The extension of MR imaging to new applications has demonstrated the limitations of the architecture of current real-time systems. Traditional real-time implementations provide continuous acquisition of data and modification of basic sequence parameters on the fly. We have extended the concept of real-time MRI by designing a system that drives the examinations from a real-time localizer and then gets reconfigured for different imaging modes. Upon operator request or automatic feedback the system can immediately generate a new pulse sequence or change fundamental aspects of the acquisition such as gradient waveforms excitation pulses and scan planes. This framework has been implemented by connecting a data processing and control workstation to a conventional clinical scanner. Key components on the design of this framework are the data communication and control mechanisms, reconstruction algorithms optimized for real-time and adaptability, flexible user interface and extensible user interaction. In this paper we describe the various components that comprise this system. Some of the applications implemented in this framework include real-time catheter tracking embedded in high frame rate real-time imaging and immediate switching between real-time localizer and high-resolution volume imaging for coronary angiography applications.
J. M. Santos, B. S. Hu, J. H. Lee, J. M. Pauly Electrical Engineering, Stanford University, Stanford, California, United States, Cardiovascular Medicine, Palo Alto Medical Foundation, Palo Alto, California, United States Introduction: We have previously demonstrated a single breath-hold whole-heart acquisition method using variable density spirals [1]. Taking advantage of the restricted FOV created by the sensitivity profile of a surface coil, controlled undersampling can reduce the acquisition time without introducing coherent aliasing artifacts. One important characteristic of the previously presented method is that it acquires the volumetric data in a multislice fashion with an ultra short acquisition widow (less than 6 ms). This provides great immunity to motion. In this abstract we present an extension using multiple acquisition coils with localized sensitivity demodulation to improve the SNR and volumetric coverage.
This article reviews the requirements for successful compressed sensing (CS), describes their natural fit to MRI, and gives examples of four interesting applications of CS in MRI. The authors emphasize on an intuitive understanding of CS by describing the CS reconstruction as a process of interference cancellation. There is also an emphasis on the understanding of the driving factors in applications, including limitations imposed by MRI hardware, by the characteristics of different types of images, and by clinical concerns.
Parallel imaging using sophisticated receiver coils has improved the clinical feasibility of magnetic resonance coronary angiography (MRCA).These techniques, however, are not readily available outside advanced imaging centers.Our custom-made 2-element phased array coil is readily and inexpensively assembled to address this limitation and enable the widespread application of MRCA.The 2-element phased array coil, comprised of two 4-inch, overlapping circular coils, is specifically designed for MRCA.We compare our prototype coil to two commercially available coils commonly used for MRCA.MRCA has been performed in 14 normal volunteers.Anatomic coverage, image quality, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) are calculated for each coil.The prototype coil has imaged 92.6% (125/135) of the segments compared to 83.7% (113/135) and 76.3% (103/135) (p = 0.002) using the surface coil and cardiac phased array coil, respectively.Excellent or good (grade 1-2) image quality has been attained in 85.9% (116/135) of all the coronary segments using the prototype coil compared to 77.0% (104/135) and 71 % (96/135) using the surface and cardiac phased array coils, respectively (p = 0.025).Overall, higher SNR and CNR have been achieved by the prototype coil compared to the surface and the cardiac phased array coils (SNR: 13.5 ± 5.3 vs 12.2 ± 3.7 vs 9.0 ± 3.1 and CNR: 7.5 ± 5.5 vs 6.2 ± 3.3 vs 3.7 ± 2.7, respectively).Compared to two commercially available coils, the 2-element phased array coil is associated with overall improved SNR and CNR and provides higher image quality with wider anatomic coverage.
