def __init__(self,
gtab,
sh_order,
smooth=0.006,
min_signal=1.,
assume_normed=False):
"""Creates a model that can be used to fit or sample diffusion data
Arguments
---------
gtab : GradientTable
Diffusion gradients used to acquire data
sh_order : even int >= 0
the spherical harmonic order of the model
smooth : float between 0 and 1, optional
The regularization parameter of the model
min_signal : float, > 0, optional
During fitting, all signal values less than `min_signal` are
clipped to `min_signal`. This is done primarily to avoid values
less than or equal to zero when taking logs.
assume_normed : bool, optional
If True, clipping and normalization of the data with respect to the
mean B0 signal are skipped during mode fitting. This is an advanced
feature and should be used with care.
See Also
--------
normalize_data
"""
OdfModel.__init__(self, gtab)
self._where_b0s = lazy_index(gtab.b0s_mask)
self._where_dwi = lazy_index(~gtab.b0s_mask)
self.assume_normed = assume_normed
self.min_signal = min_signal
x, y, z = gtab.gradients[self._where_dwi].T
r, theta, phi = cart2sphere(x, y, z)
B, m, n = real_sym_sh_basis(sh_order, theta[:, None], phi[:, None])
L = -n * (n + 1)
legendre0 = lpn(sh_order, 0)[0]
F = legendre0[n]
self.sh_order = sh_order
self.B = B
self.m = m
self.n = n
self._set_fit_matrix(B, L, F, smooth)
def __init__(self, gtab, sh_order, smooth=0.006, min_signal=1.,
assume_normed=False):
"""Creates a model that can be used to fit or sample diffusion data
Arguments
---------
gtab : GradientTable
Diffusion gradients used to acquire data
sh_order : even int >= 0
the spherical harmonic order of the model
smooth : float between 0 and 1, optional
The regularization parameter of the model
min_signal : float, > 0, optional
During fitting, all signal values less than `min_signal` are
clipped to `min_signal`. This is done primarily to avoid values
less than or equal to zero when taking logs.
assume_normed : bool, optional
If True, clipping and normalization of the data with respect to the
mean B0 signal are skipped during mode fitting. This is an advanced
feature and should be used with care.
See Also
--------
normalize_data
"""
OdfModel.__init__(self, gtab)
self._where_b0s = lazy_index(gtab.b0s_mask)
self._where_dwi = lazy_index(~gtab.b0s_mask)
self.assume_normed = assume_normed
self.min_signal = min_signal
x, y, z = gtab.gradients[self._where_dwi].T
r, theta, phi = cart2sphere(x, y, z)
B, m, n = real_sym_sh_basis(sh_order, theta[:, None], phi[:, None])
L = -n * (n + 1)
legendre0 = lpn(sh_order, 0)[0]
F = legendre0[n]
self.sh_order = sh_order
self.B = B
self.m = m
self.n = n
self._set_fit_matrix(B, L, F, smooth)
def __init__(self,
gtab,
sh_order=8,
lambda_lb=1e-3,
dec_alg='CSD',
sphere=None,
lambda_csd=1.0):
r""" Analytical and continuous modeling of the diffusion signal with
respect to the FORECAST basis [1,2,3]_.
This implementation is a modification of the original FORECAST
model presented in [1]_ adapted for multi-shell data as in [2,3]_ .
The main idea is to model the diffusion signal as the combination of a
single fiber response function $F(\mathbf{b})$ times the fODF
$\rho(\mathbf{v})$
..math::
:nowrap:
\begin{equation}
E(\mathbf{b}) = \int_{\mathbf{v} \in \mathcal{S}^2} \rho(\mathbf{v}) F({\mathbf{b}} | \mathbf{v}) d \mathbf{v}
\end{equation}
where $\mathbf{b}$ is the b-vector (b-value times gradient direction)
and $\mathbf{v}$ is an unit vector representing a fiber direction.
In FORECAST $\rho$ is modeled using real symmetric Spherical Harmonics
(SH) and $F(\mathbf(b))$ is an axially symmetric tensor.
