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Tracked Ultrasound in Navigated Spine
Interventions
Tamas Ungi, Andras Lasso and Gabor Fichtinger
Abstract Ultrasound is an increasingly popular imaging modality in image-guided
interventions, due to its safety, accessibility, and low cost. But ultrasound imaging
has a steep learning curve, and requires signi
cant coordination skills from the
operator. It is dif
cult to interpret cross-sectional anatomy in arbitrary angles, and
even more challenging to orient a needle with respect to the ultrasound plane.
Position tracking technology is a promising augmentation method to ultrasound
imaging. Both the ultrasound transducer and the needle can be tracked, enabling
computer-assisted navigation applications in ultrasound-guided spinal interven-
tions. Furthermore, the patient can also be tracked, which enables fusion of other
imaging modalities with ultrasound. In this chapter, we
first present the technical
background of tracked ultrasound. We will review how to build research systems
from commercially available components and open-source software. Then we will
review some spine-related applications of tracked ultrasound modality, including
procedural skills training, needle navigation for anesthesia, surgical navigation, and
other potential applications.
1 Introduction
Ultrasound is becoming a ubiquitous imaging tool in many medical specialties due
to its safety, portability, and low cost. Recent ultrasound devices
fit in the physi-
cians
pockets, and instantly provide real-time images of almost all anatomical
regions without radiation risks to the patient or physician. Spine is, however, one of
the particularly dif
'
cult areas for visualization with ultrasound. Bones and liga-
ments are close to the skin, and they cast acoustic shadows by re
ecting the
majority of the ultrasound waves, not letting through enough for visualization of
deeper anatomical structures. Furthermore, stiff tissue layers of spine muscles
fl
