diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..33dd462
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,12 @@
+*.py[co]
+__pycache__/
+
+# build
+/niftypet/ml/_dist_ver.py
+/build/
+/dist/
+/*.egg*/
+
+/.coverage*
+/coverage.xml
+/.pytest_cache/
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..37a25c7
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,45 @@
+default_language_version:
+  python: python3
+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v3.4.0
+  hooks:
+  - id: check-added-large-files
+  - id: check-case-conflict
+  - id: check-docstring-first
+  - id: check-executables-have-shebangs
+  - id: check-toml
+  - id: check-merge-conflict
+  - id: check-yaml
+  - id: debug-statements
+  - id: end-of-file-fixer
+  - id: mixed-line-ending
+  - id: sort-simple-yaml
+  - id: trailing-whitespace
+- repo: local
+  hooks:
+  - id: todo
+    name: Check TODO
+    language: pygrep
+    entry: TODO
+    types: [text]
+    exclude: ^(.pre-commit-config.yaml|.github/workflows/test.yml)$
+    args: [-i]
+- repo: https://gitlab.com/pycqa/flake8
+  rev: 3.8.4
+  hooks:
+  - id: flake8
+    additional_dependencies:
+    - flake8-bugbear
+    - flake8-comprehensions
+    - flake8-debugger
+    - flake8-string-format
+- repo: https://github.com/google/yapf
+  rev: 6db9374
+  hooks:
+  - id: yapf
+    args: [-i]
+- repo: https://github.com/PyCQA/isort
+  rev: 5.7.0
+  hooks:
+  - id: isort
diff --git a/LICENCE b/LICENCE
new file mode 100644
index 0000000..bc8942f
--- /dev/null
+++ b/LICENCE
@@ -0,0 +1,367 @@
+Mozilla Public License Version 2.0
+==================================
+
+1. Definitions
+--------------
+
+1.1. "Contributor"
+    means each individual or legal entity that creates, contributes to
+    the creation of, or owns Covered Software.
+
+1.2. "Contributor Version"
+    means the combination of the Contributions of others (if any) used
+    by a Contributor and that particular Contributor's Contribution.
+
+1.3. "Contribution"
+    means Covered Software of a particular Contributor.
+
+1.4. "Covered Software"
+    means Source Code Form to which the initial Contributor has attached
+    the notice in Exhibit A, the Executable Form of such Source Code
+    Form, and Modifications of such Source Code Form, in each case
+    including portions thereof.
+
+1.5. "Incompatible With Secondary Licenses"
+    means
+
+    (a) that the initial Contributor has attached the notice described
+        in Exhibit B to the Covered Software; or
+
+    (b) that the Covered Software was made available under the terms of
+        version 1.1 or earlier of the License, but not also under the
+        terms of a Secondary License.
+
+1.6. "Executable Form"
+    means any form of the work other than Source Code Form.
+
+1.7. "Larger Work"
+    means a work that combines Covered Software with other material, in
+    a separate file or files, that is not Covered Software.
+
+1.8. "License"
+    means this document.
+
+1.9. "Licensable"
+    means having the right to grant, to the maximum extent possible,
+    whether at the time of the initial grant or subsequently, any and
+    all of the rights conveyed by this License.
+
+1.10. "Modifications"
+    means any of the following:
+
+    (a) any file in Source Code Form that results from an addition to,
+        deletion from, or modification of the contents of Covered
+        Software; or
+
+    (b) any new file in Source Code Form that contains any Covered
+        Software.
+
+1.11. "Patent Claims" of a Contributor
+    means any patent claim(s), including without limitation, method,
+    process, and apparatus claims, in any patent Licensable by such
+    Contributor that would be infringed, but for the grant of the
+    License, by the making, using, selling, offering for sale, having
+    made, import, or transfer of either its Contributions or its
+    Contributor Version.
+
+1.12. "Secondary License"
+    means either the GNU General Public License, Version 2.0, the GNU
+    Lesser General Public License, Version 2.1, the GNU Affero General
+    Public License, Version 3.0, or any later versions of those
+    licenses.
