Percutaneous Ultrasound-Assisted Thyroid Laser Ablation (PLA)
PERCUTANEOUS LASER ABLATION (PLA). LASER is an acronym of Light Amplified Stimulated Emission of Radiation. Optical fibers deliver high en-ergy laser radiation to the target lesion. The penetration of laser light is only a few millimeters as a result of scattering and absorption. Scattering results in a relatively uniform distribution of absorbed energy, and heat is produced by conversion of absorbed light. Temperatures greater than 60° C result in rapid coagulation necrosis. Irreversible cell death, without preceding coagulation, also occurs at lower tem-peratures (40–45° C), but requires duration of treatment that inversely correlates with temperature.
PLA INTERVENTION. PLA is an office-based intervention. We established careful precautions for patient safety. A sterile oper-ative setting is arranged. The operator stands on the left side of the patient, while US equipment is used by the ultrasonography assistant who sits on the right side. An auxiliary monitor permits direct US vision by the operator while the assistant looks in the US machine monitor. A cardiac monitor is connected to the patient showing continuous ECG. A venous catheter is inserted in a peripheral forearm vein before starting the procedure to ensure continuous venous access. Emergency care facilities and materials are on hand in the operating room. An anesthesiologist is present during PLA. The patient is placed in the supine position with hyperextended neck with a pillow under her/his shoul-ders. Eyes are protected by special glasses. The laser machine is placed behind the patient’s head. There is room for the operator to move around the patient’s head between the bed and laser appliance. Delim-itation of the nodule by palpation with a marker pen helps to find the point of needle insertion and plan optimal needle trajectory (Figure 1). Light conscious sedation is obtained by IV diazepam (2–3 mg, re-peatable during procedure if necessary). Local anesthesia with ropivacaine subcapsular and subcuta-neous infiltration is performed under US assistance. US visualization of needle used for local anesthesia allows correct tissue lidocaine infiltration. In addition, multiplanar scans of this non-traumatic, thin nee-dle (G 29–30) help in planning subsequent 21 G Chiba PLA needle point of insertion and trajectory. Guid-ance attachment may be used for 21 G Chiba needles insertion. We prefer manual needle placement as it permits to fit needles according to variable anatomy of the nodule. Sedation and local analgesia re-duce patient anxiety, swallowing, cough or other untoward movements that could impede precise nee-dle insertion.
After needle placement, fibers are inserted through the needle sheath into the nodule and laser firing is started US images through continuous axial, longitudinal and multiplanar scans are performed by the assistant throughout laser illumination duration (10–30 minutes), allowing real time visual control of each fiber (Figure 2). A highly echogenic area due to tissue heating and vaporization slowly enlarges over time. The hyperechoic image gradually increases until coalescence between fibers is observed. Pe-ripheral capsular vascularization is preserved, while no blood flow is observed inside the nodule (Figure 3). The nonvascular, hypoechoic necrotic tissue will be reabsorbed over several weeks following PLA with consequent nodule shrinkage.
→ Dr. Roberto Valcavi has performed more than 850 thyroid laser treatments.
Dr. Roberto Valcavi, MD, FACE Endocrinologist Specialist in Ultrasound-Assisted Thyroid Treatments
Centro Palmer, Via Fratelli Cervi 75/b – 42124 Reggio Emilia, Italy. Phone: +39. 0522 792400
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Piana S, Riganti F, Froio E, Andrioli M, Pacella CM, Valcavi R. Pathological findings of thyroid nodules after percutaneous laser ablation : a series of 22 cases with cyto-histological correlation. Endocr Pathol. 2012 Jun;23(2):94-100.
Valcavi R, Piana S, Bortolan GS, Lai R, Barbieri V, Negro R. Ultrasound-guided percutaneous laser ab-lation of papillary thyroid microcarcinoma: a feasibility study on three cases with pathological and immunohistochemical evaluation. Thyroid. 2013 Dec;23(12):1578-82
Papini E, Rago T, Gambelunghe G, Valcavi R, Bizzarri G, Vitti P, De Feo P, Riganti F, Misischi I, Di Stasio E, Pacella CM. Long-term efficacy of ultrasound-guided laser ablation for benign solid thyroid nod-ules. Results of a three-year multicenter prospective randomized trial. J Clin Endocrinol Metab. 2014 Oct;99(10):3653-9.