diff --git a/docs/source/data.rst b/docs/source/data.rst
index 0de5e0c347..eab4f867af 100644
--- a/docs/source/data.rst
+++ b/docs/source/data.rst
@@ -268,6 +268,12 @@ TestTimeAugmentation
 ~~~~~~~~~~~~~~~~~~~~
 .. autoclass:: monai.data.TestTimeAugmentation
 
+N-Dim Fourier Transform
+~~~~~~~~~~~~~~~~~~~~~~~~~
+.. automodule:: monai.data.fft_utils
+.. autofunction:: monai.data.fft_utils.fftn_centered
+.. autofunction:: monai.data.fft_utils.ifftn_centered
+
 
 Meta Object
 -----------
diff --git a/docs/source/networks.rst b/docs/source/networks.rst
index 2164fe5d1b..a7b6d8cdc0 100644
--- a/docs/source/networks.rst
+++ b/docs/source/networks.rst
@@ -233,6 +233,17 @@ Blocks
 .. autoclass:: DVF2DDF
     :members:
 
+
+N-Dim Fourier Transform
+~~~~~~~~~~~~~~~~~~~~~~~~
+.. automodule:: monai.networks.blocks.fft_utils_t
+.. autofunction:: monai.networks.blocks.fft_utils_t.fftn_centered_t
+.. autofunction:: monai.networks.blocks.fft_utils_t.ifftn_centered_t
+.. autofunction:: monai.networks.blocks.fft_utils_t.roll
+.. autofunction:: monai.networks.blocks.fft_utils_t.roll_1d
+.. autofunction:: monai.networks.blocks.fft_utils_t.fftshift
+.. autofunction:: monai.networks.blocks.fft_utils_t.ifftshift
+
 Layers
 ------
 
diff --git a/monai/data/box_utils.py b/monai/data/box_utils.py
index f0f95dbc3e..47e7b6911d 100644
--- a/monai/data/box_utils.py
+++ b/monai/data/box_utils.py
@@ -621,7 +621,7 @@ def centers_in_boxes(centers: NdarrayOrTensor, boxes: NdarrayOrTensor, eps: floa
         min_center_to_border: np.ndarray = np.stack(center_to_border, axis=1).min(axis=1)
         return min_center_to_border > eps  # array[bool]
 
-    return torch.stack(center_to_border, dim=1).to(COMPUTE_DTYPE).min(dim=1)[0] > eps  # Tensor[bool]
+    return torch.stack(center_to_border, dim=1).to(COMPUTE_DTYPE).min(dim=1)[0] > eps  # type: ignore
 
 
 def boxes_center_distance(
diff --git a/monai/data/fft_utils.py b/monai/data/fft_utils.py
new file mode 100644
index 0000000000..2d38beed5e
--- /dev/null
+++ b/monai/data/fft_utils.py
@@ -0,0 +1,94 @@
+# Copyright (c) MONAI Consortium
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#     http://www.apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import torch
+
+from monai.config.type_definitions import NdarrayOrTensor
+from monai.networks.blocks.fft_utils_t import fftn_centered_t, ifftn_centered_t
+from monai.utils.type_conversion import convert_data_type, convert_to_dst_type
+
+
+def ifftn_centered(ksp: NdarrayOrTensor, spatial_dims: int, is_complex: bool = True) -> NdarrayOrTensor:
+    """
+    Pytorch-based ifft for spatial_dims-dim signals. "centered" means this function automatically takes care
+    of the required ifft and fft shifts. This function calls monai.metworks.blocks.fft_utils_t.ifftn_centered_t.