+
+1.13. "Source Code Form"
+    means the form of the work preferred for making modifications.
+
+1.14. "You" (or "Your")
+    means an individual or a legal entity exercising rights under this
+    License. For legal entities, "You" includes any entity that
+    controls, is controlled by, or is under common control with You. For
+    purposes of this definition, "control" means (a) the power, direct
+    or indirect, to cause the direction or management of such entity,
+    whether by contract or otherwise, or (b) ownership of more than
+    fifty percent (50%) of the outstanding shares or beneficial
+    ownership of such entity.
+
+2. License Grants and Conditions
+--------------------------------
+
+2.1. Grants
+
+Each Contributor hereby grants You a world-wide, royalty-free,
+non-exclusive license:
+
+(a) under intellectual property rights (other than patent or trademark)
+    Licensable by such Contributor to use, reproduce, make available,
+    modify, display, perform, distribute, and otherwise exploit its
+    Contributions, either on an unmodified basis, with Modifications, or
+    as part of a Larger Work; and
+
+(b) under Patent Claims of such Contributor to make, use, sell, offer
+    for sale, have made, import, and otherwise transfer either its
+    Contributions or its Contributor Version.
+
+2.2. Effective Date
+
+The licenses granted in Section 2.1 with respect to any Contribution
+become effective for each Contribution on the date the Contributor first
+distributes such Contribution.
+
+2.3. Limitations on Grant Scope
+
+The licenses granted in this Section 2 are the only rights granted under
+this License. No additional rights or licenses will be implied from the
+distribution or licensing of Covered Software under this License.
+Notwithstanding Section 2.1(b) above, no patent license is granted by a
+Contributor:
+
+(a) for any code that a Contributor has removed from Covered Software;
+    or
+
+(b) for infringements caused by: (i) Your and any other third party's
+    modifications of Covered Software, or (ii) the combination of its
+    Contributions with other software (except as part of its Contributor
+    Version); or
+
+(c) under Patent Claims infringed by Covered Software in the absence of
+    its Contributions.
+
+This License does not grant any rights in the trademarks, service marks,
+or logos of any Contributor (except as may be necessary to comply with
+the notice requirements in Section 3.4).
+
+2.4. Subsequent Licenses
+
+No Contributor makes additional grants as a result of Your choice to
+distribute the Covered Software under a subsequent version of this
+License (see Section 10.2) or under the terms of a Secondary License (if
+permitted under the terms of Section 3.3).
+
+2.5. Representation
+
+Each Contributor represents that the Contributor believes its
+Contributions are its original creation(s) or it has sufficient rights
+to grant the rights to its Contributions conveyed by this License.
+
+2.6. Fair Use
+
+This License is not intended to limit any rights You have under
+applicable copyright doctrines of fair use, fair dealing, or other
+equivalents.
+
+2.7. Conditions
+
+Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
+in Section 2.1.
+
+3. Responsibilities
+-------------------
+
+3.1. Distribution of Source Form
+
+All distribution of Covered Software in Source Code Form, including any
+Modifications that You create or to which You contribute, must be under
+the terms of this License. You must inform recipients that the Source
+Code Form of the Covered Software is governed by the terms of this
+License, and how they can obtain a copy of this License. You may not
+attempt to alter or restrict the recipients' rights in the Source Code
+Form.
+
+3.2. Distribution of Executable Form
+
+If You distribute Covered Software in Executable Form then:
+
+(a) such Covered Software must also be made available in Source Code
+    Form, as described in Section 3.1, and You must inform recipients of
+    the Executable Form how they can obtain a copy of such Source Code
+    Form by reasonable means in a timely manner, at a charge no more
+    than the cost of distribution to the recipient; and
+
+(b) You may distribute such Executable Form under the terms of this
+    License, or sublicense it under different terms, provided that the
+    license for the Executable Form does not attempt to limit or alter
+    the recipients' rights in the Source Code Form under this License.
