Abstract
Intensity modulated radiation therapy (IMRT) enables the calculation of the distribution of radiation doses along a 3-dimensional outline of the cancer. It requires highly precise treatment plans based on CT images. However, in the treatment of head and neck cancer, dental metal prostheses often make accurate planning difficult by inducing metal artifacts in CT images. We report the case of a patient who underwent the removal of dental metal prior to IMRT for Hypopharyngeal Cancer. The removal allowed for the reduction of metal artifacts in the CT images used for IMRT planning.
The patient was a 79-year-old man. In May 2014, he was referred to our department for oral management, including the removal of his dental metal prostheses. The number of residual teeth was 17 and metal crowns were attached to all of them. The number of teeth, including lost tooth parts, with metal crowns was 20. Before receiving dental treatment in our department, the metal crowns had induced widespread metal artifacts in CT images of the upper and lower jaws. The treatment included the removal of 9 metal crowns from mainly posterior parts, the replacement with temporary resin crowns for three abutment teeth of the maxillary denture and two others, and the extraction of 3 molar teeth with poor-prognosis and the lower right cuspid which had an apical lesion. The treatment spanned 34 days (6 visits). After the procedures, metal artifacts in the posterior parts were reduced in the IMRT planning CT images, when compared with the pretreatment CT images. IMRT (2Gy×35～70Gy) under hospitalization was carried out 14 days after the second CT scan. Some dental risks and financial issues can arise with the removal of dental metal prior to radiation therapy of the head and neck. However, it is thought that since the scope of the removal can control the position and degree of artifacts in CT images, it has a big influence on the precision of the treatment plan. We believe that the close cooperation of specialists in radiation therapy and dentistry is necessary for IMRT with a high curative effect. Furthermore, the dental treatment should be carried out as efficiently as possible so that the treatment of the cancer can be started earlier.
