Computed tomography scans (CT) have found wide application in many fields, and particularly in neurosurgery, where they can give the surgeon detailed information about the brain (Wilkins, 1996). Tumors of the head and neck can be treated with high precision radiotherapy only if the patient is accurately immobilized; the target is precisely defined; the non-target areas are also precisely defined; and 3-dimensional target conforming treatment planning, simulation, and verification is carried out (Gademann et al, 1991). Tumors of the head and neck can be treated effectively primarily or after total or subtotal resection. Because of the close proximity of radiosensitive organs, and because the tumor is localized, local treatment is preferred.
A study was conducted by Gademann et al (1991) to evaluate the clinical applicability and the advantages of a treatment system which integrates all the above factors for precision radiotherapy of head and neck tumors. CT scans were completed on all 41 patients in th study, but because of poor tumor delineation on the CT scans, 18 patients also had magnetic resonance imaging (MRI) studies. The target was defined on the MRI slices and electronically transferred to the matching CT slices for dose calculations. Overall, the technique appeared to work successfully in delivering radiotherapy precisely to its target: now the correct doses need to be deduced. However CT scanning played a considerable role in setting up the technique.
Tumors of the head and neck have also been found accidentally when CT scans were performed for other reasons. Pituitary tumors have been found in the past at autopsy in patients who showed no clinical or hormonal abnormalities, and remained undiagnosed throughout the patientÆs lifetime (Reincke, Allolio, Saeger, Menzel and Winkelmann, 1990). Eighteen patients in whom a mass was discovered in the pituitary by chance CT scans or MRI imaging while the patients ...