Traditional Posters: Functional

Traditional Posters: Functional

fMRI Acquisition

Hall B Monday 14:00-16:00

1077. Separating FID and Echo Contribution in Pass-Band BSSFP FMRI with Multiple-Phase Angle Cycling

Sung-Hong Park1,2, Tae Kim1, Ping Wang1, Timothy Q. Duong2, Seong-Gi Kim1

1Radiology, University of Pittsburgh, Pittsburgh, PA, United States; 2Research Imaging Institute, Ophthalmology/Radiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States

We acquired high resolution multiple phase-cycled bSSFP fMRI datasets in rat brains at 9.4T and separated FID and main echo components based on Fourier analysis. The FID component showed stronger fMRI signals than the main echo component, but it showed stronger correlation with both intracortical veins and cortical surface veins. The fMRI signal from the main echo component could contribute up to half of that from the FID component, implying that the main echo component should not be neglected in interpreting pass-band bSSFP fMRI signals.

1078. A Novel Multi-Echo FMRI Weighting Strategy Using Principal Component Analysis for BOLD Contrast Sensitivity Enhancement

Mark Chiew1,2, Simon James Graham1,2

1Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; 2Rotman Research Institute, Toronto, Ontario, Canada

The use of multi-echo imaging techniques for contrast enhancement in BOLD fMRI is gaining momentum, particularly in real-time fMRI applications. A novel method is presented for combining multi-echo signals in weighted summation using principal component analysis (PCA) derived weights. The method is evaluated on human volunteers performing a simple motor task at 1.5 T, and is compared to other reported weighting schemes. The data driven PCA weighting method is demonstrated to produce time-series that achieve high relative contrast-to-noise ratio gain, without requiring additional data collection.

1079. Variable Density Spiral FMRI

Catie Chang1, Gary Harold Glover1

1Electrical Engineering & Radiology, Stanford University, Stanford, CA, United States

We propose a novel variable-density (VD) spiral k-space trajectory for brain fMRI. The trajectory consists of an Archimedean spiral from the origin out to an arbitrary radius k1, extending beyond k1 with a spiral in which the sampling density decreases as the k-space radius increases. Thus, it allows for a reduction in readout time at the expense of undersampling only high spatial frequencies. We implemented the VD spiral in a single-shot 2D spiral-in/out sequence for high (128x128) resolution, and demonstrate improved activation in a sensory-motor task compared to conventional (fully Archimedean) single-shot and interleaved sequences.

1080. High Resolution BOLD FMRI Using MHASTE

Yongquan Ye1, Yan Zhuo1, Xiaohong Joe Zhou2

1State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics,CAS, Beijing, China; 2University of Illinois Medical Center, Chicago, IL, United States

High resolution BOLD fMRI data on visual cortex were acquired using mHASTE, a novel GRAPPA accelerated single shot TSE technique, and the results were compared with those of GE- and SE-EPI. Higher SNR was obtained with mHASTE than both EPIs, and increased functional activation was detected by mHASTE but not by EPI when going from low resolution to high resolution. mHASTE was also found to have greater activation than both EPI in some cases,especially at high resolution, suggesting a more robust BOLD contrast mechanism for mHASTE in high resolution fMRI.

1081. Functional Magnetic Resonance Imaging Using PROPELLER EPI

Martin Krämer1, Thies Halvor Jochimsen1, Marc Roth1, Jürgen Rainer Reichenbach1

1Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany

A method to improve spatial and temporal resolutions in fMRI using PROPELLER-EPI. First results are shown which demonstrate that a sliding window reconstruction of high resolution long-axis propeller (LAP) data is suitable for simple fMRI experiments. Additionally the results achieved by the LAP measurements are compared to the standard 64x64 EPI sequence which is usually used in fMRI. From there it is shown that the activation maps created from the LAP scans are better localized along the cortex.

1082. Passband BSSFP: Functional Contrast Compared to GRE-EPI and SE-EPI at 3T.

Pål Erik Goa1, Anders Kristoffersen1, Michael H. Chappell2, Rob H. Tijssen3, Asta K. Håberg4, Karla L. Miller3

1Dept. of Medical Imaging, St. Olavs University Hospital, Trondheim, Norway; 2Dept. of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway; 3FMRIB Centre, Oxford University, Oxford, Oxon, United Kingdom; 4Dept. of Neuromedicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway

The functional contrast in passband balanced steady-state free precession (pbSSFP) with 3D segmented EPI readout is compared to that of GRE-EPI and SE-EPI at 3T. For pbSSFP, TR is varied from 6.5 ms to 45 ms. Standard flickering checkerboard paradigm is used. We find that the best functional contrast is obtained at TR = 33 ms with corresponding EPI-factor of 40. At this TR, the functional contrast in pbSSFP is approximately half that of GRE-EPI and twice that of SE-EPI with otherwise comparable scan parameters. False detections due to banding artefacts are present in pbSSFP.

