# mri-spins

Interactive 3D demonstration of MRI spin physics.

**Live: https://concept-collection.github.io/mri-spins/**

A sample of isochromats (sphere or cube) evolves under the Bloch equations in
the rotating frame. Apply RF pulses, gradients, and a Larmor frequency offset;
adjust T1/T2 relaxation; and view the magnetization as vector arrows or
colored balls. A live trace shows the signal (real and imaginary parts of the
net transverse magnetization).

A built-in spoiled gradient echo sequence plays out 16 phase-encoded TRs,
driving the controls automatically and acquiring signal during the readout
windows. Optional gradient sounds click like a real scanner.

## Things to try

- Apply a 90° pulse: the spins precess at Δf₀ while T2 attenuates the signal
  and Mz recovers with T1.
- Turn up Gx to dephase the spins, then apply a 180° pulse to refocus them
  into a spin echo.
- Turn on sound and run the spoiled gradient echo.

Single static page, no build step — three.js is loaded from a CDN. Serve
locally with any static file server, e.g. `npx serve .`