Spitting Image : Image based prevention and measurement of radiation-induced xerostomia

Abstract

Salivary gland dysfunction is one of the prevalent side effects of the head-and-neck irradiation. The dry mouth syndrome or xerostomia predisposes a person to oral disease and discomfort and consequently to deterioted quality of life. In this thesis it was demonstrated that the implementation of a new irradiation techniques, intensity modulation radiotherapy (IMRT) can result in reduction to the mean dose to the salivary glands compared to that delivered by the conventional techniques. IMRT yields dose distributions that conform more accurately to the 3D configuration of the target volumes and consequently spare the normal tissues. The theoretical calculation of the normal tissue complication probability for xerostomia 1 year after radiotherapy could be reduced up to 68% with the IMRT technique. Furthermore in this thesis we have developed a special MRI protocol for the follow up and the radiation damage to the salivary glands and eventually the measurement of the salivary function. A novel imaging technique was used, MR sialography. Saliva itself is imaged along the full trajectory of salivary ducts and 3-dimensional images of the salivary duct system are obtained . MR sialograms of healthy volunteers at different moments in time appeared to be reproducible. In patients, however, the MR sialograms before and after radiotherapy differed due to the radiation-induced damage to the salivary system. This method offers a new insight to the problem because it provides spatial and functional information of the radiation-induced xerostomia at the same time. This information could be used for a more effective IMRT treatment planning.