Real-time Cine
What do you do if the patient can't hold her breath or has multiple intruding arrhythmias?
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These situations are precisely the clinical scenarios for which real-time cine imaging has been developed. Real-time cine comprises a group of single-shot echo-planar methods that allow acquisition of bright blood cardiac images less than 1 second per slice without breath holding. The trade-off for increased speed is decreased spatial resolution, as can be appreciated from the somewhat blurry real-time image below.
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Current commercially available real-time cardiac MRI sequences are based on modifications of traditional parallel imaging techniques (T-SENSE and T-GRAPPA). In these methods the (auto)calibration data is acquired continuously from several contiguous cardiac frames. Read conjugate symmetry and strong gradients permit echo times of less than 1 ms. Either Cartesian or radial scanning may be used.
In the example right we show a real-time T-GRAPPA cardiac image using these parameters: TR = 38 ms, TE = 0.9 ms, α = 80º, matrix = 80 x 128, slice thickness = 8 mm, and R = 3.
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Single frame from real time cardiac study
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In the near future you can expect to witness considerable improvements using a variety of innovative imaging strategies, such as radial FLASH with iterative image reconstruction or compressed sensing methods.
References
Breuer FA, Kellman P, Griswold MA, Jakob PM. Dynamic autocalibrated parallel imaging using temporal GRAPPA (TGRAPPA). Magn Reson Med 2005; 53:981-985.
Ding Y, Chung YC, Jekic M, Simonetti OP. A new approach to autocalibrated dynamic parallel imaging based on the Karhunen-Loeve transform: KL-TSENSE and KL-TGRAPPA. Magn Reson Med 2011; 65:1786-92.
Feng L, Srichai MB, Lim RP, et al. Highly accelerated real-time cardiac cine MRI using k-t SPARSE-SENSE. Magn Reson Med 2013; 70:64-74.
Madore B, Hoge WS, Chao T-C, et al. Retrospectively gated cardiac cine imaging with temporal and spatial acceleration. Magn Reson Imaging 2011; 29:457-469.
Xue H, Kellman P, Larocca G, et al. High spatial and temporal resolution retrospective cine cardiovascular magnetic resonance from shortened free breathing real-time acquisitions. J Cardiovasc Magn Reson 2013 14:15:102.
Uecker M, Zhang S, Voit D, et al. Real-time MRI at a resolution of 20 ms. NMR Biomed 2010; 23: 986-994.
Breuer FA, Kellman P, Griswold MA, Jakob PM. Dynamic autocalibrated parallel imaging using temporal GRAPPA (TGRAPPA). Magn Reson Med 2005; 53:981-985.
Ding Y, Chung YC, Jekic M, Simonetti OP. A new approach to autocalibrated dynamic parallel imaging based on the Karhunen-Loeve transform: KL-TSENSE and KL-TGRAPPA. Magn Reson Med 2011; 65:1786-92.
Feng L, Srichai MB, Lim RP, et al. Highly accelerated real-time cardiac cine MRI using k-t SPARSE-SENSE. Magn Reson Med 2013; 70:64-74.
Madore B, Hoge WS, Chao T-C, et al. Retrospectively gated cardiac cine imaging with temporal and spatial acceleration. Magn Reson Imaging 2011; 29:457-469.
Xue H, Kellman P, Larocca G, et al. High spatial and temporal resolution retrospective cine cardiovascular magnetic resonance from shortened free breathing real-time acquisitions. J Cardiovasc Magn Reson 2013 14:15:102.
Uecker M, Zhang S, Voit D, et al. Real-time MRI at a resolution of 20 ms. NMR Biomed 2010; 23: 986-994.
Related Questions
How do they make those movies of the beating heart?
How do they make those movies of the beating heart?