Motion Artifacts & Correction
Thursday 23 April 2009
Room 313BC 16:00-18:00


Heidi A. Ward and Maxim Zaitsev

16:00 749. Automatic Heart Rate Dependent Timing Adjustments in Dark Blood Turbo-Spin Echo Sequences with and Without STIR Preparation
    Wolfgang G. Rehwald1, Hannes Kutza2, Peter Weale, Jeanette Schulz-Menger3
Siemens Medical Solutions, Chicago, IL, USA; 2Humboldt Universitaet, Berlin, Germany; 3Franz-Volhard-Klinik, Charité, Berlin, Germany
    The quality of STIR TSE images can be degraded in patients with high heart rates due to poor registration of STIR preparation slab and imaging slice, and due to imperfect blood nulling. To overcome this problem, we developed an algorithm that calculates the optimal TI to null blood based on the patient’s heart rate and sets the trigger pulse, time of dark blood preparation and readout, and temporal resolution accordingly. It was implemented in a standard TSE sequence and tested in 37 patients and volunteers on a Siemens MAGNETOM Avanto. Image quality was much improved as confirmed by trained observers.
16:12 750. Hybrid US/MR System for Real-Time Compensation of Breathing Motion Artifacts in Cardiovascular MRI at 3 Tesla
    Daniel Giese1, Andre Bongers2, Jürgen Jenne2, Matthias Günther2, Bernd Jung1, Daniela Foell3, Maxim Zaitsev1, Jürgen Hennig1, Wim de Boer4, Michael Markl1
Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2mediri GmbH, Heidelberg, Germany; 3Cardiology and Angiology, University Hospital Freiburg, Freiburg, Germany; 4Institut für Experimentelle Kernphysik, Universität Karlsruhe (TH), Karlsruhe, Germany

Real-time prospective motion compensation in cardiac MR at 3 Tesla using B-mode ultrasound imaging in combination with a tracking algorithm is presented. We present first results of a hybrid MR/US system with low-latency real-time feedback to the MR sequence at 3 Tesla. In-Vivo results using single heartbeat gating show no disadvantages compared to single-heartbeat MR navigators.

In contrast to commonly used MR navigator gating, the presented ultrasound gating avoids drawbacks such as signal saturation, steady-state interruption or MR navigator induced ECG misregistration, therewith expanding the potential of the high frequency position information towards further applications including real-time slice following and ECG gating.

