Non-Contrast Enhanced Coronary & Peripheral MRA

Friday 16 May 2014

Andrew Peter Aitken¹, Markus Henningsson¹, Tobias Schaeffter¹, and Claudia Prieto^1
1Division of Imaging Sciences and Biomedical Engineering, King's College London, London, London, United Kingdom

Image navigators have been proposed as a way to improve respiratory motion correction and to increase scan efficiency in 3D coronary MR angiography. Existing approaches allow for either translational motion correction to be performed on a beat-to-beat basis or for affine correction to be performed for several respiratory bins. A new golden radial navigator is proposed that allows both beat-to-beat translational and bin-to-bin affine corrections to be performed by combining navigator data from different respiratory positions. With the proposed approach, images of comparable quality to gated scans are achieved, with affine correction showing further improvement over translational correction only.

Giulia Ginami^1,2, Gabriele Bonanno^1,2, Juerg Schwitter³, Matthias Stuber^1,2, and Davide Piccini^4,5
1Center for Biomedical Imaging (CIBM), Lausanne, Switzerland, ²Department of Radiology, University hospital (CHUV) and University of Lausanne (Unil), Lausanne, Switzerland, ³Department of Cardiology, University hospital (CHUV), Lausanne, Switzerland, ⁴Department of Radiology, Center for Biomedical Imaging (CIBM) and University hospital (CHUV), Lausanne, Switzerland, ⁵Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland

In this study, differences in the respiratory patterns of volunteers and patients were analyzed and reported using a respiratory self-navigated approach. Furthermore, a novel iterative approach for self-navigation was developed and described. This technique has the advantage of being independent from the choice of a specific respiratory reference position for motion correction, and showed improved performances with respect to a more standard approach when respiratory motion correction was applied to irregular breathing patterns of patients.

Markus Henningsson¹, Tarique Hussain¹, Gerald Greil¹, and Rene Botnar^1
1Imaging Sciences & Biomedical Engineering, King's College London, London, United Kingdom

Image-based respiratory navigation (iNAV) may overcome the problems of respiratory artifacts and long scan time in whole-heart MRI. In this study we compared iNAV to the gold standard 1D diaphragmatic navigator (1DNAV) in 28 non-anaesthetised patients with congenital heart disease. Whole-heart MRI using iNAV significantly reduced scan time, while improving qualitative and quantitative image quality scores compared to 1DNAV.

Maryam Nezafat¹, Markus Henningsson¹, David P Ripley², Nathalie Dedieu¹, Gerald Greil¹, John P Greenwood², Peter Börnert³, Sven Plein², and René M Botnar^1
1Division of Imaging Sciences & Biomedical Engineering, King's College London, London, United Kingdom, ²Multidisciplinary Cardiovascular Research Centre (MCRC), University of Leeds, Leeds, United Kingdom, ³Philips Research, Hamburg, Germany

Suppression of lipid signal is a basic requirement in CMRA because coronary arteries are embedded in epicardial fat and signal from fat can decrease coronary vessel conspicuity. Most CMRA scans are currently performed with fat suppression techniques such as SPIR. However, methods based on spectrally-selective fat saturation are sensitive to B0 and B1 field inhomogeneities. Recent improvements in chemical shift based water fat separation methods such as Dixon provide an alternative to conventional spectrally-selective fat suppression techniques. The purpose of this study was to compare the SPIR technique with Dixon water fat separation at 3T for CMRA.

Gabriele Bonanno^1,2, Davide Piccini^3,4, Bénédicte Maréchal^3,5, Michael O. Zenge⁶, and Matthias Stuber^1,2
1Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Vaud, Switzerland, ²Center for Biomedical Imaging (CIBM), Lausanne, Vaud, Switzerland, ³Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Vaud, Switzerland, ⁴Radiology, University Hospital (CHUV) and University of Lausanne (UNIL) - Center for Biomedical Imaging (CIBM), Lausanne, Vaud, Switzerland, ⁵CIBM-AIT, École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, ⁶MR Product Innovation and Definition, Healthcare Sector, Siemens AG, Erlangen, Germany

A respiratory signal is extracted from independent component analysis of fluctuations of the k-space center amplitude in all receiver coils throughout a 3D radial coronary MRA acquisition. This signal is then used to bin data in undersampled 3D sub-images related to different respiratory phases. Image-based 3D motion correction is thus enabled, without the need of additional navigators or tracking of the heart from 1D projections. In comparison to 1D self-navigation, the proposed 3D self-navigation method showed significantly improved vessel delineation in a cohort of 11 healthy adult volunteers.