1083. Isotropic Sub-Millimeter FMRI in Humans at 7T

Robin Martin Heidemann1, Dimo Ivanov1, Robert Trampel1, Joeran Lepsien1, Fabrizio Fasano2, Josef Pfeuffer3, Robert Turner1

1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Fondazione Santa Lucia, Rome, Italy; 3Siemens Healthcare Sector, Erlangen, Germany

For isotropic high resolution fMRI at ultra-high field strength, susceptibility effects and T2* decay must be properly addressed. A combination of reduced FOV imaging (zoomed imaging) and parallel imaging is optimized here, achieving acceleration factors of up to 5.5. The high acceleration reduces distortions and image blurring, while incurring no other image artifacts. With this approach, high quality single-shot EPI acquisitions can be obtained with an isotropic resolution of 0.65 mm and sufficient coverage for e.g. fMRI in the visual cortex of the human brain.

1084. Automatic Functional and Anatomical Registration for FMRI Using Optimized 3D Flyback Echo Planar Imaging

Thomas Sushil John1, Michael Lustig2,3, John Mark Pauly2

1Electrical Engineering , Stanford University, Stanford, CA, United States; 2Electrical Engineering, Stanford University, Stanford, CA, United States; 3Electrical Engineering and Computer Science, UC Berkeley, Berkeley, CA, United States

Echo planar imaging (EPI) is the most widely used method for functional MRI. However, functional images are often distorted because EPI is highly sensitive to field inhomogeneities, eddy currents, and gradient delays. Functional and neuro-anatomical registration is complicated by these distortions and by the fact that functional and anatomical images are usually obtained with different imaging sequences. This work investigates the use of an optimized 3D flyback EPI trajectory with echo time shifting to obtain functional and anatomical images that have minimal distortions and are inherently co-registered.

1085. Recovery of Signal Using Spiral-In K-Space Trajectories: Phase Coherence or Intensity Displacement?

Kimberly Brewer1,2, James Rioux1,2, Martyn Klassen3, Chris Bowen1,4, Steven Beyea1,4

1Institute for Biodiagnostics (Atlantic), National Research Council of Canada, Halifax, Nova Scotia, Canada; 2Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada; 3Robarts Research Institute, University of Western Ontario, London, Ontario, Canada; 4Physics and Atmospheric Science, Radiology and Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada

Spiral pulse sequences are commonly used in fMRI, and spiral-in is known to be considerably better than spiral-out at signal recovery in regions with strong susceptibility field gradients. Previously proposed theories in the literature do not address the probability of signal displacement or fully explain all of the differences in signal recovery between spiral-out and spiral-in. In the current work we demonstrate that the difference in image intensity is not due to differences in signal displacement between spiral-in and spiral-out, but rather the increased phase coherence of the displaced pixels when using spiral-in.

1086. Mitigating the Effects of Motion in EPI Time Series

John M. Ollinger1, Andrew L. Alexander1

1Waisman Laboratory for Brain Imaging, University of Wisconsin, Madison, WI, United States

A model for image variance due to motion is developed and validated. It can be used minimize motion effects by optimizing EPI sequence parameters. In general, variance is minimized by minimizing the partial derivative of the steady-state magnetization along the slice axis. In particular, sidelobes contribute much of the noise at high flip angles; an optimum flip angle exists for a specified degree of motion and can be computed; and inter-slice gaps increase variance due to motion rather than decrease it.

1087. Quantitative Evaluation of FMRI Acquisition Strategies at 7T Using NPAIRS

Robert L. Barry1,2, J Christopher Gatenby1,2, Allen T. Newton1,2, Stephen C. Strother3,4, John C. Gore1,2

1Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States; 2Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States; 3Rotman Research Institute of Baycrest, Toronto, ON, Canada; 4Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

Although 2D single-shot EPI is common in BOLD fMRI, recent studies have suggested that 3D multi-shot sequences such as PRESTO-SENSE may offer superior BOLD CNR through improved temporal efficiency. A four-way comparison was performed between 2D and 3D acquisition sequences at two voxel resolutions (1.19x1.19x2 mm3 and 2.19x2.19x2 mm3) at 7T. The quality of fMRI data was evaluated via independent and unbiased metrics of prediction and reproducibility using NPAIRS. Results suggest that EPI provides higher prediction and reproducibility for this study. Future work will investigate within-subject optimization, and further compare EPI with PRESTO-SENSE for an fMRI study requiring whole-brain coverage.

