% % This file was created by the Typo3 extension % sevenpack version 0.7.14 % % --- Timezone: CEST % Creation date: 2013-05-21 % Creation time: 15-08-54 % --- Number of references % 6 % @Inproceedings { 5555, title = {On Image Registration in Magnetic Resonance Imaging}, journal = {Proceedings of the First International Conference on BioMedical Engineering and Informatics (BMEI 2008)}, year = {2008}, month = {5}, pages = {753-757}, abstract = {Image registration is used in many fields for mapping one image to another. In magnetic resonance imaging (MRI) applications, one of the main uses is for correction of motion- induced artifacts so that subsequent image analysis would be more reliable. This paper gives an introduction to some image registration problems in MRI and functional MRI applications, describes certain commonly used image registration procedures, and discusses their major features. Two potential research topics for improving current image registration procedures are also discussed.}, department = {Department MRZ}, web_url = {http://www.tjut.edu.cn/BMEI2008/}, editor = {Peng, Y. , Y. Zhang}, publisher = {IEEE Computer Society}, address = {Los Alamitos, CA, USA}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Sanya, Hainan, China}, event_name = {First International Conference on BioMedical Engineering and Informatics (BMEI 2008)}, language = {en}, ISBN = {978-0-7695-3118-2}, DOI = {10.1109/BMEI.2008.33}, author = {Qiu, P and Nguyen, T} } @Poster { 5765, title = {Parallel Imaging with RASER using Multiband Frequency-modulated Excitation Pulses}, year = {2009}, month = {4}, volume = {17}, number = {2738}, abstract = {The many advantages of the recently proposed RASER sequence have been demonstrated. Hence, RASER holds great promises for functional MRI (fMRI), particularly for studies of the orbital-frontal cortex and other brain regions near air cavities, which cause distortion and signal loss in conventional EPI methods. However, the single-shot RASER sequence implemented so far inherently presents a set of temporal and spatial limitations that hinders it feasibility and full potential for fMRI applications. It is believed that parallel imaging will help overcome such restrictions. In this work, the RASER acquisition and reconstruction scheme is extended for parallel imaging using tailored pulses for simultaneous multi-band excitation.}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2009-02738.pdf}, department = {Department MRZ}, web_url = {http://www.ismrm.org/09/index.htm}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Honolulu, HI, USA}, event_name = {17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009)}, language = {en}, author = {Nguyen, T and Goerke, U and Moeller, S and Ugurbil, K and Garwood, M} } @Poster { 5766, title = {Pushing the limits: Ultrafast 2D accelerated High Resolution Whole-Head Volumetric Functional Imaging at 7 Tesla}, year = {2009}, month = {4}, volume = {17}, number = {3671}, abstract = {In the tendency towards high-field imaging, three-dimensional (3D) acquisition has potential advantages over its two-dimensional counterpart for functional MRI (fMRI). However, multi-slice 2D-EPI methods remain the conventional sequence in fMRI. Although various advanced 3D schemes have alternatively been applied, they come with individual limitations and are not widely available. The 3D-EPI sequence similarly presents temporal constraints, but holds the potential to be feasible by using the increased signal- and contrast-to-noise ratio of ultrahigh magnetic fields combined with the higher parallel imaging performance feasible at ultra-high fields. A hybrid 3D-EPI then offers the possibility for high 2D acceleration. This potential is exploited in this study at 7 Tesla to overcome the limitations and compare results with 2D acquisition and 1D acceleration. Results show the feasibility of a highly accelerated hybrid 3D-EPI scheme for high resolution whole-head acquisition in high-field fMRI, presenting excellent functional results.}, url = {http://www.kyb.tuebingen.mpg.defileadmin/user_upload/files/publications/ISMRM-2009-03671.pdf}, department = {Department MRZ}, web_url = {http://www.ismrm.org/09/index.htm}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Honolulu, HI, USA}, event_name = {17th Annual Meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2009)}, language = {en}, author = {Nguyen, T and Moeller, S and Goerke, U and Yacoub, E and Ugurbil, K} } @Poster { 5554, title = {Noise Analysis of Accelerated 3D-EPI fMRI}, year = {2007}, month = {5}, volume = {2007}, number = {3182}, pages = {613}, abstract = {The spatio-temporal noise properties fundamentally influence the functional result in fMRI. Although the significant gains of three-dimensional acquisition with parallel imaging to fMRI has been shown, the effects of their application on noise and signal properties have so far not been quantitatively considered. This study investigated these aspects by comparing results from conventional 2D multi-slice, 3D-EPI full scan and 3D-EPI with 1-dimensional reduction factors of 2 and 4. Results showed significant signal changes with high acceleration. 3D methods showed comparable signal stability levels to 2D, but yielded overall higher spatio-temporal signal correlations.