The International Society for Magnetic Resonance in Medicine. Research directions in MR imaging.

Department of Diagnostic Radiology, Stanford University School of Medicine, Lucas MRI Center, CA 94305-5488, USA.
Radiology (Impact Factor: 6.21). 06/1998; 207(2):289-95. DOI: 10.1148/radiology.207.2.9577469
Source: PubMed
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    ABSTRACT: Contrast agent free time-of-flight magnetic resonance angiography (TOF-MRA) was applied to the intraluminal thread occlusion model of experimental stroke in rat. It was combined with perfusion- and diffusion-weighted imaging (PWI and DWI) sequences to correlate occlusion and reopening of the middle cerebral artery with alterations in these well-established magnetic resonance sequences. Since TOF-MRA can be repeated without limitations, the time course of vascular patency is demonstrated during an experimental period of up to 8 h (2 h control, 1 h ischemia, 3-6 h reperfusion). With an acquisition time of 10 min, TOF-MRA proved to be suitable to analyze the vascular state of occlusion and reperfusion repetitively in longitudinal studies. Spatial resolution was sufficient to observe neurovascular structural details. In eight out of 10 animals complete vessel occlusion by the intraluminal thread could be validated by an entirely extinguished signal of the ipsilateral middle cerebral artery (MCA) in the angiograms. This was in accordance with a perfusion deficit in the MCA vascular territory detected by PWI (reduction to 30.4 +/- 7.4% relative to contralateral side) and a disturbance of water ion homeostasis monitored by DWI in this area. One animal showed a delayed occlusion after 30 min of MCA occlusion, in another animal vessel occlusion failed. In seven out of the eight successful occlusion experiments there was immediate reperfusion after withdrawal of the thread. One animal showed a delayed reperfusion after suture retraction. Remarkable hemispheric differences in vascular branching of the MCA could be recognized in three out of 10 animals. In conclusion, TOF-MRA is considered a helpful method to survey even in small laboratory animals the correct time course of vascular occlusion and reopening in experimental ischemia, and provides complementary information to the tissue perfusion status monitored by PWI and the ischemic lesion territory detected by DWI.
    NMR in Biomedicine 09/2001; 14(5):289-96. · 3.56 Impact Factor
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    ABSTRACT: In this paper we describe a hardware and software environment for making available quantitative blood flow data inside and outside the magnetic resonance (MR) scanner room during MR-guided diagnostic and therapeutic interventions. The configuration allows for triggered and nontriggered examinations and provides the interventionalist with updated results within 1 second from data acquisition. The practicality of the setup and its potential for clinical and investigative purposes are demonstrated in vitro and in vivo. J. Magn. Reson. Imaging 1999;10:845–850. © 1999 Wiley-Liss, Inc.
    Journal of Magnetic Resonance Imaging 11/1999; 10(5):845 - 850. · 2.57 Impact Factor
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    ABSTRACT: MR gradient systems with higher slew rates and gradient amplitude enable certain forms of imaging that are not practical with older gradient systems. These newer pulse sequences include single shot half-Fourier T2-weighted images and echo planar imaging. More important in MR imaging of the pelvis, these gradient systems benefit more conventional imaging methods such as gadolinium-enhanced 3D MR angiography, dynamic gradient echo contrast-enhanced images, and T2-weighted fast spin echo images, by shortening echo times. For most MR imaging of the pelvis, spatial resolution is paramount, and therefore sequences such as half-Fourier acquisition Turbo spin echo (HASTE) and 3D gadolinium-enhanced dynamic imaging play a less important role than in the upper abdomen. The potential of these techniques for diffusion or perfusion studies in the pelvis has not been explored.
    European Journal of Radiology 04/1999; 29(3):233-44. · 2.16 Impact Factor