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Fig. 1 | BMC Medical Imaging

Fig. 1

From: Automated left atrial time-resolved segmentation in MRI long-axis cine images using active contours

Fig. 1

Workflow to automatically segment the left atrium (LA) of a subject in 2-chamber (2ch) and 4-chamber (4ch) views. The left atrial appendage (LAA) in 2ch and the pulmonary veins (PVs) in 4ch are marked in purple. a Input images, with mitral valve (MV) annotations, the red and green points respectively correspond to the anterior and inferior points for 2ch or the lateral and septal points for 4ch. b Data preprocessing uses an automatically calculated threshold value and assigns a signal above the threshold to the threshold value. The polar mapping is performed using a reference point, shown in blue (defined as the MV center), and a polar grid, in purple, within the Cartesian plane (xy). c Resultant image after polar mapping \((\theta ,r)\) of the LA constrained by the MV points. The blue line represents \(r=0\) for all the angular range, which spans 180\(^{\circ }\) for 2ch and 233\(^{\circ }\) for 4ch. d The images in c are subjected to Canny edge detection followed by active contours, resulting in a final contour shown in orange. e The contours are remapped onto a Cartesian grid

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