+    This is equivalent to do fft in numpy based on numpy.fft.ifftn, numpy.fft.fftshift, and numpy.fft.ifftshift
+
+    Args:
+        ksp: k-space data that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        spatial_dims: number of spatial dimensions (e.g., is 2 for an image, and is 3 for a volume)
+        is_complex: if True, then the last dimension of the input ksp is expected to be 2 (representing real and imaginary channels)
+
+    Returns:
+        "out" which is the output image (inverse fourier of ksp)
+
+    Example:
+
+        .. code-block:: python
+
+            import torch
+            ksp = torch.ones(1,3,3,2) # the last dim belongs to real/imaginary parts
+            # output1 and output2 will be identical
+            output1 = torch.fft.ifftn(torch.view_as_complex(torch.fft.ifftshift(ksp,dim=(-3,-2))), dim=(-2,-1), norm="ortho")
+            output1 = torch.fft.fftshift( torch.view_as_real(output1), dim=(-3,-2) )
+
+            output2 = ifftn_centered(ksp, spatial_dims=2, is_complex=True)
+    """
+    # handle numpy format
+    ksp_t, *_ = convert_data_type(ksp, torch.Tensor)
+
+    # compute ifftn
+    out_t = ifftn_centered_t(ksp_t, spatial_dims=spatial_dims, is_complex=is_complex)
+
+    # handle numpy format
+    out, *_ = convert_to_dst_type(src=out_t, dst=ksp)
+    return out
+
+
+def fftn_centered(im: NdarrayOrTensor, spatial_dims: int, is_complex: bool = True) -> NdarrayOrTensor:
+    """
+    Pytorch-based fft for spatial_dims-dim signals. "centered" means this function automatically takes care
+    of the required ifft and fft shifts. This function calls monai.metworks.blocks.fft_utils_t.fftn_centered_t.
+    This is equivalent to do ifft in numpy based on numpy.fft.fftn, numpy.fft.fftshift, and numpy.fft.ifftshift
+
+    Args:
+        im: image that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        spatial_dims: number of spatial dimensions (e.g., is 2 for an image, and is 3 for a volume)
+        is_complex: if True, then the last dimension of the input im is expected to be 2 (representing real and imaginary channels)
+
+    Returns:
+        "out" which is the output kspace (fourier of im)
+
+    Example:
+
+        .. code-block:: python
+
+            import torch
+            im = torch.ones(1,3,3,2) # the last dim belongs to real/imaginary parts
+            # output1 and output2 will be identical
+            output1 = torch.fft.fftn(torch.view_as_complex(torch.fft.ifftshift(im,dim=(-3,-2))), dim=(-2,-1), norm="ortho")
+            output1 = torch.fft.fftshift( torch.view_as_real(output1), dim=(-3,-2) )
+
+            output2 = fftn_centered(im, spatial_dims=2, is_complex=True)
+    """
+    # handle numpy format
+    im_t, *_ = convert_data_type(im, torch.Tensor)
+
+    # compute ifftn
+    out_t = fftn_centered_t(im_t, spatial_dims=spatial_dims, is_complex=is_complex)
+
+    # handle numpy format
+    out, *_ = convert_to_dst_type(src=out_t, dst=im)
+    return out
diff --git a/monai/networks/blocks/feature_pyramid_network.py b/monai/networks/blocks/feature_pyramid_network.py
index 2f7b903a19..2373cfc099 100644
--- a/monai/networks/blocks/feature_pyramid_network.py
+++ b/monai/networks/blocks/feature_pyramid_network.py
@@ -193,7 +193,7 @@ def __init__(
         conv_type_: Type[nn.Module] = Conv[Conv.CONV, spatial_dims]
         for m in self.modules():
             if isinstance(m, conv_type_):
-                nn.init.kaiming_uniform_(m.weight, a=1)
+                nn.init.kaiming_uniform_(m.weight, a=1)  # type: ignore
                 nn.init.constant_(m.bias, 0.0)  # type: ignore
 
         if extra_blocks is not None:
diff --git a/monai/networks/blocks/fft_utils_t.py b/monai/networks/blocks/fft_utils_t.py
new file mode 100644
index 0000000000..0d6b99d7e1
--- /dev/null
+++ b/monai/networks/blocks/fft_utils_t.py
@@ -0,0 +1,232 @@
+# Copyright (c) MONAI Consortium
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#     http://www.apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import Optional, Sequence
+
+import torch
+from torch import Tensor
+
+from monai.utils.type_conversion import convert_data_type
+
+
+def roll_1d(x: Tensor, shift: int, shift_dim: int) -> Tensor:
+    """
+    Similar to roll but for only one dim.
