Biomedical Engineering Reference
In-Depth Information
In addition, the duration of storage before transfusion may alter the RBC function and,
therefore, influence the incidence of complications in patients. DHM was used to classify
RBCs based on their duration of storage where it can replace traditional approaches through
biomolecular assays that may be invasive, expensive, and time consuming. DHM allows for
measurement of the RBCs' biconcave profile, resulting in a discriminative dataset that can
be used by statistical clustering algorithms to discriminate the RBCs' populations. This
approach was proven successful in classifying RBCs stored for 14 and 38 days
[48]
.
The RBC MCV is a highly medically relevant parameter that can be easily calculated
[141]
using the decoupling procedure presented in
Section 5.2
. In addition, as the hemoglobin
content is mainly responsible for the refractive index of the RBC, it can be used as a direct
measure of the MCHC
[141]
. Barer
[4]
proposed a way to relate the phase signal to the
mean corpuscular hemoglobin (MCH) (in a similar relationship than with the DM presented
above in
Eq. (5.4)
):
10
ϕλS
cell
2
MCH
5
(5.5)
πα
Hb
where
is the wavelength of the
illumination light source,
S
cell
is the projected cell surface, and
ϕ
is the mean phase shift induced by the whole cell,
λ
Hb
is the hemoglobin
refraction increment (1.96
3
10
2
3
dl/g at 663 nm). This formula allows to directly and
noninvasively measure the MCH of single RBC. Knowledge of the MCV, obtained with the
decoupling procedure presented in
Section 5.3
, allows to calculate the MCHC of individual
red cells by dividing MCH by MCV.
α
In a previous paper, we showed that MCH and MCHC measurements obtained with DHM
and those obtained with two other techniques, CLSM and an impedance volume analyzer
(Sysmex KX-21), are in good agreement. The result of this comparison is presented in
Table 5.1
.
These RBCs' biophysical parameters, noninvasively monitored by DHM, are clinically
relevant parameters that can be used as diagnostic tools (e.g., involved in the anemia
classification). In addition, monitoring at a single cell level allows the investigation of
changes occurring in the RBC subpopulation.
5.3.4 Cell Membrane Fluctuations
Throughout their lifespan of 100
120 days, RBCs are squeezed as they pass capillaries
often smaller than the cell diameter. This ability can be attributed to the remarkable elastic
properties of the membrane structure, which consists of a lipid bilayer that is coupled at
specific binding sites to the underlying cytoskeleton. This structure exhibits a high
resistance to stretching ensuring that no leakage through the lipid bilayer occurs, whereas
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