DOI: 10.1148/radiol.2323031581
Obstructive Sleep Apnea: MR Imaging Volume Segmentation Analysis1
M. Bret Abbott, MD, PhD2,
Lane F. Donnelly, MD,
Bernard J. Dardzinski, PhD,
Stacy A. Poe, MS,
Barbara A. Chini, MD and
Raouf S. Amin, MD
1 From the Departments of Radiology (M.B.A., L.F.D., B.J.D.) and Pediatrics (L.F.D., B.J.D., S.A.P., B.A.C., R.S.A.) and Division of Pulmonology (B.A.C., R.S.A.), Cincinnati Children’s Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229-3090. Received October 1, 2003; revision requested December 23; revision received January 7, 2004; accepted February 2. Address correspondence to L.F.D. (e-mail: lane.donnelly@cchmc.org).
View larger version (71K):
[in a new window]
|
Figure 1a. Sequential transverse fast gradient-echo 1.5-T cine MR images (8.2/3.6; flip angle, 80°; section thickness, 12 mm; field of view, 24 cm; in-plane resolution, 256 x 256) obtained at level of hypopharynx in 63-month-old boy with OSA. Area marked with white line indicates region of interest around airway used for volume segmentation. (a) Left: Image obtained during one point of respiratory cycle shows patent hypopharynx. Right: Volume segmentation data image, with gray area that represents patent airway. (b) Left: Sequential image obtained over time shows collapsed airway. Right: Volume segmentation data image with little to no gray area, which is consistent with collapse.
|
|
View larger version (72K):
[in a new window]
|
Figure 1b. Sequential transverse fast gradient-echo 1.5-T cine MR images (8.2/3.6; flip angle, 80°; section thickness, 12 mm; field of view, 24 cm; in-plane resolution, 256 x 256) obtained at level of hypopharynx in 63-month-old boy with OSA. Area marked with white line indicates region of interest around airway used for volume segmentation. (a) Left: Image obtained during one point of respiratory cycle shows patent hypopharynx. Right: Volume segmentation data image, with gray area that represents patent airway. (b) Left: Sequential image obtained over time shows collapsed airway. Right: Volume segmentation data image with little to no gray area, which is consistent with collapse.
|
|
View larger version (57K):
[in a new window]
|
Figure 2a. Sequential transverse fast gradient-echo 1.5-T cine MR images (8.2/3.6; flip angle, 80°; section thickness, 12 mm; field of view, 24 cm; in-plane resolution, 256 x 256) obtained at level of hypopharynx in 2-month-old boy with OSA. Area marked with white line indicates region of interest around airway used for volume segmentation. (a) Left: Image obtained during one point of respiratory cycle shows patent hypopharynx. Right: Volume segmentation data image, with gray area that represents patent airway. (b) Left: Sequential image obtained over time shows collapsed airway. Right: Volume segmentation data image with little to no gray area, which is consistent with collapse.
|
|
View larger version (60K):
[in a new window]
|
Figure 2b. Sequential transverse fast gradient-echo 1.5-T cine MR images (8.2/3.6; flip angle, 80°; section thickness, 12 mm; field of view, 24 cm; in-plane resolution, 256 x 256) obtained at level of hypopharynx in 2-month-old boy with OSA. Area marked with white line indicates region of interest around airway used for volume segmentation. (a) Left: Image obtained during one point of respiratory cycle shows patent hypopharynx. Right: Volume segmentation data image, with gray area that represents patent airway. (b) Left: Sequential image obtained over time shows collapsed airway. Right: Volume segmentation data image with little to no gray area, which is consistent with collapse.
|
|
View larger version (41K):
[in a new window]
|
Figure 3a. Graphs show comparison of change in hypopharynx volume over time in child with OSA and asymptomatic control subject. Hypopharyngeal airway volumes were determined as function of time with volume segmentation of cine MR images obtained in 63-month-old boy with OSA (same subject as in Fig 1) and 66-month-old male control subject. Dark line represents control subject, and light line represents child with OSA. (a) Graph of volume of hypopharynx versus time. Control subject shows minimal variation in volume over time compared with results in child with OSA. Volume of hypopharynx is smaller in control subject than it is in child with OSA. (b) Graph of normalized volume of hypopharynx versus time. Change in volume over time is normalized for average airway volume for the subject and plotted across the time course. Normalization allows change in volume of area to be viewed in relationship to relative size of subject’s airway, as this may vary according to subject’s size, subject’s age, and plane of imaging. Relative change in volume can be compared between control subject and child with OSA.
|
|
View larger version (40K):
[in a new window]
|
Figure 3b. Graphs show comparison of change in hypopharynx volume over time in child with OSA and asymptomatic control subject. Hypopharyngeal airway volumes were determined as function of time with volume segmentation of cine MR images obtained in 63-month-old boy with OSA (same subject as in Fig 1) and 66-month-old male control subject. Dark line represents control subject, and light line represents child with OSA. (a) Graph of volume of hypopharynx versus time. Control subject shows minimal variation in volume over time compared with results in child with OSA. Volume of hypopharynx is smaller in control subject than it is in child with OSA. (b) Graph of normalized volume of hypopharynx versus time. Change in volume over time is normalized for average airway volume for the subject and plotted across the time course. Normalization allows change in volume of area to be viewed in relationship to relative size of subject’s airway, as this may vary according to subject’s size, subject’s age, and plane of imaging. Relative change in volume can be compared between control subject and child with OSA.
|
|
View larger version (52K):
[in a new window]
|
Figure 4a. Graphs show comparison of change in hypopharynx volume over time between child with OSA and asymptomatic control subject. Hypopharyngeal airway volumes were determined as function of time with volume segmentation of cine MR images obtained in 2-month-old boy with OSA (same subject as in Fig 2) and 17-month-old male control subject. Dark line represents control subject, and light line represents child with OSA. (a) Graph of volume of hypopharynx versus time. Control subject shows minimal variation in volume over time compared with results in child with OSA. Volume of hypopharynx is smaller in control subject than it is in child with OSA. (b) Graph of normalized volume of hypopharynx versus time. Relative change in volume can be compared between control subject and child with OSA.
|
|
View larger version (40K):
[in a new window]
|
Figure 4b. Graphs show comparison of change in hypopharynx volume over time between child with OSA and asymptomatic control subject. Hypopharyngeal airway volumes were determined as function of time with volume segmentation of cine MR images obtained in 2-month-old boy with OSA (same subject as in Fig 2) and 17-month-old male control subject. Dark line represents control subject, and light line represents child with OSA. (a) Graph of volume of hypopharynx versus time. Control subject shows minimal variation in volume over time compared with results in child with OSA. Volume of hypopharynx is smaller in control subject than it is in child with OSA. (b) Graph of normalized volume of hypopharynx versus time. Relative change in volume can be compared between control subject and child with OSA.
|
|
Copyright © 2004 by the Radiological Society of North America.
) and control subjects (
). Nearly horizontal trend lines (least squares fit) graphically depict the poor correlation of airway volume with subject age. Correlation coefficients of R2 = 0.027 for subjects with OSA (dashed line) and R2 = 0.144 for control subjects (solid line) suggest little dependence of airway volume on age within each group. There were a substantial number of subjects between the ages of 40 and 100 months in both groups. These subsets of subjects had different average airway volumes. Airway volume did not appear to be correlated with age within either control or OSA group, which supports the conclusion that a significant portion of the difference in airway volume between groups was associated with OSA rather than with age.