|
    
|
|
Comprehensive Quantification
of Lung Structure and
Function
6-27-01
|
-
Figure 1:
This montage depicts a stack of CT
sections (lower left); a
three-dimensional airway tree
(center); a tumor obstructing the
bronchial tree, incl.
the tumor's
association with surrounding major
vascular structures (upper and
lower
right); a bronchoscopic image of the
obstructed airway tree
(left-center); and
a superposed graph
showing objective measures of airway
cross-sectional area as a
function of
distance down the tree. Such imaging
is currently being used on a
regular
basis for custom-designed
interventions to eliminate
obstructions via laser
surgery and/or
to build custom stents to hold open
the obstructed segment.
Quantitative
methods are now allowing for the
accurate measurement of airway
segments as small as 1 mm in
diameter, with sub-millimeter
accuracy.
-
-
-
|
|
-
Figure 2: To image
pulmonary blood flow, iodinated
contrast agent is injected into
the
blood stream at the right side of
the heart. Rapid CT scanning, gated
to the
heartbeat during a breath hold,
allows for the reconstruction of the
regional
brightness changes that occur
throughout the lung in response to
the passage of the
injected agent.
Left panel: three-dimensional images
of the lungs and a
three-dimensional
heart (opened digitally by the
computer). Center: a
cross-sectional
image of the lungs shows regions of
interest from which
time-intensity
curves have been measured. Upper
right: by comparing these curves
with
the time-intensity curve sampled
from within the area of the
pulmonary artery,
it is now possible
to calculate the timing of a red
blood cell through the
microvascular
beds of the lung. Disruption of flow
parameters at the microvascular
level
is believed to provide the earliest
sign of the onset of inflammatory
lung
disease leading to, for instance,
emphysema and fibrosis.
-
-
-
-
-
|
|
-
-
-
Figure 3: Non-radioactive
xenon gas is radio-dense and serves
as a tag of regional
-
ventilation. A patient
re-breathes a fixed percentage of
xenon gas (40% or less) and
-
images are obtained through
multi-slice spiral CT scanning at
the same point of
-
each expiratory pause. The
brightness change in the
reconstructed CT image
-
provides information about the
rate of wash-in/wash-out of the
xenon gas and thus
-
regional ventilation. Upper left:
a subject in a CT scanner attached
to a computer
-
system, which monitors lung
volume and controls the delivery of
xenon gas. Upper
-
right: brightness change as xenon
gas is washed out of the lung. Lower
left: a
-
color-coded image that
quantitatively represents brightness
changes due to xenon
-
gas. Center: volumetric images of
the lung scanned at two points
within the
-
respiratory cycle.
-
-
-
-
-
-
|
|
-
Figure 4: Methods are
emerging that allow the computer to
use mathematical
formulations of
"texture." These methods describe
the patterns of bright and dark
regions in the CT images to
discriminate between tissue types
and to provide a
report of the amount
and distribution of pathologic
processes. Upper part: a
method
identifying the portion of the lung
that falls below a particular gray
scale
range, defining it as being
emphysema-like. Such a method is
useful in identifying
mild to severe
emphysema without other co-existing
patterns of disease. Using a
more
advanced form of tissue
characterization (lower part), the
computer can
evaluate the image based
upon 50 or more mathematical
formulations of the
patterns of gray
scale variations. It color-codes the
CT slice according to tissue
patterns,
such as emphysema-like, ground
glass, broncho-vascular, nodular,
honeycomb, etc.
|
|
|
