AbstractID: 9520 Title: Signal to noise ratio estimates of ultrasound depth of penetration
The maximum depth of penetration (DOP) for visualizing background echoes in a tissue-mimicking phantom is
an important performance measurement in ultrasound quality assurance (QA). DOP is the depth beyond which
details cannot be visualized, and depends on probe frequency, intensity, receiver sensitivity, and properties of
the medium. Currently, estimations of DOP are done subjectively from B-mode images. In this work, a
quantative measure of DOP based on signal to noise ratio (SNR) is correlated with subjective estimates.
Images of a conventional QA phantom (Gammex/RMI 403GS) were obtained using sensitivity settings adjusted
for maximum penetration. 3 observers independently estimated the DOP on each image, after which it was
saved to an ALI miniPACS. “Free probe” images also were recorded, where the transducer was not coupled to
the phantom, yielding information of electronic noise vs. depth for these machine settings. Images were saved
as tiff’s and transferred to a pc. Matlab was used to compute mean pixel values from small ROI’s vs. depth for
the phantom image as well as the free probe image.
Comparisons of user estimates and SNR were made for different probes and frequency settings. Preliminary
results indicate that users choose a DOP that is 3% (StDev 5%) from the depth at which SNR is 1.8 +/- .2 with
observed modest variation among them. Some variation due to size and shape of the ROI was observed. In
conclusion, objective criteria for DOP can be defined, enhancing ultrasound QA and acceptance testing.
Keyword: ultrasound depth of penetration, SNR, free probe