The use of dynamic CT imaging for tracking mandibular movements in a phantom

Abstract

Methods: A clinical 256-slice Revolution CT was used in obtaining 4D CT scans without table movement, with a novel mandibular phantom, mounted on a programmable six degrees-of-freedom Stewart Platform in motion. The phantom was used to simulate mandibular motions which are combinations of rotations with translations (depression, elevation, protrusion, retrusion and laterotrusion). The phantom was scanned five times during identical motion patterns with a dynamic CT acquisition protocol. An image processing workflow consisting of a pairwise rigid registration and semi-automatic segmentation was developed to extract kinematic parameters (cardan angles and point of interest displacements) from the dynamic sequences. Reproducibility was investigated by the 95% confidence interval and the absorbed organ dose to organs of interest in the primary beam were also estimated and compared to those of a standard CT scan of the brain Results: The maximum average 95% confidence interval for the displacement across all time points for the five repetitions was 0.61 mm (Y axis). In terms of rotations, the maximum average 95% confidence interval across all time points for the five repetitions was 1.39° (X axis). The effective dose for the dynamic scan was found to be 1.3 mSv, for a CTDIvol of 63.95 mGy and a DLP of 1023.14 mGycm. The absorbed organ doses were similar to organ doses during a clinical head CT scan. Conclusions: A framework is proposed to use 4D CT scanning as a possible methodology to evaluate the motion of the temporomandibular joint. The scanning protocol allows to visualise the motion by applying a semi-automated segmentation and registration. A graphical representation of all displacements in the three spatial dimensions can depict multiple points-of-interest at once during the same acquisition. A novel type of phantom was also introduced which simulates mandibular movement with six degrees-of-freedom (three translations and three rotations).

Exploring the Validity of an Optoelectronic Integrated Cone Beam Computed Tomography Jaw Tracking System

“…Moreover, 4D CT captures multiple CT images within a timeframe and can register the functional movements of the mandible. Huys et al [8] compared 4D CT to a phantom device equipped with a controlled motor that allowed six degrees of freedom.…”

“…The use of 4D CT for tracking the mandibular and condylar movements has also been reported [ 8 , 9 ]. Moreover, 4D CT captures multiple CT images within a timeframe and can register the functional movements of the mandible.…”

“…Moreover, 4D CT captures multiple CT images within a timeframe and can register the functional movements of the mandible. Huys et al [ 8 ] compared 4D CT to a phantom device equipped with a controlled motor that allowed six degrees of freedom. For five repetitions, the average 95% confidence interval for the x axis was 0.4 mm, for the y axis 0.6 mm and for the z axis 0.2 mm.…”