13 Oropharynx

Oropharynx 281

A 10 cm guide needle is introduced on the left side along the posterior faucial pillar, as described in point 2, to emerge in the oropharygal cavity at the same point as the plastic tube. Another 30 - 40 cm nylon thread is introduced into the oropharygal cavity through the needle and pushed through the lumen of the plastic tube until it emerges at the initial entry point on the right side of the neck. The nylon thread and the plastic tube are coupled by clamping them together at this external extremity. Traction on the left hand end of the nylon thread brings the plastic tube into its final position, spanning the oropharynx from the right side to the left, without penetrating the oropharyngeal cavity. A second plastic tube is then introduced, parallel and anterior to the first. The tube enters and exits at the right and left sides of the neck, at the marked points above the hyoid bone. The needles are introduced into the skin at these points, advanced about 5 mm posteriorly, are turned cranially to follow the anterior faucial pillars, and exit in the soft palate, close to the border with the hard palate. A Reverdin needle is again necessary to traverse the soft palate along the border with the hard palate, as described on point 3. When the uvula takes part of the clinical target volume, it may be underdosed using the described technique. In that case, the extremity of the uvula may be either stitched to the soft palate or threaded with the posterior plastic tube or removed. 7.3.2 Poseidon Technique (developed by Van Limbergen) This technique permits to treat lesions of the uvula and small central tumours of the soft palate (Fig 12.6).

Fig 12.6A: Poseidon Technique for palatal implant Fig 12.6B: Radiograph of palatal Poseidon

It also permits to cover tumour extensions to the mucosa of the oral cavity (hard palate). Three curved needles (see bladder needle technique) are implanted in a sagittal direction into the soft palate. They are inserted into the mucosa at the junction of the hard and soft palate and sort at the free border laterally and through the uvula for the central line. Then a loop is made joining the two lateral lines. Before making the loop, a larger piece of plastic tube is shoved over the implantation tubes, to fix the loop to the central tube, which will perforate the piece of plastic. Loading of the sources may be extended to the hard palate region. In that case it is advised to make a customised apparatus, covering the hard palate and with predrilled holes in it, to contain the sources close against the hard palate mucosa (Fig 12.7). The nylon tubes sort through the mouth