13 Head and Neck - Oropharynx

Head and Neck - Oropharynx

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 15/02/2021

All the non-looping loop techniques are especially useful for stepping source PDR and HDR BT afterloaders as the curves of non-looping loops have wider angles and hence there is no difficulty in passing the source. Straight tube technique [34] Needle is inserted through the suprahyoid region and pushed straight down till it comes out of the oropharynx. Needle is then threaded with plastic catheter with button at one end. Multiple such tubes are placed at a distance of 10-12 mm to make multiple planes. Additional buttons may be placed to increase the dose to the dorsum of the tongue (Figure 14,15). Figure 16 shows preRT tumour in the base of tongue and post RT (EBRT+BT) MRI showing complete resolution of the disease with organ and function preservation. 8.3 Vallecula For vallecular lesions or tumours with epiglottis infiltration, the insertion of the posterior post needles have to be done through thyrohyoid membrane using infrahyoid approach. The procedure of needle insertion remains similar to the base of tongue BT. The epiglottis gets anchored into the loop as the posterior most needle comes out through or behind the epiglottis. In this situation temporary tracheostomy is required before starting the procedure. Figure 17 shows MRI of a vallecular cancer treated with EBRT+BT. Two parallel frontal loops 15 -20 mm apart are implanted to cover the whole or two thirds of the faucial arch (Figure 18). After palpation of the position of the hyoid bone and the carotid artery, the entrance points of the needles are marked on the skin. The entrance point for the needle is decided by the bimanual palpation. Typically, the anterior loop enters 10 mm above the hyoid and will pass through the anterior faucial pillar. The entrance point of the posterior loop is marked 10 mm beneath the hyoid and will pass through the posterior pillar (Figure 18). However, the entrance pointsmay vary depending on the anatomy of that particular patient. The posterior tube is positioned first. A 10 cm guide needle is introduced under the hyoid bone perpendicular to the skin and is then advanced posteriorly about 25 mm into the neck, towards the pharyngeal mucosa, guided by a palpating finger in the oropharynx. Then the needle is turned cranially, and it is gently manoeuvred through the tissues and along the posterior faucial pillar to emerge in the oropharyngeal cavity at the junction of the inferior border of the soft palate and the posterior faucial pillar. A leader of the double-sided plastic tube is pushed through the lumen of the needle and the needle is removed. AReverdin hook or a curved hollow bladder needle (30) is inserted at the junction of the inferior border of the soft palate and the left posterior faucial pillar, and it is manoeuvred along the free border until it penetrates the oropharyngeal cavity at the same point as the plastic tube. The second leader of the double-sided plastic tube is grasped with the Reverdin and pulled through the free border of soft palate. The plastic tube is then pulled into position. Curved hollow needles may also be used directly. A guide needle is introduced on the left side along the posterior faucial pillar, as described in point 2, to emerge in the oropharyngeal 8.4 Soft Palate, Uvula [35] Classical Pernot technique

cavity at the same point as the plastic tube. Another double-sided plastic tube leader is introduced into the oropharyngeal 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. Traction on the legs 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 mmposteriorly, 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 or a curved hollow needle is again necessary to traverse the soft palate along the border with the hard palate. If curved needles are used one can reach almost up to uvula from either side. When the uvula forms 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. In certain situation two loop tubes for the soft palate can be combined with the most superior tube that is inserted through the cheek. This needle is inserted from the cheek just anterior to the retromolar trigone (RMT) and enters the soft palate. The tube is exited through the contralateral side from the RMT into the cheek. Figure 19 shows 3D CT planning of soft palate brachytherapy. Latero-lateral implantation technique It is possible to implant the soft palate as well as the posterior pharyngeal wall with latero-lateral directed plastic tubes. The use of ultrasound control of the large vessel positions (especially the internal carotid artery) is helpful. For this technique the use of a long (>25 cm) insertion needle is necessary. The first plastic tube needs to be implanted at the level of the junction of the bony hard palate and the soft palate. The needle has to enter the skin of the neck immediately behind the mandible and oriented in the first approx. 3-5 cm a bit anteriorly in order to avoid puncturing the internal branch of the carotid artery. The finger on the junction of the soft/hard palate will guide further direction. Arriving with the needle in this region, this finger can press and guide the course of the needle within the soft palate. On the other side, after the needle tip leaves the target area, the space between the posterior margin of the mandibular and the level of the large vessels can be used for exiting through the skin. The procedure is repeated for each of the other tubes – usually three tubes cover the complete soft palate (Figure 20) . In the case of posterior pharyngeal wall implantations only the level of the insertion points differ as it needs to correlate to the site of the target. The first/last plastic tube should pass the prevertebral soft tissue approximatively 5 mm cranial/caudal to the macroscopic lesion. Poseidon Technique [30] This technique is used to treat lesions of the uvula and small central tumours of the soft palate. It also permits coverage of tumour extension to the mucosa of the oral cavity (hard palate). Three curved needles 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 exit at the free border laterally and for the