}, department = {Department MRZ}, web_url = {http://www.ismrm.org/07/}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Berlin, Germany}, event_name = {2007 Joint Annual Meeting ISMRM-ESMRMB}, language = {en}, author = {Nguyen, T and Goerke, U and Ugurbil, K} } @Poster { 5553, title = {Accelerated 3D-EPI fMRI Using Parallel Imaging}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, year = {2006}, month = {9}, volume = {19}, number = {Supplement 1}, pages = {306-307}, abstract = {Introduction: Fast, three-dimensional acquisition is advantageous for fMRI1. While advanced 3D methods have been demonstrated for fMRI, 2Dmulti- slice EPI remains the convention. Extension to 3D-EPI using phaseencoding in the slice selection direction has presented feasible results2, but to our knowledge so far only within the conventional EPI temporal framework. Parallel imaging (PI) can provide a desirable improvement in both temporal resolution and CNR. This work seeks to evaluate some features of employing accelerated 3D-EPI for fMRI compared to conventional method. Methods: Data acquisition: 3T Siemens scanner, 8-channel head coil, segmented EPI sequence. Studies were performed on a healthy volunteer using four EPI schemes: conventional 2D-multi-slice, 3D full volume scan, 3D scans accelerated in 1-dimension with reduction factors R=2 and R=4. All acquisition parameters were identical except for variations inherent to the 2D sequence. Volumes of 20 slices were attained in \verb=~=7 s in 2D-multislice and down to \verb=~=2 s in 3D with R=4. Reconstruction was offline using GRAPPA. Functional imaging: motor task paradigm with self-paced, right-handed finger tapping \verb=~=30s off / 30s on blocks. Time series with 90 repetitions were acquired and activation maps (t-scores) were generated with variations in thresholds accounting for differences in intrinsic CNR and SNR (fig. 2). Results: Results show overall similar activation structure in the contralateral primary motor cortex and the supplementary motor area (fig. 1). Activation was detected consistently with all acquisition schemes (fig. 2), even with high 1-dimensional undersampling. The activation maps for R=4 showed a smaller reduction in t-scores (\verb=~=30 \%) compared to the reduction in SNR (75\%). Further, acceleration reduced total scan time up to a factor of 3.5 relative to the full k-space acquisitions. Conclusion: Acceleration offers significant gains to 3D-EPI for fMRI. Although loss of spatial SNR with shortened acquisition time is expected to reduce t-scores, acceleration is feasible due to the increase in acquired volumes per time and relatively disproportional smaller loss of CNR. Limits to acceleration are indicated in the activation maps as further reduction will give proportionally decreased CNR. However, high 1-dimensional reduction factors were shown to be feasible, achieving both spatial specificity of the functional response and higher temporal resolution than obtainable with 2Dmulti- slice within equal scan durations and spatial coverage. Additionally, a 3D scheme offers the possibility of two-dimensional acceleration for further imaging flexibility.}, department = {Department MRZ}, web_url = {http://www.springerlink.com/content/n70r05532r7q6425/fulltext.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Warsaw, Poland}, event_name = {23rd Annual Scientific Meeting of the ESMRMB 2006}, language = {en}, DOI = {10.1007/s10334-006-0043-1}, author = {Nguyen, T and Moeller, S and Goerke, U and Ugurbil, K} } @Poster { 4167, title = {Correction strategies for segmented spiral imaging at 7 Tesla}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, year = {2006}, month = {9}, volume = {19}, number = {Supplement 1}, pages = {328}, abstract = {Purpose/Introduction: Short acquisition times and short effective echo times are of prime importance for functional MR imaging studies of the brain to reduce distortion artifacts and increase SNR. The spiral sequence, specifically in the segmented version, offers these features and presents itself in specific applications as an alternative to conventional EPI. Spiral imaging is also less prone to flow and motion artifacts. But this method is more demanding on the exact gradient performance and correction mechanisms need to be implemented to achieve necessary readout gradient corrections. Subjects and Methods: To test and illustrate the performance of the implemented corrections, a geometry phantom was measured with a spin echo sequence as a reference and compared with a segmented spiral-out sequence. The measurements were performed on a 7T/ 60 cm Bruker Biospec vertical wide bore monkey MR system. A saddle coil was used in transmit and receive mode. Measurements of the k-space trajectories and images were performed[1]. With the k-space trajectory of the readout gradient the deviation from the theoretical course were calculated. From these the k-space offset, the time delay and the slope and baseline of the gradient courses were derived. The latter is done by comparing trajectories with positive and negative amplitudes. These corrections were then applied for spiral image acquisition and reconstruction. Results: The image where no corrections are applied (Fig.1, middle) shows that the edges of the rectangle inside the phantom are reproduced sharp and at the first look not distorted. It reveals although that the geometry is not at all correct compared to the reference image gained by the MSME sequence (Fig.1, left). Regarding the edges of the phantom in the lower part of the image a strong blurring occurs. Performing now the corrections before acquiring and before reconstructing the image the geometry is reproduced satisfactorily (Fig.1, right). The blurring artifact at the lower edge of the phantom is nearly fully eliminated. Discussion/Conclusion: The measurements of the trajectories and images on a geometry phantom show the efficiency of the corrections. Blurring artifacts are reduced. A misleading geometry like for an image measured with an uncorrected spiral-out EPI sequence can be avoided by applying the corrections. The corrections enable the spiral imaging sequence to be an alternative to conventional EPI in specific applications utilizing short echo times. [1] Takahashi A. et al. MagnResonMed 1995;34:446-456.}, department = {Department Logothetis}, web_url = {http://www.springerlink.com/content/n70r05532r7q6425/fulltext.pdf}, institute = {Biologische Kybernetik}, organization = {Max-Planck-Gesellschaft}, event_place = {Warsaw, Poland}, event_name = {23rd Annual Scientific Meeting of the ESMRMB 2006}, language = {en}, DOI = {10.1007/s10334-006-0043-1}, author = {Kaiser, A and Nguyen, T and Logothetis, NK and Pfeuffer, J} }