22 Penis Cancer

484 Penis Cancer

7.2.2 Gerbaulet’s glans applicator (GAG) (11,12) This system consists of 2 square plates of transparent plastic, 50mm wide and 2mm thick. These two identical plates are perforated by holes of 1mm in diameter, to allow the passage of hypodermic needles; these perforations are located at 5mm intervals from each other, forming a regular equilateral/ triangular-shaped arrangement which is ideal for a homogeneous distribution of dose according to the Paris System rules. (27) At the 4 angles of each plate, there is one hole of 3mm in diameter, which allows the passage of 4 threaded screws 2.8mm in diameter and 65mm in length, made of stainless steel or brass. These threaded screws ensure that the apparatus is held in parallel position, both at the moment of application and during irradiation. To secure the whole apparatus of screws and plates, there is a set of 16 small 5mm-exterior-diameter hexagonal nuts. Each nut is placed on the rod on each side of the plate, and tightened with a flat mini spanner. Since the four rods are in fact a kind of screw without any end, the distance between the plate, and thus between the nuts, is variable and can be adapted to the length of the hypodermic needles, which are themselves dependent on the size of the penis and the dimensions of the tumour. The whole system, with its 4 corner rods and 16 nuts, weighs 15g, and is sterilised before implant. There are also rectangular plates, 50 x 60mm, whose perforations are set at 5mm intervals and arranged in staggered rows. The first steps are strictly identical to those of the classic implant: the indications for interstitial brachytherapy are not modified by the use of this new system. The system of “plate-screw-nut” is taken apart after the urinary catheter is inserted. Plate A is placed according to the lesion to be implanted and to the projection of the tumour, which will be visible through the transparent plate, and which is drawn on the first plate (Fig 21.5).

Fig 21.5: Transfer of the tumour topography onto the template of the GAG. Fig 21.6: Transfer of the GTV on the second template of the GAG, delimitation of the PTV

Fig 21.7: Implantation of hypodermic needles into the target volume.