IEEE Robotics & Automation Magazine - September 2018 - 72

Although accessing areas is usually
technically feasible, manually steering
and positioning catheters in the target
vessel is challenging and requires the
clinician to undergo expensive, timeconsuming training [4]. This makes
the steering accuracy highly dependent
(b)
on the abilities of a clinician [5], [6].
Multiple commercial solutions have
been
designed to alleviate these prob(a)
(c)
lems. Tendon actuation and guide(h)
wires remain the most common means
(f)
of helping the clinicians navigate the
(d)
(g)
endovascular catheters with higher
accuracy [7], [8]. Nevertheless, limitations like buckling and friction of the
tendons and cables tend to surface,
(e)
limiting the solution's effectiveness [9].
In these cases, the surgical procedures
Figure 1. A representative illustration of (a) a magnetic catheter being placed (b)
inside the aorta and (c) through the aortic valve by an electromagnetic coil. The
for endovascular and cardiac repair
electromagnetic coil produces (d) an external magnetic field. A typical cardiac
may increase the risk of complications.
intervention would involve the insertion of (e) the catheter in the groin to access (f) the
These complications are caused by an
aorta or, alternatively, (g) the arm to access (h) the brachial artery. The electromagnetic
coil can also be adapted to be a permanent magnet for the same application.
artery being too narrow to permit passage of surgical instruments, the site of
duration when compared to current, manual techniques. an aneurysm being too close to a vital organ or to important
Moreover, they allow surgeons access to areas of cardiovascular aorta branches, or being inaccessible (e.g., ophthalmic or basisystems that cannot be reached with standard, minimally lar tip aneurysms) [10]. Therefore, these types of procedures
invasive techniques.
may not always be feasible for certain patients.
As a result, alternative steering methods have been devised
Flexible Surgical Instruments
to improve the accuracy and reliability of catheter navigation.
The field of surgical robotics employs technological develop- Among these methods, the magnetically controlled catheter
ments that incorporate engineering systems to assist in medi- actuation and navigation systems, or magnetic manipulation
cal procedures. This support, which has gained increased systems (MMS), have been introduced [11], [12]. Using magacceptance in the last few years, allows clinicians to complete netic systems to steer catheters (Figure 1) allows for high-precomplex surgical techniques with more precision, flexibility, cision steering in the endovascular network, less radiation
and control than what is possible with conventional tech- exposure, and shorter procedure times than conventional
niques. Endovascular surgery, one of the procedures under- navigation systems [13], [14]. Moreover, they provide enhanced
taken by clinicians, utilizes relevant anatomy knowledge along steering capabilities to clinicians performing minimally invawith cutting-edge, minimally invasive technology. Endovas- sive surgical procedures [15].
cular surgeons and clinicians treat heart conditions and probThus far, research on magnetic actuation of endovaslems affecting the blood vessels, such as aneurysms. Surgical cular catheters has been limited to single case studies,
instruments, e.g., grafts, tubes, endoscopes, or catheters (com- and little is known about the taxonomy of magnetic actumonly sharing a similar structure to continuum manipula- ation for endovascular catheterization procedures. A broad
tors), are specifically designed devices that treat such definition applies to the original para-operational device
problems. These instruments are manually inserted into the (POD), founded in the 1960s [16], and is based on exterbody, duct, or vessel, and they are used for fluid drainage, dis- nal static magnetic fields and field gradients or on alterease treatment, or reaching specific sites in the body for tar- nating magnetic fields to propel and steer magnetic
geted drug delivery [1]. Catheters are typically steered from catheter tips intravascularly. The classification of magnetthe femoral artery vein found near the groin or arm to the tar- ic actuation is characterized by the combination of the
get site (the heart).
following features: magnetic actuation system, magnetic
Flexible surgical instruments are most commonly used in catheter elements, and visualization and control methods
laparoscopic surgeries-e.g., angiography; angioplasty; and for catheter steering.
arterial, aortoiliac, renal artery, and femoropopliteal- and
infrageniculate-arterial interventions [2]. These complex pro- Magnetic Instruments and Systems
cedures share common challenges regarding precise catheter The theory of magnetic steering has experienced two major
navigation, which is required for successful treatment [3]. stages of evolution in the past decade. Original studies
72

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september 2018
IEEE Robotics & Automation Magazine - September 2018

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