Local bi‐planar gradient array design using conformal mapping and simulated annealing

Moon, Sung M.; Goodrich, K. Craig; Hadley, J. Rock; Parker, Dennis L.

doi:10.1002/cmr.b.20130

Cited by 6 publications

(4 citation statements)

References 23 publications

(29 reference statements)

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“…The cylinder-to-conventional-planar transformation is performed with the transform published previously (26), and the cylinder-to-superellipse transformation is performed with the transformation described by Equation [6] with a=1, b=0.7143, m=6, n=6.…”

Section: Resultsmentioning

confidence: 99%

“…In this study, the stream function is parameterized by a piecewise cubic hermite interpolating polynomial. The piecewise hermite interpolated stream function requires fewer control points and can create a wider range of useful stream function shapes than a simple power function (26). Further, the piecewise hermite interpolation creates smooth transitions leading to wire patterns without sharp wire bends for easier winding implementation in the actual gradient coil construction process.…”

Section: Methodsmentioning

confidence: 99%

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Superelliptical insert gradient coil with a field‐modifying layer for breast imaging

Moon

Goodrich

Hadley

et al. 2010

Magnetic Resonance in Med

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Many MRI applications such as dynamic contrast-enhanced MRI of the breast require high spatial and temporal resolution and can benefit from improved gradient performance, e.g., increased gradient strength and reduced gradient rise time. The improved gradient performance required to achieve high spatial and temporal resolution for this application may be achieved by using local insert gradients specifically designed for a target anatomy. Current flat gradient systems cannot create an imaging volume large enough to accommodate both breasts; further, their gradient fields are not homogeneous, dropping off rapidly with distance from the gradient coil surface. To attain an imaging volume adequate for bilateral breast MRI, a planar local gradient system design has been modified into a superellipse shape, creating homogeneous gradient volumes that are 182% (G x ), 57% (G y ), and 75% (G z ) wider (left/right direction) than those of the corresponding standard planar gradient. Adding an additional field-modifying gradient winding results in an additional improvement of the homogeneous gradient field near the gradient coil surface over the already enlarged homogeneous gradient volumes of the superelliptical gradients (67%, 89%, and 214% for G x , G y , and G z respectively). A prototype y-gradient insert has been built to demonstrate imaging and implementation characteristics of the superellipse gradient in a 3 T MRI system. Magn Reson Med 65:863-872, 2011. V C 2010 Wiley-Liss, Inc.Key words: superellipse gradient; breast imaging; planar gradient; insert gradient; field modifying Many imaging tasks, such as dynamic contrast-enhanced MRI for breast lesion characterization, can benefit from high spatial and temporal resolution. The improved gradient performance required for high spatial and temporal resolution may be achieved by local gradient coils such as planar insert gradients. With higher gradient strength and slew rate, the local planar gradient can attain higher spatial and temporal resolution than the body gradients.In general, local gradient coils are designed to produce a smaller homogeneous gradient volume (HGV) compared with that of the MRI system whole-body gradients. For local planar gradients, the x-gradient, which requires four fingerprint patterns per plane rather than two fingerprints as in the y-gradient, results in the most limited imaging volume. As a result, for certain applications such as breast imaging, the HGV may be too small to cover the entire desired imaging region (i.e., both breasts). Because of the small imaging volume, there have been very few attempts to image both breasts simultaneously with a local gradient system (1).MRI of the female breast is performed typically with the patient in a prone position to reduce breathinginduced motion artifacts and increase reproducibility. This position places the breast near the planar insert gradient. However, the magnetic field as well as gradient strength of uniplanar gradient systems falls off nearly exponentially with distance from the coil surfa...

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Superelliptical insert gradient coil with a field‐modifying layer for breast imaging

Moon

Goodrich

Hadley

et al. 2010

Magnetic Resonance in Med

Self Cite

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“…The cylinder‐to‐conventional planar transformation is performed with the transform published previously (26), and the cylinder‐to‐superellipse transformation is performed with the transformation described by Eq. 6 with a = 1, b = 0.7143, m = 6, n = 6.…”

Section: Resultsmentioning

confidence: 99%

Pediatric and Adult Interventional Cardiac Symposium (PICS/AICS 2010)