1088. The Effect of Parallel Imaging on the Sensitivity of BOLD Signal to Physiological Noise

Tomas Jonsson1, Tie-Qiang Li1

1Department of Medical Physics, Karolinska University Hospital, S-141 86, Stockholm, Sweden

The sensitivity to physiological noises of the reconstructed BOLD MR images is altered by the employed parallel imaging strategies. In this study, we mapped and compared the physiological noise sensitivity of BOLD fMRI data acquired with and without employing parallel imaging at two different spatial resolutions. Using higher spatial resolution reduces the signal strength and the relative sensitivity to physiological noise. This can be of SNR advantage particularly for time series fMRI data acquired at higher magnetic field.

1089. Multi-Slice Two- And Four-Fold Acceleration with Single- And Eight-Channel Coils, Respectively

Andrzej Jesmanowicz1, Shi-Jiang Li1, James S. Hyde1

1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States

Complex-valued tailored pulses have been used in an EPI sequence to excite two or more slices in human brain using a whole-brain transmit coil. One or more members of a receive-coil array have been used to acquire multi-channel image data. Complex-valued coil profiles have been used to recover slices, and parallel image formation has been demonstrated. Acceleration by a factor of 4 has been achieved with an eight-channel head coil.

1090. Detecting Single Cortical Column Activation Under Super High Spatial Resolution at 9.4 T Using Single-Shot Half K-Space GR-EPI

Rupeng Li1, Patrick Hettinger2, Younghoon Cho1, Christopher P. Pawela1, Ji-Geng Yan2, Andrzej Jesmanowicz1, Anthony Hudetz3, Hani Matloub2, James Hyde1

1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI, United States; 3Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States

Single-shot half k-space GR-EPI sequence was used to push the BOLD imaging resolution to 300 micron cubic voxel and unique single column cortical activation in the sensory cortex was detected when stimulating the middle phalange of all 8 digits of rat.

1091. Development and Evaluation of Alternative Imaging Methods for FMRI at 7 Tesla

John Sexton1,2, Jascha Swisher3, Frank Tong3, Baxter Rogers1,2, J Christopher Gatenby1,4, John C. Gore1,4

1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; 2Biomedical Engineering, Vanderbilt University, Nashville, TN, United States; 3Psychology, Vanderbilt University, Nashville, TN, United States; 4Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States

We compare single-shot gradient-echo 2D-EPI, multi-shot gradient-echo 3D-FFE and multi-shot gradient-echo 3D-PRESTO in a polar angle retinotopic mapping experiment at four isotropic resolutions (1.12mm3, 1.67mm3, 2mm3, and 3mm3) at 7 Tesla. Retinotopic maps in agreement with literature were obtained at all resolutions. The 3D sequences provided similar BOLD sensitivity and significantly less distortion compared to 2D-EPI. In addition, 3D-PRESTO provided much higher temporal resolution than 2D-EPI. Our findings suggest rich potential for high-resolution 3D imaging sequences in retinotopic mapping and other functional MRI experiments at high field.

1092. What Is the Optimum FMRI Procedure with Auditory Stimulation?

Karsten Mueller1, Toralf Mildner1, Tom Fritz1, Joeran Lepsien1, Christian Schwarzbauer2, Harald E. Möller1

1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Aberdeen Biomedical Imaging Centre, University of Aberdeen, United Kingdom

To present auditory stimuli in the absence of scanner noise, the sparse temporal sampling (STS) approach was introduced. The interleaved-silent steady-state (ISSS) technique is combining the idea of splitting image acquisition and stimulus presentation with a better sampling of the fMRI signal. We performed an auditory experiment with pleasant and unpleasant stimuli using four fMRI sessions: STS, ISSS, and simultaneous stimulus presentation and image acquisition with axial and sagittal scanning. The total acquisition time was the same in all four sessions. The best sensitivity for detecting activations of sub-cortical regions (such as the amygdala) was found for ISSS.

1093. Feasibility of BOLD Magnetic Resonance Imaging of Lung Tumors at 3T

Qing Yuan1, Yao Ding1, Rami R. Hallac1, Paul T. Weatherall1, Robert Doug Sims1, Thomas Boike2, Robert Timmerman2, Ralph P. Mason1

1Radiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, United States; 2Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, United States

It is expected that BOLD MRI should be sensitive to tumor vascular oxygenation. In lung tumors BOLD MRI is challenging due to potential image artifacts from motion, blood flow, and susceptibility. The goal of this preliminary study was to optimize the BOLD imaging technique at 3T in patients with untreated lung cancer. A respiratory-gated multi-echo gradient-echo technique is demonstrated as a feasible method to quantify T2* values of lung tumors. The response of tumor T2* measurements to an oxygen-breathing challenge should be sensitive to tumor hypoxia and could therefore serve as a prognostic indicator before therapy.

1094. Interleaved T1- And T2*-Weighted Imaging Can Evaluate Dynamic Oxygen Challenge: A Feasibility Study

Yao Ding1, Ralph P. Mason1, Qing Yuan1, Rami R. Hallac1, Roderick W. McColl1, Robert D. Sims1, Paul T. Weatherall1