Parameters
----------
gtab : GradientTable,
gradient directions and bvalues container class.
sh_order : unsigned int,
an even integer that represent the SH order of the basis (max 12)
lambda_lb: float,
Laplace-Beltrami regularization weight.
dec_alg : str,
Spherical deconvolution algorithm. The possible values are Weighted Least Squares ('WLS'),
Positivity Constraints using CVXPY ('POS') and the Constraint
Spherical Deconvolution algorithm ('CSD'). Default is 'CSD'.
sphere : array, shape (N,3),
sphere points where to enforce positivity when 'POS' or 'CSD'
dec_alg are selected.
lambda_csd : float,
CSD regularization weight.
References
----------
.. [1] Anderson A. W., "Measurement of Fiber Orientation Distributions
Using High Angular Resolution Diffusion Imaging", Magnetic
Resonance in Medicine, 2005.
.. [2] Kaden E. et al., "Quantitative Mapping of the Per-Axon Diffusion
Coefficients in Brain White Matter", Magnetic Resonance in
Medicine, 2016.
.. [3] Zucchelli M. et al., "A generalized SMT-based framework for
Diffusion MRI microstructural model estimation", MICCAI Workshop
on Computational DIFFUSION MRI (CDMRI), 2017.
Examples
--------
In this example, where the data, gradient table and sphere tessellation
used for reconstruction are provided, we model the diffusion signal
with respect to the FORECAST and compute the fODF, parallel and
perpendicular diffusivity.
>>> import warnings
>>> from dipy.data import default_sphere, get_3shell_gtab
>>> gtab = get_3shell_gtab()
>>> from dipy.sims.voxel import multi_tensor
>>> mevals = np.array(([0.0017, 0.0003, 0.0003],
... [0.0017, 0.0003, 0.0003]))
>>> angl = [(0, 0), (60, 0)]
>>> data, sticks = multi_tensor(gtab,
... mevals,
... S0=100.0,
... angles=angl,
... fractions=[50, 50],
... snr=None)
>>> from dipy.reconst.forecast import ForecastModel
>>> from dipy.reconst.shm import descoteaux07_legacy_msg
>>> with warnings.catch_warnings():
... warnings.filterwarnings(
... "ignore", message=descoteaux07_legacy_msg,
... category=PendingDeprecationWarning)
... fm = ForecastModel(gtab, sh_order=6)
>>> f_fit = fm.fit(data)
>>> d_par = f_fit.dpar
>>> d_perp = f_fit.dperp
>>> with warnings.catch_warnings():
... warnings.filterwarnings(
... "ignore", message=descoteaux07_legacy_msg,
... category=PendingDeprecationWarning)
... fodf = f_fit.odf(default_sphere)
"""
OdfModel.__init__(self, gtab)
# round the bvals in order to avoid numerical errors
self.bvals = np.round(gtab.bvals / 100) * 100
self.bvecs = gtab.bvecs
if sh_order >= 0 and not (bool(sh_order % 2)) and sh_order <= 12:
self.sh_order = sh_order
else:
msg = "sh_order must be a non-zero even positive number "
msg += "between 2 and 12"
raise ValueError(msg)
if sphere is None:
sphere = default_sphere
self.vertices = sphere.vertices[0:int(sphere.vertices.shape[0] /
2), :]
else:
self.vertices = sphere
self.b0s_mask = self.bvals == 0
self.one_0_bvals = np.r_[0, self.bvals[~self.b0s_mask]]
self.one_0_bvecs = np.r_[np.array([0, 0, 0]).reshape(1, 3),
self.bvecs[~self.b0s_mask, :]]
self.rho = rho_matrix(self.sh_order, self.one_0_bvecs)
# signal regularization matrix
self.srm = rho_matrix(4, self.one_0_bvecs)
self.lb_matrix_signal = lb_forecast(4)
self.b_unique = np.sort(np.unique(self.bvals[self.bvals > 0]))
self.wls = True
self.csd = False
self.pos = False
if dec_alg.upper() == 'POS':
if have_cvxpy:
self.wls = False
self.pos = True
else:
msg = 'cvxpy is needed to inforce positivity constraints.'
raise ValueError(msg)
if dec_alg.upper() == 'CSD':
self.csd = True
self.lb_matrix = lb_forecast(self.sh_order)
self.lambda_lb = lambda_lb
self.lambda_csd = lambda_csd
self.fod = rho_matrix(sh_order, self.vertices)
def __init__(self,
gtab,
sh_order=8,
lambda_lb=1e-3,
dec_alg='CSD',
sphere=None,
lambda_csd=1.0):
r""" Analytical and continuous modeling of the diffusion signal with
respect to the FORECAST basis [1,2,3]_.
