Resulting implant position compared to planned position of a preformed implant.

<p>Coronal views (a,b) and sagittal view (c) of the acquired implant position in relation to the planned implant position (red). Although the fit seems nice on the slices, there is a discrepancy between the planned implant position and the acquired position. In the three dimensional view (d), a rotation as well as translation of the final implant is seen; the target location has not been reached.</p

3D view of the planned and final implant position in specimen 2.

<p>The 3D view after segmentation of the implant illustrates that a roll is present: the resulting implant is rotated in a counterclockwise fashion in this view.</p

Implant position in specimen 2.

<p>Planned implant position (red) vs. final implant position (green) on the t0 scan of specimen 2. Based on the sagittal slice, a dorsal translation is present in the final implant position. The 3D view reveals that the implant is also translated laterally, this cannot be identified on the coronal and sagittal views alone.</p

Orbital Implant Positioning Frame.

<p>The orientation of the axes, as well as the rotations around the axes are visualized. For the right-sided implant, the y-axis is flipped in order to be able to compare left and right sided implants. As a consequence of flipping the y-axis, the yaw and roll direction are also opposed.</p

Differences in orbital symmetry.

<p>The mirror image of the unaffected orbit is visualized in blue. Distances are measured between unaffected bony parts of the affected orbit and the mirrored orbit. If the mirrored orbit would be used as a reference for implant position, the measurement in (a) would yield negative values at the posterior ledge; the difference in symmetry measured in (b) would add up to the dislocation measurement, since the implant would always be positioned cranial to existing bony structures.</p

Resulting implant position of a preformed implant.

<p>Intraoperative imaging coronal views (a,b) and sagittal view (c) of the position of a preformed implant after orbital reconstruction. The mirror image of the unaffected orbit is visualized in blue. Based on the coronal and sagittal view, a good implant fit in relation to the mirrored orbit is seen.</p

Lateral extension of the final implant in specimen 1.

<p>The planned implant is visualized in red, the final implant is visualized in green. Because of the rotation and translation of the implant compared to its planned position, interference of the lateral part of the implant with the inferior orbital fissure is present.</p

A Novel Region-Growing Based Semi-Automatic Segmentation Protocol for Three-Dimensional Condylar Reconstruction Using Cone Beam Computed Tomography (CBCT)

<div><p>Objective</p><p>To present and validate a semi-automatic segmentation protocol to enable an accurate 3D reconstruction of the mandibular condyles using cone beam computed tomography (CBCT).</p><p>Materials and Methods</p><p>Approval from the regional medical ethics review board was obtained for this study. Bilateral mandibular condyles in ten CBCT datasets of patients were segmented using the currently proposed semi-automatic segmentation protocol. This segmentation protocol combined 3D region-growing and local thresholding algorithms. The segmentation of a total of twenty condyles was performed by two observers. The Dice-coefficient and distance map calculations were used to evaluate the accuracy and reproducibility of the segmented and 3D rendered condyles.</p><p>Results</p><p>The mean inter-observer Dice-coefficient was 0.98 (range [0.95–0.99]). An average 90^th percentile distance of 0.32 mm was found, indicating an excellent inter-observer similarity of the segmented and 3D rendered condyles. No systematic errors were observed in the currently proposed segmentation protocol.</p><p>Conclusion</p><p>The novel semi-automated segmentation protocol is an accurate and reproducible tool to segment and render condyles in 3D. The implementation of this protocol in the clinical practice allows the CBCT to be used as an imaging modality for the quantitative analysis of condylar morphology.</p></div

A 3D rendered virtual head model of a patient from Maxilim, reconstructed from the original CBCT data.

<p>The inaccurate reconstruction of the condyle is clearly visible. No measurement of the condylar shape or volume can be made due to the discontinuity of the condylar surface.</p

Descriptive statistics of condylar volume.

<p>Standard deviation (SD).</p><p>Descriptive statistics of condylar volume.</p