%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