+
+    Args:
+        x: input data (k-space or image) that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        shift: the amount of shift along each of shift_dims dimension
+        shift_dim: the dimension over which the shift is applied
+
+    Returns:
+        1d-shifted version of x
+
+    Note:
+        This function is called when fftshift and ifftshift are not available in the running pytorch version
+    """
+    shift = shift % x.size(shift_dim)
+    if shift == 0:
+        return x
+
+    left = x.narrow(shift_dim, 0, x.size(shift_dim) - shift)
+    right = x.narrow(shift_dim, x.size(shift_dim) - shift, shift)
+
+    return torch.cat((right, left), dim=shift_dim)
+
+
+def roll(x: Tensor, shift: Sequence[int], shift_dims: Sequence[int]) -> Tensor:
+    """
+    Similar to np.roll but applies to PyTorch Tensors
+
+    Args:
+        x: input data (k-space or image) that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        shift: the amount of shift along each of shift_dims dimensions
+        shift_dims: dimensions over which the shift is applied
+
+    Returns:
+        shifted version of x
+
+    Note:
+        This function is called when fftshift and ifftshift are not available in the running pytorch version
+    """
+    if len(shift) != len(shift_dims):
+        raise ValueError(f"len(shift) != len(shift_dims), got f{len(shift)} and f{len(shift_dims)}.")
+    for s, d in zip(shift, shift_dims):
+        x = roll_1d(x, s, d)
+    return x
+
+
+def fftshift(x: Tensor, shift_dims: Optional[Sequence[int]] = None) -> Tensor:
+    """
+    Similar to np.fft.fftshift but applies to PyTorch Tensors
+
+    Args:
+        x: input data (k-space or image) that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        shift_dims: dimensions over which the shift is applied
+
+    Returns:
+        fft-shifted version of x
+
+    Note:
+        This function is called when fftshift is not available in the running pytorch version
+    """
+    if shift_dims is None:
+        # for torch.jit.script based on the fastmri repository
+        shift_dims = [0] * (x.dim())
+        for i in range(1, x.dim()):
+            shift_dims[i] = i
+    shift = [0] * len(shift_dims)
+    for i, dim_num in enumerate(shift_dims):
+        shift[i] = x.shape[dim_num] // 2
+    return roll(x, shift, shift_dims)
+
+
+def ifftshift(x: Tensor, shift_dims: Optional[Sequence[int]] = None) -> Tensor:
+    """
+    Similar to np.fft.ifftshift but applies to PyTorch Tensors
+
+    Args:
+        x: input data (k-space or image) that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        shift_dims: dimensions over which the shift is applied
+
+    Returns:
+        ifft-shifted version of x
+
+    Note:
+        This function is called when ifftshift is not available in the running pytorch version
+    """
+    if shift_dims is None:
+        # for torch.jit.script based on the fastmri repository
+        shift_dims = [0] * (x.dim())
+        for i in range(1, x.dim()):
+            shift_dims[i] = i
+    shift = [0] * len(shift_dims)
+    for i, dim_num in enumerate(shift_dims):
+        shift[i] = (x.shape[dim_num] + 1) // 2
+    return roll(x, shift, shift_dims)
+
+
+def ifftn_centered_t(ksp: Tensor, spatial_dims: int, is_complex: bool = True) -> Tensor:
+    """
+    Pytorch-based ifft for spatial_dims-dim signals. "centered" means this function automatically takes care
+    of the required ifft and fft shifts.