+
+3.3. Distribution of a Larger Work
+
+You may create and distribute a Larger Work under terms of Your choice,
+provided that You also comply with the requirements of this License for
+the Covered Software. If the Larger Work is a combination of Covered
+Software with a work governed by one or more Secondary Licenses, and the
+Covered Software is not Incompatible With Secondary Licenses, this
+License permits You to additionally distribute such Covered Software
+under the terms of such Secondary License(s), so that the recipient of
+the Larger Work may, at their option, further distribute the Covered
+Software under the terms of either this License or such Secondary
+License(s).
+
+3.4. Notices
+
+You may not remove or alter the substance of any license notices
+(including copyright notices, patent notices, disclaimers of warranty,
+or limitations of liability) contained within the Source Code Form of
+the Covered Software, except that You may alter any license notices to
+the extent required to remedy known factual inaccuracies.
+
+3.5. Application of Additional Terms
+
+You may choose to offer, and to charge a fee for, warranty, support,
+indemnity or liability obligations to one or more recipients of Covered
+Software. However, You may do so only on Your own behalf, and not on
+behalf of any Contributor. You must make it absolutely clear that any
+such warranty, support, indemnity, or liability obligation is offered by
+You alone, and You hereby agree to indemnify every Contributor for any
+liability incurred by such Contributor as a result of warranty, support,
+indemnity or liability terms You offer. You may include additional
+disclaimers of warranty and limitations of liability specific to any
+jurisdiction.
+
+4. Inability to Comply Due to Statute or Regulation
+---------------------------------------------------
+
+If it is impossible for You to comply with any of the terms of this
+License with respect to some or all of the Covered Software due to
+statute, judicial order, or regulation then You must: (a) comply with
+the terms of this License to the maximum extent possible; and (b)
+describe the limitations and the code they affect. Such description must
+be placed in a text file included with all distributions of the Covered
+Software under this License. Except to the extent prohibited by statute
+or regulation, such description must be sufficiently detailed for a
+recipient of ordinary skill to be able to understand it.
+
+5. Termination
+--------------
+
+5.1. The rights granted under this License will terminate automatically
+if You fail to comply with any of its terms. However, if You become
+compliant, then the rights granted under this License from a particular
+Contributor are reinstated (a) provisionally, unless and until such
+Contributor explicitly and finally terminates Your grants, and (b) on an
+ongoing basis, if such Contributor fails to notify You of the
+non-compliance by some reasonable means prior to 60 days after You have
+come back into compliance. Moreover, Your grants from a particular
+Contributor are reinstated on an ongoing basis if such Contributor
+notifies You of the non-compliance by some reasonable means, this is the
+first time You have received notice of non-compliance with this License
+from such Contributor, and You become compliant prior to 30 days after
+Your receipt of the notice.
+
+5.2. If You initiate litigation against any entity by asserting a patent
+infringement claim (excluding declaratory judgment actions,
+counter-claims, and cross-claims) alleging that a Contributor Version
+directly or indirectly infringes any patent, then the rights granted to
+You by any and all Contributors for the Covered Software under Section
+2.1 of this License shall terminate.
+
+5.3. In the event of termination under Sections 5.1 or 5.2 above, all
+end user license agreements (excluding distributors and resellers) which
+have been validly granted by You or Your distributors under this License
+prior to termination shall survive termination.
