|Cutting Edge Techniques for Body MRI|
Diffusion Tensor Imaging of in Vivo Human Kidney at 3
T : Robust Anisotropy Measurement in the Medulla
Hersh Chandarana1, Elizabeth Hecht1, Bachir Taouli1, Eric Edward Sigmund1
1New York University, New York, New York, USA
Diffusion tensor imaging (DTI) was performed in the kidneys of several healthy volunteers at 3 T, using an echo-planar imaging (EPI) sequence. Using data from several breathhold acquisitions that were co-registered before processing to improve SNR, robust measures of mean diffusivity (MD) and fractional anisotropy (FA) were obtained in both the cortex and medulla. Medullary compartments were found to have significantly FA than the cortex, and the principal diffusion eigenvectors were clearly observed to display the expected radial tubular orientation in the medulla. This study shows the potential for FA and other DTI markers to probe renal microstructure and function.
Strategies for Reducing Respiratory Motion Artifacts
in Quantitative Renal Perfusion Imaging with Arterial Spin Labeling
Philip Martyn Robson1, Ananth J. Madhuranthakam2, Weiying Dai1, David C. Alsop1
1Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; 2GE Healthcare, Boston, Massachusetts, USA
Quantitative perfusion imaging in the kidneys using arterial spin labeling (ASL) is of potential importance for imaging renal function without the use of gadolinium-based contrast agents. We evaluate strategies for reducing respiratory motion artifacts enabling successful application of ASL in the abdomen. Background suppression techniques used in ASL, breathing patterns, and retrospective sorting of acquired perfusion-weighted images are explored. A strategy is established for overcoming the problem of respiratory motion that is suitable for application to clinical populations. Imaging of volunteers is repeated both within the session and in a separate session to estimate the test-retest repeatability of quantitative renal perfusion imaging using ASL.
Initial Experience with RF Shimming at 3T
Using a Whole Body 8 Channel RF System
Jo V. Hajnal1, Shaihan J. Malik1, David J. Larkman1, Declan O'Regan1, Kay Nehrke2, Ulrich Katscher2, Ingmar Graesslin2, Peter Börnert2
1Hammersmith Hospital, Imperial College London, London, UK; 2Philips Research Europe, Hamburg, Germany
We report initial experience with RF shimming on a clinical 3T scanner equipped with a whole body 8 channel transmit system. Three volunteers were studied. Transmit sensitivity was measured for each coil element on each subject using a multi TR method. Field echo pelvic imaging was then performed using independent drives on each coil optimised to produce a homogeneous transmit field and this was compared to a mode of operation with all elements driven as a single coil. Results showed improved uniformity in excitation, with reduction of regional signal dropout that is common in body imaging at 3T.
Dynamic Contrast Enhanced MRI Evaluation of Crohn's
Disease Activity: A Histopathological Correlation
Shonit Punwani1, 2, Manuel Rodriguez-Justo2, Alan Bainbridge1, Enrico De Vita1, 2, Rebecca Greenhalgh2, Steve Halligan1, 2, Stuart Taylor1, 2
1University College London, London, UK; 2University College London Hospital, London, UK
The aim of this study was to correlate in-vivo DCE-MRI parameters with histologically determined mural acute inflammatory change in small bowel resection specimens from patients with known ileal Crohn’s disease. In vivo DCE-MRI of disease affected bowel was performed pre-operation. Post surgical small bowel resection specimens were scanned to enable detailed imaging-histopathology matching. Histological sections were taken through the area of bowel corresponding to the DCE-MRI images and an acute inflammatory score (AIS) derived. AIS was inversely related to semi-quantitative DCE-MRI parameters of enhancement ratio (ERdyn) and slope of enhancement (SoE). This finding is consistent with the hypothesis of reduced blood flow contributing to histopathological changes in acute Crohn's disease of the small bowel.
Diffusion-Weighted Imaging During Acute Unilateral
Ureteral Obstruction - Demonstration of the Necessity to Separate
Diffusion and Microperfusion Contributions
Tobias Binser1, Thomas M. Kessler1, Chris Boesch1, Peter Vermathen1, Harriet C. Thoeny1
1University & Inselspital Berne, Berne, Switzerland
The aim of this study was to determine whether DW MRI is able to detect changes in renal diffusion and microperfusion during acute unilateral ureteral obstruction in humans. The results with significantly decreased cortical and medullary perfusion fraction and significantly increased medullary ADC suggest that DW-MRI might provide information as to the degree of obstruction and might therefore help in the decision making of time point of therapeutic intervention. In addition, the results clearly demonstrate the validity and necessity to separate diffusion and microperfusion compartments, in order to prevent misleading findings and interpretations.
