We present laboratory measurements of scattering properties of 15 different types of coastal and inland water phytoplankton species and two types of estuarine sediments. These properties are the scattering function as well as the angular distribution of a ratio of scattering matrix elements, which in practice equals the degree of linear polarization of the scattered light if the incident light is unpolarized. Laser light with a wavelength of 633 nm was used, and a scattering angle range from 20° to 60° was covered. The results can be used in the context of waterquality studies and to test results of theoretical models. The measured scattering functions are all strongly peaked in forward directions, but not equally so. For the covered angles, they vary significantly as a function of scattering angle. The measured angular distributions of the degree of linear polarization are mostly bell shaped, showing a maximum near 90°, whose magnitude is clearly different for the phytoplankton compared to the silt particles. We find that the morphology and structural features of the particles studied play an important and complex role in their light-scattering behavior. In particular, internal cell structures such as gas vacuoles alter the scattering patterns of the phytoplankton species considerably. The external shape of the cells appears to have a much smaller influence. The experimental results are compared with results of Mie calculations and with the "standard scattering function" of San Diego Harbor water. In most cases, Mie calculations cannot provide an adequate approximation of the measured scattering behavior, which indicates that more sophisticated models are required. Only 3 of the 17 measured scattering functions resemble the San Diego Harbor standard scattering function. One of these pertains to small silt particles, showing that this function is representative for water dominated by these particles.Diverse particles occur in coastal and inland waters, such as phytoplankton particles (i.e., cyanobacteria and algae), detritus (organic nonliving particles), and mineral particles (Dekker 1993; Mobley 1994). The scattering and absorption Acknowledgments

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AimThe purpose of this study was to present and validate an innovative semi-automatic approach to quantify the accuracy of the surgical outcome in relation to 3D virtual orthognathic planning among patients who underwent bimaxillary surgery.Material and MethodFor the validation of this new semi-automatic approach, CBCT scans of ten patients who underwent bimaxillary surgery were acquired pre-operatively. Individualized 3D virtual operation plans were made for all patients prior to surgery. During surgery, the maxillary and mandibular segments were positioned as planned by using 3D milled interocclusal wafers. Consequently, post-operative CBCT scan were acquired. The 3D rendered pre- and postoperative virtual head models were aligned by voxel-based registration upon the anterior cranial base. To calculate the discrepancies between the 3D planning and the actual surgical outcome, the 3D planned maxillary and mandibular segments were segmented and superimposed upon the postoperative maxillary and mandibular segments. The translation matrices obtained from this registration process were translated into translational and rotational discrepancies between the 3D planning and the surgical outcome, by using the newly developed tool, the OrthoGnathicAnalyser. To evaluate the reproducibility of this method, the process was performed by two independent observers multiple times.ResultsLow intra-observer and inter-observer variations in measurement error (mean error < 0.25 mm) and high intraclass correlation coefficients (> 0.97) were found, supportive of the observer independent character of the OrthoGnathicAnalyser. The pitch of the maxilla and mandible showed the highest discrepancy between the 3D planning and the postoperative results, 2.72° and 2.75° respectively.ConclusionThis novel method provides a reproducible tool for the evaluation of bimaxillary surgery, making it possible to compare larger patient groups in an objective and time-efficient manner in order to optimize the current workflow in orthognathic surgery.

The implementation of augmented reality (AR) in image-guided surgery (IGS) can improve surgical interventions by presenting the image data directly on the patient at the correct position and in the actual orientation. This approach can resolve the switching focus problem, which occurs in conventional IGS systems when the surgeon has to look away from the operation field to consult the image data on a 2-dimensional screen. The Microsoft HoloLens, a headmounted AR display, was combined with an optical navigation system to create an AR-based IGS system. Experiments were performed on a phantom model to determine the accuracy of the complete system and to evaluate the effect of adding AR. The results demonstrated a mean Euclidean distance of 2.3 mm with a maximum error of 3.5 mm for the complete system. Adding AR visualization to a conventional system increased the mean error by 1.6 mm. The introduction of AR in IGS was promising. The presented system provided a solution for the switching focus problem and created a more intuitive guidance system. With a further reduction in the error and more research to optimize the visualization, many surgical applications could benefit from the advantages of AR guidance.