Spinach is an open-source magnetic resonance simulation package initially released in 2011[1] and continuously updated since.

[2] The package is written in Matlab and makes use of the built-in parallel computing and GPU interfaces of Matlab.

[3] The name of the package whimsically refers to the physical concept of spin and to Popeye the Sailor who, in the eponymous comic books, becomes stronger after consuming spinach.

[4] Spinach implements magnetic resonance spectroscopy and imaging simulations by solving the equation of motion for the density matrix

, and potentially other terms that govern spatial dynamics and coupling to other degrees of freedom:[2] Computational efficiency is achieved through the use of reduced state spaces, sparse matrix arithmetic, on-the-fly trajectory analysis, and dynamic parallelization.

[5] As of 2023, Spinach is cited in over 300 academic publications.

[1] According to the documentation[2] and academic papers citing its features, the most recent version 2.8 of the package performs: Common models of spin relaxation (Redfield theory, stochastic Liouville equation, Lindblad theory) and chemical kinetics are supported, and a library of powder averaging grids is included with the package.

[2] Spinach contains an implementation the gradient ascent pulse engineering (GRAPE) algorithm[16] for quantum optimal control.

The documentation[2] and the book describing the optimal control module of the package[17] list the following features: Dissipative background evolution generators and control operators are supported, as well as ensemble control over distributions in common instrument calibration parameters, such as control channel power and offset.