Biomedical Engineering Reference
In-Depth Information
Fig. 1.45.
The blood-flow rate distribution of cutaneous tissue of hands. The blood-
flow rate (ml/min/100 g cutaneous tissue) of both hands is calculated by (1.12).
The patient was injured on his left hand by pulling it violently in a motorbike
accident. The
right
image shows a thermogram and the
left
image shows the blood-
flow rate calculated by (1.12) using the parameters written in the right corner of the
figure. Deep body temperature was measured by a deep body thermometer, using
the Fox's method. The cutaneous tissue blood flow of the left fingers decreased to
under 5.4 ml/min/100 g tissue
Time-Sequential Image Processing.
If the thermal production of a re-
gion does not balance the thermal dissipation, we must add a heat accumula-
tion factor in (1.12). If the observation time is short and the body temperature
and the environmental temperatures (wall temperature and ambient tempe-
rature) are kept constant over this period, we can estimate the quantitative
changes of some physiological parameters under a transient status. The most
dominant parameter is blood flow.
When we administer a vasodilator as a load (Fig. 1.46) [71], or induce
reactive hyperemia using vascular occlusion [72], the environmental tempera-
ture change has negligible effects on skin-temperature control. In such cases,
we should add thermal accumulation item to the equilibrium equation (1.5)
of the thermally neutral condition. If we observe skin-temperature change
(
ΔT s
)inashortperiod(
Δt
), the following equation results:
Cs
×
ΔT s
=
ΔQc
+
ΔQm
+
ΔQb
−
(
ΔQr
+
ΔQe
+
ΔQf
)
,
(1.13)
where
Cs
is the heat capacity of skin. In this equation, we can neglect me-
tabolism (
ΔQm
) and evaporation (
ΔQe
). We analyzed the effect of the re-
gional skin-temperature change on those parameters. If the change is more
than 1
◦
C and we calculate the contribution rate of each of the parameters
