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Perfusion
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<h2 id="discovery">Discovery</h2> <p>In 1920, <a href="/facts/August_Krogh/pHaf17kY">August Krogh</a> was awarded the <a href="/facts/Nobel_Prize_in_Physiology_or_Medicine/rlnpJX84">Nobel Prize in Physiology or Medicine</a> for his discovering the mechanism of regulation of <a href="/facts/Capillaries/4BIzKJAe">capillaries</a> in <a href="/facts/Skeletal_muscle/en1tVYFN">skeletal muscle</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a><a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Krogh was the first to describe the adaptation of blood perfusion in muscle and other organs according to demands through the opening and closing of <a href="/facts/Arterioles/HYVG0g7P">arterioles</a> and <a href="/facts/Capillaries/4BIzKJAe">capillaries</a>. </p> <h2 id="malperfusion">Malperfusion</h2> <p>Malperfusion can refer to any type of incorrect perfusion though it usually refers to hypoperfusion. The meaning of the terms "overperfusion" and "underperfusion" is relative to the average level of perfusion that exists across all the tissues in an individual body. Perfusion levels also differ from person to person depending on metabolic demand. </p><p>Examples follow: </p> <ul><li><a href="/facts/Heart/fF4KSGdk">Heart</a> tissues are considered overperfused because they normally are receiving more blood than the rest of tissues in the organism; they need this blood because they are constantly working.</li> <li>In the case of skin cells, extra blood flow in them is used for <a href="/facts/Thermoregulation/V692hIjw">thermoregulation</a> of a body. In addition to delivering <a href="/facts/Oxygen/acyn6o8r">oxygen</a>, blood flow helps to <a href="/facts/Dissipation/C134STy1">dissipate</a> heat in a body by redirecting warm blood closer to its surface where it can help to cool a body through <a href="/facts/Sweating/c5zARtaT">sweating</a> and <a href="/facts/Thermal_dissipation/6WPm3enf">thermal dissipation</a>.</li> <li>Many types of <a href="/facts/Tumor/K0ytzmPz">tumors</a>, and especially certain types, have been described as "hot and bloody" because of their overperfusion relative to the body overall.</li></ul> <p>Overperfusion and underperfusion should not be confused with hypoperfusion and hyperperfusion, which relate to the perfusion level relative to a tissue's current need to meet its metabolic needs. For example, hypoperfusion can be caused when an <a href="/facts/Artery/Y1Yj0jat">artery</a> or <a href="/facts/Arteriole/HYVG0g7P">arteriole</a> that supplies blood to a volume of tissue becomes blocked by an <a href="/facts/Embolus/BtxKo3rM">embolus</a>, causing either no blood or at least not enough blood to reach the tissue. Hyperperfusion can be caused by <a href="/facts/Inflammation/Ura86MIy">inflammation</a>, producing <a href="/facts/Hyperaemia/Snf41s0k">hyperemia</a> of a body part. Malperfusion, also called poor perfusion, is any type of incorrect perfusion. There is no official or formal dividing line between hypoperfusion and <a href="/facts/Ischemia/ySL9xbCl">ischemia</a>; sometimes the latter term refers to zero perfusion, but often it refers to any hypoperfusion that is bad enough to cause <a href="/facts/Necrosis/zCPsTeWx">necrosis</a>. </p> <h2 id="measurement">Measurement</h2> <p class="note">Main article: <a href="/facts/Perfusion_scanning/SvvkLuV4">Perfusion scanning</a></p> <p>In equations, the symbol Q is sometimes used to represent perfusion when referring to <a href="/facts/Cardiac_output/7JCDn6Ht">cardiac output</a>. However, this terminology can be a source of confusion since both cardiac output and the symbol Q refer to <a href="/facts/Volumetric_flow_rate/X5KI7zzH">flow</a> (volume per unit time, for example, L/min), whereas perfusion is measured as flow per unit tissue mass (mL/(min·g)). </p> <h3>Microspheres</h3> <p class="note">Main article: <a href="/facts/Microspheres/bYKcPY7F">Microspheres</a></p> <p>Microspheres that are labeled with <a href="/facts/Radioactive_isotopes/5WpCfbdq">radioactive isotopes</a> have been widely used to measure perfusion since the 1960s. Radioactively labeled particles are injected into the test subject and a <a href="/facts/Radiation_detector/rYj0qKtA">radiation detector</a> measures radioactivity in tissues of interest.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Microspheres are used in <a href="/facts/Radionuclide_angiography/ye8JCW1y">radionuclide angiography</a>, a method of diagnosing heart problems. </p><p>In the 1990s, methods for using <a href="/facts/Fluorescent/qsJVT2qP">fluorescent</a> microspheres became a common substitute for radioactive particles.