import numpy
from six.moves import range
from radiomics import base, cMatrices
[docs]class RadiomicsGLSZM(base.RadiomicsFeaturesBase):
r"""
A Gray Level Size Zone (GLSZM) quantifies gray level zones in an image. A gray level zone is defined as a the number
of connected voxels that share the same gray level intensity. A voxel is considered connected if the distance is 1
according to the infinity norm (26-connected region in a 3D, 8-connected region in 2D).
In a gray level size zone matrix :math:`P(i,j)` the :math:`(i,j)^{\text{th}}` element equals the number of zones
with gray level :math:`i` and size :math:`j` appear in image. Contrary to GLCM and GLRLM, the GLSZM is rotation
independent, with only one matrix calculated for all directions in the ROI.
As a two dimensional example, consider the following 5x5 image, with 5 discrete gray levels:
.. math::
\textbf{I} = \begin{bmatrix}
5 & 2 & 5 & 4 & 4\\
3 & 3 & 3 & 1 & 3\\
2 & 1 & 1 & 1 & 3\\
4 & 2 & 2 & 2 & 3\\
3 & 5 & 3 & 3 & 2 \end{bmatrix}
The GLSZM then becomes:
.. math::
\textbf{P} = \begin{bmatrix}
0 & 0 & 0 & 1 & 0\\
1 & 0 & 0 & 0 & 1\\
1 & 0 & 1 & 0 & 1\\
1 & 1 & 0 & 0 & 0\\
3 & 0 & 0 & 0 & 0 \end{bmatrix}
Let:
- :math:`N_g` be the number of discreet intensity values in the image
- :math:`N_s` be the number of discreet zone sizes in the image
- :math:`N_p` be the number of voxels in the image
- :math:`N_z` be the number of zones in the ROI, which is equal to :math:`\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}
{\textbf{P}(i,j)}` and :math:`1 \leq N_z \leq N_p`
- :math:`\textbf{P}(i,j)` be the size zone matrix
- :math:`p(i,j)` be the normalized size zone matrix, defined as :math:`p(i,j) = \frac{\textbf{P}(i,j)}{N_z}`
.. note::
The mathematical formulas that define the GLSZM features correspond to the definitions of features extracted from
the GLRLM.
References
- Guillaume Thibault; Bernard Fertil; Claire Navarro; Sandrine Pereira; Pierre Cau; Nicolas Levy; Jean Sequeira;
Jean-Luc Mari (2009). "Texture Indexes and Gray Level Size Zone Matrix. Application to Cell Nuclei Classification".
Pattern Recognition and Information Processing (PRIP): 140-145.
- `<https://en.wikipedia.org/wiki/Gray_level_size_zone_matrix>`_
"""
def __init__(self, inputImage, inputMask, **kwargs):
super(RadiomicsGLSZM, self).__init__(inputImage, inputMask, **kwargs)
self.P_glszm = None
self._applyBinning()
def _initCalculation(self):
self.coefficients['Np'] = len(self.labelledVoxelCoordinates[0])
self.P_glszm = self._calculateMatrix()
self._calculateCoefficients()
self.logger.debug('GLSZM feature class initialized, calculated GLSZM with shape %s', self.P_glszm.shape)
def _calculateMatrix(self):
"""
Number of times a region with a
gray level and voxel count occurs in an image. P_glszm[level, voxel_count] = # occurrences
For 3D-images this concerns a 26-connected region, for 2D an 8-connected region
"""
self.logger.debug('Calculating GLSZM matrix in C')
Ng = self.coefficients['Ng']
Ns = self.coefficients['Np']
P_glszm, angles = cMatrices.calculate_glszm(self.matrix,
self.maskArray,
Ng,
Ns,
self.settings.get('force2D', False),
self.settings.get('force2Ddimension', 0))
# Delete rows that specify gray levels not present in the ROI
NgVector = range(1, Ng + 1) # All possible gray values
GrayLevels = self.coefficients['grayLevels'] # Gray values present in ROI
emptyGrayLevels = numpy.array(list(set(NgVector) - set(GrayLevels))) # Gray values NOT present in ROI
P_glszm = numpy.delete(P_glszm, emptyGrayLevels - 1, 0)
return P_glszm
def _calculateCoefficients(self):
self.logger.debug('Calculating GLSZM coefficients')
Nz = numpy.sum(self.P_glszm, (0, 1))
