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: Effects of the Shuffle : Validation of the Approach : Validation of the Approach

Perturbing Ground-Truth

We conducted a series of experiments to test the hypothesis that reduced registration accuracy can be detected using model specificity and generalisation. An equivalent 2D mid-brain T1-weighted slice was obtained from each of 36 subjects using a 3D acquisition. A fixed number (167) of landmark points were positioned manually on the cortical surface, ventricles, caudate nucleus and lentiform nucleus, and used to establish a ground-truth dense correspondence over the set of images, using locally affine interpolation. A statistical appearance model was constructed using the methods described in 2.2, with the set of landmark coordinates forming the shape vector $\mathbf{x}$ for each image. Keeping the shape vectors fixed, we then applied a series of smooth pseudo-random spatial warps to the training images, resulting in successively increasing mis-registration. Each warp resulted in an average point displacement of between one and two pixels. Specificity and Generalisation results were obtained for 0, 1, 5, and 10 warps per image, using $m=1000$.

Roy Schestowitz 平成17年6月23日