Biomedical Engineering Reference
In-Depth Information
Table 5.1: Results of the Measurements of Normal Erythrocytes by Different Techniques
Technique
Volume
(fl)
Surface
(
µ
m
2
)
Diameter
(
µ
m)
Refractive
Index
MCH (pg/
cell)
MCHC
(g/l)
N
DHM
Mean
83.3
46.7
7.7
1.418
29.9
362
STD
13.7
5.9
0.5
0.012
4.4
40
36
Dif
t
5.7
0.006
7
CLSM
Mean
90.7
46.9
7.7
STD
16.7
6.8
0.6
34
Impedance volume
analyzer
Mean
81.8
28.6
349
10
5
RDW
SD/CV
40.8/12.7
B
3
3
DHM, digital holographic microscopy; CLSM, confocal laser scanning microscopy; impedance volume analyzer (Sysmex
KX-21); N, number of cells; STD, standard deviation for cell population; Dif
t
, averaged difference of individual cells for
measurements taken at different times; RDW, red cell distribution width (expressed as coefficient of variation (CV, %) or
standard deviation (SD, fl)).
Source: Modified from Ref.
[141]
.
its low resistance to bending and shearing allows the cell to easily undergo morphological
changes when passing through small capillaries. As a consequence of these elastic
properties, RBCs show spontaneous cell membrane fluctuations (CMF), often called
flickering, that can be observed under the microscope
[140,142,148
151]
. This
phenomenon has been the subject of considerable scientific interest in the past. One reason
is that CMF provide information on the elastic properties of the RBC membrane structure
and might help in the diagnosis or understanding of diseases afflicting the RBC
[151,152]
.
Understanding the origin of CMF may provide information about the functional status of
erythrocyte under normal and pathological conditions.
DHM offers a powerful tool to noninvasively investigate the CMF of individual RBCs with
a nanometric resolution
[142]
. The membrane fluctuations amplitude is derived from the
deviation map (measured temporal deviation within the cell, in degrees), with the following
equation:
ðϕ
cell
Þ½
ðx
;
yÞ
3
λ
std
CMF
½
nm
ðx
;
yÞ
5
(5.6)
2
πðn
rbc
2
n
medium
Þ
cell
)[
]
(
x
,
y
)
is the deviation map expressed in degrees,
where std(
is the light source
wavelength, and
n
rbc
and
n
medium
are the refractive indices of the RBC and medium,
respectively.
n
rbc
can be measured using the decoupling procedure presented in Section 5.2.
The morphological origin of the phase signal fluctuations was verified with the decoupling
procedure.
ϕ
λ
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