https://www.theragnostics.no/en/author/ghazwan-al-haidari/ Ghazwan Al-Haidari Hugo Blox Builder (https://hugoblox.com)en-usWed, 06 Sep 2017 00:00:00 +0000 https://www.theragnostics.no/media/icon_hu14557955862192370321.png https://www.theragnostics.no/en/author/ghazwan-al-haidari/ https://www.theragnostics.no/en/publications/rusten-2017-target/ Wed, 06 Sep 2017 00:00:00 +0000 https://www.theragnostics.no/en/publications/rusten-2017-target/ <hr> <p>To compare target volume delineation of anal cancer using positron emission tomography (PET) and magnetic resonance imaging (MRI) with respect to inter-observer and inter-modality variability. Nineteen patients with anal cancer undergoing chemoradiotherapy were prospectively included. Planning computed tomography (CT) images were co-registered with 18F-fluorodexocyglucose (FDG) PET/CT images and T2 and diffusion weighted (DW) MR images. Three oncologists delineated the Gross Tumor Volume (GTV) according to national guidelines and the visible tumor tissue (GTV_T). MRI and PET based delineations were evaluated by absolute volumes and Dice similarity coefficients. The median volume of the GTVs was 27 and 31 cm³ for PET and MRI, respectively, while it was 6 and 11 cm³ for GTV_T. Both GTV and GTV_T volumes were highly correlated between delineators (r = 0.90 and r = 0.96, respectively). The median Dice similarity coefficient was 0.75 when comparing the GTVs based on PET/CT (GTV_PET) with the GTVs based on MRI and CT (GTV_MRI). The median Dice coefficient was 0.56 when comparing the visible tumor volume evaluated by PET (GTV_{T_PET}) with the same volume evaluated by MRI (GTV_{T_MRI}). Margins of 1-2 mm in the axial plane and 7-8 mm in superoinferior direction were required for coverage of the individual observer&rsquo;s GTVs. The rather good agreement between PET- and MRI-based GTVs indicates that either modality may be used for standard target delineation of anal cancer. However, larger deviations were found for GTV_T, which may impact future tumor boost strategies.</p>