Comparison of selected ultrasound performance tests with varying overall receiver gain and dynamic range, using conventional and magnified field of view.

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Most ultrasound (US) scanner vendors currently offer a feature that allows a region of the ultrasound image to be magnified or zoomed. Although the methods of magnification vary among vendors, the ability to "zoom in" on a selected portion of the image has gained clinical acceptance. However, using this feature introduces additional steps in the quality assurance (QA) measurement procedures. No studies exist that demonstrate the advantage of a magnified field of view (FOV) over the conventional FOV for QA purposes. The purpose of this study was to investigate the influence of a magnified versus nonmagnified FOV on various common QA performance tests as a function of the overall receiver gain and dynamic range. Additionally, since the performance tests are subject to variations caused by scanner settings, sets of QC tests were recorded using several different scanner settings to investigate any change in the sensitivity of the QC measurements with respect to the magnified and nonmagnified fields of view. The lateral and axial resolution, slice thickness, and caliper accuracy (vertical and horizontal) as a function of varying overall receiver gain and dynamic range, were obtained using conventional (no zoom) as well as a magnified (zoom) field of view (FOV). Each measurement was performed three times by a single observer using a 4 MHz "vector" format transducer on a single diagnostic medical ultrasound scanner. The results show no statistical significance in the variability of most recorded masurements when using the conventional versus the magnified FOV. However, in some cases, such as lateral resolution, the average value measured using the magnified FOV was typically 0.5 mm lower than when using a conventional FOV.