Tomotherapy hi art

A series of three MVCT images were collected on a TomoTherapy Hi·Art (Accuray) with one image acquired with each of the three pitch settings: coarse, medium, and fine. With the TomoTherapy Hi·Art system it was not possible to alter the exposure directly. Adjusting the pitch of MVCT scans changed the longitudinal resolution of the reconstructed images, and indirectly affected the total scan dose. As TomoTherapy uses MV fan‐beam, rather than kV cone‐beam, no additional image processing was investigated as it was considered to present significantly different information.

VMAT or HT was planned with the aim of accomplishing better homogeneity and conformity of target coverage while sparing adjacent normal organs to minimize exposure to the heart and other organs at risk. A dose-volume histogram was used to evaluate the dose constraints of the target volumes and other organs at risk. The criteria were at least 100% of the CTV was to receive 100% of the prescribed dose, at least 95% of the PTV was to receive 95–100% of the prescribed dose, and the maximal dose to the PTV region should be less than 110% of the prescribed dose. The constraints to the heart were a mean heart dose < 20 Gy, and V25 < 10%. A Pinnacle3 planning system (version 9.8.1, Philips Medical Systems, Madison, WI, USA) was used to plan VMAT, which was delivered by using a linear accelerator machine (Versa HDTM, Elekta, Crawley, West Sussex, UK). A tomotherapy Hi Art Planning system (version 5.1.3, Tomotherapy, Inc., Madison, WI, USA) was used to plan HT, which was delivered by using a Tomotherapy^® Hi-Art or HD system (Tomotherapy^®; Accuray Inc., Madison, WI, USA).

In this study, we compare four different IGRT imaging systems used in contemporary radiotherapy: cone‐beam computed tomography (CBCT) system mounted on Varian 21eX and TrueBeam clinical linear accelerators (Varian, Palo Alto, CA) as a part of On‐Board Imaging (OBI) system; TomoTherapy Hi·ART (Accuray Inc., Sunnyvale, CA) fan beam megavoltage computed tomography (MVCT); and 2D kV stereoscopic orthogonal imagers on CyberKnife treatment unit (Accuray Inc.).