A 64 MHz half-birdcage resonator for clinical imaging

Ballon, Douglas; Graham, Martin C.; Miodownik, Saul; Koutcher, Jason A.

doi:10.1016/0022-2364(90)90371-f

Cited by 25 publications

(32 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Shielded ECG leads were inserted subcutaneously in a surgery. The animal was then placed within a half sine-spaced birdcage probe (Ballon, Graham, Midownik & Koutcher, 1990) and transported to the MRI system for imaging. Images were acquired in synchrony with the R wave of the ECG.…”

Section: Animal Prepacrationmentioning

confidence: 99%

A quantitative description of dynamic left ventricular geometry in anaesthetized rats using magnetic resonance imaging

Crowley

Huang²,

Gates³

et al. 1997

Experimental Physiology

View full text Add to dashboard Cite

SUMMARYWe report a functional application of magnetic resonance imaging (MRI) for the quantitative description of left ventricular geometry through systole and diastole in normal anaesthetized Wistar rats that might be applicable for the analysis of chronic changes resulting from pathological conditions. Images of cardiac anatomy were acquired through planes both parallel and perpendicular to the principal cardiac axis at times that were synchronized to the R wave of the electrocardiogram. The images of the transverse sections were assembled into three-dimensional representations of left ventricular geometry at consecutive time points through the cardiac cycle. This confirmed the geometrical coherence of the data sets, that each slice showed circular symmetry, and that the images were correctly aligned with the appropriate anatomical axes. Different models for the three-dimensional geometry of the left ventricle were then tested against the epi-and endocardial surfaces reconstructed from images of the transverse sections of the left ventricle in both systole and diastole using least-squares minimizations in three dimensions. In agreement with previous reports in the human heart, an elliptical figure of revolution offered an optimal fit to the epicardial and endocardial geometry for the rat heart in diastole. This was in preference to models that used spherical, quartic or parabolic geometries. However, in contrast to contraction in the human heart, all these geometrical representations broke down during systolic ejection in the rat heart. We therefore introduced a more general hybrid model which described left ventricular geometry in terms of the variation of the radii r(z), independently determined for each slice, with its position z along the principal cardiac axis. The resulting function r(z) could then be described by a simple ellipsoid of revolution not only during diastole, but also throughout ventricular ejection. The findings also ruled out alternative geometrical representations. It was then possible additionally to reconstruct the luminal and total left ventricular volumes, wall thicknesses and ejection fractions through the cardiac cycle and to confirm that the predicted total ventricular wall volume was conserved throughout the cardiac cycle. Our hybrid model of cardiac geometry may thus be useful for non-invasive serial studies of chronic pathological changes that use the rat as a model experimental system.

show abstract

Section: Animal Prepacrationmentioning

confidence: 99%

A quantitative description of dynamic left ventricular geometry in anaesthetized rats using magnetic resonance imaging

Crowley

Huang²,

Gates³

et al. 1997

Experimental Physiology

View full text Add to dashboard Cite

show abstract

“…Considering the operational constraints imposed by size and access requirements of the rabbit knee to be evaluated, the present work extends the dual-frequency coil simultaneous image concept to include a double-tuned circuit with an input parallel resistor, inductor, and capacitor ( RLC ) auxiliary resonant circuit in series with an open coil design based on a geometry proposed by Ballon, et al . [4] and Jin et al . [5].…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Dual Frequency $^{1}{\rm H}$ and $^{19}{\rm F}$ Open Coil Imaging of Arthritic Rabbit Knee at 3T

Hockett

Wallace

Schmieder

et al. 2011

IEEE Trans. Med. Imaging

137

View full text Add to dashboard Cite

The combination of sensitive magnetic resonance techniques with a selective site-targeted nanoparticle contrast agent has a demonstrated utility for molecular imaging studies. By detecting a unique signature of the contrast agent, this approach can be employed to identify specific bio-molecular markers and observe cellular-level processes within a large and complex organism (e.g., in vivo rabbit). The objective of the present investigation was to design, fabricate and characterize a radio-frequency (RF) coil for the dual frequency (1H and 19F) simultaneous collection of both nuclei images in a 3T field, in order to facilitate studies of arthritic knee degradation in rabbits. The coil supports both transmit and receive modes. The supporting activities included: 1) establishing a technical database for calculating the required coil parameters, 2) selection of a favorable coil geometry, and 3) adaption of existing RF measurement techniques to the design, development and electrical evaluation of the coil. The coil is used in conjunction with a Philips Medical Systems clinical MRI scanner, requiring all RF simultaneous dual frequency (1H and 19F) coils to operate in both transmit and receive modes. A commercial version of SPICE (simulation program with integrated circuit emphasis) was used to estimate significant operational parameters prior to fabricating the imaging coil. Excellent images were obtained with the fabricated coil and no operational problems were observed that would limit the use of other coil geometries and field strengths.

