As the conventional method of geometric calibration not only needs extra-scan but also have the vulnerability to the dimensional accuracy of the dedicated phantom, we proposed a new geometric calibration scheme based on data redundancy which uses projection data of any arbitrary patient already scanned, mainly focused on a geometry of Varian’s OBI system. Using the fan-beam based data redundancy which can be applied to cone-beam projection data of either full-fan or half-fan geometry, one could successfully detect the misalignments of geometric parameters and find the values of them. The simulation studies using the XCAT numerical phantom were conducted to check the feasibility of data-redundancy-based method can detect the misalignment of geometric parameters and find true values.
We developed the asymmetry analyzing system for facial palsy patient's rehabilitation progress study. Using PC
standard imaging device, captured 640*480 RGB image is converted into HSV space. A Lip-shape mask is extracted by
thresholding. By taking 5 regions consisted in one region on lip and four regions on face skin, reasonable thresholds are
determined by Fuzzy C-Means clustering. The extreme points on the lip shape mask are extracted to get the seeds for
tracking. Segmented seed points are tracking by Iterative Lucas-Kanade tracking method in pyramids at 30 fps and
recording simultaneously. To reduce the disk writing load on computer, we use asynchronous mode file writing, which is
going to transfer to and review by clinician. Tracking shows quite reliable results, but sometimes the tracked points are
following along the lip line because of the similar contrasts. Therefore, the first strategy to improve the reliability of
tracking is using the high contrast points, such as left and right maximal point of lip shape. The second is clustering some
points near the maximal points and eliminating outlying tracking points. The third is rechecking the lip shape using lip
segmentation when the operator confirms that subject's maximal lip moving. Left and right tracking points are compared
in forms of trajectory plot.
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