Biomedical Engineering Reference
In-Depth Information
distortion of magnetic ield of magnetic tracker is not necessary. It is
necessary to study the dispersion of samples of the magnetic tracker
when sensing a coordinate at ixed location and orientation in order
to conirm that the sparse LUT is valid and that the controllers will
react at the proper location. For that, the sensor is hold collecting
samples for every reference point of
M
. If the MMCS remains at a
static position
P
M
coll
e
cti
ng
sam
ples, the average coordinate of
all the collected samples
, can be considered the correct
coordinate. Then dispersion of the samples for the evaluated point
P
could be modeled with
PXYZ
(,,)
2
2
2
E
(
X
X
)
(
Y
Y
)
(
Z
Z
)
(7.4)
P
max
max
max
2
2
2
E
(
X
X
)
(
Y
Y
)
(
Z
Z
)
(7.5)
P
min
min
min
E
are the dispersions above and below of the average.
X
max
,
Y
max
and
Z
max
are the maximum coordinates reported in the
three axes for all samples of
P
. In the same way
X
min
,
Y
min
, and
Z
min
are the minimum reported coordinates. If this dispersion is small
compared to the detection range the control method can be applied.
E
and
where
P
P
7.2
Robotic Camera for Digital Subtraction
Angiography Simulation
At surgical rooms equipped for Interventional Radiology (IVR), the
luoroscope is commonly attached to a C-arm; this robotic arm allows
changing the orientation and position of the luoroscope enabling to
visualize the development of the endovascular intervention. When
required an additional C-arm and luoroscope is set in a bi-planar
coniguration, to register radiological images in perpendicular
planes. In raw luoroscopic images, blood vessels are visible only
while contrast media is present in the blood stream; meanwhile
catheters and guide wires are visible over the background. Therefore
to visualize the progress of the catheter or guide wire through blood
vessels image processing Digital Subtraction Angiography (DSA) [1]
and
Road
M
a
p technique are used (Fig. 7.2).
A
Road
M
a
p, as described by Turski
et al
. [1], is an image processing
technique used in IVR to create a video containing simultaneously
the moving catheter and a static angiogram. First an angiogram is
registered using X-rays when contrast media is injected through the
vasculature; a clear and static image of the vasculature to be treated
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