Leotta DF, Martin RW
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Bioengineering, University of Washington, Seattle, WA,
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Anesthesiolgy, University of Washington, Seattle, WA
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<B>Three-Dimensional Spatial Compounding of Freehand Ultrasound Scans 
of the Rotator Cuff</B>
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<B>OBJECTIVE:</B> to develop a compound scanning technique which can
generate 3D
reconstructions of the shoulder rotator cuff and enhance patient diagnosis 
and monitoring.  
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<B>METHODS:</B> A 3D ultrasound imaging system based on a magnetic
tracking
device was used to capture compound scans of the rotator cuff.  Overlapping 
freehand scans acquired from four acoustic windows were combined into a 
single volume.  A semi-automatic technique measured the distance between 
surfaces extracted from the 3D compound volume, allowing measurement of 
tendon thickness.  A phantom with known thickness was imaged to validate 
the method; three normal volunteers were imaged three times each to evaluate 
in vivo reproducibility.  3D tendon thickness measurements were compared to 
manual measurements from 2D images.  
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<B>RESULTS:</B> The mean difference between the measured and true
thickness for
the phantom was 0.05 +/- 0.28 mm.  The mean difference in measured 
tendon thickness between scans for the three subjects was 0.05 +/- 0.41 mm.  
The mean difference between 2D and 3D thickness measurements in vivo was 
0.06 +/- 0.36 mm.  
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<B>CONCLUSIONS:</B> 3D freehand compounding produces accurate and
repeatable
measurements of the rotator cuff. The reconstructed volume also provides 
views of the spherical geometry of the shoulder which are not attainable 
in 2D.