Signal Processing - March 2017 - 116

Kernel Smoothed, Interpolated, Depth Justified
(Gaussian Kernel; Kernel Width = 0.05 mm)

1
0.5
0
1
0.5
0
1
0.5
0
1
0.5
0
1
0.5
0

0

200

400

600

800 1,000 1,200 1,400 1,600 15
Seconds
(a)

10

5
0
Millimeters Above Target
(b)

-5

0

200

400

600

800 1,000 1,200 1,400 1,600 15
Seconds

10

5
0
Millimeters Above Target

-5

Classifier Trends

Feature Trends (Curve Length)

Normalized Feature Data, Time Axis

(c)

(d)
Thalamus

ZI/Quiet Zone

STN

SN

figure 2. MER activity via a fuzzy clustering of multiple features for STN detection. The STN is recognizable as a red portion flanked by blue or aqua portions that
represent distinct physiology obtained from white matter tracts or other neuronal structures surrounding the STN. (a) and (b) Feature trends from a single feature
calculation (curve length). Open circles represent feature activity normalized to the data window length. STN boundaries are marked by gray boxes. (c) and (d)
Activity maps generated via fuzzy clustering of multiple features [8]. Different subcortical structures are marked by colored bars (see legend), with the target STN in
red and ventral edge located at 0 mm above target. (a) and (c) Feature trends/activity maps presented on the time-axis. (b) and (d) KDT interpolation with a Gaussian kernel (width = 0.05 mm). In (b) and (d), the thick black lines indicate the result of KDT and interpolation (with 1,000 points). For (c) and (d), the interpolation of
normalized feature trends is used.

an individual's symptom control,
polyurethane). Medtronic systems
while minimizing adverse simu lation
were FDA approved in 1997 (ET) and
effects (thereby maximizing the ther-
2002/2003 (PD), while St. Jude's Infin-
apeutic window).
ity system was FDA approved for
both in September 2016. Boston
Scientific won the approval of Con-
Steering the neurostimulation
formité Européene in September 2015,
Directional current steering is offered
and the Aleva stimulating lead system
by the Boston Scientific (Vercise)
is still undergoing clinical trials.
and St. Jude's (Infinity) DBS systems,
When active, DBS
with only the Infin-
systems deliver a
ity currently being
Much of the split ring
continuous train of
available in the Unit-
annular electrodes may
asymmetric biphasic
ed States. Horizon-
salvage the benefit of DBs tal steering of the
square waves, either
for nonoptimally placed
current or voltage based,
stimulation fields
leads.
whose set ting of mul-
emitted by the two
tiple contact configu-
middle annular con-
rations and programmable parameters
tacts of the quadripolar electrode is
of amplitude, pulse width, and frequ-
achieved by segmenting the annular
ency can be adjusted to maximize
ring into three 120° partitions that
116

IEEE Signal Processing Magazine

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March 2017

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can be individually activated or deac-
tivated. Thus, if the stimulating elec-
trode is placed more medially than
it should, the more lateral facing seg-
ments of the split ring can be activated
selectively, preventing medial spillage
of the stimulation field outside the
desirable target region to reduce side
effects. Aleva Neurotherapeutics has
also engineered a similar three-way
split ring stimulating electrode, except
utilizing the lower two annular contacts
of the quadripolar stimulation lead.
These electrodes were recently trialed
intraoperatively, exhibiting greater
benefit for directional over omnidi-
rectional stimulation in 13 movement
disorder DBS candidates [6].
Much of the split ring annular elec-
trodes may salvage the benefit of DBS
Table of Contents for the Digital Edition of Signal Processing - March 2017
