Experimental And Clinical Studies On Thermal Ablation Of Benign Thyroid Nodules

PurposeTo obtain the treatment parameters of laser ablation and microwave ablation such asablation shape, scope and temperature rise curve. To evaluate the feasibility ofultrasound guided percutaneous microwave ablation of benign thyroid nodules.Materials and MethodsEcho Laser integrated laser interventional ultrasound system was used to ablate freshporcine liver. The lesion diameters achieved in different groups (2W,3W,4W,5W,6W,7W;2,5,10minutes) were compared.Microwave ablations were induced by using different power outputs (5,10,15,20,25and30W at2450MHz) and different treatment time (3,7,10,12and15minutes).Iron-constantan thermocouple (TC) was used to be inserted in the tissue5mm,10mm and15mm from the electrode radiating segment to measure the temperature.MWA was performed in18patients with18benign thyroid nodules. Male to femaleratio=3:15; mean age,48±8years. Tumor size was3.1±1.3（range,1.6～6.8）cm.Ultrasound scan, laboratory data and clinical symptoms were evaluated before and1day,1,3,6,9and12months after the procedure.ResultsEx vivo laser ablation study: Vaporization, carbonization, coagulation and edemaappeared on laser ablated lesion. The long-axis and short-axis diameters enlargedwith the increase of laser energy.Ex vivo MWA study: All ablated lesions were ellipsoidal. Four well-defined zones ofthe ablated lesion were noted around the antenna: charring zone, coagulation zone,congestion zone and normal liver parenchyma. The long-axis and short-axisdiameters enlarged with the increase of microwave energy nonlinearly. The meantemperature at5mm site from the electrode showed that tissue temperatures weredriven rapidly high while the maximum temperatures at10mm and15mm were low. Clinical study: The follow-up periods ranged from1to9months. At the lastfollow-up, the largest diameter decreased from3.15±1.29(range,1.6～6.8) cm to2.12±1.06(range,0.4～5.2) cm (p<0.01), and the volume decreased from11.78±19.94(range,0.89～81.65) mL to4.94±8.63(range,0.02～36.39) mL(p<0.01). The volume reduction ratio was48.05±28.03%(range,10.56%-98.15%).T3, fT4and TSH changed differently after MWA. The cosmetic grading score wasreduced from3.28±0.75to2.39±0.85(P<0.01). One patient experienced temporarynerve palsy and was recovered within2months after treatment.ConclusionMicrowave ablation can yield larger ablated lesions than laser ablation, andultrasound guided percutaneous microwave ablation is a feasible technique forbenign thyroid nodules.