ARTICLES |
Author - Kalia YN
Author - Guy RH
Title - Interaction between penetration enhancers
and
iontophoresis:
Effect on human skin impedance in vivo.
- English
- Article
- Guy RH, Univ Calif
San Francisco, Dept Biopharmaceut Sci,
San Francisco,CA
94143 USA
- Purpose: The objective
of this study was to develop a non-
invasive
technique to assess the interaction between
chemical
and electrical modes of percutaneous penetration
enhancement
in vivo. Methods: Impedance spectroscopy, a
non-invasive
biophysical technique, was used to monitor
the effect
of iontophoresis on skin and to determine the
extent
to which this effect was modulated by pretreatment
with penetration
enhancers of different physicochemical
properties.
Results: Azone(R)/propylene glycol and sodium
lauryl
sulfate had a profound effect on post-iontophoretic
skin impedance,
considerably amplifying the effect of
current
passage. Post-iontophoretic impedance spectra of
skin pretreated
with oleic acid showed a smaller decrease
in skin
impedance. Neither stearic acid nor linoleic acid
had comparable
effects, however. For these enhancers, the
changes
observed were attributable to the vehicle,
propylene
glycol, which complemented the action of
iontophoresis
and increased its effectiveness. A
parameter,
analogous to the membrane time constant, was
introduced
that enabled the degree of perturbation and the
rate of
recovery of skin impedance to be gauged.
Conclusions:
This study provides the first direct in vivo
measurements
of the interaction between chemical and
electrical
enhancement, the two principal techniques used
to promote
transdermal drug delivery. Changes in the
reduction
of skin impedance induced by the passage of
current
have been used as indicators of the interaction
between
an array of diverse penetration enhancers and
iontophoresis.
The post-iontophoretic impedance data have
been fitted
to a circuit model involving the parallel
arrangement
of a resistor and a constant-phase element,
and the
modulation of the effect of iontophoresis by the
penetration
enhancers has been determined from changes in
the equivalent
circuit parameter values.
Journal - J Control Release 1997 FEB 1;44(1):33-42
Kee, W.C.; Kingma, Y.J.; Mintchev, M.P.; Bowes, K.L.
Optimal placement of impedance epigastrography electrodes
Annals of Biomedical Engineering
24
2
MAR-APR
1996
328-332
MP Mintchev
Univ Alberta
Dept Elect Engn
238 Civil Elect Bldg
Edmonton
Ab T6G 2N1, Canada
0090-6964
epigastric impedance; gastric motility; electrogastrography
Impedance electrogastrography (IE) is a noninvasive method
to assess gastric contractile activity. This indirect
method uses a four-terminal impedance measuring method to
determine impedance variations of the gastric region of the
torso. These variations can be related to changes in the
stomach shape and, therefore, to gastric contractions.
Because the impedance variations are very small, the
placement of the measuring electrodes on the skin is
critical. In this study, a three-dimensional resistor model
consisting of 4,466 resistors was used to simulate the
human torso. The model was implemented on a personal
computer, and the experimentally obtained optimal electrode
locations were found to be superior to the commonly used
ones. Measurements of volunteers confirmed these findings.
Kleinermann, F.; Avis, N.J.; Judah, S.K.; Barber, D.C.
Title Three-dimensional image reconstruction for electrical
impedance tomography
Journal Physiological Measurement
17
Suppl. 4A
NOV
Year 1996
Page A77-A83
Address F Kleinermann
Univ Hull
Dept Comp Sci
Kingston Hull HU6 7RX
N Humberside, England
Serial# 0967-3334
Abs. Very little work has been conducted on three-dimensional
aspects of electrical impedance
tomography (EIT), partly
due to the increased computational
complexity over the two-
dimensional aspects of EIT.
Nevertheless, extending EIT to
three-dimensional data acquisition
and image reconstruction
may afford significant advantages
such as an increase in
the size of the independent
data set and improved spatial
resolution. However, considerable
challenges are associated
with the software aspects
of three-dimensional EIT systems
due to the requirement for
accurate three-dimensional
forward problem modelling
and the derivation of three-
dimensional image reconstruction
algorithms.
This paper outlines the
work performed to date to derive a
three-dimensional image
reconstruction algorithm for EIT
based on the inversion of
the sensitivity matrix approach
for a finite right circular
cylinder. A comparison in terms
of the singular-value spectra
and the singular vectors
between the sensitivity
matrices for a three-dimensional
cylinder and a two-dimensional
disc has been performed.
This comparison shows that
the three-dimensional image
reconstruction algorithm
recruits more central information
at lower condition numbers
than the two-dimensional image
reconstruction algorithm.
Kohno-H; Tanaka-H; Honda-S
Therapeutic Assessment of Childhood Obesity with Body Composition
Measured by Bioelectrical Impedance Analysis.
Fukuoka Acta Medica 85(9): 267-270
1994
Japanese
This study was conducted to assess the changes in body
composition, such as body fat mass (F) and lean body mass (LBM),
after the treatment of obesity with a low calorie balanced diet (
LCBD) in out patient clinics. Body composition was measured by a
bioelectrical impedance analysis (RJL Systems, Detroit, Michigan,
USA). 67 patients with over 30% of obesity index (01), 36 males
and 31 females, aged 3-15 years old were studied. 41% of the males
and 13% of the females showed an increasing trend of 01 after a
temporary improvement of obesity (P lt 0.001) during a one year
treatment period. F and LBM, however, did not change
significantly, irrespective of the 01 increment (P lt 0.001),
which was due to the increase of LBM. These observations indicated
that the effects of treatment with LCBD for obesity should be
assessed by the changes in F and LBM.
Koksal, A.; Eyuboglu, B.M.
Title Determination of optimum injected current patterns
in
electrical impedance tomography
Journal Physiological Measurement
16
Suppl. 3A
AUG
Year 1995
Page A99-A109
Address A Koksal
Hacettepe Univ
Dept Elect & Electr
Engn
Ankara 06532, Turkey
Serial# 0967-3334
Keys CURRENT COMPUTED-TOMOGRAPHY; DISTINGUISHABILITY
Abs. The problem of finding the optimum current under
different
constraints in electrical
impedance tomography is cast into
a non-linear optimization
problem. Optimum currents are
investigated for a two-dimensional
cylindrical body with a
concentric or an eccentric
inhomogeneity under the
constraints of constant
dissipated power and constant total
injected current. For a
concentric inhomogeneity, it is
shown that the opposite
drive results in a better
distinguishability than
the cosine current pattern under
the constant-injected-current
constraint. The results for
the concentric case are
extended to the eccentric case
directly using the properties
of the conformal
transformation and of the
constraints involved.
Distinguishability and the
minimum detectable object size
achieved by the optimized
currents are compared with the
ones achieved by the cosine
current pattern for
conductivity distributions
with the concentric and
eccentric inhomogeneity.
Koksal, A.; Eyuboglu, B.M.
Title Determination of optimum injected current patterns
in
electrical impedance tomography
Journal Physiological Measurement
16
Suppl. 3A
AUG
Year 1995
Page A99-A109
Address A Koksal
Hacettepe Univ
Dept Elect & Electr
Engn
Ankara 06532, Turkey
Serial# 0967-3334
Keys CURRENT COMPUTED-TOMOGRAPHY; DISTINGUISHABILITY
Abs. The problem of finding the optimum current under
different
constraints in electrical
impedance tomography is cast into
a non-linear optimization
problem. Optimum currents are
investigated for a two-dimensional
cylindrical body with a
concentric or an eccentric
inhomogeneity under the
constraints of constant
dissipated power and constant total
injected current. For a
concentric inhomogeneity, it is
shown that the opposite
drive results in a better
distinguishability than
the cosine current pattern under
the constant-injected-current
constraint. The results for
the concentric case are
extended to the eccentric case
directly using the properties
of the conformal
transformation and of the
constraints involved.
Distinguishability and the
minimum detectable object size
achieved by the optimized
currents are compared with the
ones achieved by the cosine
current pattern for
conductivity distributions
with the concentric and
eccentric inhomogeneity.
Konishi, Y.; Morimoto, T.; Kinouchi, Y.; Iritani, T.;
Monden, Y.
