Objectives
This study investigates the effect of scanning parameters on the
accuracy of measurements from three-dimensional multi-detector computed
tomography (3D-CT) mandible renderings. A broader range of acceptable
parameters can increase the availability of CT studies for retrospective
analysis.
Study Design
Three human mandibles and a phantom object were scanned using 18
combinations of slice thickness, field of view, and reconstruction algorithm
and three different threshold-based segmentations. Measurements of 3D-CT
models and specimens were compared.
Results
Linear and angular measurements were accurate, irrespective of
scanner parameters or rendering technique. Volume measurements were accurate
with a slice thickness of 1.25 mm, but not 2.5 mm. Surface area measurements
were consistently inflated.
Conclusions
Linear, angular and volumetric measurements of mandible 3D-CT models
can be confidently obtained from a range of parameters and rendering
techniques. Slice thickness is the primary factor affecting volume
measurements. These findings should also apply to 3D rendering using
cone-beam-CT.
The hyoid bone anchors and supports the vocal tract. Its complex shape is best studied in three dimensions, but it is difficult to capture on computed tomography (CT) images and three-dimensional volume renderings. The goal of this study was to determine the optimal CT scanning and rendering parameters to accurately measure the growth and developmental anatomy of the hyoid and to determine whether it is feasible and necessary to use these parameters in the measurement of hyoids from in vivo CT scans. Direct linear and volumetric measurements of skeletonized hyoid bone specimens were compared to corresponding CT images to determine the most accurate scanning parameters and three-dimensional rendering techniques. A pilot study was undertaken using in vivo scans from a retrospective CT database to determine feasibility of quantifying hyoid growth. Scanning parameters and rendering technique affected accuracy of measurements. Most linear CT measurements were within 10% of direct measurements; however, volume was overestimated when CT scans were acquired with a slice thickness greater than 1.25 mm. Slice-by-slice thresholding of hyoid images decreased volume overestimation. The pilot study revealed that the linear measurements tested correlate with age. A fine-tuned rendering approach applied to small slice thickness CT scans produces the most accurate measurements of hyoid bones. However, linear measurements can be accurately assessed from in vivo CT scans at a larger slice thickness. Such findings imply that investigation into the growth and development of the hyoid bone, and the vocal tract as a whole, can now be performed using these techniques.
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