+
+************************************************************************
+*                                                                      *
+*  6. Disclaimer of Warranty                                           *
+*  -------------------------                                           *
+*                                                                      *
+*  Covered Software is provided under this License on an "as is"       *
+*  basis, without warranty of any kind, either expressed, implied, or  *
+*  statutory, including, without limitation, warranties that the       *
+*  Covered Software is free of defects, merchantable, fit for a        *
+*  particular purpose or non-infringing. The entire risk as to the     *
+*  quality and performance of the Covered Software is with You.        *
+*  Should any Covered Software prove defective in any respect, You     *
+*  (not any Contributor) assume the cost of any necessary servicing,   *
+*  repair, or correction. This disclaimer of warranty constitutes an   *
+*  essential part of this License. No use of any Covered Software is   *
+*  authorized under this License except under this disclaimer.         *
+*                                                                      *
+************************************************************************
+
+************************************************************************
+*                                                                      *
+*  7. Limitation of Liability                                          *
+*  --------------------------                                          *
+*                                                                      *
+*  Under no circumstances and under no legal theory, whether tort      *
+*  (including negligence), contract, or otherwise, shall any           *
+*  Contributor, or anyone who distributes Covered Software as          *
+*  permitted above, be liable to You for any direct, indirect,         *
+*  special, incidental, or consequential damages of any character      *
+*  including, without limitation, damages for lost profits, loss of    *
+*  goodwill, work stoppage, computer failure or malfunction, or any    *
+*  and all other commercial damages or losses, even if such party      *
+*  shall have been informed of the possibility of such damages. This   *
+*  limitation of liability shall not apply to liability for death or   *
+*  personal injury resulting from such party's negligence to the       *
+*  extent applicable law prohibits such limitation. Some               *
+*  jurisdictions do not allow the exclusion or limitation of           *
+*  incidental or consequential damages, so this exclusion and          *
+*  limitation may not apply to You.                                    *
+*                                                                      *
+************************************************************************
+
+8. Litigation
+-------------
+
+Any litigation relating to this License may be brought only in the
+courts of a jurisdiction where the defendant maintains its principal
+place of business and such litigation shall be governed by laws of that
+jurisdiction, without reference to its conflict-of-law provisions.
+Nothing in this Section shall prevent a party's ability to bring
+cross-claims or counter-claims.
+
+9. Miscellaneous
+----------------
+
+This License represents the complete agreement concerning the subject
+matter hereof. If any provision of this License is held to be
+unenforceable, such provision shall be reformed only to the extent
+necessary to make it enforceable. Any law or regulation which provides
+that the language of a contract shall be construed against the drafter
+shall not be used to construe this License against a Contributor.
+
+10. Versions of the License
+---------------------------
+
+10.1. New Versions
+
+Mozilla Foundation is the license steward. Except as provided in Section
+10.3, no one other than the license steward has the right to modify or
+publish new versions of this License. Each version will be given a
+distinguishing version number.
+
+10.2. Effect of New Versions
+
+You may distribute the Covered Software under the terms of the version
+of the License under which You originally received the Covered Software,
+or under the terms of any subsequent version published by the license
+steward.
+
+10.3. Modified Versions
+
+If you create software not governed by this License, and you want to
+create a new license for such software, you may create and use a
+modified version of this License if you rename the license and remove
+any references to the name of the license steward (except to note that
+such modified license differs from this License).
+
+10.4. Distributing Source Code Form that is Incompatible With Secondary
+Licenses
+
+If You choose to distribute Source Code Form that is Incompatible With
+Secondary Licenses under the terms of this version of the License, the
+notice described in Exhibit B of this License must be attached.
+
+Exhibit A - Source Code Form License Notice
+-------------------------------------------
+
+  This Source Code Form is subject to the terms of the Mozilla Public
+  License, v. 2.0. If a copy of the MPL was not distributed with this
+  file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular
+file, then You may include the notice in a location (such as a LICENSE
+file in a relevant directory) where a recipient would be likely to look
+for such a notice.
+
+You may add additional accurate notices of copyright ownership.