This implementation is a modification of the original FORECAST
model presented in [1]_ adapted for multi-shell data as in [2,3]_ .
The main idea is to model the diffusion signal as the combination of a
single fiber response function $F(\mathbf{b})$ times the fODF
$\rho(\mathbf{v})$
..math::
:nowrap:
\begin{equation}
E(\mathbf{b}) = \int_{\mathbf{v} \in \mathcal{S}^2} \rho(\mathbf{v}) F({\mathbf{b}} | \mathbf{v}) d \mathbf{v}
\end{equation}
where $\mathbf{b}$ is the b-vector (b-value times gradient direction)
and $\mathbf{v}$ is an unit vector representing a fiber direction.
In FORECAST $\rho$ is modeled using real symmetric Spherical Harmonics
(SH) and $F(\mathbf(b))$ is an axially symmetric tensor.
Parameters
----------
gtab : GradientTable,
gradient directions and bvalues container class.
sh_order : unsigned int,
an even integer that represent the SH order of the basis (max 12)
lambda_lb: float,
Laplace-Beltrami regularization weight.
dec_alg : str,
Spherical deconvolution algorithm. The possible values are Weighted Least Squares ('WLS'),
Positivity Constraints using CVXPY ('POS') and the Constraint
Spherical Deconvolution algorithm ('CSD'). Default is 'CSD'.
sphere : array, shape (N,3),
sphere points where to enforce positivity when 'POS' or 'CSD'
dec_alg are selected.
lambda_csd : float,
CSD regularization weight.
References
----------
.. [1] Anderson A. W., "Measurement of Fiber Orientation Distributions
Using High Angular Resolution Diffusion Imaging", Magnetic
Resonance in Medicine, 2005.
.. [2] Kaden E. et al., "Quantitative Mapping of the Per-Axon Diffusion
Coefficients in Brain White Matter", Magnetic Resonance in
Medicine, 2016.
.. [3] Zucchelli M. et al., "A generalized SMT-based framework for
Diffusion MRI microstructural model estimation", MICCAI Workshop
on Computational DIFFUSION MRI (CDMRI), 2017.
Examples
--------
In this example, where the data, gradient table and sphere tessellation
used for reconstruction are provided, we model the diffusion signal
with respect to the FORECAST and compute the fODF, parallel and
perpendicular diffusivity.
>>> from dipy.data import get_sphere, get_3shell_gtab
>>> gtab = get_3shell_gtab()
>>> from dipy.sims.voxel import MultiTensor
>>> mevals = np.array(([0.0017, 0.0003, 0.0003],
... [0.0017, 0.0003, 0.0003]))
>>> angl = [(0, 0), (60, 0)]
>>> data, sticks = MultiTensor(gtab,
... mevals,
... S0=100.0,
... angles=angl,
... fractions=[50, 50],
... snr=None)
>>> from dipy.reconst.forecast import ForecastModel
>>> fm = ForecastModel(gtab, sh_order=6)
>>> f_fit = fm.fit(data)
>>> d_par = f_fit.dpar
>>> d_perp = f_fit.dperp
>>> sphere = get_sphere('symmetric724')
>>> fodf = f_fit.odf(sphere)
"""
OdfModel.__init__(self, gtab)
# round the bvals in order to avoid numerical errors
self.bvals = np.round(gtab.bvals/100) * 100
self.bvecs = gtab.bvecs
if sh_order >= 0 and not(bool(sh_order % 2)) and sh_order <= 12:
self.sh_order = sh_order
else:
msg = "sh_order must be a non-zero even positive number "
msg += "between 2 and 12"
raise ValueError(msg)
if sphere is None:
sphere = get_sphere('repulsion724')
self.vertices = sphere.vertices[
0:int(sphere.vertices.shape[0]/2), :]
else:
self.vertices = sphere
self.b0s_mask = self.bvals == 0
self.one_0_bvals = np.r_[0, self.bvals[~self.b0s_mask]]
self.one_0_bvecs = np.r_[np.array([0, 0, 0]).reshape(
1, 3), self.bvecs[~self.b0s_mask, :]]
self.rho = rho_matrix(self.sh_order, self.one_0_bvecs)
# signal regularization matrix
self.srm = rho_matrix(4, self.one_0_bvecs)
self.lb_matrix_signal = lb_forecast(4)
self.b_unique = np.sort(np.unique(self.bvals[self.bvals > 0]))
self.wls = True
self.csd = False
self.pos = False
if dec_alg.upper() == 'POS':
if have_cvxpy:
self.wls = False
self.pos = True
else:
msg = 'cvxpy is needed to inforce positivity constraints.'
