Magnetic resonance imaging: Difference between revisions
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==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"/> | |||
{| class="wikitable" align="right" | {| class="wikitable" align="right" | ||
|+ MRI pulse sequences | |+ MRI pulse sequences | ||
! Pulse sequence !! Description | ! Pulse sequence !! Description !!Application | ||
|- | |- | ||
| colspan= | | colspan=3 align="center" |Standard pulse sequences | ||
|- | |- | ||
| Spin density | | Spin density || Proton density|| | ||
|- | |- | ||
| T1 | | 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"/> | ||
|- | |- | ||
| T2 - spin | | T2 relaxation time || Spin-spin relation time|| Water (including [[cerebrospinal fluid|CSF, [[urine]], cysts, [[abscess]]es]]) is bright<ref name="PMID8433731"/> | ||
|- | |- | ||
| colspan= | | colspan=3 align="center" |Other pulse sequences | ||
|- | |- | ||
| DWI (diffusion-weighted imaging)|| | | DWI (diffusion-weighted imaging)|| || | ||
|- | |- | ||
| ADC (apparent diffusion coefficient) || | | ADC (apparent diffusion coefficient) || || | ||
|- | |- | ||
| GRE (gradient echo) pulse sequences || | | GRE (gradient echo) pulse sequences || || Blood flow is bright | ||
|- | |- | ||
| PWI (perfusion-weighted imaging) || | | PWI (perfusion-weighted imaging) || || | ||
|} | |} | ||
==References== | ==References== | ||
<references/> | <references/> | ||
Revision as of 23:32, 28 July 2008
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]
| Pulse sequence | Description | Application |
|---|---|---|
| Standard pulse sequences | ||
| Spin density | Proton density | |
| 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[4] |
| T2 relaxation time | Spin-spin relation time | Water (including [[cerebrospinal fluid|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
- ↑ Anonymous (2024), Magnetic resonance imaging (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ 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
- ↑ Hendee WR, Morgan CJ. Magnetic resonance imaging. Part II--Clinical applications. West J Med. 1984 Nov;141(5):638-48. PMID 6516335
- ↑ 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
- ↑ Edelman RR, Warach S. Magnetic resonance imaging - Second of Two Parts. N Engl J Med. 1993 Mar 18;328(11):785-91. PMID 8369029
- ↑ Berger A. Magnetic resonance imaging. BMJ. 2002 Jan 5;324(7328):35. PMID 11777806
- ↑ Gilman S. Imaging the brain. First of two parts. N Engl J Med. 1998 Mar 19;338(12):812-20. PMID 9504943
- ↑ Gilman S. Imaging the brain. Second of two parts. N Engl J Med. 1998 Mar 26;338(13):889-96. PMID 9516225