diff --git a/README.rst b/README.rst
new file mode 100644
index 0000000..704807d
--- /dev/null
+++ b/README.rst
@@ -0,0 +1,21 @@
+PET-MR Machine Learning
+=======================
+
+|Version| |Py-Versions| |Licence| |Tests|
+
+
+Licence
+~~~~~~~
+
+|Licence|
+
+Copyright 2021
+
+.. |Licence| image:: https://img.shields.io/pypi/l/niftyml.svg?label=licence
+   :target: https://github.com/NiftyPET/niftyml/blob/master/LICENCE
+.. |Tests| image:: https://img.shields.io/github/workflow/status/NiftyPET/niftyml/Test?logo=GitHub
+   :target: https://github.com/NiftyPET/niftyml/actions
+.. |Version| image:: https://img.shields.io/pypi/v/niftyml.svg?logo=python&logoColor=white
+   :target: https://github.com/NiftyPET/niftyml/releases
+.. |Py-Versions| image:: https://img.shields.io/pypi/pyversions/niftyml.svg?logo=python&logoColor=white
+   :target: https://pypi.org/project/niftyml
diff --git a/niftypet/__init__.py b/niftypet/__init__.py
new file mode 100644
index 0000000..8db66d3
--- /dev/null
+++ b/niftypet/__init__.py
@@ -0,0 +1 @@
+__path__ = __import__("pkgutil").extend_path(__path__, __name__)
diff --git a/niftypet/ml/__init__.py b/niftypet/ml/__init__.py
new file mode 100644
index 0000000..6aa4af7
--- /dev/null
+++ b/niftypet/ml/__init__.py
@@ -0,0 +1,18 @@
+"""
+Neuro-image Machine Learning.
+"""
+__author__ = "Casper da Costa-Luis <imaging@cdcl.ml>"
+__date__ = "2021"
+# version detector. Precedence: installed dist, git, 'UNKNOWN'
+try:
+    from ._dist_ver import __version__
+except ImportError:
+    try:
+        from setuptools_scm import get_version
+
+        __version__ = get_version(root="../..", relative_to=__file__)
+    except (ImportError, LookupError):
+        __version__ = "UNKNOWN"
+
+from .layers import *  # NOQA, yapf: disable
+from .models import *  # NOQA, yapf: disable
diff --git a/niftypet/ml/layers.py b/niftypet/ml/layers.py
new file mode 100644
index 0000000..06e80eb
--- /dev/null
+++ b/niftypet/ml/layers.py
@@ -0,0 +1,135 @@
+import logging
+from collections import Iterable
+
+from tensorflow import keras
+from tensorflow import math as tfm
+
+log = logging.getLogger(__name__)
+
+
+def nrmse(y_true, y_pred):
+    return tfm.sqrt(
+        tfm.reduce_mean(tfm.squared_difference(y_true, y_pred)) / tfm.reduce_mean(y_true**2))
+
+
+class Norm(keras.layers.Layer):
+    """per-channel mean and std normalisation"""
+    def __init__(self, mean=False, std=True, eps=1e-6, batch=False, **kwargs):
+        self.mean = mean
+        self.std = std
+        self.eps = eps
+        self.batch = batch
+        super(Norm, self).__init__(**kwargs)
+
+    def get_config(self):
+        config = super(Norm, self).get_config().copy()
+        config.update(mean=self.mean)
+        config.update(std=self.std)
+        config.update(eps=self.eps)
+        config.update(batch=self.batch)
+        return config
+
+    def compute_output_shape(self, input_shape):
+        return input_shape
+
+    def call(self, x):
+        input_shape = x.shape.as_list()
+        axis = tuple(range(0 if self.batch else 1, len(input_shape) if input_shape else 4))
+        if self.mean:
+            x = x - tfm.reduce_mean(x, axis=axis, keepdims=True)
+            if self.std:
+                std = tfm.sqrt(tfm.reduce_mean(tfm.square(x), axis=axis, keepdims=True))
+        elif self.std:
+            std = tfm.reduce_std(x, axis=axis, keepdims=True)
+        return x / ((self.eps + std) if self.eps else std) if self.std else x
+
+
+class LocalityAdaptive(keras.layers.Layer):
+    """
+    Locality Adaptive[1]: per-ROI convolution.
