SU-E-I-114: Clinical Ultrasound Transducer Degradation Effects on the Accuracy of Spectral Doppler Velocity Measurements.

Abstract

Ultrasound Doppler velocity measurements are routinely used to determine the severity of a stenosis in the carotid, renal or peripheral arteries. The objective of this study is to investigate and demonstrate the relationship between Doppler velocity measurements and transducer degradation conditions encountered in a clinical environment. Assessing transducer performance was accomplished using the First Call aPerio Test System transducer analyzer (Sonora Medical Systems, Longmont, CO). This system was used to conduct 1,145 semi-annual transducer assessments at 7 clinical sites from September 2007 to February 2012 as part of a comprehensive quality control program. The results were evaluated to determine the degree of transducer degradation encountered in the clinical environment. A Siemens Acuson S2000 (Siemens AG, Erlangen, Germany) ultrasound system was employed with the 1425A LE Doppler Flow System (Gammex, Middleton, WI) to determine Doppler velocity measurements. A transducer fixation device was fabricated to provide accurate, repeatable velocity measurements. Transducers with the most severe degradation were evaluated by comparing velocity measurements to those without defects. Using several matched transducer pairs, simulated failure modes were tested. The Doppler measured time-average mean (TAMn) and time-average maximum (TAMx) velocities were obtained and reported. This investigation found that 4.5% of the transducers surveyed during this 5-year period of time failed at least one acceptance criteria. Many (346 or 30%) had at least one defect. Typical findings include dead elements, lens delamination, wire cuts, and capacitance shorts. Only the most severe transducer defects and degradation conditions resulted in a noticeable deviation in the velocity measurements. Simulated transducer degradation testing confirmed this finding. The relationship between Doppler velocity measurements and transducer degradation conditions is limited, becoming significant for only the most severe degradation conditions. Based on our experience, this level of transducer degradation is rarely encountered in the clinical environment.