Quantitative Assessment of Air Trapping in Chronic Obstructive Pulmonary Disease Using Inspiratory and Expiratory Volumetric MDCT
Shin Matsuoka1,2,
Yasuyuki Kurihara1,
Kunihiro Yagihashi1,
Makoto Hoshino3,
Naoto Watanabe3 and
Yasuo Nakajima1
1 Department of Radiology, St. Marianna University School of Medicine, 2-16-1
Sugao, Miyamae-Ku, Kawasaki City, Kanagawa 216-8511, Japan.
2 Present address: Department of Radiology, Brigham and Women's Hospital,
Harvard Medical School, 75 Francis St., Boston, MA 02115.
3 Division of Respiratory and Infectious Diseases, Department of Internal
Medicine, St. Marianna University School of Medicine, Kanagawa, Japan.
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Fig. 1A —74-year-old man with chronic obstructive pulmonary disease.
Three-dimensional images, anterior view, reconstructed from inspiratory and
expiratory MDCT. Segmented whole-lung volume with voxels of attenuation values
between –500 and –1,024 H on inspiratory CT (blue).
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Fig. 1B —74-year-old man with chronic obstructive pulmonary disease.
Three-dimensional images, anterior view, reconstructed from inspiratory and
expiratory MDCT. Segmented lung volume with attenuation values less than
–860 H in inspiratory CT (red).
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Fig. 1C —74-year-old man with chronic obstructive pulmonary disease.
Three-dimensional images, anterior view, reconstructed from inspiratory and
expiratory MDCT. Segmented lung volume with attenuation values less than
–860 H in expiratory CT (red). Relative volumes for whole lung
with attenuation value less than –860 H are calculated as follows:
relative volume on inspiratory CT (inspiratory relative
volume<–860) = (red in B)/(blue
in A), and relative volume on expiratory CT (expiratory relative
volume<–860) = (red in C)/segmented
whole-lung volume on expiratory CT. Relative volume
change<–860 (%) = expiratory relative
volume<–860 – inspiratory relative
volume<–860.
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Fig. 1D —74-year-old man with chronic obstructive pulmonary disease.
Three-dimensional images, anterior view, reconstructed from inspiratory and
expiratory MDCT. Segmented limited-lung volume with voxels having attenuation
values between –500 and –950 H on inspiratory CT
(yellow).
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Fig. 1E —74-year-old man with chronic obstructive pulmonary disease.
Three-dimensional images, anterior view, reconstructed from inspiratory and
expiratory MDCT. Segmented lung volume with attenuation values between
–860 and –950 H at upper threshold of –860 H on inspiratory
CT (green).
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Fig. 1F —74-year-old man with chronic obstructive pulmonary disease.
Three-dimensional images, anterior view, reconstructed from inspiratory and
expiratory MDCT. Segmented lung volume with attenuation values between
–860 and –950 H at upper threshold of –860 H on expiratory
CT (green). Relative volume for limited lung is obtained as follows:
relative volume on inspiratory CT (inspiratory relative
volume860–950) = (green in
E)/(yellow in D), and relative volume on expiratory CT
(expiratory relative volume860–950) = (green in
F)/segmented limited-lung volume on expiratory CT. Relative volume
change860–950 (%) = expiratory relative
volume860–950 – inspiratory relative
volume860–950.
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Fig. 2A —Relationships with relative volume change. Excellent
correlation is observed at upper threshold value of –860 H with
pulmonary function tests that reflect peripheral airway obstruction and air
trapping. Graphs show relationships between relative volume
change860–950 and forced expiratory flow
(FEF)25–75% (r = –0.75, p < 0.001)
(A) and between relative volume change860–950 and
ratio of residual volume to total lung capacity (RV/TLC) (r = 0.70,
p < 0.001) (B).
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Fig. 2B —Relationships with relative volume change. Excellent
correlation is observed at upper threshold value of –860 H with
pulmonary function tests that reflect peripheral airway obstruction and air
trapping. Graphs show relationships between relative volume
change860–950 and forced expiratory flow
(FEF)25–75% (r = –0.75, p < 0.001)
(A) and between relative volume change860–950 and
ratio of residual volume to total lung capacity (RV/TLC) (r = 0.70,
p < 0.001) (B).
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Fig. 3 —Frequency distribution of pixels in lung on inspiratory
(•) and expiratory ( ) CT in this study. Percentages of pixels at
attenuation of –860 H on both inspiratory and expiratory CT are
equivalent; at more than –860 H, percentage of pixels on expiratory CT
is greater than on inspiratory CT.
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Copyright © 2008 by the American Roentgen Ray Society.
