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# PyPulseq: A Python Package for MRI Pulse Sequence Design
Pulse sequence design is a significant component of MRI research. However, multi-vendor studies require researchers to
be acquainted with each hardware platform's programming environment.
PyPulseq enables vendor-neutral pulse sequence design in Python [[1,2]](#references). The pulse sequences can be
exported as a `.seq` file to be run on Siemens/[GE]/[Bruker] hardware by leveraging their respective
Pulseq interpreters. This tool is targeted at MRI pulse sequence designers, researchers, students and other interested
users. It is a translation of the Pulseq framework originally written in Matlab [[3]](#references). Currently,
PyPulseq is compatible with Pulseq 1.2.0.
It is strongly recommended to first read the [Pulseq specification] before proceeding. The specification
document defines the concepts required for pulse sequence design using PyPulseq. API docs can be found [here][api-docs].
If you use PyPulseq in your work, cite as:
```
Ravi, Keerthi, Sairam Geethanath, and John Vaughan. "PyPulseq: A Python Package for MRI Pulse Sequence Design." Journal
of Open Source Software 4.42 (2019): 1725.
Ravi, Keerthi Sravan, et al. "Pulseq-Graphical Programming Interface: Open source visual environment for prototyping
pulse sequences and integrated magnetic resonance imaging algorithm development." Magnetic resonance imaging 52 (2018):
9-15.
```
## 📢 Pulse sequence development in your browser!
Design pulse sequences using `pypulseq` in your browser! Check out the [Lightning-start ⚡][lightning-start] section to
learn how!
---
## [Relevant literature][scholar-citations] (reverse chronological)
1. Ravi, Keerthi Sravan, and Sairam Geethanath. "Autonomous Magnetic Resonance Imaging." medRxiv (2020).
2. Nunes, Rita G., et al. "Implementation of a Diffusion-Weighted Echo Planar Imaging sequence using the Open Source
Hardware-Independent PyPulseq Tool." ISMRM & SMRT Virtual Conference & Exhibition, International Society for Magnetic
Resonance in Medicine (ISMRM) (2020).
3. Loktyushin, Alexander, et al. "MRzero--Fully automated invention of MRI sequences using supervised learning." arXiv
preprint arXiv:2002.04265 (2020).
4. Jimeno, Marina Manso, et al. "Cross-vendor implementation of a Stack-of-spirals PRESTO BOLD fMRI sequence using
TOPPE and Pulseq." ISMRM & SMRT Virtual Conference & Exhibition, International Society for Magnetic Resonance in
Medicine (ISMRM) (2020).
5. Clarke, William T., et al. "Multi-site harmonization of 7 tesla MRI neuroimaging protocols." NeuroImage 206 (2020): 116335.
6. Geethanath, Sairam, and John Thomas Vaughan Jr. "Accessible magnetic resonance imaging: a review." Journal of
Magnetic Resonance Imaging 49.7 (2019): e65-e77.
7. Tong, Gehua, et al. "Virtual Scanner: MRI on a Browser." Journal of Open Source Software 4.43 (2019): 1637.
8. Archipovas, Saulius, et al. "A prototype of a fully integrated environment for a collaborative work in MR sequence
development for a reproducible research." ISMRM 27th Annual Meeting & Exhibition, International Society for
Magnetic Resonance in Medicine (ISMRM) (2019).
9. Pizetta, Daniel Cosmo. PyMR: a framework for programming magnetic resonance systems. Diss. Universidade de São
Paulo (2018).
---
## Installation
\>=Python 3.6, virtual environment recommended:
```pip install pypulseq```
## Lightning-start ⚡ - PyPulseq in your browser!
1. Create a new notebook on [Google Colab][google-colab]
2. [Install][installation] PyPulseq
3. Get going!
Or, explore an example notebook:
1. Copy URL of an example notebook from [here][notebook-examples]
2. On [Google Colab][google-colab], insert the copied link to get started
## Quickstart 🏃‍♂ - example scripts
Every example script creates a pulse sequence, plots the pulse timing diagram and writes a `.seq` file to disk.
