Caipirinha is Brazil's national cocktail, made from sugar cane liqueur (cachaça), sugar, ice, and lime. It received some recent increased world-wide recognition as the result of news coverage of the 2014 FIFA World Cup.
In MRI, however, CAIPIRINHA is a parallel imaging technique offered by Siemens and used primarily for 3D breath-hold abdominal imaging. The acronym stands for Controlled Aliasing in Parallel Imaging Results in Higher Acceleration.
CAIPIRINHA uses a group unique k-space sampling patterns to reduce pixel aliasing and overlap on reconstructed images. Acquired points in k-space are shifted from one another by applying additional offsets to the phase-encoding gradient tables.
In the second diagram a better strategy has been adopted with the acceleration evenly split between the ky and kz directions. Every other line of data has thus been skipped in each of the two phase-encode directions. The total acceleration remains at 4 (R = 2 x 2).
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Additional Notes on CAIPIRINHA
Although an example using GRAPPA was shown above, CAIPIRINHA can be used with either SENSE or GRAPPA algorithms. It may also be used with non-cartesian methods.
In addition to the so-called Δ=2 alternating phase method shown in the third diagram above, many different CAIPIRINHA sampling patterns are possible. The number of possibilities exponentially increases with the acceleration factor (R).
Caipirinha. Wikipedia, the Free Encyclopedia.
Breuer F, Blaimer M, Griswold M, Jakob P. Controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA). MAGNETOM Flash 2012;1:2-7. (Siemens promotional brochure).
Breuer FA, Blaimer M, Mueller MF, et al. Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA). Magn Reson Med 2006; 55:549-556.
Yutzy SR, Seiberlich N, Duerk JL, Griswold MA. Improvements in multislice parallel imaging using radial CAIPIRINHA. Magn Reson Med 2011; 65:1630-1637.
What is parallel imaging? How does this differ from "regular" imaging?