Stereotaktik Radyocerrahi ve Stereotaktik Beden Radyoterapisi Uygulamalarında Manyetik Rezonans Görüntüleme Tabanlı Tedavi Planlama Sisteminin Kullanılabilirliği

Abstract

In this study, feasibility of Magnetic Resonance Imaging (MRI) based treatment planning system instead of computed tomography (CT) in SRC and SBRT was evaluated. Three different scenarios were created for density and hounsfield unit (HU) values of different tissues on MRI images and treatment plans were generated according to those values. In the first scenario, the density of all tissues in the MRI image was defined as 1 g/cm³ (MR1 plan). In the second scenario, three different structures, namely air (0 g/cm³), soft tissue (1 g/cm³) and bone (1,35 g/cm³), were defined (MR3 plan). In the third scenario, 10 different tissue density scales were defined as expanded (MR10 plan). Then, using the automatic segmentation tool in RayStation® TPS, the automatic assignment of the segmented structures on MRI was tested. In cases with brain tumors, no statistically significant difference was found between the reference CT plan and MRI plans made in the other three scenarios. In prostate cancer cases, when the reference CT and MR1 plans were compared, statistically significant differences were found between PTVmean and PTVD2 doses (p <0,05). There was no significant difference between reference CT and MR3 and MR10 in patients with prostate cancer. In conculusion, we found that MRI plans made in three different scenarios can be used instead of CT-based treatment planning in SRC planning of brain tumors, and MR3 and MR10 plans can be used instead of CT-based planning in SBRT planning, but the MR1 plan cannot be used in cases with prostate cancer. Automatic contouring results showed that the segmented contours should not be transferred onto the MRI by using the automatic contouring tool in Raystation® TPS.