Fusion technique for target volume delineation of head and neck cancer in radiotherapy

Purpose: The aim of this study was to make fusion by two different methods in head and neck cancer patients between planning Computed Tomography (CT) images and Magnetic Resonance Imaging (MRI) images taken in treatment position and diagnostic purpose, afterwards, to determine whether there is a differency between fusion, planning CT and MR images for determining gross tumor volumes (GTV).Patients and Method: Images of the twelve patients with head and neck cancer who were received radiotherapy in our clinic were taken in this study. Computed Tomography and MR images of the six patients were taken in treatment position with immobilisation mask (Group I). Computed Tomography images of other 6 patients were taken in treatment position with immobilisation mask while MR images were taken without immobilisation mask (Group II). After CT and MR images obtained, the fusion between images were carried out with two different methods (manually and automatically) for each patient. Afterwards, by comparing the deviation values of these two fusion methods (length, shift, rotation) evaluated whether there is a difference and whether these values have been affected by the position of the patient. In the following stage; GTV was identified separately in planning CT, MR and fusion images for all patients, and the statistically significant differencies between them were evaluated.Results: When the deviation values of Group I and II were compared, no significant difference between two fusion methods was shown. In the comparision of GTV values GTV values of fusion and MR images were significantly larger than CT images. There were no differencies between MR and fusion images. When the two patient groups compared, there was no effect of patient position for volume delineation.Conclusion: Our study demonstrated that different fusion methods and different patient positioning had no effect on the accuracy of the fusion. However, significant differencies between target volumes in CT and MR, fusion images showed that CT images are insufficient in accurate tumor volume delineation for head and neck radiotherapy.