Method for assessing augmented reality needle guidance using a virtual biopsy task

The Sonic Flashlight is a device that permits real-time in. situ visualization of ultrasound images by reflecting calibrated images displayed on a flat-panel monitor from a partially transparent half silvered mirror [1]. This system presents the illusion that the ultrasound slice is "floating" within the patient's body, and we believe it will be a useful visualization technique during ultrasound guided interventional procedures. While our preliminary research indicates that the Sonic Flashlight is practical in a clinical setting [2], we lack empirical data that demonstrate our hypothesized improvement in needle placement accuracy. To this end, we have designed a system that presents "virtual phantoms" to the operator by tracking a non-scanning Sonic Flashlight and a mock needle with a minibird (TM)(Ascension Technology) magnetic tracking device. This system allows us to present the correct slice through a stored image volume and compute the error in position between the needle tip and the center of the virtual target. Preliminary data suggest that our device is capable of acquiring data that is consistent with the physical movement observed during the test and is qualitatively similar to data acquired in an earlier analysis of surgical tool movement[3]. While it is not yet possible to draw definitive conclusions about the impact of the Sonic Flashlight on needle guidance, these data suggest that such a study will be possible using the virtual phantom system that we have developed.