16:24 751. Real-Time Adaptive Suppression of MR Gradient Artifacts on Electrocardiograms Using a New 3D Hall Probe
    Julien Oster1,2, Joris Pascal3, Olivier Pietquin1,4, Michel Kraemer5, Jean-Philippe Blondé3, Jacques Felblinger1,2
U947, Inserm, Nancy, France; 2IADI, Nancy-Université, Nancy, France; 3InESS, CNRS - Université de Strasbourg, Strasbourg, France; 4IMS Research Group, SUPELEC Metz Campus, Metz, France; 5Schiller Médical, Wissembourg, France
    Cardiac MR Acquisitions have to be synchronized with heart activity to avoid motion artifacts. Electrocardiogram (ECG) is the most accurate tool for this purpose. MR environment induces artifacts on ECG signals due to static magnetic field, Radiofrequency pulses and magnetic gradients. In this paper a new real-time gradient artifact reduction method, which does not require any connection to the MR system, is presented. A new Hall probe, integrated on a 0.35um CMOS technology provides information on magnetic gradients. The presented method gives similar results than state of art and enables real-time triggering.
16:36 752. An Alternative Concept for Non-Sequence Interfering, Contact-Free Respiration Monitoring
    Ingmar Graesslin1, Henry Stahl1, Kay Nehrke1, Paul Harvey2, Jouke Smink2, Giel Mens2, Andreas Senn1, Peter Börnert1
Philips Research Europe, Hamburg, Germany; 2Philips Healthcare, Best, Netherlands
    Respiratory motion is a challenging problem in MRI, especially in abdominal and cardiac imaging. Recently, a new principle was proposed for respiratory motion detection, which has the potential to overcome problems associated with respiratory navigators. It is based on the evaluation of motion-induced changes in the properties of the employed RF transmit coil. Thus, real-time information on respiratory motion can be obtained completely independent from the MR image acquisition sequence. The present method was implemented on a clinical MR system, and the measured respiratory motion curve was compared with that obtained with conventional respiratory navigators.
16:48 753. Assessing and Correcting Respiration Induced Variation of B1 in the Liver
    Francesco Padormo1, Shaihan Malik1, Joseph V. Hajnal1, David J. Larkman1
Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, UK
    Quantitative sequences, such as those used in the liver, require accurate knowledge of flip angle. This work explores the effect of breathing on the B1 field in the liver. An average change of δθ = 4.8±0.8° within an ROI was seen between the inhale and exhale states in six subjects. A subject was then imaged with an 8 transmit channel whole body coil and RF shimming used to correct the variation between maximum inhalation and maximum exhalation. The variation between states was reduced from 1.6° to 0.97° for this subject.
17:00 754. High Precision Translational Motion Correction for Micro-MRI of Trabecular Bone Using Cartesian Navigators
    Hamidreza Saligheh Rad1, Micheal J. Wald1, Jeremy F. Magland1, Felix W. Wehrli1
Radiology, University of Pennsylvania, Philadelphia, PA, USA
    High-resolution MRI has demonstrated potential for in-vivo quantification of trabecular network integrity. Since scan times are relatively long displacements due to involuntary subject motion usually occur in spite of tight immobilization, causing substantial errors in the derived structural parameters. Correction via navigator tracking of motion significantly improves image sharpness and thus reproducibility. We show that accuracy of motion correction critically hinges on navigator SNR, and propose optimal design of the navigators within the framework of 3D FLASE pulse sequence. Performance improvements achieved are expected to yield improved reproducibility for the study of drug intervention in patients undergoing treatment for osteoporosis.
17:12 755. 3D SAP-EPI Motion-Corrected Fast Susceptibility Weighted Imaging
    Samantha J. Holdsworth1, Stefan Skare1, Karley Marty1, Matus Straka1, Roland Bammer1
Lucas MRS/I Center, Stanford University, Stanford, CA, USA
    Typically, the 3D GRE sequence has been used for susceptibility-weighted imaging (SWI). However, this suffers from a long scan time, which decreases patient through-put and increases the chances of motion artifacts. A 3D GRE-EPI trajectory has been proposed as a faster alternative. However, unless the data are acquired with several interleaves, the images may suffer from considerable blurring and geometric distortion artifacts. Here, a 3D short-axis readout propeller (SAP)-EPI trajectory used with parallel imaging is suggested as an alternative approach to both 3D GRE and 3D GRE-EPI. With its inherent ability to allow motion correction and fast scan time, 3D SAP-EPI may be a useful candidate for SWI, particularly in uncooperative patients.
17:24 756. Motion Compensation with Floating Navigator and GRAPPA Operators
    Wei Lin1, Feng Huang1, Yu Li1, Charles Saylor1, Arne Reykowski1
Invivo Corp., Philips Healthcare, Gainesville, FL, USA
    A method for motion correction in multi-coil imaging applications, involving both data collection and reconstruction, is presented. Floating navigator (FNAV) method, which acquires a readout line along ky≠0 line, is expanded to detect translation/rotation and non-consistent motion, using a correlation measure. The flexibility of GRAPPA operator is exploited by (a) extrapolating readout lines to fill in missing “pie-slice” of k-space caused by rotational motion, and (b) regenerating full k-space from a reduced dataset, therefore allowing subsequent correction or the replacement of rejected non-consistent views. In vivo turbo spin-echo brain imaging experiments demonstrate the correction of severe motion artifacts.
17:36 757. Multi Channel Self Navigated Motion Correction
    Jason Mendes1, Dennis L. Parker1
UCAIR, University of Utah, Salt Lake City, UT, USA
    The use of phase correlation to detect rigid-body translational motion is reviewed and applied to individual echotrains in turbo-spin-echo data acquisition. It is shown that when the same echotrain is acquired twice, the subsampled correlation provides an array of delta-functions, from which the motion that occurred between the acquisitions of the two echotrains can be measured. It is shown further that a similar correlation can be found between two sets of equally spaced measurements that are adjacent in k-space.
17:48 758. MR-Assisted PET Motion Correction for Neurological Applications
    Ciprian Catana1, Andre van der Kouwe1, Thomas Benner1, Michael Hamm2, Bastien Guerin3, Larry Byars4, Christian Michel4, Georges El Fakhri3, Matthias Schmand4, Bruce R. Rosen1, A. Gregory Sorensen1
MGH, Radiology, A.A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA; 2Siemens Medical Solutions USA Inc., Charlestown, MA, USA; 3Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, MA, USA; 4Siemens Medical Solutions USA Inc., Knoxville, TN, USA
    Integrated MR-PET scanners capable of simultaneous data acquisition have recently been developed. An application that could benefit from simultaneity is MR-assisted PET motion correction. Typically, subject motion is difficult to avoid; in longer studies (more than a few minutes) or in uncooperative patients this motion leads to degradation (blurring) of PET images and in more severe cases to introduction of artifacts. Improved motion correction could be very beneficial to PET and an elegant solution presents itself in a combined MR-PET instrument.