13 Oropharynx

Oropharynx 277

least 10 mm. In tumours of the base of tongue, a larger safety margin may be taken because delineation of the gross disease may be problematic, leading in most cases to the need to cover the whole organ.

7

Technique

7.1 Base of tongue The classical plastic loop technique is described. Under general anaesthesia with nasal intubation, the patients lying in supine position with the neck in hyperextension, three or four sagitally oriented parallel loops, spaced 15 - 20 mm, are implanted to irradiate all or most of the base of tongue (Fig 12.1). Following skin antisepsis, a projection of the tumour is outlined on the skin of the anterior neck. The posterior branch of the central loop is first implanted. A guide needle is inserted perpendicularly to the skin above the hyoid bone. The needle is guided into the pharynx, in most cases into the vallecula, with the index fingertip. A nylon filament is introduced into the needle. Then the needle is removed. A 40 cm long nylon tube is advanced along the nylon filament, and the two are clamped together. Then the tube is pulled into oropharyngeal cavity. The filament is removed. A second needle is implanted anteriorly into the base of tongue, and a filament is advanced into the needle. The needle is removed and the filament inserted into the first plastic tube. The two are clamped together and pulled through tongue and skin, so completing the loop. The filament is removed. The two or three other sagittal loops are implanted with the same method, paying great attention to keeping them parallel. The loops are secured with plastic spacers and buttons.

Fig 12.1: Plastic tube technique for implantation of base of tongue (by courtesy of M. Pernot).