+
+    >>> x = keras.backend.variable(np.arange(3*64*32*2).reshape(3,64,32,2))
+    >>> lALayer = LocalityAdaptive(roi_size=32)
+    >>> out = lALayer(x)
+    >>> lALayer.set_weights([np.array([[0.5, 0.5], [0.9, 0.1]])[:, None, :, None]])
+    >>> out = lALayer(x)
+    >>> assert out.shape[:-1] == x.shape[:-1]
+    >>> assert keras.backend.all(sum(x[0, 1, 1] * [0.5, 0.5]) - out[0, 1, 1] < 1e-6)
+    >>> assert keras.backend.all(sum(x[0, -1, -1] * [0.9, 0.1]) - out[0, -1, -1] < 1e-6)
+
+    [1] Wang et al. 2019 TMI 38(6) 1328-1339
+    "3D Auto-Context-Based Locality Adaptive Multi-Modality GANs for PET Synthesis"
+    """
+    def __init__(self, filters=1, roi_size=32, **kwargs):
+        assert filters == 1, NotImplementedError
+        self.filters = filters
+        self.roi_size = roi_size
+        super(LocalityAdaptive, self).__init__(**kwargs)
+        # assert self.data_format and self.data_format != "channels_first"
+
+    def get_config(self):
+        config = super(LocalityAdaptive, self).get_config().copy()
+        config.update(filters=self.filters)
+        config.update(roi_size=self.roi_size)
+        return config
+
+    def build(self, input_shape):
+        in_dims = input_shape[1:-1]
+        roi = self.roi_size
+        if not isinstance(roi, Iterable):
+            roi = (roi,) * len(in_dims)
+
+        in_ch = input_shape[-1]
+        self.kernel = self.add_weight(
+            name="kernel",
+            shape=tuple((i+j-1) // j for i, j in zip(in_dims, roi)) + (in_ch, self.filters),
+            initializer=keras.initializers.constant(1.0 / in_ch),
+            trainable=True,
+        )
+        super(LocalityAdaptive, self).build(input_shape)
+
+    @staticmethod
+    def _call_helper(x, knl, roi, axis=0):
+        """
+        Recursive helper using concatenation.
+        Required since tensors cannot be assinged to.
+
+        x  : shape [N, x0, ..., xn-1, C]
+        knl  : shape [s0, ..., sn-1, C, filters]: weights
+          Note that there are `s0*...*sn` patches,
+          each with its own kernel of shape [1, C, filters]
+        roi  : shape [r0, ..., rn-1]: patch shape
+        axis  : in range(n), which axis to expand/concatenate over
+        """
+        assert axis >= 0
+        # s0, ..., sn-1, C, filters
+        shp_knl = knl.shape.as_list()
+        padding = (slice(0, None),) * axis
+        log.debug("knl.shape:{}, axis:{}".format(shp_knl, axis))
+        KB = keras.backend
+        if axis == len(shp_knl) - 3:
+            conv = {3: KB.conv1d, 4: KB.conv2d, 5: KB.conv3d}[len(shp_knl)]
+            out = [
+                conv(
+                    x[(slice(0, None),) + padding + (slice(i * roi[axis], (i+1) * roi[axis]),)],
+                    knl[padding + (slice(i, i + 1),)],
+                ) for i in range(shp_knl[axis])]
+        else:
+            out = [
+                LocalityAdaptive._call_helper(
+                    x[(slice(0, None),) + padding + (slice(i * roi[axis], (i+1) * roi[axis]),)],
+                    knl[padding + (slice(i, i + 1),)],
+                    roi,
+                    axis=axis + 1,
+                ) for i in range(shp_knl[axis])]
+        return KB.concatenate(out, axis=1 + axis)
+
+    def call(self, x):
+        in_dims = x.shape.as_list()[1:-1]
+        roi = self.roi_size
+        if not isinstance(roi, Iterable):
+            roi = (roi,) * len(in_dims)
+        return self._call_helper(x, self.kernel, roi)
+
+    def compute_output_shape(self, input_shape):
+        return input_shape[:-1] + (self.filters,)
diff --git a/niftypet/ml/models.py b/niftypet/ml/models.py
new file mode 100644
index 0000000..c2d790a
--- /dev/null
+++ b/niftypet/ml/models.py
@@ -0,0 +1,117 @@
+"""
+PET-MR denoising CNNs.