raise ValueError(msg)
if dec_alg.upper() == 'CSD':
self.csd = True
self.lb_matrix = lb_forecast(self.sh_order)
self.lambda_lb = lambda_lb
self.lambda_csd = lambda_csd
self.fod = rho_matrix(sh_order, self.vertices)
def __init__(self,
gtab,
method='gqi2',
sampling_length=1.2,
normalize_peaks=False):
r""" Generalized Q-Sampling Imaging [1]_
This model has the same assumptions as the DSI method i.e. Cartesian
grid sampling in q-space and fast gradient switching.
Implements equations 2.14 from [2]_ for standard GQI and equation 2.16
from [2]_ for GQI2. You can think of GQI2 as an analytical solution of
the DSI ODF.
Parameters
----------
gtab : object,
GradientTable
method : str,
'standard' or 'gqi2'
sampling_length : float,
diffusion sampling length (lambda in eq. 2.14 and 2.16)
References
----------
.. [1] Yeh F-C et al., "Generalized Q-Sampling Imaging", IEEE TMI, 2010
.. [2] Garyfallidis E, "Towards an accurate brain tractography", PhD
thesis, University of Cambridge, 2012.
Notes
-----
As of version 0.9, range of the sampling length in GQI2 has changed
to match the same scale used in the 'standard' method [1]_. This
means that the value of `sampling_length` should be approximately
1 - 1.3 (see [1]_, pg. 1628).
Examples
--------
Here we create an example where we provide the data, a gradient table
and a reconstruction sphere and calculate the ODF for the first
voxel in the data.
>>> from dipy.data import dsi_voxels
>>> data, gtab = dsi_voxels()
>>> from dipy.core.subdivide_octahedron import create_unit_sphere
>>> sphere = create_unit_sphere(5)
>>> from dipy.reconst.gqi import GeneralizedQSamplingModel
>>> gq = GeneralizedQSamplingModel(gtab, 'gqi2', 1.1)
>>> voxel_signal = data[0, 0, 0]
>>> odf = gq.fit(voxel_signal).odf(sphere)
See Also
--------
dipy.reconst.dsi.DiffusionSpectrumModel
"""
OdfModel.__init__(self, gtab)
self.method = method
self.Lambda = sampling_length
self.normalize_peaks = normalize_peaks
# 0.01506 = 6*D where D is the free water diffusion coefficient
# l_values sqrt(6 D tau) D free water diffusion coefficient and
# tau included in the b-value
scaling = np.sqrt(self.gtab.bvals * 0.01506)
tmp = np.tile(scaling, (3, 1))
gradsT = self.gtab.bvecs.T
b_vector = gradsT * tmp # element-wise product
self.b_vector = b_vector.T
def __init__(self, gtab, response, reg_sphere=None, sh_order=8, lambda_=1,
tau=0.1):
r""" Constrained Spherical Deconvolution (CSD) [1]_.
Spherical deconvolution computes a fiber orientation distribution
(FOD), also called fiber ODF (fODF) [2]_, as opposed to a diffusion ODF
as the QballModel or the CsaOdfModel. This results in a sharper angular
profile with better angular resolution that is the best object to be
used for later deterministic and probabilistic tractography [3]_.
