2D and 3D visualisation of head and neck tumours from spiral-CT data.

Purpose: This paper intends to demonstrate the possibilities of two- and three-dimensional visualisation methods from spiral-CT data sets in the head and neck region and demonstrates their value based on various studies.
Material and Methods: The scanner was a Somatom PLUS 4 (Siemens, Forchheim/Germany). The patients were scanned using a slice thickness of 3 mm and a table feed of 5 mm (pitch 1,6). The images were reconstructed with an increment of 1 mm. Contrast agent (150 ml) was applied intravenously with a flow of 2.5 ml/s and a start delay of 80 s. In one study the start delay was 20 s in order to visualise the carotid arteries (extracranial aneurysm). Volumetric data sets were postprocessed with 'Vitrea' and 'VoxelView' (Vital Images) volume rendering software on a Silicon Graphics O2 workstation (virtual laryngoscopy). Multiplanar reformation and colour-coded 3D-reconstruction were done on a Prominence workstation (Siemens/Forchheim/Germany).
Results: In every region of the head and neck MPRs are useful as additional planes (with the exception of the hypopharynx and the larynx), SSDs are always useful if there is extensive bony destruction (skull, spine, skeleton larynx). Colour-coded three-dimensional reformations may be done for extensive tumours and before multi-specialty surgery. Perspective volume rendering is already in use for virtual endoscopy of the paranasal sinuses and the virtual laryngoscopy. In temporal bone evaluation, perspective volume rendering is a new and promising method of the future to assess the inner ear.
Summary: Two- and three-dimensional displays are used to visualise pathological findings in their topographic relation to anatomical leading structures. Thus, the radiologist can point out to the clinician the pathological findings by some essential images without having to demonstrate all axial slices.