# set sum to numpy.spacing(1) if sum is 0?
if Nz == 0:
Nz = 1
ps = numpy.sum(self.P_glszm, 0)
pg = numpy.sum(self.P_glszm, 1)
ivector = self.coefficients['grayLevels']
jvector = numpy.arange(1, self.P_glszm.shape[1] + 1, dtype=numpy.float64)
# Delete columns that specify zone sizes not present in the ROI
emptyZoneSizes = numpy.where(ps == 0)
self.P_glszm = numpy.delete(self.P_glszm, emptyZoneSizes, 1)
jvector = numpy.delete(jvector, emptyZoneSizes)
ps = numpy.delete(ps, emptyZoneSizes)
self.coefficients['Nz'] = Nz
self.coefficients['ps'] = ps
self.coefficients['pg'] = pg
self.coefficients['ivector'] = ivector
self.coefficients['jvector'] = jvector
[docs] def getSmallAreaEmphasisFeatureValue(self):
r"""
**1. Small Area Emphasis (SAE)**
.. math::
\textit{SAE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\frac{\textbf{P}(i,j)}{j^2}}}{N_z}
SAE is a measure of the distribution of small size zones, with a greater value indicative of more smaller size zones
and more fine textures.
"""
ps = self.coefficients['ps']
jvector = self.coefficients['jvector']
Nz = self.coefficients['Nz']
sae = numpy.sum(ps / (jvector ** 2)) / Nz
return sae
[docs] def getLargeAreaEmphasisFeatureValue(self):
r"""
**2. Large Area Emphasis (LAE)**
.. math::
\textit{LAE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\textbf{P}(i,j)j^2}}{N_z}
LAE is a measure of the distribution of large area size zones, with a greater value indicative of more larger size
zones and more coarse textures.
"""
ps = self.coefficients['ps']
jvector = self.coefficients['jvector']
Nz = self.coefficients['Nz']
lae = numpy.sum(ps * (jvector ** 2)) / Nz
return lae
[docs] def getZonePercentageFeatureValue(self):
r"""
**7. Zone Percentage (ZP)**
.. math::
\textit{ZP} = \frac{N_z}{N_p}
ZP measures the coarseness of the texture by taking the ratio of number of zones and number of voxels in the ROI.
Values are in range :math:`\frac{1}{N_p} \leq ZP \leq 1`, with higher values indicating a larger portion of the ROI
consists of small zones (indicates a more fine texture).
"""
Nz = self.coefficients['Nz']
Np = self.coefficients['Np']
zp = Nz / Np
return zp
[docs] def getGrayLevelVarianceFeatureValue(self):
r"""
**8. Gray Level Variance (GLV)**
.. math::
\textit{GLV} = \displaystyle\sum^{N_g}_{i=1}\displaystyle\sum^{N_s}_{j=1}{p(i,j)(i - \mu)^2}
Here, :math:`\mu = \displaystyle\sum^{N_g}_{i=1}\displaystyle\sum^{N_s}_{j=1}{p(i,j)i}`
GLV measures the variance in gray level intensities for the zones.
"""
ivector = self.coefficients['ivector']
Nz = self.coefficients['Nz']
pg = self.coefficients['pg'] / Nz # divide by Nz to get the normalized matrix
u_i = numpy.sum(pg * ivector)
glv = numpy.sum(pg * (ivector - u_i) ** 2)
return glv
[docs] def getZoneVarianceFeatureValue(self):
r"""
**9. Zone Variance (ZV)**
.. math::
\textit{ZV} = \displaystyle\sum^{N_g}_{i=1}\displaystyle\sum^{N_s}_{j=1}{p(i,j)(j - \mu)^2}
Here, :math:`\mu = \displaystyle\sum^{N_g}_{i=1}\displaystyle\sum^{N_s}_{j=1}{p(i,j)j}`
ZV measures the variance in zone size volumes for the zones.
"""
jvector = self.coefficients['jvector']
Nz = self.coefficients['Nz']
ps = self.coefficients['ps'] / Nz # divide by Nz to get the normalized matrix
u_j = numpy.sum(ps * jvector)
zv = numpy.sum(ps * (jvector - u_j) ** 2)
return zv
[docs] def getZoneEntropyFeatureValue(self):
r"""
**10. Zone Entropy (ZE)**
.. math::
\textit{ZE} = -\displaystyle\sum^{N_g}_{i=1}\displaystyle\sum^{N_s}_{j=1}{p(i,j)\log_{2}(p(i,j)+\epsilon)}
Here, :math:`\epsilon` is an arbitrarily small positive number (:math:`\approx 2.2\times10^{-16}`).