+    This is equivalent to do fft in numpy based on numpy.fft.ifftn, numpy.fft.fftshift, and numpy.fft.ifftshift
+
+    Args:
+        ksp: k-space data that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        spatial_dims: number of spatial dimensions (e.g., is 2 for an image, and is 3 for a volume)
+        is_complex: if True, then the last dimension of the input ksp is expected to be 2 (representing real and imaginary channels)
+
+    Returns:
+        "out" which is the output image (inverse fourier of ksp)
+
+    Example:
+
+        .. code-block:: python
+
+            import torch
+            ksp = torch.ones(1,3,3,2) # the last dim belongs to real/imaginary parts
+            # output1 and output2 will be identical
+            output1 = torch.fft.ifftn(torch.view_as_complex(torch.fft.ifftshift(ksp,dim=(-3,-2))), dim=(-2,-1), norm="ortho")
+            output1 = torch.fft.fftshift( torch.view_as_real(output1), dim=(-3,-2) )
+
+            output2 = ifftn_centered(ksp, spatial_dims=2, is_complex=True)
+    """
+    # define spatial dims to perform ifftshift, fftshift, and ifft
+    shift = tuple(range(-spatial_dims, 0))
+    if is_complex:
+        if ksp.shape[-1] != 2:
+            raise ValueError(f"ksp.shape[-1] is not 2 ({ksp.shape[-1]}).")
+        shift = tuple(range(-spatial_dims - 1, -1))
+    dims = tuple(range(-spatial_dims, 0))
+
+    # apply ifft
+    if hasattr(torch.fft, "ifftshift"):  # ifftshift was added in pytorch 1.8
+        x = torch.fft.ifftshift(ksp, dim=shift)
+    else:
+        x = ifftshift(ksp, shift)
+
+    if is_complex:
+        x = torch.view_as_real(torch.fft.ifftn(torch.view_as_complex(x), dim=dims, norm="ortho"))
+    else:
+        x = torch.view_as_real(torch.fft.ifftn(x, dim=dims, norm="ortho"))
+
+    if hasattr(torch.fft, "fftshift"):
+        out = convert_data_type(torch.fft.fftshift(x, dim=shift), torch.Tensor)[0]
+    else:
+        out = convert_data_type(fftshift(x, shift), torch.Tensor)[0]
+
+    return out
+
+
+def fftn_centered_t(im: Tensor, spatial_dims: int, is_complex: bool = True) -> Tensor:
+    """
+    Pytorch-based fft for spatial_dims-dim signals. "centered" means this function automatically takes care
+    of the required ifft and fft shifts.
+    This is equivalent to do ifft in numpy based on numpy.fft.fftn, numpy.fft.fftshift, and numpy.fft.ifftshift
+
+    Args:
+        im: image that can be
+            1) real-valued: the shape is (C,H,W) for 2D spatial inputs and (C,H,W,D) for 3D, or
+            2) complex-valued: the shape is (C,H,W,2) for 2D spatial data and (C,H,W,D,2) for 3D. C is the number of channels.
+        spatial_dims: number of spatial dimensions (e.g., is 2 for an image, and is 3 for a volume)
+        is_complex: if True, then the last dimension of the input im is expected to be 2 (representing real and imaginary channels)
+
+    Returns:
+        "out" which is the output kspace (fourier of im)
+
+    Example:
+
+        .. code-block:: python
+
+            import torch
+            im = torch.ones(1,3,3,2) # the last dim belongs to real/imaginary parts
+            # output1 and output2 will be identical
+            output1 = torch.fft.fftn(torch.view_as_complex(torch.fft.ifftshift(im,dim=(-3,-2))), dim=(-2,-1), norm="ortho")
+            output1 = torch.fft.fftshift( torch.view_as_real(output1), dim=(-3,-2) )
+
+            output2 = fftn_centered(im, spatial_dims=2, is_complex=True)
+    """
+    # define spatial dims to perform ifftshift, fftshift, and fft
+    shift = tuple(range(-spatial_dims, 0))
+    if is_complex:
+        if im.shape[-1] != 2:
+            raise ValueError(f"img.shape[-1] is not 2 ({im.shape[-1]}).")
