Trans-Esophageal Ultrasonography Guided Left Stellate Ganglion Ablation By Catheterized Focused Ultrasound In Canine

PART Ⅰ DEVELOPMENT AND EVALUATION OF THE TRANS-ESOPHAGEAL UNLTRASOUND CATHETERObjectives: The aim of this part was to design and assemble a trans-esophageal ultrasound catheter integrated with ultrasound imaging and focusing ultrasound array, and evaluate the focus performance in fresh bovine liver.Methods: We designed a parametric 3D model of the pedal with a theoretical focal length of 1.7 cm according to the ultrasound beam focusing theory, and printed it with stainless steel. Six PZT piezoelectric ceramic transducers were placed on the pedal symmetrically. We used fresh bovine liver to evaluate its focusing performance and observed the heat distribution of the ablated liver. The focused ultrasound array was catheterized with the ultrasound imaging transducer after the evaluation. The coplanarity of the focusing array and the ultrasound imaging transducer was evaluated after the catheterization.Results: The pedal was printed with stainless steel according to the parametric 3D model and ultrasound focusing array with theoretical focal length of 1.7 cm and frequency of 3.8 MHz was assembled. The focal point was in a triangle shape in the fresh liver, the size was 1.0 cm × 0.7 cm, the nearest distance between the array and the focal point was 0.8 cm, the farthest distance was 1.5 cm, no serious damage of the acoustic path was observed. The infrared thermography revealed that the highest temperature was in the focal point, and heat was in a focus-centered radial distribution. The trans-esophageal ultrasound catheter was integrated with ultrasound imaging and focusing ultrasound array, the transducers could be irrigated with degased water, and there was an eccentric balloon on the opposite side of the array. There was good coplanarity between the ultrasound imaging transducer and the focal point.Conclusion: Trans-esophageal ultrasound catheter integrated with ultrasound imaging and focusing ultrasound array was designed and assembled, the catheter had favorable focusing performance, the focal point had the right size, and there was good coplanarity between the ultrasound imaging transducer and the focal point. The catheter was able to meet the in vivo canine stellate ganglion ablation requirements. PART Ⅱ ULTRASOUND IMAGING OF THE STELLATE GANGLIONObjectives: The aim of this part was to acquire the ultrasound image of the stellate ganglion and anatomical relationship relative to the surrounding tissue in vitro and in vivo, provide the basic ultrasound image for the ultrasound image guidance stellate ganglion ablation.Methods: Fresh stellate ganglions were used in in vitro study, the stellate ganglion was emerged in the degased water after retrieve. The imaging host computer was turned on after the catheter was connected with it, and the stellated ganglion image was acquired in the degased water. The in vivo experiment used 3 healthy dogs, homemade trans-esophageal ultrasound catheter was insert into the canine esophagus, according to the in vitro image, the in vivo stellate ganglion ultrasound image was acquired by adjusting the depth and direction of the catheter. And the position was determined by pulling the ganglion and removing the longus colli muscle.Results: The in vitro ultrasound image of the stellate ganglion exhibited an inhomogeneous echo area with two hyperechoic border. The in vivo stellate ganglion image shared the similar ultrasound structure with the in vitro ganglion, but the in vivo stellate ganglion image had anatomical characteristic, the cranial portion had branches, the body portion was in a strip shape, and the caudal portion had the feature of transition of SG and sympathetic trunk, a strand structure with an expanded portion. The distances between the SG and the array were different among the three portions, the nearest distances of cranial portion was 0.7 cm, the distances of body portion was 0.9 cm, and the caudal portion was 1.1 cm. the position was determined by pulling the ganglion and removing the longus colli muscle.Conclusion: Ultrasound image of the stellate ganglion generally exhibited an inhomogeneous echo area with two hyperechoic border, and different portion had different ultrasound characteristics. the results of this part provided the foundation of the ultrasound guided stellate ganglion ablation.PART Ⅲ TRANS-ESOPHAGUS ULTRASONOGRAPHY GUIDED LEFT STELLATE GANGLION ABLATION BY CATHETERIZED FOCUSED ULTRASOUND IN CANINEObjectives: Demonstrated the feasibility and efficiency of stellate ganglion(SG) ablation with the catheter through in vivo experiment.Methods: Fourteen healthy mongrel canines(10 for ablation group, 4 for sham group) were used for animal experiment. Left SG was ablated with the catheter after the ultrasound image of the stellate ganglion was acquired and the position was localized, the ablation strategy was 6 W × 10 s, with 10 s intermediate space, the total ablation time for one point was 60 s, two ablation points with 15 degree interval for each portion, and leadⅡECG was recorded before, immediately after and 2 weeks after ablation. RR interval, QT interval, QTc and QT variability index(QTVI) were analyzed. The canines was executed two weeks after ablation, the left stellate ganglion and surrounding tissue was retrieved for gross evaluation, and SG was stained for H.E.. Canines in the sham group were taken all procedures except the ablation.Results: All of the 10 dogs in the ablation group were taken the ablation procedure and survived until 2 weeks after, the RR interval and QT interval variability index(QTVI) were not significantly changed immediately after the ablation procedure, nor 2 weeks after. The mean QT interval reduced immediately after the ablation procedure and 2 weeks after the procedure, but there was no significant difference between the ablation group and the sham group. Mean QTc was shortened immediately after the ablation procedure and 2 weeks after the procedure, and the mean QTc was shortened about 14.5% compared with the baseline 2 weeks after the procedure, it was significantly different from the baseline(p=0.029), and the difference between the two groups was significant. RR, QT, QTc, QTVI were not significant different at all of the time points. Serious damages were not revealed by gross evaluation, ablation points was observed on longus colli muscle and thoracic wall, but no muscle rupture, abscess, rib fracture and pneumothorax was revealed. The ablation part of the stellate ganglion was congestion, swelling, and the tissue density was decreased, the histological study revealed neuron necrosis in ablated area. No procedure related complications were observed.Conclusion: Stellate ganglion could be ablated by a trans-esophagus catheter with ultrasound imaging transducer and focused ultrasound transducer, this new strategy may provide an alternative option for SG intervention.