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B. Cochener, P. Josselin, M. Lamard; 3 Dimensional Free-Hand Reconstruction of Ocular Anterior Segment Using High Frequency Ultra-Sounds Scan. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3676.
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Free hand three dimension ultrasound reconstruction of the ocular globe will represent a great progress in the management of patients care. Our goal is to develop a prototype in order to improve the customized sizing of implants for refractive surgery
Data acquisition of the anterior segment is carried out by a 50MHz high frequency ultrasound probe. The acquisition protocol is close to the standard clinical routine. The probe pans across the cornea at a constant speed allowing between 50 to 80 images regularly distributed. To achieve the reconstruction, the position of each image generated by the ultrasound scan must be known in a global frame of reference. The probe is equipped with a rigid body connected to an active tracking system (©Atracsys). This platform makes it possible to obtain in real time the position of the probe in the coordinate system of the room. To optimize the quality rebuilding of rebuilding, the change of coordinate system between the probe and image pixels is obtained by phantom calibration. Currently, image segmentation is manually performed (Amira software).The authors developed all algorithms for virtual model construction, viewing and handling. The anterior segment appears as a virtual 3D volume made up of colored triangles.
Accuracy and precision of the system was assessed by an in vitro study. The precision means value was about 0.18 ± 0.08mm on a volume of size identical in an eye. Nowadays three anterior segments were rebuilt. Quality of the results was good and makes possible the adjustment of the size of a virtual intraocular lens using the real measure of the patient anterior segment.
These preliminary outcome are encouraging and confirm the adequate methodological choices we made. A complementary work must be conducted in order to accelerate the segmentation for potential application in clinical practice.
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