Arterial resistivity index
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| name = Arterial resistivity index
| image = ResistivityPourcelotIndexLDH.gif
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| caption = Arterial resistivity index (right) from retinal laser Doppler imaging (left).
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| purpose = measure of pulsatile blood flow
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The arterial resistivity index (also called as Resistance index, abbreviated as RI), developed by Léandre Pourcelot [https://fr.wikipedia.org/wiki/Léandre_Pourcelot], is a measure of pulsatile blood flow that reflects the resistance to blood flow caused by microvascular bed distal to the site of measurement. It is primarily used in ultrasound imaging to evaluate arteries and solid organ damage.
Calculation
The formula used to calculate resistance index is:{{cite book|last=Sistrom|first=Theodore E. Keats, Christopher|title=Atlas de medidas radiológicas|url=https://archive.org/details/atlasdemedidasra00keat|url-access=limited|year=2002|publisher=Harcourt|location=Madrid|isbn=978-84-8174-612-9|pages=[https://archive.org/details/atlasdemedidasra00keat/page/n482 481]}}
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Description
| class="wikitable" | |
| Resistance index | Description |
|---|---|
| 0 | Continuous flow |
| 1 | Systolic flow, but no diastolic flow |
| >1 | Reversed diastolic flow |
The RI is altered not by vascular resistance alone but by the combination of vascular resistance and vascular compliance.{{cite journal|last=Bude|first=RO|author2=Rubin, JM|title=Relationship between the resistive index and vascular compliance and resistance.|journal=Radiology|date=May 1999|volume=211|issue=2|pages=411–7|pmid=10228522|doi=10.1148/radiology.211.2.r99ma48411}}{{cite journal |vauthors=Boas FE, Desser TS, Kamaya A |title=Does separating the resistive index into pre- and post-glomerular resistance and vascular compliance improve the diagnostic accuracy of renal transplant doppler ultrasound? |journal=American Journal of Roentgenology |volume=196 |issue=5 |pages=A84–A87 |year=2011 |url=http://www.stanford.edu/~boas/science/RI/index.html|doi=10.2214/ajr.196.5_supplement.0a84}}
Normal mean renal artery RI for an adult is 0.6 with 0.7 the upper limit of normal. In children, RI commonly exceeds 0.7 through 12 months of age and can remain above 0.7 through 4 years of age.American Journal of Roentgenology. 2003;180: 885-892. 10.2214/ajr.180.4.1800885
Medical uses
It is used in ultrasound testing of umbilical artery for placental insufficiency. RI should not exceed 0.60 at 30 weeks of gestation.{{cite book|last=Hobbins|first=John C.|title=Obstetric ultrasound : artistry in practice|year=2007|publisher=Blackwell|location=Oxford|isbn=978-1-4051-5815-2|pages=37}}
It is also used to assess the kidneys for medical renal disease, as can occur with diabetes or kidney transplants damaged by rejection.{{cite journal |last1=K C |first1=T |last2=Das |first2=SK |last3=Shetty |first3=MS |title=Renal Resistive Index: Revisited. |journal=Cureus |date=March 2023 |volume=15 |issue=3 |pages=e36091 |doi=10.7759/cureus.36091 |doi-access=free |pmid=37065373 |pmc=10096815 }} Following kidney transplantation, patients with an RI > 0.8 have an increased mortality.N Engl J Med. 2013 Nov 7;369(19):1797-806. doi: 10.1056/NEJMoa1301064.
Mapping of the local arterial resistivity index from laser Doppler imaging enables unambiguous identification of retinal arteries and veins on the basis of their systole-diastole variations, and reveal ocular hemodynamics in human eyes.Puyo, Léo, Michel Paques, Mathias Fink, José-Alain Sahel, and Michael Atlan. "Waveform analysis of human retinal and choroidal blood flow with laser Doppler holography." Biomedical Optics Express 10, no. 10 (2019): 4942-4963.
See also
- Pulsatility index
- Leandre Pourcelot (French)