Ultrasound-CT registration of vertebrae without reconstruction.
OBJECTIVE
While robust and accurate, our previously developed volume-to-volume ultrasound-CT registration of vertebrae required that the 2D ultrasound slices be reconstructed into a 3D volume, a time-consuming step that increased the total registration time per vertebra. We have modified our registration technique to a slices-to-volume strategy to eliminate the ultrasound reconstruction step in order to make the total registration time more practical intraoperatively.


METHODS
The slices-to-volume registration is achieved by performing backward scan line tracing on individual ultrasound slices as they are acquired, and then registering them as a group to the posterior vertebral surface extracted from the pre-operative CT image. The technique is validated using a lumbosacral Sawbones phantom and the lumbosacral section of three porcine cadavers.


RESULTS
The slices-to-volume registration reduced the total registration time per vertebra from 8 to 4 min. The registration accuracy and robustness of the slices-to-volume registration were found to be equal or superior to those of our previous volume-to-volume registration. In addition, a trade-off was found between registration accuracy and registration speed by changing the number of ultrasound slices used in the registration.


CONCLUSIONS
The slices-to-volume ultrasound-CT registration significantly reduces the total registration time per vertebra, making this automated technique more practical intraoperatively.
McConnell Brain Imaging Centre, Montreal Neurological Institute, 3801 Rue University, Montreal, QC, H3A 2B4, Canada. charlesyan@gmail.com
Charles X B
CX
Yan
Benoît
B
Goulet
Donatella
D
Tampieri
D Louis
DL
Collins
D000818:Animals; D002102:Cadaver; D021621:Imaging, Three-Dimensional; D019047:Phantoms, Imaging; D013131:Spine / Q000000981:diagnostic imaging* / Q000601:surgery; D018709:Statistics, Nonparametric; D013552:Swine; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*