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Multiple Coils (multiple + coil)
Selected AbstractsAccelerating non-contrast-enhanced MR angiography with inflow inversion recovery imaging by skipped phase encoding and edge deghosting (SPEED)JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2010Zheng Chang PhD Abstract Purpose: To accelerate non-contrast-enhanced MR angiography (MRA) with inflow inversion recovery (IFIR) with a fast imaging method, Skipped Phase Encoding and Edge Deghosting (SPEED). Materials and Methods: IFIR imaging uses a preparatory inversion pulse to reduce signals from static tissue, while leaving inflow arterial blood unaffected, resulting in sparse arterial vasculature on modest tissue background. By taking advantage of vascular sparsity, SPEED can be simplified with a single-layer model to achieve higher efficiency in both scan time reduction and image reconstruction. SPEED can also make use of information available in multiple coils for further acceleration. The techniques are demonstrated with a three-dimensional renal non-contrast-enhanced IFIR MRA study. Results: Images are reconstructed by SPEED based on a single-layer model to achieve an undersampling factor of up to 2.5 using one skipped phase encoding direction. By making use of information available in multiple coils, SPEED can achieve an undersampling factor of up to 8.3 with four receiver coils. The reconstructed images generally have comparable quality as that of the reference images reconstructed from full k -space data. Conclusion: As demonstrated with a three-dimensional renal IFIR scan, SPEED based on a single-layer model is able to reduce scan time further and achieve higher computational efficiency than the original SPEED. J. Magn. Reson. Imaging 2010;31:757,765. © 2010 Wiley-Liss, Inc. [source] Transvenous Embolization of Small Patent Ductus Arteriosus with Single Detachable Coils in DogsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 3 2001Matthias Schneider Transvenous embolization of small patent ductus arteriosus (PDA; , 4 mm) with a single detachable coil was attempted in 24 dogs (median age 5.7 months, range, 2.6,65.5 months; median body weight 5.5 kg, range, 1.5,30.0 kg). Angiographic imaging of the duct and pressure measurements were made before and after embolization. The minimal ductal diameter was 2.7 ± 0.7 mm. In all dogs, a single coil was employed regardless of residual shunting. Ten dogs (PDA minimal diameter range, 1.5-2.2 mm) received a 5-mm coil, and 14 dogs (PDA minimal diameter range, 2.9-3.6 mm) received a 8-mm coil. After coil embolization the angiographic shunt grade decreased significantly (n = 20, P < .001). Residual shunts were assessed by angiography 15 minutes after and by Doppler echocardiography 1,3 days and 3 months after the intervention. In the dogs treated with the 5-mm coils the residual shunt rate was low (0%, 10%, and 0% for angiography and Doppler echocardiography at 1,3 days and 3 months, respectively), in contrast to the dogs treated with the 8-mm coils (91%, 79%, and 67% for angiography and Doppler echocardiography at 1,3 days and 3 months, respectively). After 3 months, no residual murmur was found in dogs treated with the 5-mm coils (0/7), in contrast to murmurs in 5 of 12 (42%) dogs treated with the 8-mm coils. Despite incomplete closure in these dogs, volume loading of the left heart decreased in all dogs. Pulmonic or aortic coil embolism did not occur. Analysis of initial results shows that single detachable coil embolization is possible in all dogs with a small PDA (, 4 mm), but only very small PDA (s 2.5) could be treated effectively, and for the moderate PDA (2.6-4.0 mm) longer coils or multiple coils may be necessary to achieve complete occlusion. [source] Transcatheter Closure of Patent Ductus Arteriosus Using Occluding Spring CoilsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 4 2000A. A. Stokhof The purpose of this study is to report our initial experience with the use of spring coils to close the patent ductus arteriosus in the dog. There are few large-patient series reported in the veterinary literature. Coil closure was attempted in 15 dogs (median weight, 6.5 kg; range, 1.2 to 38.7 kg) presenting with a patent ductus arteriosus between May 1997 and May 1999. Arterial catheterization followed by angiography was used to decide if coil placement was adequate. A 5- or 8-mm embolization coil, depending on the angiographic diameter of the ductus, was delivered, with 1 loop in the pulmonary arterial side and the remainder of the coil in the aortic side of the duct. Additional coils were used if a residual shunt was present, and closure was confirmed by aortography. Patients were discharged the day after the procedure. Successful coil closure, without residual shunt on angiography, was achieved in 11 of 13 dogs in which coils were released. In 6 dogs, a coil embolized to the pulmonary artery. Four of these dogs had successful closure with multiple coils, and 2 others had surgery. None of these dogs experienced adverse effects. In 2 dogs with conical patent ductus arteriosus >5 mm in minimal diameter, coil closure was not done. We conclude that the patent ductus arteriosus size and anatomical shape are crucial in deciding whether coil closure is the method of choice. In selected cases, coil closure represents an elegant alternative to surgical ligation. Although pulmonary embolism occurred commonly, it did not cause any obvious clinical problem. [source] Undersampled radial MRI with multiple coils.MAGNETIC RESONANCE IN MEDICINE, Issue 6 2007Iterative image reconstruction using a total variation constraint Abstract The reconstruction of artifact-free images from radially encoded MRI acquisitions poses a difficult task for undersampled data sets, that is for a much lower number of spokes in k-space than data samples per spoke. Here, we developed an iterative reconstruction method for undersampled radial MRI which (i) is based on a nonlinear optimization, (ii) allows for the incorporation of prior knowledge with use of penalty functions, and (iii) deals with data from multiple coils. The procedure arises as a two-step mechanism which first estimates the coil profiles and then renders a final image that complies with the actual observations. Prior knowledge is introduced by penalizing edges in coil profiles and by a total variation constraint for the final image. The latter condition leads to an effective suppression of undersampling (streaking) artifacts and further adds a certain degree of denoising. Apart from simulations, experimental results for a radial spin-echo MRI sequence are presented for phantoms and human brain in vivo at 2.9 T using 24, 48, and 96 spokes with 256 data samples. In comparison to conventional reconstructions (regridding) the proposed method yielded visually improved image quality in all cases. Magn Reson Med 57:1086,1098, 2007. © 2007 Wiley-Liss, Inc. [source] Evaluating the multiple coil configurations of the EM38DD and DUALEM-21S sensors to detect archaeological anomaliesARCHAEOLOGICAL PROSPECTION, Issue 2 2009David Simpson Abstract The multiple coil configurations of two electromagnetic induction sensors were tested on a field with strong electrical and magnetic contrasts. The first sensor, EM38DD, measures either the apparent electrical conductivity (ECa or ,a) or the apparent magnetic susceptibility (MSa or ,a) of the soil at two coil orientations. The second sensor, DUALEM-21S, measures both ECa and MSa at two coil orientations and two coil separations. The goal was to test if measuring with the multiple coils resulted in a better detection of near-surface artefacts and the natural soil variability. The ECa of all coil configurations was closely related to the depth of a clay substrate beneath the topsoil sandy loam, which was verified by soil augering. Configurations with a shallower theoretical depth of exploration were less influenced by the clay substrate. Combining two coil configurations revealed important ECa anomalies, not visible on individual measurements, associated with a brick wall foundation and a former ditch. The MSa maps showed totally different anomaly patterns, related to anthropogenic disturbances in the soil, such as the filling-in with brick rubble of a former pond. Depending on the depth and thickness of the disturbance and the relative response of the sensor configurations, the MSa anomalies were entirely positive for one configuration but other configurations also had negative anomalies. It was concluded that multiple coil configurations provide a better insight into the build-up of the soil profile and are better able to detect anomalies than single measurements. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||