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Evaluation of treatment planning system monitor unit calculations for three intensity modulated radiotherapy delivery techniques
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M.N. Anjum   , W. Parker , I. Aldahlawi , R. Ruo , M. Afzal |
| , muhammad.anjum@mail.mcgill.ca |
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Abstract: (12546 Views) |
| Background: We have validated the monitor unit
calculations from a commercially available treatment
planning system (TPS) for three intensity modulated
radiotherapy (IMRT) planning techniques for
tangential breast irradiation by using ionization
chamber measurements. Materials and Methods:
Treatment plans were generated for forty-two breast
patients by a forward planned field in field technique,
electronic tissue compensation (ETC), and an inverse
planned sliding window technique. We also
performed a reproducibility of delivery and dose
linearity analysis for each technique. The treatments
were delivered to a phantom using a Varian CL21EX
linear accelerator. A 2571 0.6 cm3 Farmer type ionization
chamber and Farmer 2570/1 electrometer
from NE Technology was used to measure output of
the linear accelerator and the dose at predefined
point in the verification plan. Results: The agreement
between the measured and calculated dose was
-0.87% ± 0.54% for field in field technique, -0.74% ±
0.23% for electronic tissue compensators, and
-1.26% ± 0.48% for the inverse planning technique
and. In terms of reproducibility the mean deviation
was -1.10% ± 0.44% for the field in field technique,
-0.38% ± 0.42% for electronic tissue compensators,
-1.04% ± 0.42% for inverse planning technique. Dose
linearity experiments showed no significant variations
for clinical situations but a breakdown was observed
in relative dose for very low monitor units.
Conclusion: We have found that the monitor unit
calculations for all three planning techniques are
correct to the order of 1%, and that the plans can be
delivered in a reproducible and accurate manner.
Iran. J. Radiat. Res., 2011 9(3): 145-150
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| Keywords: IMRT QA, dose delivery system, dose calculation accuracy, electronic tissue compensators, reproducibility, dose linearity |
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Full-Text [PDF 335 kb]
(4652 Downloads)
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Type of Study: Original Research |
Subject:
Radiation Biology
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