University of Pennsylvania

Walter R T Witschey

Francisco Contijoch

Robert C Gorman

Ravinder Reddy

Ari Borthakur

Mark A Elliott

Yuchi Han

Joseph H Gorman, Iii

Mark Elliot

Eugene E Gualtieri

An adaptive real-time radial k-space sampling trajectory (ARKS) can respond to a physiologic feedback signal to reduce motion effects and ensure sampling uniformity. In this adaptive k-space sampling strategy, the most recent signals from an ECG waveform can be continuously matched to the previous signal history, new radial k-space locations were determined, and these MR signals combined using multi-shot or single-shot radial acquisition schemes. The disclosed methods allow for improved MRI imaging.

Method and device for magnetic resonance imaging data acquisition guided by physiologic feedback

Electrocardiogram (ECG)-gated cardiac magnetic resonance imaging (MRI) alone may be unable to capture the hemodynamics associated with arrhythmic events. As a result, values such as ejection fraction are acquisition dependent. The desired RR-duration determines the arrhythmia rejection. By combining real-time volume measurements with ECG recordings, beat morphologies can be categorized and a more comprehensive evaluation of ventricular function during arrhythmia can be provided.

Assessment of hemodynamic function in arrhythmia patients

A retrospective reconstruction method uses cardiac self-gating for patients with severe arrhythmias. Self-gated myocardial systolic and diastolic motion is determined from low-spatial and high-temporal resolution images and then the MRI-dataset is retrospectively reconstructed to obtain high quality images. The method uses undersampled image reconstruction to obtain the low-spatial and high-temporal resolution images, including those of different beat morphologies. Processing of these images is utilized to generate a cardiac phase signal. This signal allows for arrhythmia detection and cardiac phase sorting. The cardiac phase signal allows for detection of end-systolic and diastolic events which allows for improved sampling efficiency. In the case of frequent and severe arrhythmia, the method utilizes data from the normal and interrupted beats to improve sampling and image quality.

Non-cartesian retrospective reconstruction of cardiac motion in patients with severe arrhythmia

A spin locked balanced steady-state free precession (slSSFP) pulse sequence combines a balanced gradient echo acquisition with an off-resonance spin lock pulse for fast MRI. The transient and steady-state magnetization trajectory is solved numerically using the Bloch equations and is shown to be similar to balanced steady-state free precession (bSSFP) for a range of T2/T1 and flip angles, although the slSSFP steady-state could be maintained with considerably lower RF power. In both simulations and brain scans performed at 7T, slSSFP is shown to exhibit similar contrast and SNR efficiency to bSSFP, but with significantly lower power.

Spin locked balanced steady-state free precession (slSSFP) with off-resonance spin locked pulses interleaved with imaging gradients

Methods of, and systems for, simultaneously compensating for external-magnetic-field inhomogeneity as well as radiofrequency magnetic-field inhomogeneity in an MRI system. In one method embodiment, a pulse sequence is applied when the transmitter-reference frequency is delivered on resonance. The pulse sequence includes radiofrequency pulses which may be applied at arbitrary-excitation-flip angles that are not necessarily 90&#xb0; degrees. The pulse sequence also includes spin-locking pulses applied in concert with a refocusing-composite pulse. In another method embodiment, a pulse sequence is applied when the transmitter-reference frequency is delivered off resonance. This off-resonance-pulse sequence includes radiofrequency pulses which may be applied at arbitrary-excitation-flip angles that are not necessarily 90&#xb0; degrees. Sandwiched between the excitation-flip angles are at least two off-resonance-spin-lock pulses applied at an inverse phase and frequency from each other.

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Philadelphia, PA, United States of America

Walter R T Witschey