 Gy per fraction, to several
small volumes located in a large radiation field.
This can be performed using a grid block. The current
work has concentrated on the dosimetric characteristics
of a designed mega-voltage grid, used for a
unique treatment modality. Materials and Methods:
All measurements performed using a Neptune linear
accelerator (9 MV photon beam). A square 16 × 16
array grid block was designed and fabricated. Several
dosimetric characteristics including: depth dose,
Valley To Peak (VTP) ratio, and grid out-put factor
were evaluated using a calibrated diode dosimeter for
a range of radiation fields. Results: The percent depth
dose curves, measured in the presence of grid block,
lie within those measured for the corresponding open
field and a narrow beam. At the Dmax, the VTP ratio
was found to be within 17% - 28%, while these ranges
between 23% - 35% at a depth of 10 cm. The grid out
-put factor found to be 0.78 and it slightly decreases
with increasing of radiation field size. Conclusion:
The VTP ratio found to be dependent strongly on the
grid design and manufacturing properties. However,
other parameters such as radiation field size and the
depth of measurement should also be addressed as
important factors. The measured dosimetric characteristics
of grid block indicate that the mega-voltage
grid therapy can be applied as a possible clinical
modality for palliative cases. Iran. J. Radiat. Res., 2011
9(1): 49-56 |
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| Keywords: Grid therapy, palliation, mega-voltage, radiation dosimetry. |
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Full-Text [PDF 1199 kb]
(2325 Downloads)
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Type of Study: Original Research |
Subject:
Radiation Biology
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