|MRA: Contrast Without the Agent|
Improving Non-Contrast Enhanced SSFP Angiography with
Tolga Çukur1, Michael Lustig1, Dwight Georger Nishimura1
1Stanford University, Stanford, California , USA
Flow-independent angiography offers the ability to produce vessel images without contrast agents. 3D magnetization-prepared balanced SSFP can be used to acquire these angiograms, where the phase encodes are interleaved and preparation is repeated prior to the start of each interleave. However, frequent repetition of the preparation significantly reduces the scan efficiency. The sparsity of the angiograms allows for the use of compressed sensing to undersample the phase encodes and save scan time. These savings can be allotted for preparing the magnetization more often, or alternatively, improving resolution.
Flow-Dependent Arterial and Venous Imaging by
Non-Contrast-Enhanced Subtraction Angiography
Andrew Nicholas Priest1, Martin John Graves1, Pauline Wong1, David John Lomas1
1Addenbrooke's Hospital and University of Cambridge, Cambridge, UK
Preparation modules containing ‘diffusion weighting’ or motion-sensitising gradients have recently been used to suppress the blood signal in images of the vessel wall. Since the blood suppression can be selectively applied, it is possible to produce subtraction images which selectively depict the vascular anatomy while suppressing the signal from static tissues. Furthermore, by acquiring images with different degrees of suppression, images which selectively depict either arteries or veins can be produced. This work demonstrates high-resolution 3D vascular images in the lower leg in healthy volunteers, and might be applied to clinical situations which currently require contrast agent administration.
Quantification of Reactive Hyperemia in
the Femoral Artery and Vein by MRI-Based Blood Oximetry
Michael Langham1, Tom Floyd1, Jeremy Magland1, Emile Mohler, III1, Felix W. Wehrli1
1University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
We demonstrate MR susceptometry-based oximetric quantification of reactive hyperemia in response to cuff-induced ischemia by making direct time-course measurement of oxygen saturation level in the femoral artery and vein of both normal subjects and patients with peripheral arterial disease (PAD). The washout time and the upslope were significantly longer and less, respectively, for PAD patients compared to normal. The washout time refers to the time required to observe oxygen depleted venous blood that is washed out of the capillary bed during the reactive hyperemia and the upslope correspond to the reoxygenation rate in the vein after the washout.
Interactive Two-Dimensional Fresh Blood Imaging
Pauline Wong1, Martin John Graves1, David John Lomas1
1University of Cambridge and Addenbrooke's Hospital, Cambridge, UK
Fresh Blood Imaging, a non-contrast enhanced 3D MRA technique, has been implemented for the real-time imaging environment and demonstrated in healthy volunteers. As the technique is directly related to the pulsatility of the vessel flow, a time consuming prep scan is typically used to calculate the systole and diastole trigger delays. We have implemented a 2D version in real-time and used a rapid flow measurement as the prep scan for calculating trigger delays. Localisation, navigation, flow measurement and FBI angiography were performed in a single scan/sequence. Results in peripheral vessels are shown with Tacq~0.5-1min (8 averages).
A Novel Non-Contrast MR Angiography Technique Using
Triggered Non-Selective Refocused SPACE for Improved Spatial Resolution
Jian Xu1, Peter Weale1, Laub Gerhard1, Peter Schmitt2, Jaeseok Park2, Bernd Stoeckel1, Qun Chen3, Ruth P. Lim3, Andrew Hardie3, Pippa Storey3, Elizabeth Hecht3, Kellyanne Mcgorty3, Vivian S. Lee3
1Siemens Medical Solutions USA Inc., Malvern, Pennsylvania, USA; 2Siemens Medical Solutions, Erlangen, Germany; 3New York University, New York, New York, USA
A Novel Non-contrast MRA Technique using Triggered 3D SPACE for Improved Spatial Resolution and Speed is developed, which uses selective RF excitation, non selective RF refocusing pulses and variable flip angles for contrast manipulation. SPACE helps achieve lower SAR and shorter ETS, resulting in total acquisition windows of around 100ms, a slice turbo factor in 3D direction can speed up the acquisition. We performed a comparison between the SPACE and the TSE based approaches in terms of spatial resolution and reduced blurring and small vessel conspicuity.
