Page 36 - Fisica In Medicina n° 1/2017

^Äëíê~Åí=cáëáÅá= =Frameless intracranial radiosurgery with Helical Tomotherapy: preliminary resultsM. IACCO1,2, C.ZUCCHETTI1, M. LUPATTELLI3,C. FULCHERI 1,M.MARCANTONINI1, C. ARISTEI2,3, R.TARDUCCI11Santa Maria della Misericordia Hospital, Medical Physics Department, Perugia, Italy2University of Perugia, Surgery and Biomedicine Department, Perugia, Italy3Santa Maria della Misericordia Hospital, Radiation Oncology Department, Perugia, ItalyIntroductionThe aim of this work was to report the preliminary results of radiosurgery treatments with Helical Tomotherapy (HT) by means of a non-invasive frame.Materials and MethodsBetween April and October 2016, 6 patients underwent radiosurgery with HT for treatment of 10 brain lesions with a median dose prescription of 20 Gy (range 15-22 Gy). The planning target volume (PTV) was created expanding 2mm in all directions the gross tumor volume (GTV). The median PTV was 1.5cc (range 0.6-7.7cc). Treatment plans were performed with the following parameters: field width of 1.05cm, pitch in the range 0.108-0.150, and modulation factor (MF) in the range 1.5-3.5, leading to a final MF of 1.6 on average (range 1.1-2.2). All plans were prescribed according to ICRU83 at the median of PTV, trying to limiting cold (D98%>95%) and hot spots (D2%<107%). In addition, 12Gy-volumes (V12Gy) of the healthy brain, associated with symptomatic radiation risk of necrosis, was reduced below 10cc. Treatment plans were analyzed recording D98%, Dmean and D2% of the PTV. Moreover the conformity, homogeneity and gradient score indexes were calculated and compared with published reports of HT radiosurgery. Furthermore, the V12Gy of the healthy brain was also evaluated. A mask-based fixation system has been chosen, because of its high intracranial repositioning accuracy (always <1mm, further details have been discussed in another our work).27