def _project_grad(op, grad):
'''
Compute the gradient of the projection op by invoking the backprojector.
'''
reco = pyronn_layers.fan_backprojection2d(
sinogram=grad,
volume_shape=op.inputs[0].shape[1:],
volume_origin=op.inputs[2],
detector_origin=op.inputs[3],
volume_spacing=op.inputs[4],
detector_spacing=op.inputs[5],
source_2_isocenter_distance=op.inputs[6],
source_2_detector_distance=op.inputs[7],
central_ray_vectors=op.inputs[8],
)
return [
reco,
tf.stop_gradient(op.inputs[1]),
tf.stop_gradient(op.inputs[2]),
tf.stop_gradient(op.inputs[3]),
tf.stop_gradient(op.inputs[4]),
tf.stop_gradient(op.inputs[5]),
tf.stop_gradient(op.inputs[6]),
tf.stop_gradient(op.inputs[7]),
tf.stop_gradient(op.inputs[8])
]
def fan_backprojection2d(sinogram, geometry):
"""
Wrapper function for making the layer call.
Args:
volume: Input volume to project.
geometry: Corresponding GeometryFan2D Object defining parameters.
Returns:
Initialized lme_custom_ops.fan_backprojection2d layer.
"""
batch = np.shape(sinogram)[0]
return pyronn_layers.fan_backprojection2d(
sinogram,
volume_shape=geometry.volume_shape,
volume_origin=np.broadcast_to(
geometry.volume_origin,
[batch, *np.shape(geometry.volume_origin)]),
detector_origin=np.broadcast_to(
geometry.detector_origin,
[batch, *np.shape(geometry.detector_origin)]),
volume_spacing=np.broadcast_to(
geometry.volume_spacing,
[batch, *np.shape(geometry.volume_spacing)]),
detector_spacing=np.broadcast_to(
geometry.detector_spacing,
[batch, *np.shape(geometry.detector_spacing)]),
source_2_isocenter_distance=np.broadcast_to(
geometry.source_isocenter_distance,
[batch, *np.shape(geometry.source_isocenter_distance)]),
source_2_detector_distance=np.broadcast_to(
geometry.source_detector_distance,
[batch, *np.shape(geometry.source_detector_distance)]),
central_ray_vectors=np.broadcast_to(
geometry.central_ray_vectors,
[batch, *np.shape(geometry.central_ray_vectors)]))
def _project_grad(op, grad):
'''
Compute the gradient of the projection op by invoking the backprojector.
'''
reco = pyronn_layers.fan_backprojection2d(
sinogram=grad,
sinogram_shape=op.get_attr("projection_shape"),
volume_shape=op.get_attr("volume_shape"),
volume_origin=op.get_attr("volume_origin"),
detector_origin=op.get_attr("detector_origin"),
volume_spacing=op.get_attr("volume_spacing"),
detector_spacing=op.get_attr("detector_spacing"),
source_2_isocenter_distance=op.get_attr("source_2_isocenter_distance"),
source_2_detector_distance=op.get_attr("source_2_detector_distance"),
central_ray_vectors=op.get_attr("central_ray_vectors"),
)
return [reco]