The following instructions assume that you have installed Nix and enabled the modern nix interface which includes the nix command and flakes. In short, after installing Nix, you should add the line

experimental-features = nix-command flakes

to one of

• /etc/nix/nix.conf
• ~/.config/nix/nix.conf

For users

The instructions in this section are useful in cases where you want to run the software, but don't intend to modify it. If you want to modify the software, see the For developers section.

To install the tools provided in this repository, as a user, you have a number of options. For casual users, I recommend the first two.

1. Ephemeral installation with nix shell

   nix shell github:jacg/petalo

   This will place you in a shell in which (the most recent version of) all the tools are available. In this shell, try mlem --help. If the installation succeeded, this last command should show you the help for the main image reconstruction program.

   See Available tools for a list of the provided utilities.

   As soon as you exit the shell, the tools 'disappear'.

   On the first invocation, entering the shell will take a considerable amount of time as the software needs to be downloaded and compiled. On subsequent invocations, it should be instantaneous, unless

   1. A newer version is available (TODO discuss selecting revs)
   2. You have garbage collected your Nix store

2. Ad-hoc installation with nix build

   nix build github:jacg/petalo

   This will create a link called result in the working directory, which points to a bin directory containing all the available tools.

   After having run this command, you can try result/bin/mlem --help.

3. Classical package manager-like installation with nix profile

   This looks convenient and 'normal' to those used to non-Nix package managers, but swims against the current of the principles which make Nix great: it is therefore NOT RECOMMENDED!

   nix profile install github:jacg/petalo

   All the tools should now be available in your PATH: try mlem --help.

4. Home Manager TODO

   This is the recommended approach for the long term. Utilities to make home-manager installation easy, are in the works.

For developers

Getting the source

You can obtain the source code by cloning the repository directly via git. But Nix flakes provide an alternative:

nix flake clone github:jacg/petalo --dest petalorust

Development tools

The Nix flake in the repository provides an environment containing the tools needed to work on the code, which can be activated with nix develop:

cd petalorust  # or wherever you cloned the repository
nix develop

nix develop places you in a shell containing all the necessary development tools for the project. Exit the shell do disable the development environment.

Automatic environment switching with direnv

I recommend using direnv to automate provision of development tools.

If direnv is enabled, the environment required to work on this project will be enabled automatically, after you have given direnv permission to work in this directory with direnv allow. You can revoke permission with direnv deny. The first time the environment is enable, it will have to install all the required dependencies, which may take a significant amount of time. Thereafter, it should be instantaneous.

direnv will disable the environment as soon as you leave the directory. If you want to use the environment in a different directory, you can always ask for it explicitly with either of these commands

• nix develop <path-to-your-clone-of-the-project>
• `nix develop github:jacg/petalo

direnv also automatically switches the environment to match the currently checked-out version of the project.

Without Nix

If you haven't installed Nix ... well, it's a few orders of magnitude easier to install Nix, than to attempt to run this software without it.

Testing

Running just should compile and test all components, including Rust, Python and Rust/Python bindings..

Available tools

• mlem: Reconstruction of images via Maximum Likelihood Expectation Maximization (MLEM) or Ordered Subsets Expectation Maximization (OSEM).

  This includes the ability to correct for scatter and attenuation.

• makelor: Reconstruction of coincidence lines of response (LORs) from Monte Carlo simulations of detectors.

• make_sensitivity_image: Generate sensitivity image (for use in mlem attenuation correction) from a density map of the field of view (FOV).

• viewraw.py: Interactively view 2D slices through 3D reconstructed images produced by mlem.

• foms: Calculate Figures of Merit (FOMs) for reconstructed images of Jaszczak or NEMA7 phantoms.

• TODO: This on is currently missing! foms.py: Calculate and plot FOMs for a sequence of reconstructed images produced by mlem.

• imageprimaries: Create a 3D image of the distribution of primary vertices (back-to-back gamma production points) in a MC simulation. Can be viewed with viewraw.py.

• vislor: Visualize the interaction of an individual LOR with the FOV.