Objectives: To demonstrate in vitro that changes in ultrasound cavitation threshold might be used for non-invasively distinguishing high viscosity mucinous fluid from low viscosity serous fluid in cystic masses, based...Objectives: To demonstrate in vitro that changes in ultrasound cavitation threshold might be used for non-invasively distinguishing high viscosity mucinous fluid from low viscosity serous fluid in cystic masses, based on the facts that cavitation threshold increases with increasing viscosity and that cavitation microbubbles are observable with diagnostic ultrasound. Methods: An in vitro model of a cyst was designed using dilutions of ultrasonic gel, and the cavitation threshold of this model was determined using focused and unfocused ultrasound for bubble initiation and clinical ultrasound b-scan for detection. Results: Viscosities of dilutions between 0% and 30% gel were had viscosities measuring between 1.05 ± 0.08 cP and 6600 ± 875 cP. Inertial cavitation in the latter was determined to require an order of magnitude greater intensity, at 1 MHz and 100% duty cycle, than the former (>2.2 W/cm2 vs. <0.19 W/cm2) using unfocused ultrasound. A four-fold increase in the peak negative pressure was required to initiate significant bubble activity using 1.1 MHz and 50% duty cycle focused ultrasound in the 6600 cP fluid compared with the 1 cP fluid. Based on these results, it was estimated that a threshold could be defined that would result in no bubbles in 99.9% of mucinous cysts and just 22% of serous cysts. The remaining 78% of patients presenting with serous cysts would be positively identified by detection of bubbles, and would be spared an unnecessary biopsy. Conclusions: The cavitation threshold may be used non-invasively to distinguish between high viscosity and low viscosity fluids in cysts and reduce biopsies on serous cysts.展开更多
文摘Objectives: To demonstrate in vitro that changes in ultrasound cavitation threshold might be used for non-invasively distinguishing high viscosity mucinous fluid from low viscosity serous fluid in cystic masses, based on the facts that cavitation threshold increases with increasing viscosity and that cavitation microbubbles are observable with diagnostic ultrasound. Methods: An in vitro model of a cyst was designed using dilutions of ultrasonic gel, and the cavitation threshold of this model was determined using focused and unfocused ultrasound for bubble initiation and clinical ultrasound b-scan for detection. Results: Viscosities of dilutions between 0% and 30% gel were had viscosities measuring between 1.05 ± 0.08 cP and 6600 ± 875 cP. Inertial cavitation in the latter was determined to require an order of magnitude greater intensity, at 1 MHz and 100% duty cycle, than the former (>2.2 W/cm2 vs. <0.19 W/cm2) using unfocused ultrasound. A four-fold increase in the peak negative pressure was required to initiate significant bubble activity using 1.1 MHz and 50% duty cycle focused ultrasound in the 6600 cP fluid compared with the 1 cP fluid. Based on these results, it was estimated that a threshold could be defined that would result in no bubbles in 99.9% of mucinous cysts and just 22% of serous cysts. The remaining 78% of patients presenting with serous cysts would be positively identified by detection of bubbles, and would be spared an unnecessary biopsy. Conclusions: The cavitation threshold may be used non-invasively to distinguish between high viscosity and low viscosity fluids in cysts and reduce biopsies on serous cysts.