+"""
+import functools
+import logging
+
+from tensorflow import keras
+
+from .layers import Norm as NormLayer
+from .layers import nrmse
+
+__author__ = "Casper da Costa-Luis <imaging@cdcl.ml>"
+log = logging.getLogger(__name__)
+L = keras.layers
+CONV_ND = {2: L.Conv1D, 3: L.Conv2D, 4: L.Conv3D}
+MAXPOOL_ND = {2: L.MaxPool1D, 3: L.MaxPool2D, 4: L.MaxPool3D}
+UPSAMPLE_ND = {2: L.UpSampling1D, 3: L.UpSampling2D, 4: L.UpSampling3D}
+
+
+def dcl2020(input_shape, n_filters=None, filter_sizes=None, activations=None, prenorm=None, eps=0,
+            lr=1e-3, dtype="float32"):
+    """
+    Micro-net implementation based on:
+    C. O. da Costa-Luis and A. J. Reader 2021 IEEE Trans. Radiat. Plasma Med. Sci. 5(2) 202-212
+    "Micro-Networks for Robust MR-Guided Low Count PET Imaging"
+
+    Args:
+      n_filters: default [32, 32, 1]
+      filter_sizes: default [5, 3, 1]
+      activations: default ['sigmoid', ..., 'sigmoid', 'elu']
+      prenorm: default is `activation[-1] != 'sigmoid'`
+      wd: weigth for discriminator loss term
+    """
+    n_filters = n_filters or [32, 32, 1]
+    filter_sizes = filter_sizes or [5, 3, 1]
+    activations = activations or ["sigmoid"] * (len(n_filters) - 1) + ["elu"]
+
+    Conv = CONV_ND[len(input_shape)]
+
+    x = inputs = L.Input(input_shape, dtype=dtype)
+
+    largs = {
+        'kernel_initializer': "he_normal", 'bias_initializer': "he_normal", 'padding': "same",
+        'strides': 1}
+    Norm = functools.partial(NormLayer, eps=eps, std=True, batch=True)
+
+    inputs = x = L.Input(input_shape, dtype=dtype)
+    if prenorm is None:
+        prenorm = activations[-1] != 'sigmoid'
+    if prenorm:
+        x = L.concatenate([Norm(mean=True)(x[..., :1]), Norm(mean=False)(x[..., 1:])]) # MR  # PET
+
+    for filters, kernel_size, activation in zip(n_filters, filter_sizes, activations):
+        x = Conv(filters, kernel_size, activation=activation, **largs)(x)
+    # x = L.Multiply()((x, std))  # un-norm
+
+    model = keras.Model(inputs=inputs, outputs=x)
+    if lr:
+        opt = keras.optimizers.Adam(lr)
+        model.compile(opt, metrics=[nrmse], loss=nrmse)
+        model.summary(print_fn=log.debug)
+    return model
+
+
+def chen2019(input_shape, residual_input_channel=1, lr=2e-4, dtype="float32"):
+    """
+    Residual U-net implementation based on:
+    K. T. Chen et al. 2019 Radiol. 290(3) 649-656
+    "Ultra-Low-Dose 18F-Florbetaben Amyloid PET Imaging Using Deep Learning
+    with Multi-Contrast MRI Inputs"
+
+    >>> model = network(input_data.shape[1:])
+    >>> model.fit(input_data, output_date, epochs=100, batch_size=input_data.shape[0] // 4, ...)
