It is possible to resolve micrometer movements in B-mode images

We have proposed an echo localization estimator which theoretically gives infinite resolution in the axial direction in ultrasonic B-mode images during 1) echo structure tracking and 2) distance measurements of distinct echoes. The performance of the estimator was evaluated using a HDI5000 (Philips Medical Systems, Bothell, WA, USA) with a 35 mm 5-12 MHz linear array transducer. The resulting pixel size in the B-mode image was 100 mu m. The controlled setup consisted of a small water container lined with ultrasound absorber carpet and placed on a micrometer table, a triangulation laser (M5L/2, MEL Mikroelektronik GmbH, Eching, Germany) connected to a high-performance digital multimeter HP 34401A (Agilent Technologies, USA) and a thermometer TESTO 925 (Testo AG, Germany). In each of the three measurement series the micrometer table was moved approximately 15 mu m in 10-12 steps. The echo localization estimator succeeded to resolve the minute movement (< 20 mu m) with high agreement with the reference method in all three series. The correlation was (R>0.998; p <10-e38; 0.86<k<0.92). The standard deviation in the recorded 25 image cineloops ranged between 97 and 195 nm. Using B-Mode images with pixel size of 100 mu m as a base, our echo localization estimator can resolve micrometer movement accurately in a controlled set-up.