US techniques
The sUS system used was a GE Logiq S7 expert (General Electric) with a matrix linear probe (ML 6-15) (Fig. The AR in situ US was composed of a conventional US system (SuperSonic Aixplorer Ultimate) with a linear probe (SL 18-5) and custom-developed software that transmitted the US image to an industry-grade head-mounted AR display (Microsoft Hololens). Furthermore, a QR code that tracked the probe to any position within the room was attached to the US probe (Fig. Ultrasound guided biopsy using augmented reality (AR US). The location of the image to be displayed below the US probe at the exact anatomical position was calculated using the world coordinate system of the head-mounted device and adjusted for a relative offset generated by the US probe head, marked with the QR code. The geometrical properties of the US probe head are exactly known and, together with the applied QR tracking code, an initial calibration to anchor the in situ image correctly in space, as already reported in our previously performed phantom study [This in situ image was relatively small, showing the actual dimensions without magnification (1:1); however, it supports the direct eye-hand coordination for the interventional steps by avoiding size and spatial abstraction (Fig. 