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Patient 1
Pick a weighting, fire the 90 degree pulse, time the 180 and read the echo!
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About Spin Echo

Fire 90 and 180 degree RF pulses, time the refocusing echo and encode k-space with gradient coils to diagnose tumor, fat and fluid in this free online MRI spin echo game.

Spin Echo is a free online MRI physics game where you run the actual pulse sequence a magnetic resonance scanner uses to make pictures. An MRI machine never photographs anything. It parks your body in a huge magnetic field, slaps hydrogen protons sideways with a 90 degree radio pulse and then listens to the faint radio echo they give back. Every mechanic in the game is a real line in a radiologist's console: RF pulses, gradient coils, echo time, repetition time and tissue relaxation.

The physics underneath is nuclear magnetic resonance. Protons precess at the Larmor frequency, about 63.9 MHz per tesla. Once the 90 degree pulse tips them into the transverse plane, tiny field imperfections make them drift out of phase, the T2 star decay you watch as a fan-out. The 180 degree refocusing pulse flips their phases so they re-converge into a spin echo at twice the delay, exactly the trick Erwin Hahn discovered in 1950. Gradient coils then make precession depend on position: a frequency gradient labels columns by pitch during readout while a phase gradient blip tags rows, which is real k-space spatial encoding.

Tissues betray themselves through relaxation times. Fat recovers fastest, so it shines on T1-weighted scans. Fluid relaxes slowest, so it glows on T2 and vanishes on FLAIR. Tumors and edema both run long on T2 and only careful comparison across weightings, plus shape, tells them apart, which is precisely the diagnostic puzzle real radiologists solve. This matters because MRI is the safest high-resolution look inside a living body: no ionizing radiation, just spins, pulses and math. Master the echo here and every hospital scan stops being magic.

Key Science Concepts

What You'll Learn

Grade Level: High School, College

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How to play

  1. Pick a Weighting Choose T1w, PDw, T2w or FLAIR on the console. Each weighting makes a different tissue glow, so match it to the referral.
  2. Fire the 90 The 90 pulse tips every proton spin sideways. Watch them fan out as field inhomogeneity drives T2 star dephasing.
  3. Time the 180 Tap the refocus pulse right on the marker. Spins reverse, chase each other and snap back into an echo at twice your delay.
  4. Encode k-Space Blip GY during dephase to tag the rows and hold GX through readout to label columns by pitch. Skip them and the image smears.
  5. Read the Echo Each tissue owns a brightness signature across weightings. Scan again with a different preset when a blob looks ambiguous.
  6. Mark and Comfort Tap voxels to mark the target tissue, then submit the read. Tap the calm gauge whenever Jitters starts to squirm.

Frequently asked questions

Is Spin Echo free to play?
Yes. Spin Echo is completely free to play in your browser. There is no download, install or account needed.
What grade level is Spin Echo for?
Spin Echo is designed for High School, College students and works well as a classroom activity or homework.
Does Spin Echo work on phones and tablets?
Yes. Spin Echo runs in any modern browser on desktop computers, Chromebooks, tablets and phones in landscape mode.

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