%0 Journal Article
%T Investigation of Hot-Spots in TomoDirect 3DCRT Breast Treatment
%A Quan Chen
%A Matthew Mallory
%A Edwin Crandley
%A Shiv Khandelwal
%J International Journal of Medical Physics,Clinical Engineering and Radiation Oncology
%P 376-390
%@ 2168-5444
%D 2018
%I Scientific Research Publishing
%R 10.4236/ijmpcero.2018.73031
%X Background: Conventional tomotherapy
platforms only allow for the delivery of helical IMRT. However the use of IMRT
and helical delivery in breast cancer treatment is non-standard. Newer
tomotherapy units are equipped with a static-beam mode with 3DCRT capabilities.
During the clinical use, we frequently observe hot-spots in the plan that
renders the plan clinically unacceptable. The purpose of this study is to
investigate the underlying cause of the hot-spots in tomotherapy static-beam
breast treatment and possible solutions. Materials/Methods: Theories
about the formation of the hot-spot were developed. Eight lumpectomy patients
contoured according to RTOG-1005 specifications were also used to illustrate
the magnitude of hot-spots under various planning strategies. Two tangential
beams were used for the whole breast irradiation plan with prescription dose of
40 Gy in 15 fractions. Results: The hot-spot was identified as the
behavior of the optimization engine when part of the target region was blocked.
With the current design of tomotherapy¡¯s 3DCRT planning where user adjustment
was greatly limited, none of the planning strategies were able to reduce the
hot-spots to acceptable levels in the eight patients studied. The best strategy
still produced an average of 48.5 Gy (121% of prescription dose) hot-spot dose
and 30.4 cc hot-spot volume (volume receiving > 110% prescription dose). It is also shown that the
hot-spot was not a result of energy or other physical limitation of the
radiation device. By manually adjusting the plan sinogram, the maximum hot-spot
dose drops from 121% to 111% and the hot-spot volume drops from 30 cc to 6 cc on average. Conclusions: While
TomoDirect 3DCRT showed great promise in breast treatment, treatment
planning software improvements may be needed in order to improve the clinical
acceptability by reducing hot-spots in normal tissue.
%K TomoTherapy
%K TomoDirect
%K Accelerated Whole Breast Irradiation
%K 3DCRT
%K RTOG-1005
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=86752