Biomedical Engineering Reference
In-Depth Information
diameters respectively, and
a
is the effective emission diameter of the trans-
ducer. Typical arterial lumen diameter of coronary arteries is
D
≈
3 mm [18, 19].
From Fig. 1.14 we can see that
D
M
≈
0
.
84 mm and
a
=
0
.
60 mm. Using Eq. (1.10)
we obtain the sweeping volume of the transducer beam approximately as
V
b
≈
3
.
91 mm
3
. The RBCs can be approximated by spherical scatterers having
a volume of 87
µ
m
3
[20], which corresponds to a radius of 2
.
75
µ
m (diameter,
d
g
=
5.5
µ
m). Considering a typical hematocrit concentration [21] of 35%, we
can estimate the RBCs number by the beam sweeping volume. The RBCs sweep-
ing volume is
V
RBC
=
1
.
36 mm
3
, and the typical human RBCs number is approx-
imately
N
≈
4
.
1
×
10
6
cells
/
mm
3
[21]. Thus, the RBCs number by the sweep-
ing volume is
N
o
≈
5
.
61
×
10
6
cells. The maximal axial resolution at 40 MHz
is approximately
d
r
=
38
µ
m, at which we can observe the order of
d
r
/
d
g
≈
7
RBCs. If we take the scatterers as perfect spheres with radius
d
r
at maximal
axial resolution, we would have scatterers of the order of 1
.
37
×
10
7
to be sim-
ulated. It is not possible to estimate this value for RBCs scatterers with a com-
puter. In order to generate the number of scatterers possible to emulate, we
generate scatterers groups namely “voxel” [11]. In Table 1.2, the most impor-
tant numerical data used by this simulation model is summarized. The mini-
mal structure dimensions that can be measured by an IVUS image at 40 MHz
is 1
/
25 mm
/
pixel
≈
0
.
04 mm. We take this dimension to estimate the minimal
Table 1.2:
Important features and the corresponding
approximated values used in this simulation model
Feature
Approximated values
Arterial diameter
D
=
3 [mm]
Sheathing transducer diameter
D
M
=
0
84 [mm]
.
Transducer diameter
a
0
60 [mm]
=
.
Sweeping volume by the beam
V
b
=
3
91 [mm
3
]
.
RBC volume
87 [
m
3
]
µ
Hematocrit concentration
35%
RBC volume by 35% of
V
b
1.36 [mm
3
]
N
=
4
.
1
×
10
6
[cells
/
mm
3
]
Typical human RBC number
Maximal axial resolution at 40 MHz
d
r
=
38 [
µ
m]
IVUS image resolution
(1
/
25)
≈
0
.
04 [mm
/
pixel]
6
.
4
×
10
−
5
[mm
3
]
Minimal voxel volume
Total RBC voxel
360 [voxels]
1
.
5
×
10
4
RBC voxel to be emulated
[voxels]
