Principles of MRI - Department of Radiology
Principles of MRI - Department of Radiology
Principles of MRI - Department of Radiology
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Evolution <strong>of</strong> <strong>Radiology</strong>:<br />
Focus on MSK <strong>MRI</strong><br />
The Evolution <strong>of</strong> <strong>Radiology</strong><br />
Radiographs<br />
Tomography<br />
CT<br />
MR<br />
Signal<br />
Sequences<br />
Coils<br />
Magnets<br />
Safety<br />
Hardware<br />
www.schreibman.info<br />
© 2011 Ken L Schreibman, PhD/MD<br />
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Focus on Musculoskeletal <strong>MRI</strong><br />
How MR Scanner Works<br />
Magnet<br />
‣Aligns spins <strong>of</strong> protons in hydrogen nuclei<br />
Align in direction <strong>of</strong> magnetic field, B 0<br />
Coil<br />
1)Sends RF pulse to flip spinning protons<br />
After RF pulse is <strong>of</strong>f, protons realign to B 0<br />
As protons realign, resonate RF energy<br />
2)Measures strength <strong>of</strong> resonant RF echo<br />
At a specific time, T E , “Echo Time”<br />
Steps 1&2 repeated many times / image slice<br />
At a specific “Repetition Time”, T R<br />
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Slide 19 <strong>of</strong> 88<br />
The Evolution <strong>of</strong> <strong>Radiology</strong><br />
page 4 <strong>of</strong> 15<br />
Radiographs<br />
Specific tissue types<br />
Tomography have specific resonant echoes (T1, T2)<br />
CT<br />
depending upon specified T R & T E<br />
MR ‣ Fluid (Hydrogen protons in H 2 O)<br />
Signal Cysts<br />
Sequences Joint effusions<br />
Edema (in s<strong>of</strong>t tissues, in bone marrow)<br />
Coils<br />
‣ Fat (Hydrogen protons in fat)<br />
Magnets Sub-cutaneous fat<br />
Safety Fatty yellow bone marrow<br />
Hardware ‣ Dense Stuff (with few Hydrogen protons)<br />
Cortical bone<br />
Ligaments, tendons<br />
Menisci<br />
www.schreibman.info<br />
© 2011 Ken L Schreibman, PhD/MD<br />
<br />
Key to <strong>MRI</strong><br />
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Focus on Musculoskeletal <strong>MRI</strong><br />
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Slide 20 <strong>of</strong> 88<br />
The Evolution <strong>of</strong> <strong>Radiology</strong><br />
Radiographs<br />
High<br />
Tomography<br />
CT<br />
MR<br />
Signal<br />
Sequences Signal<br />
Coils<br />
Magnets<br />
Safety<br />
Hardware<br />
Low<br />
www.schreibman.info<br />
© 2011 Ken L Schreibman, PhD/MD<br />
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Focus on Musculoskeletal <strong>MRI</strong><br />
T1 Recovery Curve (T R ~500ms)<br />
Fat<br />
10ms<br />
Fluid<br />
Dense<br />
Stuff<br />
T1-weighted image<br />
(T R : short, T E : short)<br />
‣Fat: High<br />
‣Fluid: Low<br />
‣Dense Stuff: Low<br />
Time to Echo T E (ms)<br />
Jump to<br />
next slide Slide 21 <strong>of</strong> 88<br />
The Evolution <strong>of</strong> <strong>Radiology</strong><br />
Radiographs<br />
Tomography<br />
CT<br />
MR<br />
Signal<br />
Sequences<br />
Coils<br />
Magnets<br />
Safety<br />
Hardware<br />
High<br />
Signal<br />
Low<br />
www.schreibman.info<br />
© 2011 Ken L Schreibman, PhD/MD<br />
Dense<br />
Stuff<br />
80ms<br />
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Focus on Musculoskeletal <strong>MRI</strong><br />
T2 Decay Curve (T R ~2,000ms)<br />
T2-weighted image<br />
(T R : long, T E : long)<br />
‣Fluid: Intermed.<br />
‣Fat: Intermediate<br />
‣Dense Stuff: Low<br />
Fluid To increase separation <strong>of</strong><br />
fluid from fat, can apply<br />
“Fat-Suppression”<br />
(“Fat-Saturation”)<br />
Fat<br />
Time to Echo T E (ms)<br />
Jump to<br />
next slide Slide 22 <strong>of</strong> 88<br />
The Evolution <strong>of</strong> <strong>Radiology</strong><br />
Radiographs<br />
High<br />
Tomography<br />
CT<br />
MR<br />
Signal<br />
Sequences Signal<br />
Coils<br />
Magnets<br />
Safety<br />
Hardware<br />
Low<br />
www.schreibman.info<br />
© 2011 Ken L Schreibman, PhD/MD<br />
Dense<br />
Stuff<br />
80ms<br />
Jump to last<br />
slide viewed<br />
Focus on Musculoskeletal <strong>MRI</strong><br />
Fat-Sat T2 Decay Curve (T R ~2,000ms)<br />
It is always preferable to<br />
suppress the fat on T2<br />
to increase fluid<br />
conspicuity.<br />
Inversion Recovery<br />
(IR, STIR) is<br />
equivalent<br />
T2-weighted image<br />
(T R : long, T E : long)<br />
‣Fluid: Intermed.<br />
‣Fat: Low (suppressed)<br />
‣Dense Stuff: Low<br />
Fluid To increase separation <strong>of</strong><br />
fluid from fat, can apply<br />
“Fat-Suppression”<br />
(“Fat-Saturation”)<br />
Fat<br />
Time to Echo T E (ms)<br />
Jump to<br />
next slide Slide 23 <strong>of</strong> 88<br />
The Evolution <strong>of</strong> <strong>Radiology</strong><br />
Radiographs<br />
Tomography<br />
CT<br />
MR<br />
Signal<br />
Sequences<br />
Coils<br />
Magnets<br />
Safety<br />
Hardware<br />
www.schreibman.info<br />
© 2011 Ken L Schreibman, PhD/MD<br />
Dense<br />
Stuff<br />
Fluid<br />
80ms<br />
Jump to last<br />
slide viewed<br />
Focus on Musculoskeletal <strong>MRI</strong><br />
Fat-Sat T2 Decay Curve (T R ~2,000ms)<br />
Compress<br />
signal<br />
scale<br />
<br />
<br />
<br />
<br />
<br />
High<br />
Signal<br />
Low<br />
T2-weighted image<br />
(T R : long, T E : long)<br />
‣Fluid: High (relatively)<br />
‣Fat: Low (suppressed)<br />
‣Dense Stuff: Low<br />
Fat<br />
Time to Echo T E (ms)<br />
Jump to<br />
next slide Slide 24 <strong>of</strong> 88<br />
©Ken L Schreibman, PhD/MD 10/10/11 www.schreibman.info
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