Abstract
Background
This investigation focused on the clinical implications of the use of the Collapsed
Cone Convolution algorithm (CCC) in breast radiotherapy and investigated the dosimetric
differences as respect to Pencil Beam Convolution algorithm (PBC).
Material and methods
15 breast treatment plans produced using the PBC algorithm were re-calculated using
the CCC algorithm with the same MUs. In a second step, plans were re-optimized using
CCC algorithm with modification of wedges and beam weightings to achieve optimal coverage
(CCCr plans). For each patient, dosimetric comparison was performed using the standard
tangential technique (SWT) and a forward-planned IMRT technique (f-IMRT).
Results
The CCC algorithm showed significant increased dose inhomogeneity. Mean and minimum
PTV doses decreased by 1.4% and 2.8% (both techniques). Mean V95% decreased to 83.7%
and 90.3%, respectively for the SWT and f-IMRT. V95% was correlated to the ratio of
PTV and lung volumes into the treatment field. The re-optimized CCCr plans achieved
similar target coverage, but high-dose volume was significantly larger (V107%: 7.6%
vs 2.3% (SWT), 7.1% vs 2.1% (f-IMRT). There was a significantly increase in the ipsilateral
lung volume receiving low doses (V5 Gy: 31.3% vs 26.2% in SWT, 27.0% vs 23.0% in f-IMRT).
MUs needed for PTV coverage in CCCr plans were higher by 3%.
Conclusions
The PBC algorithm overestimated PTV coverage in terms of all important dosimetric
metrics. If previous clinical experience are based on the use of PBC model, especially
needed is discussion between medical physicists and radiation oncologists to fully
understand the dosimetric changes.
Keywords
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Article info
Publication history
Published online: February 03, 2014
Accepted:
January 11,
2014
Received in revised form:
January 9,
2014
Received:
September 26,
2013
Identification
Copyright
© 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Inc. All rights reserved.
