Dan Rettmann

PROMO: Real-time prospective motion correction in MRI using image-based tracking.

Artifacts caused by patient motion during scanning remain a serious problem in most MRI applications. The prospective motion correction technique attempts to address this problem at its source by keeping the measurement coordinate system fixed with respect to the patient throughout the entire scan process. In this study, a new image‐based approach for prospective motion correction is described, which utilizes three orthogonal two‐dimensional spiral navigator acquisitions, along with a flexible image‐based tracking method based on the extended Kalman filter algorithm for online motion measurement. The spiral navigator/extended Kalman filter framework offers the advantages of image‐domain tracking within patient‐specific regions‐of‐interest and reduced sensitivity to off‐resonance‐induced corruption of rigid‐body motion estimates. The performance of the method was tested using offline computer simulations and online in vivo head motion experiments. In vivo validation results covering a broad range of staged head motions indicate a steady‐state error of less than 10% of the motion magnitude, even for large compound motions that included rotations over 15 deg. A preliminary in vivo application in three‐dimensional inversion recovery spoiled gradient echo (IR‐SPGR) and three‐dimensional fast spin echo (FSE) sequences demonstrates the effectiveness of the spiral navigator/extended Kalman filter framework for correcting three‐dimensional rigid‐body head motion artifacts prospectively in high‐resolution three‐dimensional MRI scans. Magn Reson Med, 2010.

Prospective motion correction of high-resolution magnetic resonance imaging data in children

Motion artifacts pose significant problems for the acquisition and analysis of high-resolution magnetic resonance imaging data. These artifacts can be particularly severe when studying pediatric populations, where greater patient movement reduces the ability to clearly view and reliably measure anatomy. In this study, we tested the effectiveness of a new prospective motion correction technique, called PROMO, as applied to making neuroanatomical measures in typically developing school-age children. This method attempts to address the problem of motion at its source by keeping the measurement coordinate system fixed with respect to the subject throughout image acquisition. The technique also performs automatic rescanning of images that were acquired during intervals of particularly severe motion. Unlike many previous techniques, this approach adjusts for both in-plane and through-plane movement, greatly reducing image artifacts without the need for additional equipment. Results show that the use of PROMO notably enhances subjective image quality, reduces errors in Freesurfer cortical surface reconstructions, and significantly improves the subcortical volumetric segmentation of brain structures. Further applications of PROMO for clinical and cognitive neuroscience are discussed.

DIfferential Subsampling with Cartesian Ordering (DISCO): a high spatio-temporal resolution Dixon imaging sequence for multiphasic contrast enhanced abdominal imaging.

To develop and evaluate a multiphasic contrast‐enhanced MRI method called DIfferential Sub‐sampling with Cartesian Ordering (DISCO) for abdominal imaging.

Prospective motion correction improves diagnostic utility of pediatric MRI scans

A new technique for prospectively correcting head motion (called PROMO) during acquisition of high-resolution MRI scans has been developed to reduce motion artifacts. To evaluate the efficacy of PROMO, four T1-weighted image volumes (two with PROMO enabled, two uncorrected) were acquired for each of nine children. A radiologist, blind to whether PROMO was used, rated image quality and artifacts on all sagittal slices of every volume. These ratings were significantly better in scans collected with PROMO relative to those collected without PROMO (Mann-Whitney U test, P < 0.0001). The use of PROMO, especially in motion-prone patients, should improve the accuracy of measurements made for clinical care and research, and potentially reduce the need for sedation in children.

Magnetic resonance imaging in Alzheimer's Disease Neuroimaging Initiative 2

Alzheimers Disease Neuroimaging Initiative (ADNI) is now in its 10th year. The primary objective of the magnetic resonance imaging (MRI) core of ADNI has been to improve methods for clinical trials in Alzheimers disease (AD) and related disorders.

Multiecho time-resolved acquisition (META): a high spatiotemporal resolution Dixon imaging sequence for dynamic contrast-enhanced MRI.

To evaluate a new dynamic contrast‐enhanced (DCE) imaging technique called multiecho time‐resolved acquisition (META) for abdominal/pelvic imaging. META combines an elliptical centric time‐resolved three‐dimensional (3D) spoiled gradient‐recalled echo (SPGR) imaging scheme with a Dixon‐based fat‐water separation algorithm to generate high spatiotemporal resolution volumes.

Variable spatiotemporal resolution three-dimensional dixon sequence for rapid dynamic contrast-enhanced breast MRI

To investigate a new variable spatiotemporal resolution dynamic contrast‐enhanced (DCE) MRI method termed DIfferential Subsampling with Cartesian Ordering (DISCO), for imaging of breast cancer.

High temporal resolution breathheld 3D FIESTA CINE imaging: Validation of ventricular function in patients with chronic myocardial infarction

To develop a gated single‐breathhold, high temporal resolution three‐dimensional (3D) CINE imaging technique and to evaluate its accuracy in volumetric and functional quantification in patients with chronic myocardial infarction.

Contrast-enhanced intracranial magnetic resonance angiography with a spherical shells trajectory and online gridding reconstruction.

To evaluate the feasibility of applying the shells trajectory to single‐phase contrast‐enhanced magnetic resonance angiography.

Zero filled partial fourier phase contrast MR imaging: In vitro and in vivo assessment†

To validate partial Fourier phase contrast magnetic resonance (PC MR) with full number of excitation (NEX) PC MR measurements in vitro and in vivo.