R. C. Roth and M. DePauw, "Facial Overlay Analysis - Combined Repositioning and Computer Alignment", in Proc. of 4th Int. Conf. on 3D Body Scanning Technologies, Long Beach CA, USA, 2013, pp. 21-30, http://dx.doi.org/10.15221/13.021.
Facial Overlay Analysis - Combined Repositioning and Computer Alignment
Richard C. ROTH, Matthew DEPAUW
Advanced Imaging and Measurement Laboratory, Analytical Sciences, Amway, Ada MI, USA
Differential comparison of two- and three-dimensional images require aligned subjects in order to discern small structural and contour changes to the facial area. Overlay of subject images at different times and dates is reliant on the ability to precisely align the subject during each clinical visit. The alignment device must be capable of providing sufficient adjustment to accommodate a wide variety of subject body and facial characteristics, and be re-adjusted rapidly and accurately. Changes observed in facial contour are valuable in the analysis of topical cosmetic formulations and in demonstrating efficacy of anti-aging, sagging, and lifting interventions.
Stereotactic devices are intended to maintain an orientation of the head for a limited period of time, but not for repeated use. Those employed for surgery are required to prevent movement, but disregard subject imaging. In most imaging alignment devices, restraining alignments encumber the face and neck preventing full image collection by obstruction of view or distortion of facial features. A device to reproducibly position the face and head was previously reported and has been utilized in third party clinical studies. Clinical results have shown positive alignments of subjects, but also identified operational variability associated with subject seating, parameter setting, imaging, training, and subject compliance. The device provided a novel alignment process including, gross subject alignment, fine subject alignment, and direction-of-gaze.
At the baseline clinical visit, a "subject fitting" defines the subject orientation and device parameters utilized during subsequent imaging sessions. Head touch points at the back and top of the head are maintained by the subject and allow undistorted full facial imaging and analysis of the face, jaw, and neck regions. Subject specific device parameters are maintained within 0.1-0.2mm. The alignment system includes staff and subject education and training. Subject cooperation and staff oversight are critical in the realignment procedures. Integrated positioning devices reseat the subject body, co-locate the head, and maintain the direction-of-gaze of the subject. Overlay comparison results for 3D imaging have indicated excellent correlation of the entire facial region. Combinations of 3D contour and 2D image overlays were used to evaluate subject profile changes and illustrate locations of facial lifting associated with topical treatments.
Facial overlay routines usually attempt to co-locate the entire facial area for comparison. Full face surface analysis does not separate topically treated and reference regions. Consequently, changes in treated regions are trivialized through averaging the overall facial evaluation. Side-by-side comparison of the inclusive/exclusive region processes demonstrates the need to require separation of treated and non-treated surfaces. Utilizing only reference regions, the treated regions of the face are excluded from the overlay comparison and are considered "experimental surfaces". Only stable untreated facial regions are considered as reference surfaces within the algorithm.
The reference technique maintains the facial reference locations, and allows other non-aligned surfaces to be identified. Movements associated with the neck, upper torso, and shoulders between clinical visits are identified, as well as small facial gestures that might go un-noticed in standard 2D image comparisons. Identification of these movements permits modification of the system and protocol while still capturing full 3D facial contour.
3D, cosmetic, alignment, face
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