Author: Paul L. Carson, Sander Dekker, Stephen Z Pinter, Megan K. Russ 👨🔬
Affiliation: Clinical Imaging Physics Group, Department of Radiology, Duke University Health System, University of Michigan, Cablon Medical B.V., Univ of Michigan, Dept. of Radiology 🌍
Purpose:
To promote a simplified, inexpensive, but rigorous set of ultrasound QA tests and to evaluate their potential using a Randomly-placed very Hypoechoic Sphere Phantom (RHSP) in comparison to two competing methods.
Methods:
The sensitivities of the RHSP, a crossed wire phantom and an established uniformity phantom were compared for detecting physically simulated, common transducer defects, using commercially available automated analysis. To block some of the linear array elements, a layer of Styrofoam was taped over various parts of the array. Scanning methods and analysis, generally described in IEC TS62736, provided median lesion signal to noise ratio (LSNRm) and other measures on the spheres, -6dB pulse echo response widths on the wires and median signal level on the uniformity phantom and RHSP.
Results:
The RHSP phantom/analysis gave consistent results, with delineation of the lateral and the full elevational disruptions, but only meager delineation of the partial elevational disruption given chosen settings. Beam width measurements on the 90º/45º wire phantom delineated all three disruptions but were more difficult to perform and functioned over limited settings. The uniformity measurements revealed only the lateral disruption. An update on current automated analysis software will be provided.
Conclusion:
The RHSP phantom should now be available at lower cost than wire-based phantoms. It demonstrated good detection of all but the subtlest disruption. We recommend this phantom for ultrasound system user QA and performance evaluation, after initial verification on each model, of the gray scale characteristic curve and spatial measurements. Quantitative expectations for different US systems will develop rapidly, as more users will be implementing this simpler QA. Software or phantom modifications can add evaluation of spatial measurements and make QA as simple on curved as on linear arrays. A uniformity phantom is useful for more frequent tests. A crossed wire phantom serves well for initial validations.