Cryotrack: Planning and Navigation for Computer Assisted Cryoablation

Needle guidance in thermal ablation procedures is challenging due to the absence of a free line-of-sight. To date, the needle trajectory is manually planned on a pre-operative CT slice, and then the entry point is transferred with a ruler on patient and needle. Usually, the needle is inserted in multiple strokes with interleaved control CTs, increasing the number of exchanges between OR and control room and exposure of the patient to radiation. This procedure is not only tedious, but also introduces a navigation error of several centimeters if the entry point was not chosen precisely. In this paper, we present Cryotrack, a pre- and intra-operative planning assistant for needle guidance in cryoablation. Cryotrack computes possible insertion areas under the use of a pre-operative CT and its segmentation, considering obstacles (bones) and risk structures. During the intervention, cryotrack supports the clinician by supplying intraoperative guidance with a user-friendly 3D interface. Our system is evaluated in a phantom study with an experienced surgeon and two novice operators, showing that Cryotrack reduces the overall time of the intervention to a fourth while being on par with the traditional planning in terms of safety and accuracy, and being usable by novices.