Evaluation of Acute Hepatic Ischemia in Rats Using
23Na and 1H Diffusion-Weighted MRI
Paige Nicole Hopewell1, Navin Bansal1
1Indiana University School of Medicine, Indianapolis, Indiana, USA
Due to excessive motion artifact with ADC calculation from DWI, SQ and MQF 23NaMRI is superior for acute hepatic ischemia evaluation in rats.
Characterization of Focal Renal Masses
Evaluated Only with DW Imaging and Non-Enhanced MR Sequences
senta m. Berggruen1, dava Grundhoefer, jenny Huang, nancy Hammond1, paul Nikolaidis1, frank h. Miller1
1Northwestern University, Chicago, Illinois, USA
With the advent of nephrogenic systemic fibrosis (NSF), the new restrictions of gadolinium usage pose an altered approach to MR imaging and interpretation in certain patients. The purpose of this study was to evaluate the accuracy of non-gadolinium enhanced sequences, in conjunction with diffusion-weighted sequences, to differentiate benign from malignant renal lesions. Our preliminary study demonstrates that differentiation of benign from malignant renal lesions and accurate evaluation of renal masses is possible with non-gadolinium enhanced sequences, in conjunction with diffusion-weighted MR imaging. Our data supports that AML have restricted diffusion with lower mean ADC values than renal cell carcinomas.
Effect of Field Strength and Software on Apparent
Diffusion Coefficient Measurements in Diffusion-Weighted Imaging of the
Abdomen at 1.5 and 3 Tesla
Adam Charles Braithwaite1, Brian M. Dale2, Daniel T. Boll1, Elmar M. Merkle1
1Duke University Medical Center, Durham, North Carolina, USA; 2Siemens Medical Solutions, Cary, North Carolina, USA
With the emergence of high field strength magnets used in clinical practice, it would be useful to determine if there is any difference in ADC measurements at 3 T compared to the standard 1.5 T. If ADC values are indeed independent of field strength, then the monitoring of tumor response to treatment can be performed at both 1.5 T and 3 T. Our study shows that ADC values in abdominal organs are stable over 5 months but are highly sensitive to changes in post processing or sequences such as those that can occur during routine software upgrades. Longitudinal studies will need to incorporate some calibration methods to properly compare data across such inevitable changes. The ADC values in some tissues, such as liver, are sensitive to changes in field strength. For those tissues care must be taken that follow-up studies are performed at the same field strength.
ROtated Slab Excitation (ROSE) for Reduced Foldover
Artifacts in Coronal 3D Abdominal Imaging
Anja C.S. Brau1, Ersin Bayram2, Manoj Saranathan3, Akira Kawashima4
1GE Healthcare, Menlo Park, California , USA; 2GE Healthcare, Waukesha, Wisconsin, USA; 3GE Healthcare, Rochester, Minnesota, USA; 4Mayo Clinic, Rochester, Minnesota, USA
Three-dimensional coronal abdominal imaging is frequently performed for hepatic and renal imaging applications. However, applying the phase-encoding gradient in the left/right direction renders the acquisition vulnerable to foldover aliasing artifacts that potentially obscure the anatomy of interest. This work demonstrates the utility of a rotated slab excitation (ROSE) scheme for 3D coronal abdominal imaging that significantly reduces the severity of foldover artifacts for improved anatomical visualization with minimal, if any, effect on scan time, spatial resolution, or other imaging parameters.
MRI Monitoring of the Influence of US Contrast Agent
Destruction for Local Delivery of a MRI Blood Pool Contrast Agent in the
Nora Frulio1, Hervé Trillaud1, Omer Eker1, Roel Deckers1, Sebastien Lepreux2, Christophe Laurent3, Claire Corot4, Chrit Moonen1, bruno Quesson1
1Laboratory IMF, Bordeaux, France; 2CHU Pellegrin, Bordeaux, France; 3CHU Saint André, Bordeaux, France; 4Guerbet, Paris, FranceThe temporal evolution of T1 values in the liver of rats was measured by repetition of a look-locker MRI sequence, before and after intravenous co-administration of a blood pool MRI contrast agent (Vistarem®) and an ultrasound contrast agent (Sonovue®). These microbubbles were then destroyed by ultrasound in one group of animals. T1 values resulting from a fit of the MRI data for the group with ultrasound were systematically lower than those of the control group, indicative of a change of the interaction between Vistarem® and surrounding tissue due to ultrasonic microbubble destruction.