Ismail M, Afzal M, Nadeem M, Rana A, Amjad S, Buzdar S. Evaluation of depth dose characteristics of superficial X-rays machine using different kVp and applicators diameter. Int J Radiat Res 2011; 9 (3) :159-166
URL:
http://ijrr.com/article-1-802-en.html
, ismaeel_malik@yahoo.com
Abstract: (12266 Views)
Background: Radiotherapy Treatment Planning
requires different dosimetric quantities as input in
order to calculate a desired dose distribution. This
study has been focused to evaluate the depth dose
characteristics of superficial X-rays being used for
radiotherapy treatment. Materials and Methods:
Computerized 3-D water phantom of multi-data
system was used. The measurements were made
through PTW (Physikalirsch-Technische Werkstalten)
farmer type NT-30006 waterproof ionization chamber
of 0.6cc, and PTW electrometer for digital dose rate
reading in Gy/min using five different diameter
applicators and filters at five different values of accelerating
potentials (kVps). Results: The dose rate at
various kVp X-ray beams was observed to decrease
significantly with increasing depth in water phantom
for all applicator diameters from 98% (at 0.1cm
depth) down to 43% (at 2cm i.e. reference condition).
The dose rate increases by increasing the value of
kVp with a maximum at 150 kVp (1.6 and 0.93 Gy/
min for respective applicator diameters 2.5cm and
10cm). Applicator with 2.5cm diameter demonstrates
better dose rate at 85kVp at different depths. PDD
decreases lower than 50% for all combination of
applicators and kVps at/or above 2cm depth so these
measurements should not be considered for
treatment planning. Conclusion: Higher energy X-rays
are suggested to be used for applicators of higher
diameters and smaller energy X-rays for applicators
having smaller diameters. Iran. J. Radiat. Res., 2011
9(3): 159-166
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