+        shift = tuple(range(-spatial_dims - 1, -1))
+    dims = tuple(range(-spatial_dims, 0))
+
+    # apply fft
+    if hasattr(torch.fft, "ifftshift"):  # ifftshift was added in pytorch 1.8
+        x = torch.fft.ifftshift(im, dim=shift)
+    else:
+        x = ifftshift(im, shift)
+
+    if is_complex:
+        x = torch.view_as_real(torch.fft.fftn(torch.view_as_complex(x), dim=dims, norm="ortho"))
+    else:
+        x = torch.view_as_real(torch.fft.fftn(x, dim=dims, norm="ortho"))
+
+    if hasattr(torch.fft, "fftshift"):
+        out = convert_data_type(torch.fft.fftshift(x, dim=shift), torch.Tensor)[0]
+    else:
+        out = convert_data_type(fftshift(x, shift), torch.Tensor)[0]
+
+    return out
diff --git a/monai/transforms/utility/array.py b/monai/transforms/utility/array.py
index 0d5bafb026..d50505fe84 100644
--- a/monai/transforms/utility/array.py
+++ b/monai/transforms/utility/array.py
@@ -313,10 +313,10 @@ def __call__(self, img: NdarrayOrTensor) -> List[NdarrayOrTensor]:
         if isinstance(img, torch.Tensor):
             outputs = list(torch.split(img, 1, self.dim))
         else:
-            outputs = np.split(img, n_out, self.dim)
+            outputs = np.split(img, n_out, self.dim)  # type: ignore
         if not self.keepdim:
             outputs = [o.squeeze(self.dim) for o in outputs]
-        return outputs
+        return outputs  # type: ignore
 
 
 @deprecated(since="0.8", msg_suffix="please use `SplitDim` instead.")
diff --git a/tests/test_fft_utils.py b/tests/test_fft_utils.py
new file mode 100644
index 0000000000..d5e3a22eaa
--- /dev/null
+++ b/tests/test_fft_utils.py
@@ -0,0 +1,63 @@
+# Copyright (c) MONAI Consortium
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#     http://www.apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+from parameterized import parameterized
+
+from monai.data.fft_utils import fftn_centered, ifftn_centered
+from tests.utils import TEST_NDARRAYS, assert_allclose
+
+#
+im = [[[1.0, 1.0, 1.0], [1.0, 1.0, 1.0], [1.0, 1.0, 1.0]]]
+res = [
+    [[[0.0, 0.0], [0.0, 3.0], [0.0, 0.0]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]]
+]
+TESTS = []
+for p in TEST_NDARRAYS:
+    TESTS.append((p(im), p(res)))
+
+#
+TESTS_CONSISTENCY = []
+for p in TEST_NDARRAYS:
+    TESTS_CONSISTENCY.append(p(im))
+
+#
+im_complex = [
+    [[[1.0, 1.0], [1.0, 1.0], [1.0, 1.0]], [[1.0, 1.0], [1.0, 1.0], [1.0, 1.0]], [[1.0, 1.0], [1.0, 1.0], [1.0, 1.0]]]
+]
+TESTS_CONSISTENCY_COMPLEX = []
+for p in TEST_NDARRAYS:
+    TESTS_CONSISTENCY_COMPLEX.append(p(im_complex))
+
+
+class TestFFT(unittest.TestCase):
+    @parameterized.expand(TESTS)
+    def test(self, test_data, res_data):
+        result = fftn_centered(test_data, spatial_dims=2, is_complex=False)
+        assert_allclose(result, res_data, type_test=True)
+
+    @parameterized.expand(TESTS_CONSISTENCY)
+    def test_consistency(self, test_data):
+        result = fftn_centered(test_data, spatial_dims=2, is_complex=False)
+        result = ifftn_centered(result, spatial_dims=2, is_complex=True)
+        result = (result[..., 0] ** 2 + result[..., 1] ** 2) ** 0.5
+        assert_allclose(result, test_data, type_test=False)
+
+    @parameterized.expand(TESTS_CONSISTENCY_COMPLEX)
+    def test_consistency_complex(self, test_data):
+        result = fftn_centered(test_data, spatial_dims=2)
+        result = ifftn_centered(result, spatial_dims=2)
+        assert_allclose(result, test_data, type_test=False)
+
+
+if __name__ == "__main__":
+    unittest.main()