naa a22 4500 510807097 CHVBK 20180411083423.0 cr unu---uuuuu 180411e20131101xx s 000 0 eng 10.1007/s11548-013-0904-9 doi (NATIONALLICENCE)springer-10.1007/s11548-013-0904-9 Improving N-wire phantom-based freehand ultrasound calibration [Elektronische Daten] [Guillermo Carbajal, Andras Lasso, Álvaro Gómez, Gabor Fichtinger] Purpose: Freehand tracked ultrasound imaging is an inexpensive non-invasive technique used in several guided interventions. This technique requires spatial calibration between the tracker and the ultrasound image plane. Several calibration devices (a.k.a. phantoms) use N-wires that are convenient for automatic procedures since the segmentation of fiducials in the images and the localization of the middle wires in space are straightforward and can be performed in real time. The procedures reported in literature consider only the spatial position of the middle wire. We investigate if better results can be achieved if the information of all the wires is equally taken into account. We also evaluated the precision and accuracy of the implemented methods to allow comparison with other methods. Methods: We consider a cost function based on the in-plane errors between the intersection of all the wires with the image plane and their respective segmented points in the image. This cost function is minimized iteratively starting from a seed computed with a closed-form solution based on the middle wires. Results: Mean calibration precision achieved with the N-wire phantom was about 0.5mm using a shallow probe, and mean accuracy was around 1.4mm with all implemented methods. Precision was about 2.0mm using a deep probe. Conclusions: Precision and accuracy achieved with the N-wire phantom and a shallow probe are at least comparable to that obtained with other methods traditionally considered more precise. Calibration using N-wires can be done more consistently if the parameters are optimized with the proposed cost function. CARS, 2013 Freehand ultrasound nationallicence Calibration nationallicence N-wire phantom nationallicence Accuracy nationallicence Carbajal Guillermo Facultad de Ingeniería, Universidad de la República, Montevideo, Uruguay aut Lasso Andras Laboratory for Percutaneous Surgery, School of Computing, Queen's University, Kingston, Canada aut Gómez Álvaro Facultad de Ingeniería, Universidad de la República, Montevideo, Uruguay aut Fichtinger Gabor Laboratory for Percutaneous Surgery, School of Computing, Queen's University, Kingston, Canada aut International Journal of Computer Assisted Radiology and Surgery Springer Berlin Heidelberg 8/6(2013-11-01), 1063-1072 1861-6410 8:6<1063 2013 8 11548 https://doi.org/10.1007/s11548-013-0904-9 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11548-013-0904-9 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Carbajal Guillermo Facultad de Ingeniería, Universidad de la República, Montevideo, Uruguay aut NATIONALLICENCE 700 1- Lasso Andras Laboratory for Percutaneous Surgery, School of Computing, Queen's University, Kingston, Canada aut NATIONALLICENCE 700 1- Gómez Álvaro Facultad de Ingeniería, Universidad de la República, Montevideo, Uruguay aut NATIONALLICENCE 700 1- Fichtinger Gabor Laboratory for Percutaneous Surgery, School of Computing, Queen's University, Kingston, Canada aut NATIONALLICENCE 773 0- International Journal of Computer Assisted Radiology and Surgery Springer Berlin Heidelberg 8/6(2013-11-01), 1063-1072 1861-6410 8:6<1063 2013 8 11548 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer