Methods Supplement:
An aerosol-based biomarker to measure liquid absorption in
the cystic fibrosis airway
Timothy E Corcoran Ph.D., Kristina M. Thomas B.S., Michael
M. Myerburg M.D., Ashok Muthukrishnan M.D., Lawrence Weber,
Raymond Frizzell Ph.D., Joseph M Pilewski M.D.
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Supplemental materials:
Aerosol delivery:
Subjects were enrolled in two sequential groups (n=11: 6
controls,
inhaled
(Vital
oxygen.
5
the
CF;
n=10:
test
Signs
controls,
aerosols
Inc.,
Group
5
1
from
Englewood,
inhaled
the
5
a
CF).
Both
Whisper-Jet
CO)
driven
aerosol
by
without
groups
nebulizer
8
LPM
of
delivery
controls for 8 minutes while group 2 inhaled the aerosol
for 4 minutes using visual feedback from a pneumotach to
control inhalation flowrate (at 0.5 liters per second) and
audible feedback to maintain a set respiratory frequency
and
pattern
exhalation).
(12
breaths/minute;
The
change
in
2
s
technique
inhalation,
was
3
intended
improve the inter-subject uniformity of dosing.
s
to
The test
aerosols utilized in these studies contained Technetium 99m
bound to sulfur colloid (Tc-SC) and Indium 111 bound to
DTPA
5ml).
(In-DTPA)
dissolved
in
normal
saline
(total
volume
A loaded dose of 8 mCi of Tc-SC was used for both
sequential groups. Loaded In-DTPA activity was increased in
group 2 (1.5 mCi vs. 1.0 mCi in group 1). All subjects were
seated during aerosol delivery.
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Imaging and analysis:
Independent
windows
(based
on
photon
energy
level)
were
used to depict the clearance of Tc-SC and In-DTPA.
The
photon energy levels of the radioisotopes are 140.5 keV for
Tc99m and 171/245 keV for In111(E1).
For In-DTPA, only the
higher
This
energy
level
radiopharmaceuticals
was
is
utilized.
commonly
used
combination
to
of
differentiate
solid and liquid transit in gastric emptying scans (E2).
Since
In-DTPA
is
cleared
both
through
absorption
and
mucociliary clearance in the lung and Tc-SC is cleared only
through mucociliary clearance, the difference between their
clearance rates represents the absorptive clearance rate of
In-DTPA.
After
aerosol
minutes
while
continuous,
collected.
delivery
lying
the
subjects
recumbent.
sequential,
30s,
were
In
128
imaged
sequential
x
128
for
group
images
60
1
were
In group 2, one 30 s image was collected every
60 seconds and a larger camera matrix size was used 256 x
256.
Medium energy collimators were used for imaging in
both cases.
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After
the
conclusion
of
clearance
measurements,
the
subjects inhaled Xenon-133 gas and equilibrium images were
collected.
Outlines of the lungs were defined using the
equilibrium
images.
These
(lung
shaped)
outlines
were
applied to the clearance images in order to measure whole
lung clearance. Central lung clearance was measured within
a rectangular zone with one-half the height and one-half
the width of a rectangle containing the whole lung outline,
positioned at the central edge of the image at mid-height.
The peripheral lung zone contained the difference between
the whole lung outline and the central lung zone.
Only the
right
possible
lung
was
used
for
analysis
to
interference from counts in the stomach.
avoid
Posterior images
were utilized for the analysis. We estimate the radiation
exposure
inhalation
associated
to
be
with
aerosol
approximately
delivery
68
mREM
and
(0.68
Xenon
mSv)
-
effective dose equivalent.
Counts obtained from the clearance images were corrected
for decay time and background.
The different energy levels
associated with Tc99m and In111 allowed these isotopes to
be mostly differentiated during camera processing, however
some
minimal
spillover
correction
was
required.
Phantom
studies conducted prior to clinical testing demonstrated
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that In111 contributed to counts in the Tc99m window at
approximately 20% of the rate measured in the In111 window,
and that Tc99m contributed to the In111 window count rate
at a much lower level (approximately 1%).
were used for correction.
These factors
The effects of spillover were
minimized through a careful choice of the ratio of Tc99m to
In111
dose
and
the
actual
effect
of
the
spillover
correction was minimal. Corrected counts were normalized by
the starting counts in each zone and fit to exponential
functions.
These functions were evaluated at 60 minutes in
order to estimate a one-hour clearance rate for both Tc-SC
and In-DTPA.
subject
based
Absorptive clearance was calculated for each
on
the
evaluated at 60 minutes.
difference
between
these
rates
No attempt was made to correct
for peripheral clearance into the central zones during the
time of the study.
Central to peripheral (c/p) dose ratios
were calculated for both Tc-SC and In-111.
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References:
E1.
Kuni, C., duCret, R.P. 1997. Manual of Nuclear
Medicine Imaging. Thieme.
E2.
Saha, G. 2004. Fundamentals of Nuclear Pharmacy, Fifth
Addition. Springer.
5803-12.
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