(Sunday, 7/14/2019) 2:00 PM - 3:00 PM
Room: 303
Purpose: Probe face degradation has been observed in our transvaginal GE IC5-9 transducers while routine QC tests could not reveal differences. This study aimed to investigate methods to reliably demonstrate and quantify probe face degradation effects on image quality, which included development of an easy-to-make low-cost phantom.
Methods: Three approaches were investigated: CIRS 040 phantom and Skolnick measurement of elevational resolution (Skolnick, 1991), Gammex 404 phantom and measurement of anechoic cylinder contrast, and a custom slice thickness (ST) phantom and measurement of elevational resolution. The custom ST phantom involves a 400-grit sand paper surface set at 45 degree submerged in a 9.5% ethanol/water bath. Three relatively new IC5-9 transducers and three with various degrees of degradation were tested. Five images were acquired at multiple elevational slice profile depths and transmit frequencies. Full-width half-maximum (FWHM) of the slice profile was measured using MATLAB.
Results: Commercial general-purpose phantoms and common performance measurements (e.g. Skolnick measurements of slice thickness and measurements of anechoic cylinder contrast) were not easy to perform, and did not clearly demonstrate the imaging effects, which could be partially due to target depth and difficult target alignment with IC5-9 probes. ST phantom clearly demonstrated the effects of probe face degradation, and effect variations with transmit frequency and depth. Transmit frequency and depth that best demonstrated the effects were 9 MHz (highest frequency) and slice profile at 3 cm (elevational focal depth). FWHM measurements with these scan parameters showed clear differences: mean slice thickness ranged from 2.9-4.0 mm and 5.4-7.2 mm for 3 undamaged and 3 degraded probes, respectively.
Conclusion: ST phantom is superior to general-purpose phantoms for demonstrating imaging effects of probe face degradation, especially for the whole length of the tightly-curved IC5-9 probes. Effects of probe face degradation can vary widely depending on transmit frequency and depth.
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