class_docstr: Class for fitting the Diffusion Kurtosis Model
docstr: Return the kurtosis tensor (KFA) [1]_
  
  Notes
  -----
  The KFA is defined as [1]_:
  
  .. math::
  
       KFA \equiv
       \frac{||\mathbf{W} - MKT \mathbf{I}^{(4)}||_F}{||\mathbf{W}||_F}
  
  where $W$ is the kurtosis tensor, MKT the kurtosis tensor mean, $I^(4)$
  is the fully symmetric rank 2 isotropic tensor and $||...||_F$ is the
  tensor's Frobenius norm [1]_.
  
  References
  ----------
  .. [1] Glenn, G. R., Helpern, J. A., Tabesh, A., and Jensen, J. H.
         (2015). Quantitative assessment of diffusional kurtosis
         anisotropy. NMR in Biomedicine 28, 448–459. doi:10.1002/nbm.3271
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code: def kfa(self):
      r"""Return the kurtosis tensor (KFA) [1]_
  
      Notes
      -----
      The KFA is defined as [1]_:
  
      .. math::
  
           KFA \equiv
           \frac{||\mathbf{W} - MKT \mathbf{I}^{(4)}||_F}{||\mathbf{W}||_F}
  
      where $W$ is the kurtosis tensor, MKT the kurtosis tensor mean, $I^(4)$
      is the fully symmetric rank 2 isotropic tensor and $||...||_F$ is the
      tensor's Frobenius norm [1]_.
  
      References
      ----------
      .. [1] Glenn, G. R., Helpern, J. A., Tabesh, A., and Jensen, J. H.
             (2015). Quantitative assessment of diffusional kurtosis
             anisotropy. NMR in Biomedicine 28, 448–459. doi:10.1002/nbm.3271
  
      """
      return kurtosis_fractional_anisotropy(self.model_params)
  
imports: import numpy
  import warnings
  import scipy.optimize
  import dipy.core.sphere
  from dipy.reconst.multi_voxel import multi_voxel_fit
  from dipy.reconst.dti import TensorFit, mean_diffusivity, from_lower_triangular, lower_triangular, decompose_tensor, MIN_POSITIVE_SIGNAL, nlls_fit_tensor, restore_fit_tensor
  from dipy.reconst.utils import dki_design_matrix
  from dipy.reconst.recspeed import local_maxima
  from dipy.reconst.base import ReconstModel
  from dipy.core.ndindex import ndindex
  from dipy.core.geometry import sphere2cart, cart2sphere, perpendicular_directions
  from dipy.core.optimize import PositiveDefiniteLeastSquares
  from dipy.data import get_sphere, get_fnames, load_sdp_constraints
  from dipy.reconst.vec_val_sum import vec_val_vect
  from dipy.core.gradients import check_multi_b
label_desc: Use image node_id 9 for calling the DiffusionKurtosisFit obj's underlying member method code with example usage: obj.kfa() and returns: kurtosis_fractional_anisotropy