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <h3>Nuclear medicine</h3> <p class="note">Main article: <a href="/facts/Nuclear_medicine/L9Dzjd90">Nuclear medicine</a></p> <p>Perfusion of various tissues can be readily measured <a href="/facts/In_vivo/kWcWyl6f">in vivo</a> with nuclear medicine methods which are mainly <a href="/facts/Positron_emission_tomography/5SmcW6qz">positron emission tomography</a> (PET) and <a href="/facts/Single_photon_emission_computed_tomography/ag6of05C">single photon emission computed tomography</a> (SPECT). Various radiopharmaceuticals targeted at specific organs are also available, some of the most common are: </p> <ul><li><a href="/facts/Technetium-99m/HgIqtvrv">99mTc</a> labelled <a href="/facts/HMPAO/J4tW12pN">HMPAO</a> and ECD for brain perfusion (<a href="/facts/Cerebral_blood_flow/e9E1ED4B">rCBF</a>) studied with SPECT</li> <li><a href="/facts/Technetium-99m/HgIqtvrv">99mTc</a> labelled <a href="/facts/Tetrofosmin/CIXgsmSU">Tetrofosmin</a> and <a href="/facts/Technetium_(99mTc)_sestamibi/o1BrcIl9">Sestamibi</a> for <a href="/facts/Myocardial_perfusion_imaging/fqu6TaN8">myocardial perfusion imaging</a> with SPECT</li> <li><a href="/facts/Xe-133/Yz78R52h">133Xe</a>-gas for absolute quantification of brain perfusion (<a href="/facts/Cerebral_blood_flow/e9E1ED4B">rCBF</a>) with SPECT</li> <li><a href="/facts/Oxygen-15/ektDXb8B">15O</a>-labeled water for brain perfusion (<a href="/facts/Cerebral_blood_flow/e9E1ED4B">rCBF</a>) with PET (absolute quantification is possible when measuring arterial radioactivity concentration)</li> <li><a href="/facts/Rubidium-82_chloride/sFfyYHfh">82Rb-chloride</a> for measuring myocardial perfusion with PET (absolute quantification is possible)</li></ul> <h3>Magnetic resonance imaging</h3> <p class="note">Main article: <a href="/facts/Magnetic_resonance_imaging/Vh9yG9qq">Magnetic resonance imaging</a></p> <p>Two main categories of magnetic resonance imaging (MRI) techniques can be used to measure tissue perfusion <a href="/facts/In_vivo/kWcWyl6f">in vivo</a>. </p> <ul><li>The first is based on the use of an injected <a href="/facts/Contrast_agent/uVoPWL7Q">contrast agent</a> that changes the <a href="/facts/Magnetic_susceptibility/hWMbGTjP">magnetic susceptibility</a> of blood and thereby the MR signal which is repeatedly measured during <a href="/facts/Bolus_(medicine)/R1HoCrB8">bolus</a> passage.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a></li> <li>The other category is based on <a href="/facts/Arterial_spin_labelling/N2jaA3p5">arterial spin labelling</a> (ASL), where arterial blood is <a href="/facts/Magnet/vvrg6VSk">magnetically</a> tagged before it enters into the tissue being examined and the amount of labelling that is measured and compared to a control recording obtained without spin labelling.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a></li></ul> <h3>Computed tomography (CT)</h3> <p class="note">Main article: <a href="/facts/Computed_tomography/NusPJ2S8">Computed tomography</a></p> <p>Brain perfusion (more correctly transit times) can be estimated with contrast-enhanced computed tomography.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <h3>Thermal diffusion</h3> <p class="note">Main article: <a href="/facts/Molecular_diffusion/lcIz28qY">Molecular diffusion</a></p> <p>Perfusion can be determined by measuring the total <a href="/facts/Molecular_diffusion/lcIz28qY">thermal diffusion</a> and then separating it into <a href="/facts/Thermal_conductivity/qWnSG3nQ">thermal conductivity</a> and perfusion components.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> <a href="/facts/RCBF/e9E1ED4B">rCBF</a> is usually measured continuously in time. It is necessary to stop the measurement periodically to cool down and reassess the <a href="/facts/Thermal_conductivity/qWnSG3nQ">thermal conductivity</a>. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Reperfusion_injury/3MWNux98">Reperfusion injury</a> – Tissue damage after return of blood supply following ischemia or hypoxia</li> <li><a href="/facts/Machine_perfusion/gRW6uT0n">Machine perfusion</a></li> <li><a href="/facts/Perfusionist/VtxVW2lH">Perfusionist</a> – Healthcare professional who uses the cardiopulmonary bypass machine</li> <li><a href="/facts/Myocardial_perfusion_imaging/fqu6TaN8">Myocardial perfusion imaging</a> – Nuclear medicine imaging method</li> <li><a href="/facts/Cerebral_circulation/e9E1ED4B">rCBF</a> – Brain blood supply</li> <li><a href="/facts/Cerebral_edema/UDlqKHrV">Cerebral edema</a> – Excess accumulation of fluid in the brain</li> <li><a href="/facts/Pressure_ulcer/YGEFxHbo">Pressure ulcer</a> — continuous external pressure impairs perfusion</li> <li><a