Medical Design Briefs - August 2022 - 37

Surgical Navigation
Electromagnetic Tracking: Detecting and Mitigating
Distortion Advances Surgical Navigation
Electromagnetic sensors paired with distortion detection and mitigation
pioneer new applications.
A
dvancing minimally invasive surgery and its usefulness in
diagnosis and treatment in more healthcare situations is
a direct challenge for medical device OEMs. Transforming
these image-guided and interventional procedures requires
precise surgical navigation that empowers physicians when
there is no line of sight. Electromagnetic (EM) tracking systems
- once hindered by the presence of metals and other equipment
in a surgical setting - are gaining ground on this front.
Distortion detection and mitigation caused by equipment in
a surgical setting, coupled with advanced EM sensors, improve
accuracy and precision to enable a flexible platform approach
for a greater number of devices and procedures. This combination
of characteristics represents a breakthrough advancement
for devices requiring highly accurate surgical navigation. Solving
inherent distortion challenges and enabling a broadly viable
EM solution empowers physicians to navigate more areas of
the human body with greater accuracy and precision.
Overcoming Obstacles
EM surgical navigation is currently deployed in a variety of
interventional and surgical domains, including electrophysiology,
ear nose and throat (ENT), pulmonology, neurology, and
other emerging procedures. These systems are used wherever
the surgical procedures are performed - operating rooms or
interventional suites in hospitals, outpatient centers, ambulatory
surgical centers, etc.
And yet, the Achilles heel of EM tracking is inaccuracy due to
distortion and interference with other equipment in a surgical
setting. When metal is present in a sensing volume, the soluRight:
Thin, light, modular antennas can be easily
assembled to generate large sensing volumes.
Radiotranslucent construction makes it compatible
with intraoperative fluoroscopy and CT imaging.
(Credit: Radwave/TT Electronics)
tion's sensors may either not be tracked or will be tracked inaccurately.
Physicians and other clinicians won't know that their
surgical navigation tool position is incorrect, or they just won't
get the location information they need - a silent failure of the
tracking system.
How prevalent is this issue? In today's minimally invasive surgical
(MIS) and robotic procedures, there are many more types
of imaging equipment and robotic arms in any procedure
room; their presence speaks to EM interference. For example,
surgical tables and patient beds often contain conductive materials
that cause distortions. However, since these are static structures,
the resulting interference can be " mapped " prior to the
procedure and taken into consideration to correct any distortion
of sensor location.
At the same time, the procedure space also houses metal
structures that move around, in, and out of the surgical field
- these cannot be mapped before the procedure. In spinal
surgery, for example, metal structures in the procedure space
may include the fluoroscopic C-Arm, metal robot parts, and
various surgical and fixation tools.
The issue of frequency interference compounds these challenges.
Older EM systems may utilize wide EM frequency bands,
creating interference with medical equipment like an electrocardiogram,
other biopotential signals, and the image from the fluoroscopic
C-Arm. In these cases, the legacy EM system cannot be
used simultaneously or in proximity to certain other pieces of
surgical equipment or tools. In this less-than-ideal scenario, clinicians
would be forced to minimize active equipment in the surgical
suite as a trade-off to gain surgical navigation beyond the
Left: A control unit enables seamless tracking of
multiple sensors and tools at the same time with
flexible port configurations and high sampling rates.
(Credit: Radwave/TT Electronics)
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Medical Design Briefs - August 2022

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