Wave-CAIPI - XA31
This Video reviews Wave-CAIPI a fast new acqusition technique.
MRI is an imaging technique where acquisition speed still remains a challenge. Fast MRI acquisitions often rely on efficient subsampling of all raw data points in what is known as the case space subsampling trajectory's an achievable acceleration factors are typically restricted by hardware limitations. Wave Kai is a fast acquisition method that is based on the idea of controlled aliasing. While providing multi planar views and eliminating the need for redundant acquisitions in different planes, wave Kipi uses a Corkscrew readout trajectory combined with the 2D Kuiper ENEA subsampling pattern to efficiently encode the case base and spread the voxel aliasing. It is a combination of the following two imaging techniques. The first one is wave. This is referring to the gradient waveforms where oscillating phase encoding gradients. GY and GZ are played during the readout. The standard Cartesian 3D acquisition is displayed here as red lines for comparison. The gradient waveforms results in a Corkscrew K space trajectory along the readout direction. The second one is Chi. Chi is short for Kyrenia. This is the acronym for controlled aliasing in parallel imaging results in higher acceleration. Chi is an improved parallel imaging technique that makes optimal use of coil sensitivity profile information by adapting the case based subsampling. The acquired points in case base are shifted from one another by applying additional offsets in the phase encoding direction. An algorithm then reconstructs the missing gaps from the K space by combining information from the acquired points. This means you can spread the aliasing and achieve higher acceleration in combination with kyp. The gradient waveforms result in Corkscrew trajectory zancai space which are staggered due to the kipi sampling. Please note this case space shows the projection of the 3D wave trajectory onto the 2D K space. Therefore the point spread function PSF needs to be considered in parallel. Imaging reconstruction to recover the image. In the image domain, the additional phase due to the Corkscrew trajectory results in voxel spreading along the readout direction, which varies linearly as a function of the spatial Y&Z position. When combined with the inner slice shifts from 2D Kuiper Enia, a well distributed aliasing pattern is created across all three spatial dimensions. This allows wave kipi to take full advantage of the 3D coil sensitivity information and enables higher acceleration factors compared to standard parallel imaging, such as grappa or two D Kuiper ENEA. Furthermore, noise amplification and residual artifact level is reduced when comparing similar acceleration factors for standard parallel image ingane wave chi. Consequently, you can either improve image quality while maintaining the acceleration factor, or you can increase the acceleration factor while maintaining acceptable noise amplification or residual artifact level. In order to use wave kipi you need the Wave Coyote license. To avoid folden artifacts, the transversal orientation needs to be selected, and an external reference scan is mandatory. The Wave Copy protocol is available for 3DS Wii Head acquisitions with the Grem wave sequence. To start wave Kipi protocol, go to the Dot cockpit, select under head SWI in the library, the Wave Copy protocol. The selected protocol can be easilly loaded into the examination Q via drag and drop. Wave Kipi is the only enabled acceleration mode in the grem wave sequence. Under the routine and Resolution task card, you can set different dimmed options. Such as slice oversampling contrasts. Both contrasts are flow compensated interpolation slice phase, partial Fourier asymmetric echo. As soon as the acquisition starts, please inform the patient that the acoustic noise is higher compared to conventional imaging.
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