show abstract

“…The imaging gradients were produced using conventional Maxwell and Golay coils wound on a former of internal diameter 15 cm; each gradient axis was powered by two Techron 7560 and 7570 amplifiers (Crown International Inc., Elkhart, IN, USA) arranged in a series slaveÏmaster configuration (Carpenter et al 1989). The RF coil was a home-built half-sine-spaced birdcage probe (Ballon et al 1990) of internal diameter 4·5 cm. Images were obtained using a multislice gradient-echo sequence, with an echo time of approximately 5 ms.…”

Section: Magnetic Resonance Imagingmentioning

confidence: 99%

“…This subsequently enabled image acquisition to be synchronized or gated to the QRS complex of the electrocardiogram. The animal was then placed within a half sinespaced birdcage radio frequency (RF) probe (Ballon et al 1990), an oscillating circuit which was tuned to the frequency of the proton resonance (83·6 MHz). The probe was approximately half-cylindrical in shape, with an internal diameter of 4·5 cm and a length of 14 cm, and with open ends.…”

Section: Physiological Protocolsmentioning

confidence: 99%

Magnetic resonance imaging analysis of left ventricular function in normal and spontaneously hypertensive rats

Wise

Huang

Gresham

et al. 1998

The Journal of Physiology

View full text Add to dashboard Cite

We have used magnetic resonance imaging (MRI) to examine acute morphological changes in the left ventricle throughout the cardiac cycle in normal Wistar Kyoto rats (WKY) and also to follow the development of chronic changes in spontaneously hypertensive rats (SHR). This involved the development of MRI and quantitative analysis techniques for characterizing contractile changes during the cardiac cycle. Images of the cardiac anatomy in two age groups (8 and 12 weeks old) of young anaesthetized adult normal WKY and SHR were acquired in planes both parallel and perpendicular to the principal cardiac axis. Complete coverage of the heart by imaging planes was achieved with high time resolution (13 ms), with typically 12 time frames in the cardiac cycle, using a short echo time (5 ms) multislice gradient‐echo imaging sequence. Imaging was synchronized to the R wave of the electrocardiogram. The image slices could be reconstructed into complete geometrically and temporally coherent three‐dimensional data sets. Left ventricular (LV) volumes were thus reconstructed throughout the cardiac cycle by combining transverse cardiac image sections. This volume analysis revealed structural and functional differences between the normal WKY and SHR in both age groups of 8 and 12 weeks. Measurements from the cardiac images were additionally validated against histological measurements. The SHR showed a raised LV end‐systolic volume and a correspondingly poorer ejection fraction as well as LV hypertrophy when compared with the controls. Left ventricular function in the SHR appeared stable between the two age groups. We developed a simple geometrical model of the left ventricle based on a single longitudinal image section and successfully used this to describe some functional parameters of the left ventricle in the WKY and SHR. This geometrical model has the potential to greatly reduce the imaging time needed to study the beating heart in future serial investigations of cardiac physiology in rats. Our experimental and analytical methods together form a powerful set of quantitative techniques which combine both imaging and functional analysis and will be applicable for future studies of chronic physiological changes in animal disease models.

show abstract

A 64 MHz half-birdcage resonator for clinical imaging

Cited by 25 publications

References 1 publication

A quantitative description of dynamic left ventricular geometry in anaesthetized rats using magnetic resonance imaging

A quantitative description of dynamic left ventricular geometry in anaesthetized rats using magnetic resonance imaging

Simultaneous Dual Frequency $^{1}{\rm H}$ and $^{19}{\rm F}$ Open Coil Imaging of Arthritic Rabbit Knee at 3T

Magnetic resonance imaging analysis of left ventricular function in normal and spontaneously hypertensive rats

Contact Info

Product

Resources

About