Clinical experience with rapid 2DFT SSFP imaging at low field strength (original) (raw)
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Clinical experience with rapid 2DFT SSFP imaging of the brain at low field strength
Magnetic Resonance Imaging, 1987
A rei rospecl ive analysjs of clinical imaging using 2DFT SSFP al 0.14 T is presented. The technique's potential for tissue charncterization and ils utility for clinical di agnosis were tested by both in virro measurements of various tissues and in vh-'o clinical images. Different pulse angles not only influenced image confrast, bul also helped char acterize lesio ns, particularly thosc containing fat. In addition, the pulse angle changed the signal £rom venous now perpendicular (0 the imagcd slice. The slow' flow' sensith'ily of the 2DFT SSFP technique was de monstruted in Ih e deteclion of CSF molion. Rapid SSFP offers flow' se nsWvity and adequate lesion detecting ab ility, along with high palicnl throughput. Keywords: Fast imaging; 20FT SSFP; Tissue contrast; Flow se nsilivity; rf pulse angle; Low field stre ngth. RECEIVED 8/ 31/ 87; ACCEPTED 12/ 9/ 87 . This work was supported in part by Natio nal Institutes Address correspondence and reprint requesrs (0 Ferenc A , of HealUl grants 1 K04 NSOI 083-02 and 1 ROI NS Jo lesz. M .D " Depanrnent of Radiology. Bdgham a nd Wo 23093-02. men 's Hospital , 75 Francis Street, BOSlo n, MA 02 ) 15, 397
Magnetic Resonance Imaging, 2011
Accurate depiction of the vessels of the lower leg, foot, or hand benefits from suppression of bright MR signal from lipid (such as bone marrow) and long-T1 fluid (such as synovial fluid and edema). Signal independence of blood flow velocities, good arterial/muscle contrast, and arterial/ venous separation are also desirable. The high SNR, short scan times, and flow properties of balanced steady-state free precession (SSFP) make it an excellent candidate for flow-independent angiography. In this work, a new magnetization-prepared 3D SSFP sequence for flow-independent peripheral angiography is presented. The technique combines a number of component techniques (phase-sensitive fat detection, inversion recovery, T2-preparation, and square-spiral phase-encode ordering) to achieve high-contrast peripheral angiograms at only a modest scan time penalty over simple 3D SSFP. The technique is described in detail, a parameter optimization performed, and preliminary results presented achieving high contrast and 1 mm isotropic resolution in a normal foot.
Imaging of slow flow by three-dimensional MP-SSFP
Journal of Magnetic Resonance (1969), 1991
Missing-pulse steady-state free precession (MP-SSFP) imaging has been described by Sattin (I) and analyzed by Patz (2) as an SSFP variant which avoids the static inhomogeneity artifacts inherent in gradient-refocused SSFP imaging sequences . Although the sensitivity to motion was noted and later demonstrated by Patz ) the full form of the response, and particularly the versatility of MP-SSFP as a threedimensional imaging tool, has yet to be fully exploited. Since most real flow systems show a 3D structure, the collection of a true 3D dataset is particularly valuable, and it is that which we demonstrate in this Communication. Importantly, we note that it is possible to optimize the imaging sequence to the sample properties for a particular fluid system.
Magnetic Resonance in Medicine, 1990
In tissue perfusion studies, FT velocity distribution imaging (VDI) intrinsically distinguishes signals from moving blood and volume-averaged tissue. Results in human thyroid gland, in vivo, using VDI line scan technique demonstrated separation of moving blood signal from glandular tissue. while VDI inner-volume echo-planar imaging of brain showed only CSF velocity above the image noise level. New alternating polarity gradient sequences which permit separation of diffusion and slow velocity are discussed. A novel method of 3D FT imaging (two spatial and one velocity dimension) combining inner-volume imaging and echo-planar imaging with velocity resolution of 0.15 mm/s per pixel is demonstrated. A novel graphical method of calculation and display of diffusion dependence in pulsed gradient sequences is presented. ci 1990 Academic Press. Inc. sensitive to stresses and deformation of nonfluid materials, i.e., myocardium and brain tissue. VDI revealed reproducible patterns, timing, and direction of internal brain motion (7), demonstrating a brain pumping action on CSF within the ventricular system and producing a to-and-fro movement of CSF. To sensitize an image to velocity, the Stejskal and Tanner (ST) sequence (1 1) of two unipolar gradient pulses separated by an RF inverting pulse is commonly used. Either phase images for velocity (12-15) or magnitude images for diffusion (1 6 , 1 7) can be encoded by changing the strength of the ST gradients. Similarly, a bipolar gradient pulse (6) can be used to produce velocity phase shifts, as Firmin et al. (18) have recently combined with echo-planar and inner-volume imaging techniques.
A noncontrast-enhanced pulse sequence optimized to visualize human peripheral vessels
European Radiology, 2009
A noncontrast-enhanced pulse sequence optimized to visualize human peripheral vessels Abstract The purpose of this paper is to present a pulse sequence optimized to visualize human peripheral vessels. The optimized MR technique is a 3D multi-shot balanced non-SSFP gradient echo pulse sequence with fat suppression. Several imaging parameters were adjusted to find the best compromise between the contrast of vascular structures and muscle, fat, and bone. Most of the optimization was performed in the knee and calf regions using multi-channel SENSE coils. To verify potential clinical use, images of both healthy volunteers and volunteers with varicose veins were produced. The balanced non-SSFP sequence can produce highspatial-resolution images of the human peripheral vessels without the need for an intravenous contrast agent. Both arteries and veins are displayed along with other body fluids. Due to the high spatial resolution of the axial plane source or reconstructed images, the need for procedures to separate arteries from veins is limited. We demonstrate that high signals from synovial joint fluid and cystic structures can be suppressed by applying an inversion prepulse but at the expense of reduced image signalto-noise and overall image quality.
1J-1 Blood Flow Velocity Vector Imaging with High Frame Rate Imaging Methods
2006 IEEE Ultrasonics Symposium, 2006
Conventional blood flow imaging is an important medical diagnostic tool. In this paper, the same processing technique is applied to the high frame rate (HFR) imaging method developed previously to obtain two-dimensional (2D) (in principle, the method is also applicable to three-dimensional (3D)) blood flow velocity vector images. This takes advantage of the HFR imaging method where multiple 2D or 3D images, instead of a single line, can be reconstructed from a single transmission with multiple reception beams steered at different angles. To show the feasibility of the method, an in vivo experiment of an artery of the right arm of a volunteer was performed with a home-made HFR imaging system. In the experiment, a broadband linear array transducer of 128 elements, 5-MHz center frequency, 38.4-mm aperture, 5-mm elevation width, and 20-mm elevation focal distance was used. The transducer was excited with a one-cycle sine wave centered at the frequency of the transducer to produce pulsed plane waves at a repetition period of 80 microseconds. Echo signals were digitized at 40-MHz and 12-bit resolution. A set of two 2D radio-frequency (RF) (before the envelope detection) images steered at 0 (perpendicular to the transducer surface) and 15 degrees in reception, respectively, was reconstructed from each transmission. Blood flow velocity component images were reconstructed simultaneously from these images with the conventional color flow processing techniques using 16 transmissions. Combining the velocity component images, velocity vector images at a frame rate of 12,000 frames/s can be obtained.