Image-guided therapies are reliant on the spatial tracking of surgical tools for navigation. Ensuring that tracking is non-intrusive and accurate is therefore important. As tracking sensors become smaller, it is important to determine their effective range in comparison to the sensors that have been previously evaluated. We tested three different electromagnetic sensor sizes in the context of a surgical navigation system. Three different sized electromagnetic sensors were tested for tracking accuracy using optical tracking as the ground truth. An algorithm was developed to calculate the error between the data collected from the electromagnetic sensors with respect to the ground-truth measurements. Contours were generated to visualize the areas where tracking error is under certain threshold values. Multiple contours from electromagnetic sensors of different sizes were generated. To reduce noise in the measurements, repeated results were averaged. Results: The 8 mm and 2 mm length sensors performed comparably, both within acceptable error in the center of the tracking system’s workspace (50 cm away from the transmitter). The accuracy of the 0.5 mm sensor was acceptable up to 40 cm away from the transmitter. A distance greater than 20 cm led to a loss of consistent accuracy from the electromagnetic sensor. The 8 mm sensor and the 2 mm sensor shared similar iso-surface volumes, establishing that the 8 mm sensor could be substituted for the 2 mm sensor, which would be clinically beneficial typically. This would allow for electromagnetic sensors to be less intrusive in the operating room when tracking surgical and percutaneous intervention tools. The 0.5 mm sensor was not able to present the clinical required accuracy ranges.
Up to 30% of breast-conserving surgery patients require secondary surgery to remove cancerous tissue missed in the initial intervention. We hypothesize that tracked tissue sensing can improve the success rate of breast-conserving surgery. Tissue sensor tracking allows the surgeon to intraoperatively scan the tumor bed for leftover cancerous tissue. In this study, we characterize the performance of our tracked optical scanning testbed using an experimental pipeline. We assess the Dice similarity coefficient, accuracy, and latency of the testbed.
Ultrasound-guided interventions are progressively incorporating additional augmented reality (AR) components to improve navigation. A fundamental requirement to integrate ultrasound (US) images into AR environments is US probe calibration, which places images from a tracked US probe in the context of the tracker. To improve the incompatibility of common US probe calibration methods with clinical environments, Chen et al. developed an US calibration method (GUScal) with a focus for intraoperative application. To understand the effect of image quality and tracking accuracy on this calibration method, novice users were recruited to perform the calibration under three different conditions: (1) free-hand with one focal depth, (2) free-hand with three focal depths, and (3) using a mechanical arm to fix the needle with one focal depth. An expert user repeated this process 15 times per condition. The resultant transformation matrices and associated times were recorded for all calibrations. Numerical and visual analysis was conducted to compare the users calibrations results to each other and to the expert results. Based on our results we concluded including multiple focal depths produced the most precise calibrations for novice users. The expert user results showed that stabilizing the needle through a mechanical arm improved the calibration with practice. We recommend the inclusion of additional focal depths and a method to stabilize the needle to produce an accurate calibration in approximately 5 minutes.
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