Furthermore, new predicate devices were tested to establish a baseline for comparison using a statistical process control (3-sigma distribution). The performance of reprocessed catheters was quantitatively compared to original specifications of new catheters. Additional supplementary tests such as mechanical, electrical and acoustic output were conducted, but are not included in the scope of this study. Data from those studies demonstrated substantial equivalence to predicate AcuNav catheters.

Image Quality

Since image quality and resolution are perceived to be the most critical clinical aspects of ultrasound, each catheter was subjected to element-by-element testing. To clearly detect element failure or potential degradation after reprocessing, each sample was tested on a commercially available transducer testing platform, FirstCall 2000. This system is a high-speed, portable probe testing system and has a custom fixture for signal acquisition. This equipment was used to measure basic acoustic performance parameters within a population of reprocessed AcuNav catheters. The repeatability of the FirstCall testing was analyzed in a separate study, and was found to be acceptable for all the testing parameters. The following data was collected and analyzed: element sensitivity, capacitance, pulse width, center frequency, fractional bandwidth, weak or dead elements. However, only element sensitivity and capacitance is being reported in this article to limit the scope.

Dielectric Strength

Reprocessed AcuNav catheters were subjected to 100% hipot (high potential) and leakage current testing. In hipot testing, often called the voltage breakdown or dielectric strength test, the AcuNav's outer shaft was electrically stressed at a worse case to withstand electric stress gradients at elevated voltages for prolonged durations. Fundamentally, the test is designed to evaluate how well the outer shaft contains and insulates from voltage leaks and how resistant the insulation is to voltage arcing. As shown in Figure 2, sparking or arcing is characterized by rapid variations in voltage or current that typically results in failure. If kinks, cuts or abrasions are present within the material, an escape path is created for the voltage. Maintaining an adequate dielectric barrier between the electrical power and the patient is critical in terms of power surges. In case of malfunctioning equipment or unsteady electrical current, breached dielectric insulation can result in patient or end user shock or electrocution. The testing sequence includes submerging the catheter shaft into a saline bath enclosed in a custom-designed test vessel. Elevated voltages and currents are transmitted through the length of the catheter from the handle to the distal transducer. Dielectric testing measurements were performed in accordance to the industry-accepted standard UL 2601-1 Medical Electrical Equipment, Part 1: General Requirements for Safety.7 All tested catheters were found to be within the specification set by the industry-acceptable standard.

Leakage Current