1. [Install][installation] PyPulseq
2. Download and run any of the [example][script-examples] scripts.
## Deep dive 🤿 - custom pulse sequences
Getting started with pulse sequence design using `PyPulseq` is simple:
1. [Install][installation] PyPulseq
2. First, define system limits in `Opts` and then create a `Sequence` object with it:
```python
from pypulseq.opts import Opts
from pypulseq.sequence.sequence import Sequence
system = Opts(max_grad=32, grad_unit='mT/m', max_slew=130, slew_unit='mT/m/s')
seq = Sequence(system=system)
```
3. Then, design gradient, RF or ADC pulse sequence events:
```python
from pypulseq.make_sinc_pulse import make_sinc_pulse
from pypulseq.make_trap_pulse import make_trapezoid
from pypulseq.make_adc import make_adc
Nx, Ny = 256, 256 # matrix size
fov = 220e-3 # field of view
delta_k = fov / Nx
# RF sinc pulse with a 90 degree flip angle
rf90, _, _ = make_sinc_pulse(flip_angle=90, duration=2e-3, system=system, slice_thickness=5e-3, apodization=0.5,
time_bw_product=4)
# Frequency encode, trapezoidal event
gx = make_trapezoid(channel='x', flat_area=Nx * delta_k, flat_time=6.4e-3, system=system)
# ADC readout
adc = make_adc(num_samples=Nx, duration=gx.flat_time, delay=gx.rise_time, system=system)
```
4. Add these pulse sequence events to the `Sequence` object from step 2. One or more events can be executed
simultaneously, simply pass them all to the `add_block()` method. For example, the `gx` and `adc` pulse sequence events
need to be executed simultaneously:
```python
seq.add_block(rf90)
seq.add_block(gx, adc)
```
5. Visualize plots:
```python
seq.plot()
```
6. Generate a `.seq` file to be executed on a real MR scanner:
```python
seq.write('demo.seq')
```
**Get in touch regarding running the `.seq` files on your Siemens/[GE]/[Bruker] scanner.**
## Contributing and Community guidelines
`PyPulseq` adheres to a code of conduct adapted from the [Contributor Covenant] code of conduct.
Contributing guidelines can be found [here][contrib-guidelines].
---
## References
1. Ravi, Keerthi, Sairam Geethanath, and John Vaughan. "PyPulseq: A Python Package for MRI Pulse Sequence Design."
Journal of Open Source Software 4.42 (2019): 1725.
2. Ravi, Keerthi Sravan, et al. "Pulseq-Graphical Programming Interface: Open source visual environment for prototyping
pulse sequences and integrated magnetic resonance imaging algorithm development." Magnetic resonance imaging 52 (2018):
9-15.
3. Layton, Kelvin J., et al. "Pulseq: a rapid and hardware‐independent pulse sequence prototyping framework." Magnetic
resonance in medicine 77.4 (2017): 1544-1552.
[api-docs]: https://pypulseq.readthedocs.io/en/latest
[Bruker]: https://github.com/pulseq/bruker_interpreter
[Contributor Covenant]: http://contributor-covenant.org
[contrib-guidelines]: https://github.com/imr-framework/pypulseq/blob/master/CONTRIBUTING.md
[GE]: https://toppemri.github.io
[google-colab]: https://colab.research.google.com/
[installation]: #installation
[lightning-start]: #lightning-start----pypulseq-in-your-browser
[notebook-examples]: https://github.com/imr-framework/pypulseq/tree/dev/pypulseq/seq_examples/notebooks
[Pulseq specification]: https://pulseq.github.io/specification.pdf
[scholar-citations]: https://scholar.google.com/scholar?oi=bibs&hl=en&cites=16703093871665262997
[script-examples]: https://github.com/imr-framework/pypulseq/tree/master/pypulseq/seq_examples/scripts
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