ZE measures the uncertainty/randomness in the distribution of zone sizes and gray levels. A higher value indicates
more heterogeneneity in the texture patterns.
"""
eps = numpy.spacing(1)
Nz = self.coefficients['Nz']
p_glszm = self.P_glszm / Nz # divide by Nz to get the normalized matrix
ze = -numpy.sum(p_glszm * numpy.log2(p_glszm + eps))
return ze
[docs] def getLowGrayLevelZoneEmphasisFeatureValue(self):
r"""
**11. Low Gray Level Zone Emphasis (LGLZE)**
.. math::
\textit{LGLZE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\frac{\textbf{P}(i,j)}{i^2}}}{N_z}
LGLZE measures the distribution of lower gray-level size zones, with a higher value indicating a greater proportion
of lower gray-level values and size zones in the image.
"""
pg = self.coefficients['pg']
ivector = self.coefficients['ivector']
Nz = self.coefficients['Nz']
lie = numpy.sum(pg / (ivector ** 2)) / Nz
return lie
[docs] def getHighGrayLevelZoneEmphasisFeatureValue(self):
r"""
**12. High Gray Level Zone Emphasis (HGLZE)**
.. math::
\textit{HGLZE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\textbf{P}(i,j)i^2}}{N_z}
HGLZE measures the distribution of the higher gray-level values, with a higher value indicating a greater proportion
of higher gray-level values and size zones in the image.
"""
pg = self.coefficients['pg']
ivector = self.coefficients['ivector']
Nz = self.coefficients['Nz']
hie = numpy.sum(pg * (ivector ** 2)) / Nz
return hie
[docs] def getSmallAreaLowGrayLevelEmphasisFeatureValue(self):
r"""
**13. Small Area Low Gray Level Emphasis (SALGLE)**
.. math::
\textit{SALGLE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\frac{\textbf{P}(i,j)}{i^2j^2}}}{N_z}
SALGLE measures the proportion in the image of the joint distribution of smaller size zones with lower gray-level
values.
"""
ivector = self.coefficients['ivector']
jvector = self.coefficients['jvector']
Nz = self.coefficients['Nz']
lisae = numpy.sum(self.P_glszm / ((ivector[:, None] ** 2) * (jvector[None, :] ** 2))) / Nz
return lisae
[docs] def getSmallAreaHighGrayLevelEmphasisFeatureValue(self):
r"""
**14. Small Area High Gray Level Emphasis (SAHGLE)**
.. math::
\textit{SAHGLE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\frac{\textbf{P}(i,j)i^2}{j^2}}}{N_z}
SAHGLE measures the proportion in the image of the joint distribution of smaller size zones with higher gray-level
values.
"""
ivector = self.coefficients['ivector']
jvector = self.coefficients['jvector']
Nz = self.coefficients['Nz']
hisae = numpy.sum(self.P_glszm * (ivector[:, None] ** 2) / (jvector[None, :] ** 2)) / Nz
return hisae
[docs] def getLargeAreaLowGrayLevelEmphasisFeatureValue(self):
r"""
**15. Large Area Low Gray Level Emphasis (LALGLE)**
.. math::
\textit{LALGLE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\frac{\textbf{P}(i,j)j^2}{i^2}}}{N_z}
LALGLE measures the proportion in the image of the joint distribution of larger size zones with lower gray-level
values.
"""
ivector = self.coefficients['ivector']
jvector = self.coefficients['jvector']
Nz = self.coefficients['Nz']
lilae = numpy.sum(self.P_glszm * (jvector[None, :] ** 2) / (ivector[:, None] ** 2)) / Nz
return lilae
[docs] def getLargeAreaHighGrayLevelEmphasisFeatureValue(self):
r"""
**16. Large Area High Gray Level Emphasis (LAHGLE)**
.. math::
\textit{LAHGLE} = \frac{\sum^{N_g}_{i=1}\sum^{N_s}_{j=1}{\textbf{P}(i,j)i^2j^2}}{N_z}
LAHGLE measures the proportion in the image of the joint distribution of larger size zones with higher gray-level
values.
"""
ivector = self.coefficients['ivector']
jvector = self.coefficients['jvector']
Nz = self.coefficients['Nz']
hilae = numpy.sum(self.P_glszm * (ivector[:, None] ** 2) * (jvector[None, :] ** 2)) / Nz
return hilae