Technique

A CT scan is performed to localize the tumor precisely. CT is used to measure the diameter of the nidus. The largest diameter of the nidus determines the energy that will be necessary to coagulate the tumor. For diameters larger than 10 mm, we use usually two fibers to ensure tumor destruction. The entry point and the pathway are determined by CT, avoiding nervous, vascular, and visceral structures. The penetration of the needle into the nidus is always extremely painful; therefore, ILP is performed under general anesthesia or regional block. The procedure is performed under strictly sterile conditions. The 18-gauge needle is guided safely under CT guidance. Fluoroscopy is used in conjunction with CT whenever drilling is necessary.

The tip of an 18-gauge needle must be placed into the central part of the nidus. Sometimes, bone drilling is required to reach the nidus, depending on perilesional hyperostosis (Fig. 1).

Subperiostal nidi or cortical nidi without major ossification are directly punctured with an 18-gauge spinal needle (Becton Dickinson, Rutherford, New Jersey, U.S.A.). In cases with mild ossification or small cortex surrounding the lesion, a 14-gauge bone biopsy needle is more adequate (Ostycut, Angiomed/Bard, Karlsruhe, Germany). In cases of dense ossification, or of dense cortical bone surrounding the lesion, drilling is necessary.

In these cases, we use a 2-mm diameter hand drill or a 14-gauge Bonopty Penetration set (Radi Medical Systems Uppsala, Sweden) to allow insertion of the 18-gauge needle.

The 18-gauge needle tip is inserted into the center of the nidus. Before the optical fiber is placed, it is inserted in an 18-gauge needle mounted by a sidearm fitting to measure the

FIGURE 1 Diagram representing the technique of interstitial laser photocoagulation under computed tomography (CT) guidance. (A) Percutaneous trocar needle (14 gauge) placement under CT guidance. (B) Perforation of cortical bone with a coaxial drill. (C) Coaxial insertion of the 18-gauge needle with the optical fiber in the center of the nidus. (D) End of the procedure.

FIGURE 1 Diagram representing the technique of interstitial laser photocoagulation under computed tomography (CT) guidance. (A) Percutaneous trocar needle (14 gauge) placement under CT guidance. (B) Perforation of cortical bone with a coaxial drill. (C) Coaxial insertion of the 18-gauge needle with the optical fiber in the center of the nidus. (D) End of the procedure.

appropriate length of the fiber. The 400-pm precharred fiber is then inserted through the needle; the needle is withdrawn about 5 mm so that the tip of the bare fiber lies within the center of the tumor.

The diode laser (805 nm) is turned on in continuous wave mode, at a power of 2 W for 200 to 600 seconds, depending on the nidus size (energy delivered 400-1200 J). CT control scans are performed during the procedure to detect vaporization gas.

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