Magnetic resonance imaging: Difference between revisions

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imported>Robert Badgett
imported>Robert Badgett
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| Spin density  || Proton density||  
| Spin density  || Proton density||  
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| T1 relaxation time || Spin-lattice relaxation time|| Lipids (including white matter, yellow bone marrow) is bright. T1 images can be obtained faster and also better display contract from [[gadolinium]] [[contrast medium]]<ref name="PMID8433731"/>
| T1 relaxation time || Spin-lattice relaxation time|| 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 relation time|| Water (including [[cerebrospinal fluid|CSF, [[urine]], cysts, [[abscess]]es]]) is bright<ref name="PMID8433731"/>
| T2 relaxation time || Spin-spin relation time|| Water (including [[cerebrospinal fluid|CSF]], [[urine]], cysts, [[abscess]]es) is bright<ref name="PMID8433731"/>
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| colspan=3 align="center" |Other pulse sequences
| colspan=3 align="center" |Other pulse sequences

Revision as of 23:57, 28 July 2008

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Magnetic resonance imaging (commonly known as an MRI scan) is a type of neuroimaging performed in health care. It 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]

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.[2][3][4][5][6][7][8] 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.[2]

MRI pulse sequences
Pulse sequence Description Application
Standard pulse sequences
Spin density Proton density  
T1 relaxation time Spin-lattice relaxation time 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[4]
T2 relaxation time Spin-spin relation time Water (including CSF, urine, cysts, abscesses) is bright[4]
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. 2.0 2.1 Hendee WR, Morgan CJ. Magnetic resonance imaging. Part I--physical principles. West J Med. 1984 Oct;141(4):491-500. PMID 6506686
  3. Hendee WR, Morgan CJ. Magnetic resonance imaging. Part II--Clinical applications. West J Med. 1984 Nov;141(5):638-48. PMID 6516335
  4. 4.0 4.1 4.2 Edelman RR, Warach S. Magnetic resonance imaging - First of Two Parts. N Engl J Med. 1993 Mar 11;328(10):708-16. PMID 8433731
  5. Edelman RR, Warach S. Magnetic resonance imaging - Second of Two Parts. N Engl J Med. 1993 Mar 18;328(11):785-91. PMID 8369029
  6. Berger A. Magnetic resonance imaging. BMJ. 2002 Jan 5;324(7328):35. PMID 11777806
  7. Gilman S. Imaging the brain. First of two parts. N Engl J Med. 1998 Mar 19;338(12):812-20. PMID 9504943
  8. Gilman S. Imaging the brain. Second of two parts. N Engl J Med. 1998 Mar 26;338(13):889-96. PMID 9516225