A sharp fODF is obtained because a single fiber *response* function is
injected as *a priori* knowledge. The response function is often
data-driven and is thus provided as input to the
ConstrainedSphericalDeconvModel. It will be used as deconvolution
kernel, as described in [1]_.
Parameters
----------
gtab : GradientTable
response : tuple
A tuple with two elements. The first is the eigen-values as an (3,)
ndarray and the second is the signal value for the response
function without diffusion weighting. This is to be able to
generate a single fiber synthetic signal. The response function
will be used as deconvolution kernel ([1]_)
reg_sphere : Sphere (optional)
sphere used to build the regularization B matrix.
Default: 'symmetric362'.
sh_order : int (optional)
maximal spherical harmonics order. Default: 8
lambda_ : float (optional)
weight given to the constrained-positivity regularization part of the
deconvolution equation (see [1]_). Default: 1
tau : float (optional)
threshold controlling the amplitude below which the corresponding
fODF is assumed to be zero. Ideally, tau should be set to
zero. However, to improve the stability of the algorithm, tau is
set to tau*100 % of the mean fODF amplitude (here, 10% by default)
(see [1]_). Default: 0.1
References
----------
.. [1] Tournier, J.D., et al. NeuroImage 2007. Robust determination of
the fibre orientation distribution in diffusion MRI:
Non-negativity constrained super-resolved spherical
deconvolution
.. [2] Descoteaux, M., et al. IEEE TMI 2009. Deterministic and
Probabilistic Tractography Based on Complex Fibre Orientation
Distributions
.. [3] C\^ot\'e, M-A., et al. Medical Image Analysis 2013. Tractometer:
Towards validation of tractography pipelines
.. [4] Tournier, J.D, et al. Imaging Systems and Technology
2012. MRtrix: Diffusion Tractography in Crossing Fiber Regions
"""
# Initialize the parent class:
OdfModel.__init__(self, gtab)
m, n = sph_harm_ind_list(sh_order)
self.m, self.n = m, n
self._where_b0s = lazy_index(gtab.b0s_mask)
self._where_dwi = lazy_index(~gtab.b0s_mask)
no_params = ((sh_order + 1) * (sh_order + 2)) / 2
if no_params > np.sum(gtab.b0s_mask == False):
msg = "Number of parameters required for the fit are more "
msg += "than the actual data points"
warnings.warn(msg, UserWarning)
x, y, z = gtab.gradients[self._where_dwi].T
r, theta, phi = cart2sphere(x, y, z)
# for the gradient sphere
self.B_dwi = real_sph_harm(m, n, theta[:, None], phi[:, None])
# for the sphere used in the regularization positivity constraint
if reg_sphere is None:
self.sphere = get_sphere('symmetric362')
else:
self.sphere = reg_sphere
r, theta, phi = cart2sphere(self.sphere.x, self.sphere.y, self.sphere.z)
self.B_reg = real_sph_harm(m, n, theta[:, None], phi[:, None])
if response is None:
self.response = (np.array([0.0015, 0.0003, 0.0003]), 1)
else:
self.response = response
self.S_r = estimate_response(gtab, self.response[0], self.response[1])
self.response_scaling = response[1]
r_sh = np.linalg.lstsq(self.B_dwi, self.S_r[self._where_dwi])[0]
r_rh = sh_to_rh(r_sh, m, n)
self.R = forward_sdeconv_mat(r_rh, n)
# scale lambda_ to account for differences in the number of
# SH coefficients and number of mapped directions
# This is exactly what is done in [4]_
self.lambda_ = (lambda_ * self.R.shape[0] * r_rh[0] /
(np.sqrt(self.B_reg.shape[0]) * np.sqrt(362.))
)
self.sh_order = sh_order
self.tau = tau
def __init__(self,
gtab,
method='gqi2',
sampling_length=1.2,
normalize_peaks=False):
r""" Generalized Q-Sampling Imaging [1]_
This model has the same assumptions as the DSI method i.e. Cartesian
grid sampling in q-space and fast gradient switching.