Title Electrical properties of extracted rat liver tissue
Journal Research in Experimental Medicine
195
4
AUG
Year 1995
Page 183-192
Address T Morimoto
Univ Tokushima
Sch Med Sci
Kuramoto CHO 3
Tokushima 770, Japan
Serial# 0300-9130
Keys electrical impedance; rat liver; ischemia; time
course;
incubation temperature
ISCHEMIA; NECROSIS; INJURY
Abs. We attempted to investigate the process of ischemia-induced
disturbances in the rat
liver, employing the electrical bio-
impedance technique. The
electrical bio-impedance was
measured continuously over
6 h by the 4-electrode method,
at various incubation temperatures,
in six liver samples
extracted from male Wistar
rats. The electrical properties
of biological tissues can
be expressed in terms of three
parameters: extracellular
resistance (Re), intracellular
resistance (Ri) and cell
membrane capacitance (Cm). These
three parameters were calculated
from the measured values
of the electrical impedance
by the curve-fitting technique,
using a computer program.
The Re value increased rapidly
after the rat livers were
extracted, and then decreased
slowly. The Re value reached
a peak after about 13 min at
36 degrees C, and then decreased
slowly, becoming constant
after 3 h. There was a negative
correlation between the
Tmax of Re (the time when
Re reached a maximum) and the
incubation temperature (R=-0.973,
P<0.001). The Ri value
decreased once in the early
stage after extraction,
followed by almost no change
and then an increase after 4 h
at 36 degrees C. The Cm
showed a similar pattern of change
to the Re value, and a negative
correlation was also found
between the Tmax of Cm and
the incubation temperature (R=-
0.969, P<0.001). The
increases in the Re and Cm values, and
the decrease in the Ri value
for quite long periods after
the blood flow has stopped,
suggest an increase in the
resistance of extracellular
fluid due to a decrease in its
volume, an increase in cell
membrane capacitance due to
cell swelling, and a decrease
in cellular fluid resistance
due to an increase in its
volume. The time when the Cm
value decreases rapidly
after an initial gradual decrease
after the peak corresponds
well with the time when the Ri
value begins to increase,
from which it is estimated that
cell lysis proceeds and
that the flow of extracellular
fluid into the cell begins
at this time. The findings of
this study suggest the possibility
of estimating the
changes in liver tissue
or the tissue structure due to
ischemia.
Konishi, Y.; Morimoto, T.; Kinouchi, Y.; Iritani, T.;
Monden, Y.
Title Electrical properties of extracted rat liver tissue
Journal Research in Experimental Medicine
195
4
AUG
Year 1995
Page 183-192
Address T Morimoto
Univ Tokushima
Sch Med Sci
Kuramoto CHO 3
Tokushima 770, Japan
Serial# 0300-9130
Keys electrical impedance; rat liver; ischemia; time
course;
incubation temperature
ISCHEMIA; NECROSIS; INJURY
Abs. We attempted to investigate the process of ischemia-induced
disturbances in the rat
liver, employing the electrical bio-
impedance technique. The
electrical bio-impedance was
measured continuously over
6 h by the 4-electrode method,
at various incubation temperatures,
in six liver samples
extracted from male Wistar
rats. The electrical properties
of biological tissues can
be expressed in terms of three
parameters: extracellular
resistance (Re), intracellular
resistance (Ri) and cell
membrane capacitance (Cm). These
three parameters were calculated
from the measured values
of the electrical impedance
by the curve-fitting technique,
using a computer program.
The Re value increased rapidly
after the rat livers were
extracted, and then decreased
slowly. The Re value reached
a peak after about 13 min at
36 degrees C, and then decreased
slowly, becoming constant
after 3 h. There was a negative
correlation between the
Tmax of Re (the time when
Re reached a maximum) and the
incubation temperature (R=-0.973,
P<0.001). The Ri value
decreased once in the early
stage after extraction,
followed by almost no change
and then an increase after 4 h
at 36 degrees C. The Cm
showed a similar pattern of change
to the Re value, and a negative
correlation was also found
between the Tmax of Cm and
the incubation temperature (R=-
0.969, P<0.001). The
increases in the Re and Cm values, and
the decrease in the Ri value
for quite long periods after
the blood flow has stopped,
suggest an increase in the
resistance of extracellular
fluid due to a decrease in its
volume, an increase in cell
membrane capacitance due to
cell swelling, and a decrease
in cellular fluid resistance
due to an increase in its
volume. The time when the Cm
value decreases rapidly
after an initial gradual decrease
after the peak corresponds
well with the time when the Ri
value begins to increase,
from which it is estimated that
cell lysis proceeds and
that the flow of extracellular
fluid into the cell begins
at this time. The findings of
this study suggest the possibility
of estimating the
changes in liver tissue
or the tissue structure due to
ischemia.
Kotre, C.J.
Title Subsurface electrical impedance imaging: Measurement
strategy,
image reconstruction and
in vivo results
Journal Physiological Measurement
17
Suppl. 4A
NOV
Year 1996
Page A197-A204
Address CJ Kotre
Newcastle Gen Hosp
Dept Reg Med Phys
Newcastle Tyne NE4 6BE
Tyne & Wear, England
Serial# 0967-3334
Keys TOMOGRAPHY
Abs. In conventional cross-sectional electrical impedance
tomography, most of the
spatial information is concentrated
at the periphery of the
image, close to the measurement
electrodes. Increasing the
number of electrodes tends not
to increase the poor resolution
at the centre of the cross-
sectional image due to the
physics of three-dimensional
current flow. in this work
an alternative approach, INSEIT
(imaging near the surface
by electrical impedance
tomography), is explored
in which the image plane lies at a
selected depth in the object
parallel to a surface
electrode array. This approach
has been investigated using
a prototype data measurement
system The preliminary in vivo
results include subsurface
images of respiration, the
gastro-intestinal tract
and limb blood flow.
Author - Kotre CJ
Title - Variations in in vivo electrical impedance
tomography
images
due to inaccuracy in boundary representation.
- English
- Article
- Kotre CJ, Newcastle
Gen Hosp, Dept Reg Med Phys, Newcastle
Tyne NE4
6BE, Tyne & Wear, ENGLAND
- A comparison of
in vivo image results is performed for
five image-reconstruction
programs, featuring an increase
in accuracy
of boundary modelling from a simple 2-D disk
to a true
boundary shape with each current drive field
individually
calculated. Variations are found both in the
positions
of imaged features and their appearance,but
reasonable
consistency in reconstructed impedance changes
is obtained
for both phantom : and in vivo data. In terms
of quantitative
measurements, the programs based on the
simpler
boundary assumptions generally perform more
reliably
than the more complex versions. It is concluded
that the
quantitative use of EIT with simple boundary
assumptions
is not compromised by body contour variations
between
patients, provided that the appropriate regions of
interest
can be correctly identified.
Journal - Med Biol Eng Comput 1996 SEP;34(5):355-358
Kurata, M.; Ishizuka, N.; Matsuzawa, M.; Haruta, K.;
Takeda, K.
Title A comparative study of whole-blood platelet aggregation
in
laboratory animals: Its
species differences and comparison
with turbidimetric method
Journal Comparative Biochemistry and Physiology C - Pharmacology
Toxicology & Endocrinology
112
3
NOV
Year 1995
Page 359-365
Address M Kurata
Chugai Pharmaceut Co Ltd
Toxicol Lab
Minowa
Nagano 39946, Japan
Serial# 0742-8413
Keys platelet aggregation; whole-blood platelet aggregation;
impedance method; turbidimetry;
platelet function; blood
cells; species difference;
laboratory animals; animal models;
comparative study
ACTIVATING FACTOR PAF; ELECTRICAL
AGGREGOMETRY; INHIBITION;
DOGS; DIPYRIDAMOLE; SECRETION;
IMPEDANCE; BINDING; RABBIT; PIG
Abs. We undertook a systematic comparison of whole-blood
platelet aggregation concerning
species difference of
commonly used laboratory
animals (rabbits, guinea pigs,
rats and dogs), agonist
difference (collagen, ADP and
platelet activating factor
[PAF] and technical difference
against a traditional method
of turbidimetry, Collagen-
induced aggregation with
whole-blood aggregometry was less
variable among species tested
and was similar to the
results obtained by turbidimetry,
which measures platelet
aggregation in citrated
plasma, In contrast, whole-blood
aggregometry in responses
to ADP and PAF showed marked
species difference, being
different from turbidimetry. Our
results provide species
difference among laboratory animals
and suggest that the modulations
of platelet aggregation by
other blood elements probably
differ in each species and
with stimulating agonists.