href="/facts/Cerebral_perfusion_pressure/r1bEug1s">Cerebral perfusion pressure</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://iperfusion.org/">International Perfusion Association</a></li> <li><a href="https://web.archive.org/web/20150801033810/http://cardiacsurgeryportal.com/">Cardiac Surgery Portal</a></li> <li><a href="https://perfusioneducation.com/blog/">Perfusion Education Portal</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>American Psychological Association (APA): perfusion. (n.d.). Dictionary.com Unabridged (v 1.1). Retrieved March 20, 2008, from Dictionary.com website: http://dictionary.reference.com/browse/perfusion <a href="http://dictionary.reference.com/browse/perfusion" target="_blank">http://dictionary.reference.com/browse/perfusion</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Thomas DL, Lythgoe MF, Pell GS, Calamante F, Ordidge RJ (2000). "The measurement of diffusion and perfusion in biological systems using magnetic resonance imaging". Phys Med Biol. 45 (8): R97-138. doi:10.1088/0031-9155/45/8/201. PMID 10958179. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Engblom H, Xue H, Akil S, Carlsson M, Hindorf C, Oddstig J, Hedeer F, Hansen MS, Aletras AH, Kellman P, Arheden H (2017). "Fully quantitative cardiovascular magnetic resonance myocardial perfusion ready for clinical use: a comparison between cardiovascular magnetic resonance imaging and positron emission tomography". J Cardiovasc Magn Reson. 19 (1): 78. doi:10.1186/s12968-017-0388-9. PMC 5648469. PMID 29047385. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5648469" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5648469</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Perfusion > What is Perfusion?". Cardiovascular Perfusion Forum. <a href="http://www.perfusion.com/cgi-bin/absolutenm/templates/articledisplay.asp?articleid=1548#.VKv4idKrqQM" target="_blank">http://www.perfusion.com/cgi-bin/absolutenm/templates/articledisplay.asp?articleid=1548#.VKv4idKrqQM</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"Perfusion > Perfusion Services". Specialty Care Services Group. Archived from the original on 2018-12-17. Retrieved 2017-01-02. <a href="https://web.archive.org/web/20181217175649/http://www.specialtycare.net/services/perfusion/" target="_blank">https://web.archive.org/web/20181217175649/http://www.specialtycare.net/services/perfusion/</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Larsen, E. H. (2007). "August Krogh (1874–1949): 1920 Nobel Prize". Ugeskrift for Laeger. 169 (35): 2878. PMID 17877986. <a href="/wiki/PMID_(identifier)" target="_blank">/wiki/PMID_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Sulek, K. (1967). "Nobel prize for August Krogh in 1920 for his discovery of regulative mechanism in the capillaries". Wiadomosci Lekarskie. 20 (19): 1829. PMID 4870667. <a href="/wiki/PMID_(identifier)" target="_blank">/wiki/PMID_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Studies of the Circulation with Radioactive Microspheres., Wagner et al, Invest. Radiol., 1969. 4(6): p. 374-386. <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"Fluorescent Microspheres" (PDF). Fluorescent Microsphere Resource Center. Archived from the original (PDF) on 2012-10-02. <a href="https://web.archive.org/web/20121002175850/http://fmrc.pulmcc.washington.edu/DOCUMENTS/FMRCMAN99.pdf" target="_blank">https://web.archive.org/web/20121002175850/http://fmrc.pulmcc.washington.edu/DOCUMENTS/FMRCMAN99.pdf</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Huettel, S. A.; Song, A. W.; McCarthy, G. (2009), Functional Magnetic Resonance Imaging (2 ed.), Massachusetts: Sinauer, ISBN 978-0-87893-286-3 <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Detre, John A.; Rao, Hengyi; Wang, Danny J. J.; Chen, Yu Fen; Wang, Ze (2012-05-01). "Applications of arterial spin labeled MRI in the brain". Journal of Magnetic Resonance Imaging. 35 (5): 1026–1037. doi:10.1002/jmri.23581. ISSN 1522-2586. PMC 3326188. PMID 22246782. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3326188" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3326188</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>L. Axel. Cerebral blood flow determination by rapid-sequence computed-tomography: theoretical analysis. Radiology 137: 679–686, December 1980 <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Vajkoczy P, Roth H, Horn P, et al. (August 2000). "Continuous monitoring of regional cerebral blood flow: experimental and clinical validation of a novel thermal diffusion microprobe". Journal of Neurosurgery. 93 (2): 265–74. doi:10.3171/jns.2000.93.2.0265. PMID 10930012. S2CID 30375395. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> </ol>