Anatomicoradiological Boundaries
With the introduction in clinical practice of new radiological imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) the need was felt to transfer onto CT scans the anatomical boundaries of lymph node stations as describ
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Anatomicoradiological Boundaries
With the introduction in clinical practice of new radiological imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) the need was felt to transfer onto CT scans the anatomical boundaries of lymph node stations as described by surgeons. Computed tomography images are not always able to visualize what the surgeon has described; however, by means of identifiable structures, they provide anatomicoradiological references for the identification of lymph node sites. Specifically, progress in radiotherapy technology and the introduction of conformational techniques have made it necessary to provide exact definition of the boundaries of anatomical structures which are sites of macroscopic or microscopic tumors. In this regard, a landmark guide is provided by the volume published by Gregoire, Scalliet, and Ang in 2004 [6] which defines the criteria for appropriate definition of clinical target volumes (CTVs) [7, 8] in modern conformal radiotherapy and in intensity modulated radiation therapy (IMRT). In Italy, again in 2004, Valentini et al. developed a software tool called TIGER (Tutorial for Image Guided External Radiotherapy) [66] intended as a contouring training tool and based on the set of images of the Visible Human Project, with the purpose of facilitating the interpretation of CT images and, especially, the contouring of radiotherapy volumes.
Based on our experience, for the four anatomical regions considered, we report the anatomicoradiological boundaries for identifying lymph node structures.
3.1 Head and Neck Region Definition of the nodal neck levels and related anatomical boundaries described by Robbins were originally proposed for surgical procedures and are not always easily identifiable on CT scans. Adapting the anatomicosurgical boundaries in order to identify CTVs for radiotherapy is neither simple nor easy. Moreover, in radiotherapy the neck is immobilized without rotation of the head, while in surgery the position of the neck can be rotated. In 1999, a group of authors from the school of Rotterdam [67] addressed the issue of CT-based definition of target volumes for stage N0 of the neck and published an initial transposition of the boundaries of the six surgical levels of the neck on CT scans, based on an anatomical study of human cadavers. In the same year, other authors also published their contributions to this topic, in particular, Som [68, 69], a radiologist and member of the committee of the AHNS for the 1998 revision of the 1991 AAOHNS classification. Som attempted to introduce boundaries for the nodal levels of the Robbins classification that would be easily visible in radiological
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A Guide for D elineation of Lymph Nodal Clinical Target Volume in R adiation Therapy
imaging (CT and MRI), in order to provide a system which, being consistent with that established in the previous literature, could unify anatomical imaging criteria with the AJCC and AAO-HNS nodal classifications and clarify some uncertainties. In the same per
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