Magnetic resonance imaging: Difference between revisions

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imported>Robert Badgett
(Changed focus so MRI is not seen as only a neuroimaging.)
imported>Robert Badgett
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| Spin density  || Proton density||  
| Spin density  || Proton density||  
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| T1 relaxation time || Spin-lattice (longitudinal) relaxation time. Short TR & TE|| More solid and less mobile molecules (including [[lipid]]s, cerebral white matter, yellow bone marrow) are bright.<br>T1 images can be obtained faster.<br>T1 images better display [[gadolinium]] [[contrast medium]]<ref name="PMID8433731"/>
| T1 relaxation time || Spin-lattice (longitudinal) relaxation time. Short repitition time (TR) & echo time (TE)|| More solid and less mobile molecules (including [[lipid]]s, cerebral white matter, yellow bone marrow) are bright.<br>T1 images can be obtained faster.<br>T1 images better display [[gadolinium]] [[contrast medium]]<ref name="PMID8433731"/>
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| T2 relaxation time || Spin-spin (transverse) relaxation time. Long TR & TE|| Water (including [[cerebrospinal fluid|CSF]], [[urine]], cysts, [[abscess]]es) is bright<ref name="PMID8433731"/>
| T2 relaxation time || Spin-spin (transverse) relaxation time. Long TR & TE|| Water (including [[cerebrospinal fluid|CSF]], [[urine]], cysts, [[abscess]]es) is bright<ref name="PMID8433731"/>

Revision as of 19:51, 30 July 2008

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In diagnostic imaging, magnetic resonance imaging (commonly known as an MRI scan) has been described as a "non-invasive method of demonstrating internal anatomy, based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves - which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques."[1] MRI is commonly used in neuroimaging.

Classification

Physical principles

In contrast to x-ray computed tomography which is based on the density of electrons in tissues, MRI is based on several properties of protons.[6][7][8][9][10]Atoms with an odd number of protons, such as hydrogen, inherently create a small magnetic field that can be measured, then manipulated by MRI, then measured again as the tissue relaxes after the external field is turned off.[6]

MRI pulse sequences
Pulse sequence Description Application
Standard pulse sequences
Spin density Proton density  
T1 relaxation time Spin-lattice (longitudinal) relaxation time. Short repitition time (TR) & echo time (TE) More solid and less mobile molecules (including lipids, cerebral white matter, yellow bone marrow) are bright.
T1 images can be obtained faster.
T1 images better display gadolinium contrast medium[8]
T2 relaxation time Spin-spin (transverse) relaxation time. Long TR & TE Water (including CSF, urine, cysts, abscesses) is bright[8]
Other pulse sequences
DWI (diffusion-weighted imaging)    
ADC (apparent diffusion coefficient)    
GRE (gradient echo) pulse sequences   Blood flow is bright
PWI (perfusion-weighted imaging)    

References

  1. Anonymous (2024), Magnetic resonance imaging (English). Medical Subject Headings. U.S. National Library of Medicine.
  2. Le Bihan D, Jezzard P, Haxby J, Sadato N, Rueckert L, Mattay V. Functional magnetic resonance imaging of the brain. Ann Intern Med. 1995 Feb 15;122(4):296-303. PMID 7825767
  3. Gilman S. Imaging the brain. First of two parts. N Engl J Med. 1998 Mar 19;338(12):812-20. PMID 9504943
  4. Gilman S. Imaging the brain. Second of two parts. N Engl J Med. 1998 Mar 26;338(13):889-96. PMID 9516225
  5. Fisher M, Prichard JW, Warach S. New magnetic resonance techniques for acute ischemic stroke. JAMA. 1995 Sep 20;274(11):908-11. PMID 7674506
  6. 6.0 6.1 Hendee WR, Morgan CJ. Magnetic resonance imaging. Part I--physical principles. West J Med. 1984 Oct;141(4):491-500. PMID 6506686
  7. Hendee WR, Morgan CJ. Magnetic resonance imaging. Part II--Clinical applications. West J Med. 1984 Nov;141(5):638-48. PMID 6516335
  8. 8.0 8.1 8.2 Edelman RR, Warach S. Magnetic resonance imaging - First of Two Parts. N Engl J Med. 1993 Mar 11;328(10):708-16. PMID 8433731
  9. Edelman RR, Warach S. Magnetic resonance imaging - Second of Two Parts. N Engl J Med. 1993 Mar 18;328(11):785-91. PMID 8369029
  10. Berger A. Magnetic resonance imaging. BMJ. 2002 Jan 5;324(7328):35. PMID 11777806