+
+    Args:
+      input_shape (tuple): (num_slices, slice_height, slice_width, num_channels)
+      residual_input_channel  : input channel index to use for residual addition
+    """
+    Conv = CONV_ND[len(input_shape)]
+    MaxPool = MAXPOOL_ND[len(input_shape)]
+    Upsample = UPSAMPLE_ND[len(input_shape)]
+
+    x = inputs = L.Input(input_shape, dtype=dtype)
+
+    def block(x, filters):
+        x = Conv(filters, 3, padding="same", use_bias=False, dtype=dtype)(x)
+        x = L.BatchNormalization(dtype=dtype)(x)
+        x = L.ReLU(dtype=dtype)(x)
+        return x
+
+    # U-net
+    filters = [16, 32, 64, 128]
+    # # encode
+    convs = []
+    for i in filters[:-1]:
+        x = block(x, i)
+        x = block(x, i)
+        convs.append(x)
+        x = MaxPool(dtype=dtype, padding="same")(x)
+    x = block(x, filters[-1])
+    x = block(x, filters[-1])
+    # # decode
+    for i in filters[:-1][::-1]:
+        x = Upsample(interpolation="bilinear", dtype=dtype)(x)
+        x = L.Concatenate()([x, convs.pop()])
+        x = block(x, i)
+        x = block(x, i)
+    x = Conv(1, 1, padding="same", dtype=dtype, name="residual")(x)
+    x = L.Add(name="generated")([
+        inputs[..., residual_input_channel:residual_input_channel + 1], x])
+
+    model = keras.Model(inputs=inputs, outputs=x)
+    if lr:
+        opt = keras.optimizers.Adam(lr)
+        model.compile(opt, metrics=[nrmse], loss="mae")
+        model.summary(print_fn=log.debug)
+    return model
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..4eb7149
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,6 @@
+[build-system]
+requires = ["setuptools>=42", "wheel", "setuptools_scm[toml]>=3.4"]
+
+[tool.setuptools_scm]
+write_to = "niftypet/ml/_dist_ver.py"
+write_to_template = "__version__ = '{version}'\n"
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..89e3eb1
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,80 @@
+[metadata]
+name=niftyml
+description=PET-MR Machine Learning
+long_description=file: README.rst
+long_description_content_type=text/x-rst
+license=MPL 2.0
+license_file=LICENCE
+url=https://github.com/NiftyPET/niftyml
+project_urls=
+    Changelog=https://github.com/NiftyPET/niftyml/releases
+author=Casper da Costa-Luis
+author_email=imaging@cdcl.ml
+keywords=PET, ML
+provides=niftypet.ml
+classifiers=
+    Development Status :: 4 - Beta
+    Intended Audience :: Developers
+    Intended Audience :: Education
+    Intended Audience :: Science/Research
+    License :: OSI Approved :: Mozilla Public License 2.0 (MPL 2.0)
+    Operating System :: MacOS
+    Operating System :: Microsoft :: Windows
+    Operating System :: POSIX :: Linux
+    Operating System :: Unix
+    Programming Language :: Python
+    Programming Language :: Python :: 3
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
+    Programming Language :: Python :: 3.9
+    Topic :: Software Development :: Libraries
+    Topic :: Software Development :: Libraries :: Python Modules
+[options]
+python_requires=>=3.6
+install_requires=numpy
+packages=find:
+[options.extras_require]
+dev=
+    pre-commit
+    pytest
+    pytest-cov
+    pytest-timeout
+    codecov
+[options.packages.find]
+exclude=tests
+
+[yapf]
+spaces_before_comment=15, 20
+arithmetic_precedence_indication=true
+allow_split_before_dict_value=false
+coalesce_brackets=True
+column_limit=99
+each_dict_entry_on_separate_line=False
+space_between_ending_comma_and_closing_bracket=False
+split_before_named_assigns=False
+split_before_closing_bracket=False
+
+[isort]
+profile=black
+line_length=99
+known_first_party=niftypet,tests
+
+[flake8]
+statistics=True
+max_line_length=99
+extend-ignore=E261,P101
+exclude=.git,__pycache__,build,dist,.eggs
+
+[tool:pytest]
+timeout=30
+log_level=INFO
+python_files=tests/test_*.py
+addopts=-v --tb=short -rxs -W=error --durations=0 --durations-min=1 --cov=niftypet.ml --cov-report=term-missing --cov-report=xml
+
+[coverage:run]
+branch=True
+include=niftypet/ml/*
+relative_files=True
+[coverage:report]
+show_missing=True
diff --git a/setup.py b/setup.py
new file mode 100644
index 0000000..d5d43d7
--- /dev/null
+++ b/setup.py
@@ -0,0 +1,3 @@
+from setuptools import setup
+
+setup(use_scm_version=True)
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29