|Noncontrast MRA of Renal Artery Using Flow-Prep
FIESTA for Evaluation of Patients with Suspected Renal Tumor: Comparison
of Dynamic Contrast MRA
Takayuki Masui1, Motoyuki Katayama1, Kimihiko Sato1, Hidekazu Seo1, Hiroki Ikuma1, Akihiko Kutsuna1, Masayoshi Sugimura1, Kazuhiko Ito1, Mitsuaharu Miyoshi2, Tetsuji Tsukamoto2
1Seirei Hamamatsu General Hospital, Hamamatsu, Japan; 2GEYMS, Hino, Japan
In the evaluation of 63 patients with suspected renal tumor, respiratory triggered ECG gated non-contrast (NC) MRA using FIESTA with Flow-Preparation pulse and contrast dynamic (C) MRA were performed. With successfully triggered ECG, identical information of the middle to proximal renal arteries and entire abdominal aorta could be obtained with NC and C-MRA. Peripheral portions of the renal arteries were better depicted on NC MRA than C MRA without overlap of the other structures. Consequently, in case of contraindication to use of MR contrast agents, NC MRA can give anatomical information of renal arteries, preoperatively.
STARBURST Peripheral MR Venography
Robert R. Edelman1, Ioannis Koktzoglou1
1Evanston Northwestern Healthcare, Evanston, Illinois, USA
STARBURST (Selectively Targeted Angiographic Rendering using Bloodâ€™s Unique Relaxation properties and Subtraction Technique) was used to create flow-independent peripheral MR venograms. The method involves the acquisition of two image sets (with one set being tagged by a spatially non-selective radiofrequency pulse) that are subtracted to render an angiogram. Extensive lengths of the veins were shown including submillimeter branch vessels; the arteries were almost completely suppressed with the application of spatially selective pre-inversion. The results demonstrate the feasibility of high resolution MR venography of the lower extremities with suppression of arterial signal and without the need for contrast administration.
Non-Contrast Enhanced Renal MR Angiography with PC
Kevin Michael Johnson1, Darren Lum1, Chistopher J. Francois1, Scott B. Reeder1, Reede F. Busse2, Tom M. Grist1, Oliver Wieben1
1University of Wisconsin - Madison, Madison, Wisconsin, USA; 2MR Applied Science Lab, GE Healthcare, Madison, Wisconsin, USA
This study investigates the use of a modified phase contrast VIPR sequence for volumetric 3D velocity imaging of the renal arteries without a contrast agent. With the addition of adaptive respiratory gating, high quality angiograms were obtained in volunteers and patients. This approach provides an excellent alternative for patients that are excluded from contrast enhanced MRA otherwise. This includes subjects with compromised kidney function due to potential nephrogenic systemic fibrosis issues and kidney transplant patients for regular follow-ups.
Micro MR Angiography of the Finger as a Potential
Biomarker in Systemic Sclerosis
Jinnan Wang1, Vasily L. Yarnykh1, Baocheng Chu1, Jerry Molitor2, Richard Nash, Fei Liu1, Stephen Schwartz1, Chun Yuan1
1University of Washington, Seattle, Washington, USA; 2University of Minnesota, Minneapolis, Minnesota, USA
In this study, we report the initial experience in high resolution MR angiography of scleroderma digital vasculature imaging. Micro MR angiography sequence was optimized for finger vessel imaging. Based on the angiography images, significant differences were found on arterial lumen size, number of visible veins and vascular scores, between scleroderma patients and normal volunteers. These quantitative variables can be potentially used as prospective biomarkers for scleroderma disease evaluation.
Carotid Artery Imaging at 7T: SNR Improvements Using
Anatomically Tailored Surface Coils
Marco Piccirelli1, Nicola DeZanche1, Jurek Nordmeyer-Massner1, Michaela Soellinger1, Michael Wyss1, Gérard Crelier1, Klaas Paul Pruessmann1, Sebastian Kozerke1
1University and ETH Zurich, Zurich, Switzerland
Shape, blood flow, and wall shear stress of the carotid artery are associated with its function. The determination of related parameters relies on accurate angiographic and velocity data. We present a dedicated 7T receive-only, two-element surface coil for carotid imaging. The coil geometry was tailored to the neck and jaw anatomy. Comparison of the surface coil with a standard T/R-volume head coil showed a drastic SNR improvement making high-quality phase-contrast imaging possible. Particle traces in small branches of the carotid blood flow demonstrate the excellent SNR performance of the coil.