Magnetic resonance imaging: Difference between revisions

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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."<ref>{{MeSH}}</ref>
'''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."<ref>{{MeSH}}</ref>
==Classification==
* [[Echo-planar imaging]] allows much faster acquisition of images.
* [[Functional magnetic resonance imaging]] uses echo-planar imaging and measures changes in oxygenation status of hemoglobin in response to specific sensory or motor stimulation.<ref name="PMID7825767">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</ref><ref name="PMID9504943">Gilman S. [http://content.nejm.org/cgi/content/full/338/12/812 Imaging the brain. First of two parts.] N Engl J Med. 1998 Mar 19;338(12):812-20. PMID 9504943</ref><ref name="PMID9516225">Gilman S. [http://content.nejm.org/cgi/content/full/338/13/889 Imaging the brain. Second of two parts]. N Engl J Med. 1998 Mar 26;338(13):889-96. PMID 9516225</ref>
* [[Magnetic resonance angiography]]
* [[Magnetic resonance spectroscopy]]
* [[Cine magnetic resonance imaging]] is primarily used in cardiology.
* [[Diffusion magnetic resonance imaging]] usually uses echo-planar imaging and  measures changes in the apparent diffusion coefficient (ADC).


==Physical principles==
==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.<ref name="PMID6506686">Hendee WR, Morgan CJ. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=6506686 Magnetic resonance imaging. Part I--physical principles]. West J Med. 1984 Oct;141(4):491-500. PMID 6506686</ref><ref name="PMID6516335">Hendee WR, Morgan CJ. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=6516335 Magnetic resonance imaging. Part II--Clinical applications]. West J Med. 1984 Nov;141(5):638-48. PMID 6516335</ref><ref name="PMID8433731">Edelman RR, Warach S. [http://content.nejm.org/cgi/content/full/328/10/708 Magnetic resonance imaging - First of Two Parts]. N Engl J Med. 1993 Mar 11;328(10):708-16. PMID 8433731</ref><ref name"PMID8369029">Edelman RR, Warach S. [http://content.nejm.org/cgi/content/full/328/11/785 Magnetic resonance imaging - Second of Two Parts]. N Engl J Med. 1993 Mar 18;328(11):785-91. PMID 8369029</ref><ref name="PMID11777806">Berger A. [http://www.bmj.com/cgi/content/full/324/7328/35 Magnetic resonance imaging]. BMJ. 2002 Jan 5;324(7328):35. PMID 11777806</ref><ref name="PMID9504943">Gilman S. [http://content.nejm.org/cgi/content/full/338/12/812 Imaging the brain. First of two parts.] N Engl J Med. 1998 Mar 19;338(12):812-20. PMID 9504943</ref><ref name="PMID9516225">Gilman S. [http://content.nejm.org/cgi/content/full/338/13/889 Imaging the brain. Second of two parts]. N Engl J Med. 1998 Mar 26;338(13):889-96. PMID 9516225</ref> 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.<ref name="PMID6506686"/>
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.<ref name="PMID6506686">Hendee WR, Morgan CJ. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=6506686 Magnetic resonance imaging. Part I--physical principles]. West J Med. 1984 Oct;141(4):491-500. PMID 6506686</ref><ref name="PMID6516335">Hendee WR, Morgan CJ. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=6516335 Magnetic resonance imaging. Part II--Clinical applications]. West J Med. 1984 Nov;141(5):638-48. PMID 6516335</ref><ref name="PMID8433731">Edelman RR, Warach S. [http://content.nejm.org/cgi/content/full/328/10/708 Magnetic resonance imaging - First of Two Parts]. N Engl J Med. 1993 Mar 11;328(10):708-16. PMID 8433731</ref><ref name"PMID8369029">Edelman RR, Warach S. [http://content.nejm.org/cgi/content/full/328/11/785 Magnetic resonance imaging - Second of Two Parts]. N Engl J Med. 1993 Mar 18;328(11):785-91. PMID 8369029</ref><ref name="PMID11777806">Berger A. [http://www.bmj.com/cgi/content/full/324/7328/35 Magnetic resonance imaging]. BMJ. 2002 Jan 5;324(7328):35. PMID 11777806</ref>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.<ref name="PMID6506686"/>


{| class="wikitable" align="right"
{| class="wikitable" align="right"
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! Pulse sequence !! Description !!Application
! Pulse sequence !! Description !!Application
|-
|-
| colspan=3 align="center" |Standard pulse sequences
| colspan=3 align="center" |'''Standard pulse sequences'''
|-
|-
| Spin density  || Proton density|| &nbsp;
| Spin density  || Proton density|| &nbsp;
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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"/>
|-
|-
| colspan=3 align="center" |Other pulse sequences
| colspan=3 align="center" |'''Other pulse sequences'''
|-
|-
| DWI (diffusion-weighted imaging)|| &nbsp;|| &nbsp;
| DWI (diffusion-weighted imaging)|| &nbsp;|| &nbsp;
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| PWI (perfusion-weighted imaging) || &nbsp;|| &nbsp;
| PWI (perfusion-weighted imaging) || &nbsp;|| &nbsp;
|}
|}


==References==
==References==
<references/>
<references/>

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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]

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.[5][6][7][8][9]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.[5]

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[7]
T2 relaxation time Spin-spin relation time Water (including CSF, urine, cysts, abscesses) is bright[7]
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. ↑ 5.0 5.1 Hendee WR, Morgan CJ. Magnetic resonance imaging. Part I--physical principles. West J Med. 1984 Oct;141(4):491-500. PMID 6506686
  6. ↑ Hendee WR, Morgan CJ. Magnetic resonance imaging. Part II--Clinical applications. West J Med. 1984 Nov;141(5):638-48. PMID 6516335
  7. ↑ 7.0 7.1 7.2 Edelman RR, Warach S. Magnetic resonance imaging - First of Two Parts. N Engl J Med. 1993 Mar 11;328(10):708-16. PMID 8433731
  8. ↑ Edelman RR, Warach S. Magnetic resonance imaging - Second of Two Parts. N Engl J Med. 1993 Mar 18;328(11):785-91. PMID 8369029
  9. ↑ Berger A. Magnetic resonance imaging. BMJ. 2002 Jan 5;324(7328):35. PMID 11777806
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