Implements equations 2.14 from [2]_ for standard GQI and equation 2.16
from [2]_ for GQI2. You can think of GQI2 as an analytical solution of
the DSI ODF.
Parameters
----------
gtab : object,
GradientTable
method : str,
'standard' or 'gqi2'
sampling_length : float,
diffusion sampling length (lambda in eq. 2.14 and 2.16)
References
----------
.. [1] Yeh F-C et. al, "Generalized Q-Sampling Imaging", IEEE TMI, 2010
.. [2] Garyfallidis E, "Towards an accurate brain tractography", PhD
thesis, University of Cambridge, 2012.
Notes
-----
As of version 0.9, range of the sampling length in GQI2 has changed
to match the same scale used in the 'standard' method [1]_. This
means that the value of `sampling_length` should be approximately
1 - 1.3 (see [1]_, pg. 1628).
Examples
--------
Here we create an example where we provide the data, a gradient table
and a reconstruction sphere and calculate the ODF for the first
voxel in the data.
>>> from dipy.data import dsi_voxels
>>> data, gtab = dsi_voxels()
>>> from dipy.core.subdivide_octahedron import create_unit_sphere
>>> sphere = create_unit_sphere(5)
>>> from dipy.reconst.gqi import GeneralizedQSamplingModel
>>> gq = GeneralizedQSamplingModel(gtab, 'gqi2', 1.1)
>>> voxel_signal = data[0, 0, 0]
>>> odf = gq.fit(voxel_signal).odf(sphere)
See Also
--------
dipy.reconst.dsi.DiffusionSpectrumModel
"""
OdfModel.__init__(self, gtab)
self.method = method
self.Lambda = sampling_length
self.normalize_peaks = normalize_peaks
# 0.01506 = 6*D where D is the free water diffusion coefficient
# l_values sqrt(6 D tau) D free water diffusion coefficient and
# tau included in the b-value
scaling = np.sqrt(self.gtab.bvals * 0.01506)
tmp = np.tile(scaling, (3, 1))
gradsT = self.gtab.bvecs.T
b_vector = gradsT * tmp # element-wise product
self.b_vector = b_vector.T
def __init__(self,
gtab,
wm_response=np.array([1.7e-3, 0.2e-3, 0.2e-3]),
gm_response=0.8e-3,
csf_response=3.0e-3,
n_iter=600,
recon_type='smf',
n_coils=1,
R=1,
voxelwise=True,
use_tv=False,
sphere=None,
verbose=False):
'''
Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) [1]_
Modification of the Richardson-Lucy algorithm accounting for Rician
and Noncentral Chi noise distributions, which more accurately
represent MRI noise. Computes a maximum likelihood estimation of the
fiber orientation density function (fODF) at each voxel. Includes
white matter compartments alongside optional GM and CSF compartments
to account for partial volume effects. This fit can be performed
voxelwise or globally. The global fit will proceed more quickly than
the voxelwise fit provided that the computer has adequate RAM (>= 16 GB
should be sufficient for most datasets).
Kernel for deconvolution constructed using a priori knowledge of white
matter response function, as well as the mean diffusivity of GM and/or
CSF. RUMBA-SD is robust against impulse response imprecision, and thus
the default diffusivity values are often adequate [2]_.
Parameters
----------
gtab : GradientTable
wm_response : 1d ndarray or 2d ndarray or AxSymShResponse, optional
Tensor eigenvalues as a (3,) ndarray, multishell eigenvalues as
a (len(unique_bvals_tolerance(gtab.bvals))-1, 3) ndarray in
order of smallest to largest b-value, or an AxSymShResponse.
Default: np.array([1.7e-3, 0.2e-3, 0.2e-3])
gm_response : float, optional
Mean diffusivity for GM compartment. If `None`, then grey
matter volume fraction is not computed. Default: 0.8e-3
csf_response : float, optional
Mean diffusivity for CSF compartment. If `None`, then CSF
volume fraction is not computed. Default: 3.0e-3
n_iter : int, optional
Number of iterations for fODF estimation. Must be a positive int.