Jian Xu^1,2, Li Feng³, Davide Piccini^4,5, Ricardo Otazo³, Gabriele Bonanno⁵, Florian Knoll³, Edward K. Wong¹, and Daniel K. Sodickson^3
1Department of Computer Science and Engineering, Polytechnic Insitute of New York University, Brooklyn, NY, United States, ²Siemens Healthcare USA, New York, NY, United States, ³Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ⁴Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland, ⁵Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL) / Center for Biomedical Imaging (CIBM), Lausanne, Switzerland

The feasibility of rapid free-breathing coronary MRA with isotropic spatial resolution was demonstrated at different acceleration rates using a joint multicoil compressed sensing reconstruction (Sparse-SENSE) with a 3D radial phyllotaxis trajectory. Respiratory motion correction was implemented in radial k-space before reconstruction to achieve 100% acquisition efficiency. Results with adequate image quality can be achieved by using data acquired in only 144 heartbeats, which corresponds to a total acquisition time of approximately 2 minutes. The proposed method can be a potentially useful tool for free-breathing coronary MRA in clinically acceptable scan times.

Robert R. Edelman^1,2, Oisin Flanagan², Shivraman Giri³, Peter Speier⁴, and Ioannis Koktzoglou^1,5
1Radiology, NorthShore University HealthSystem, Evanston, IL, United States, ²Radiology, Northwestern University, Chicago, IL, United States,³Siemens Healthcare, Chicago, IL, United States, ⁴Siemens Healthcare, Erlangen, Germany, ⁵Radiology, University of Chicago Pritzker School of Medicine, Chicago, IL, United States

Nonenhanced MRA is useful for patients with peripheral arterial disease, and particularly for those with impaired renal function. Existing techniques for nonenhanced MRA, such as subtractive fast spin echo and QISS MRA, require cardiac gating. Moreover, specialized peripheral vascular phased array coils are required to provide sufficient signal-to-noise ratios (SNR) over the extensive peripheral arterial territory. UnQISS MRA allows peripheral nonenhanced MRA to be acquired without the need for cardiac gating. Moreover, the use of a lengthy echo train improves SNR and avoids the needs for parallel imaging, so that imaging can be done just using the body coil.

Michael C Langham¹, Cheng Li¹, and Felix Wehrli^1
1Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States

We demonstrate a new subtractive flow-independent non-contrast MRA using flow insensitive and sensitive SSFP-echo signal. The balanced SSFP spectral signal can be sampled by acquiring multiple data sets with different linear phase increments. The 1D Fourier transform of the phase-cycled data sets resolves the modes of the SSFP normally coalesced in a bSSFP pulse sequence, including the desired flow-insensitive SSFP-echo. On the other hand, unbalanced SSFP pulse sequence can be used to isolate flow-sensitive SSFP-echo signal. Subtraction removes the muscle tissue and lipid signals whereas contrast between arterial and venous blood is maximized by exploiting arterial blood’s longer T2.

Susan G Singh¹, Gerard Smith¹, Leighton Kearney², Emma K Hornsey¹, Michael Galea¹, Mark Begbie¹, Brenden McColl¹, Jennifer Shoobridge¹, Rinku Rayoo², Jasmin Grewal², Jian Xu³, Melanie Rayner¹, George Matalanis⁴, and Ruth P Lim^1
1Department of Radiology, Austin Health, Melbourne, Victoria, Australia, ²Department of Cardiology, Austin Health, Melbourne, Victoria, Australia,³Siemens Medical Solutions, New York City, New York, United States, ⁴Department of Cardiothoracics, Austin Health, Melbourne, Victoria, Australia

ECG-gated CTA is the clinical standard for non-invasive assessment of the thoracic aorta, but exposes patients to ionizing radiation and nephrotoxic contrast. An ECG-gated 3D breath hold non-enhanced balanced steady state free precession (bSSFP) MRA technique (NE MRA) has recently been described that offers a contrast and radiation-free alternative, particularly applicable to long-term surveillance of younger patients. We evaluate its performance in a clinical population, with eCTA as the reference standard. In our preliminary experience, NE MRA identifies aortic pathology with satisfactory diagnostic confidence and image quality, inferior to eCTA. Measured aortic dimensions in the proximal thoracic aorta are comparable.

Yutaka Natsuaki¹, Xiaoming Bi¹, Michael Zenge², Peter Speier², Peter Schmitt², and Gerhard Laub^3
1Siemens Healthcare, Los Angeles, CA, United States, ²Siemens AG Healthcare Sector, Erlangen, Germany, ³Siemens Healthcare, San Francisco, CA, United States

Despite its high potential in significant scan time reduction and its immense popularity, MRI applications of compressed sensing (CS) have yet to reach daily clinical usage. With a modest acceleration factor and with a careful selection of the intended application, the CS can be fully implemented on today’s clinical MR scanners. The current work successfully demonstrates this with the Time-of-Flight application (TOFu), achieving factor of 2 scan time reduction (net acceleration 3.8) over the conventional intracranial TOF (acceleration factor of 2 from parallel MRI) without compromises in image quality.