def __call__(self, sample: Dict[str, Any]):
"""
Parameters
----------
sample: dict
Returns
-------
data dictionary
"""
kspace = sample["kspace"]
sensitivity_map = sample.get("sensitivity_map", None)
filename = sample["filename"]
if "sampling_mask" in sample:
if self.mask_func is not None:
warnings.warn(
f"`sampling_mask` is passed by the Dataset class, yet `mask_func` is also set. "
f"This will be ignored and the `sampling_mask` will be used instead. "
f"Be aware of this as it can lead to unexpected results. "
f"This warning will be issued only once."
)
mask_func = sample["sampling_mask"]
else:
mask_func = self.mask_func
seed = None if not self.use_seed else tuple(map(ord, str(filename)))
if np.random.random() >= self.kspace_crop_probability:
kspace, backprojected_kspace, sensitivity_map = self.__random_image_crop(
kspace, sensitivity_map
)
masked_kspace, sampling_mask = T.apply_mask(kspace, mask_func, seed)
else:
masked_kspace, sampling_mask = T.apply_mask(kspace, mask_func, seed)
(
kspace,
masked_kspace,
sampling_mask,
backprojected_kspace,
sensitivity_map,
) = self.__central_kspace_crop(
kspace, masked_kspace, sampling_mask, sensitivity_map
)
sample["target"] = T.root_sum_of_squares(backprojected_kspace, dim="coil")
del sample["kspace"]
sample["masked_kspace"] = masked_kspace
sample["sampling_mask"] = sampling_mask
if sensitivity_map is not None:
sample["sensitivity_map"] = sensitivity_map
return sample
def estimate_sensitivity_map(self, sample):
kspace_data = sample[self.kspace_key]
if kspace_data.shape[0] == 1:
warnings.warn(
f"`Single-coil data, skipping estimation of sensitivity map. "
f"This warning will be displayed only once."
)
return sample
if "sensitivity_map" in sample:
warnings.warn(
f"`sensitivity_map` is given, but will be overwritten. "
f"This warning will be displayed only once."
)
kspace_acs = T.apply_mask(kspace_data, sample["acs_mask"], return_mask=False)
# Get complex-valued data solution
image = self.backward_operator(kspace_acs)
rss_image = T.root_sum_of_squares(image, dim="coil").align_as(image)
# TODO(jt): Safe divide.
sensitivity_mask = torch.where(
rss_image.rename(None) == 0,
torch.tensor([0.0], dtype=rss_image.dtype).to(rss_image.device),
(image / rss_image).rename(None),
).refine_names(*image.names)
return sensitivity_mask
def __call__(self, sample: Dict[str, Any]):
"""
Parameters
----------
sample: dict
Returns
-------
data dictionary
"""
kspace = sample['kspace']
sensitivity_map = sample.get('sensitivity_map', None)
filename = sample['filename']
if 'sampling_mask' in sample and self.mask_func is not None:
warnings.warn(f'`sampling_mask` is passed by the Dataset class, yet `mask_func` is also set. '
f'This will be ignored and the `sampling_mask` will be used instead. '
f'Be aware of this as it can lead to unexpected results. '
f'This warning will be issued only once.')
raise NotImplementedError('This is required when a mask is present,'
' but in this case this should be applied differently!')
seed = None if not self.use_seed else tuple(map(ord, str(filename)))
if np.random.random() >= self.kspace_crop_probability:
kspace, backprojected_kspace, sensitivity_map = self.__random_image_crop(kspace, sensitivity_map)
masked_kspace, sampling_mask = transforms.apply_mask(kspace, self.mask_func, seed)
else:
masked_kspace, sampling_mask = transforms.apply_mask(kspace, self.mask_func, seed)
kspace, masked_kspace, sampling_mask, backprojected_kspace, sensitivity_map = self.__central_kspace_crop(
kspace, masked_kspace, sampling_mask, sensitivity_map)
sample['target'] = transforms.root_sum_of_squares(backprojected_kspace, dim='coil')
del sample['kspace']
sample['masked_kspace'] = masked_kspace
sample['sampling_mask'] = sampling_mask
if sensitivity_map is not None:
sample['sensitivity_map'] = sensitivity_map
return sample
def test_apply_mask_fastmri(shape, center_fractions, accelerations):
mask_func = FastMRIMaskFunc(center_fractions=center_fractions,
accelerations=accelerations,
uniform_range=False)
expected_mask = mask_func(shape[1:], seed=123)
data = create_input(shape, named=True)
output, mask = transforms.apply_mask(data, mask_func, seed=123)
assert output.shape == data.shape
assert mask.shape == expected_mask.shape
assert np.all(expected_mask.numpy() == mask.numpy())
assert np.all(
np.where(mask.numpy() == 0, 0, output.numpy()) == output.numpy())
def __call__(self, sample: Dict[str, Any]):
"""
Parameters
----------
sample: dict
Returns
-------
data dictionary
"""
kspace = sample["kspace"]
# Image-space croppable objects
croppable_images = ["sensitivity_map", "input_image"]
sensitivity_map = sample.get("sensitivity_map", None)
sampling_mask = sample["sampling_mask"]
backprojected_kspace = self.backward_operator(kspace)
# TODO: Also create a kspace-like crop function
if self.crop:
cropped_output = self.crop_func(
[
backprojected_kspace,
*[sample[_] for _ in croppable_images if _ in sample],
],
self.crop,
contiguous=True,
)
backprojected_kspace = cropped_output[0]
for idx, key in enumerate(croppable_images):
sample[key] = cropped_output[1 + idx]
# Compute new k-space for the cropped input_image
kspace = self.forward_operator(backprojected_kspace)
masked_kspace, sampling_mask = T.apply_mask(kspace, sampling_mask)
sample["target"] = T.root_sum_of_squares(backprojected_kspace,
dim="coil")
sample["masked_kspace"] = masked_kspace
sample["sampling_mask"] = sampling_mask
sample["kspace"] = kspace # The cropped kspace
if sensitivity_map is not None:
sample["sensitivity_map"] = sensitivity_map
return sample