Default: 600
recon_type : {'smf', 'sos'}, optional
MRI reconstruction method: spatial matched filter (SMF) or
sum-of-squares (SoS). SMF reconstruction generates Rician noise
while SoS reconstruction generates Noncentral Chi noise.
Default: 'smf'
n_coils : int, optional
Number of coils in MRI scanner -- only relevant in SoS
reconstruction. Must be a positive int. Default: 1
R : int, optional
Acceleration factor of the acquisition. For SIEMENS,
R = iPAT factor. For GE, R = ASSET factor. For PHILIPS,
R = SENSE factor. Typical values are 1 or 2. Must be a positive
int. Default: 1
voxelwise : bool, optional
If true, performs a voxelwise fit. If false, performs a global fit
on the entire brain at once. The global fit requires a 4D brain
volume in `fit`. Default: True
use_tv : bool, optional
If true, applies total variation regularization. This only takes
effect in a global fit (`voxelwise` is set to `False`). TV can only
be applied to 4D brain volumes with no singleton dimensions.
Default: False
sphere : Sphere, optional
Sphere on which to construct fODF. If None, uses `repulsion724`.
Default: None
verbose : bool, optional
If true, logs updates on estimated signal-to-noise ratio after each
iteration. This only takes effect in a global fit (`voxelwise` is
set to `False`). Default: False
References
----------
.. [1] Canales-Rodríguez, E. J., Daducci, A., Sotiropoulos, S. N.,
Caruyer, E., Aja-Fernández, S., Radua, J., Mendizabal, J. M. Y.,
Iturria-Medina, Y., Melie-García, L., Alemán-Gómez, Y.,
Thiran, J.-P., Sarró, S., Pomarol-Clotet, E., & Salvador, R.
(2015). Spherical Deconvolution of Multichannel Diffusion MRI
Data with Non-Gaussian Noise Models and Spatial Regularization.
PLOS ONE, 10(10), e0138910.
https://doi.org/10.1371/journal.pone.0138910
.. [2] Dell’Acqua, F., Rizzo, G., Scifo, P., Clarke, R., Scotti, G., &
Fazio, F. (2007). A Model-Based Deconvolution Approach to Solve
Fiber Crossing in Diffusion-Weighted MR Imaging. IEEE
Transactions on Bio-Medical Engineering, 54, 462–472.
https://doi.org/10.1109/TBME.2006.888830
'''
if not np.any(gtab.b0s_mask):
raise ValueError("Gradient table has no b0 measurements")
self.gtab_orig = gtab # save for prediction
# Masks to extract b0/non-b0 measurements
self.where_b0s = lazy_index(gtab.b0s_mask)
self.where_dwi = lazy_index(~gtab.b0s_mask)
# Correct gradient table to contain b0 data at the beginning
bvals_cor = np.concatenate(([0], gtab.bvals[self.where_dwi]))
bvecs_cor = np.concatenate(([[0, 0, 0]], gtab.bvecs[self.where_dwi]))
gtab_cor = gradient_table(bvals_cor, bvecs_cor)
# Initialize self.gtab
OdfModel.__init__(self, gtab_cor)
# Store responses
self.wm_response = wm_response
self.gm_response = gm_response
self.csf_response = csf_response
# Initializing remaining parameters
if R < 1 or n_iter < 1 or n_coils < 1:
raise ValueError(
f"R, n_iter, and n_coils must be >= 1, but R={R}," +
f"n_iter={n_iter}, and n_coils={n_coils} ")
self.R = R
self.n_iter = n_iter
self.recon_type = recon_type
self.n_coils = n_coils
if voxelwise and use_tv:
raise ValueError("Total variation has no effect in voxelwise fit")
if voxelwise and verbose:
warnings.warn("Verbosity has no effect in voxelwise fit",
UserWarning)
self.voxelwise = voxelwise
self.use_tv = use_tv
self.verbose = verbose
if sphere is None:
self.sphere = get_sphere('repulsion724')
else:
self.sphere = sphere
if voxelwise:
self.fit = self._voxelwise_fit
else:
self.fit = self._global_fit
# Fitting parameters
self.kernel = None