2010

Cathet Cardio Intervent

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Introduction: Pulmonary artery (PA) rehabilitation is one of the most common procedures performed in the cardiac catheterization laboratory, but solid data on procedure-related adverse events (AE) is scarce with most studies reporting small retrospective, single center experiences. Methods: Data was prospectively collected using a multi-center registry (C3PO). Between 02/07 and 12/09, 8 institutions submitted details on 1315 procedures (proc) that included either balloon angioplasty or stent implantation within a proximal or lobar branch PA. Results: The majority of patients (pts) had either complex 2-ventricle circulation (71%), or single-ventricle physiology (22%). The median age was 3.5 years (1d -70yr). Out of 2894 PA intervention, balloon angioplasty was performed in 51% (>8Atm in 34%), cutting balloon angioplasty in 14%, stent-angioplasty in 14%, and stent implantation in 21%. Procedures included interventions on proximal PAs in 60%, lobar branches in 17%, or both in 23%. Four or more PA lesions were treated in 9% proc. 81% of cutting balloons were used in lobar branches, whereas 82% of all stents were used in proximal branch PAs. Additional interventions were performed in 38% proc. Out of 324 total AE 53% were observed in 815 proc without additional cath interventions: No more than minor AE were documented in 9% proc; moderate/major/ catastrophic (level 3-5) AE were documented in 9% proc. 0.1% patients died as a direct result of the procedure. Type of AE included arrhythmias (16%), hypoxia or hypotension (10%), bleed via ET tube/reperfusion injury (16%), vascular trauma/tear/ aneurysm (19%), balloon rupture/stent migration/ malposition and stentrelated problems (14%), AE at vascular entry site (9%), and other AE (16%). AE were classified as not preventable in 49%, as possibly preventable in 43%, and as preventable in 8%. Factors associated with an increased incidence of level 3-5 AE included age <1 month (31% vs. 10%), date since last surgery <30 days (22% vs. 9%), number of treated lesions >4 (20% vs. 9%). There was a trend for increased risk of AE in pts with complex 2-ventricle and suprasystemic RV (21% vs. 14%). The incidence of level 3-5 AE was not related to weight, use of inotropes at start, location (proximal/lobar) and single vs. complex 2v. Conclusion: PA rehab is associated with not insignificant morbidity. Neonates, early postop period, and multi-level rehab are risk factors for level 3-5 AE.Background: Transcatheter treatment of many congenital and structural heart defects became the method of treatment. Recently new device -Cardio-O-Fix (COF) was introduced into clinical practice. Methods: Five patients aged 0,5 -69 years were included to the study -2 with ASD, 1 with PFO and cryptogenic stroke, and 2 with PDA (one 6 months old infant with additional hypertrophied cardiomyopathy, and 53 y old women after previous ligation of PDA with its recanalization). All were treated percuatneously with Cardio-O-Fix Occluders. There were no preliminary patient selection -the only limitation was the size o...

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“…These gradient coils consist of two planar coils: one positioned below the subject and the other above. Uniplanar gradient coils have also been designed (Li et al 2007, Yoda 1990, Vegh et al 2005, Petropoulos 1999, Moon et al 2007 and built (Aksel et al 2007, Roemer et al 1988, Lemdiasov et al 2004, Shi et al 1996, Cho and Yi 1991, Green et al 2002 in both single-axis (Green et al 2002, Roemer et al 1988, Lemdiasov et al 2004, Shi et al 1996 and three-axis (Cho and Yi 1991, Aksel et al 2007, Demyanenko et al 2009 configurations. These gradient coils are located beneath the subject and are capable of producing high gradient efficiencies and slew rates over local regions of interest.…”

Section: Introductionmentioning

confidence: 99%

A cradle-shaped gradient coil to expand the clear-bore width of an animal MRI scanner

Gilbert¹,

Gati

Klassen

et al. 2009

Phys. Med. Biol.

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The never ending quest for higher magnetic field strengths in MRI and MRS has led to small and medium bore scanners at 9.4 T and above for both human and animal use; however, these bore diameters restrict the size of object that can be accommodated when using a conventional gradient coil. By replacing a cylindrical gradient-coil insert with a single-sided gradient coil, the scanner's functionality can be extended to include localized imaging of wider samples. As a prototype, a three-axis, cradle-shaped gradient coil was designed, fabricated and implemented in a 9.4 T animal MRI scanner. Since gradient fields are required only to be monotonic over the desired field of view, the cradle gradient coil was designed to produce high gradient efficiencies (up to 2.25 mT m(-1) A(-1) over a 5 cm imaging region) at the expense of gradient linearity. A dedicated three-dimensional algorithm was developed to correct the resultant image distortion. Preliminary images of a grid phantom and a mouse demonstrated the fidelity of the algorithm in correcting image distortion of greater than 200%. Eddy currents were measured along each gradient axis. A large 65.2 (Hz mT(-1) m) B(0) eddy current was produced by the y-axis, suggesting potential limitations of single-sided gradient coils.

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Local bi‐planar gradient array design using conformal mapping and simulated annealing

Cited by 6 publications

References 23 publications

Superelliptical insert gradient coil with a field‐modifying layer for breast imaging

Superelliptical insert gradient coil with a field‐modifying layer for breast imaging

Pediatric and Adult Interventional Cardiac Symposium (PICS/AICS 2010)

A cradle-shaped gradient coil to expand the clear-bore width of an animal MRI scanner

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