Rajiv Ramasawmy¹, Jack Anthony Wells¹, Magdalena Sokolska², James A. Meakin³, Sean Peter Johnson¹, Adrienne E. Campbell-Washburn⁴, Rosamund Barbara Pedley⁵, Mark Francis Lythgoe†¹, and Simon Walker-Samuel†^1
1Centre for Advanced Biomedical Imaging, University College London, London, Greater London, United Kingdom, ²Institute of Neurology, University College London, London, Greater London, United Kingdom, ³Oxford University, Oxfordshire, United Kingdom, ⁴National Heart Lung and Blood Institute, National Institutes of Health, Maryland, United States, ⁵Cancer Institute, University College London, London, Greater London, United Kingdom

Liver perfusion measurements could be used to monitor hepatic disease progression and therapy in pre-clinical models. This study investigated the feasibility of using pseudo-continuous ASL (pCASL) to measure mouse liver perfusion, in which both the portal venous and arterial supply to the liver were separately tagged: the mean ratio of perfusion estimates agreed well with the expected vascular contributions. Finally, the technique was applied to a mouse model of liver metastasis, which showed tumours to be exclusively arterially supplied.

Xinlei Pan¹, Robert Smith², Mayank Jog², Tianyi Qian³, Holden H Wu², Kyunghyun Sung², Kuncheng Li⁴, Kui Ying⁵, and Danny JJ Wang^2
1Department of Biomedical Engineering, Tsinghua University, Beijing, Beijing, China, ²Department of Bioengineering, UCLA, CA, United States, ³Siemens Healthcare, MR Collaboration NE Asia, Beijing, China, ⁴Department of Radiology, Xuanwu Hospital of Capital Medical University, Beijing, China, ⁵Department of Engineering Physics, Tsinghua University, Beijing, China

This study tested the feasibility of quantitative liver perfusion measurements using a multi-delay pseudo-continuous ASL (pCASL) protocol that selectively labels the hepatic artery and hepatic portal vein respectively. Estimated mean blood flow of hepatic artery labeled (44±14 ml/100ml/min) and hepatic portal vein labeled (140±9 ml/100ml/min) as well as the corresponding transit times (1020±396,1892±164ms) showed good accordance with the literature. The capability of non-invasively and selectively labeling the hepatic artery and portal vein is a unique strength of pCASL for quantitative liver perfusion imaging.

Joshua S. Greer^1,2, Yue Zhang², Ivan Pedrosa^2,3, and Ananth J. Madhuranthakam^2,3
1Bioengineering, UT Dallas, Dallas, TX, United States, ²Radiology, UT Southwestern Medical Center, Dallas, TX, United States, ³Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States

Recently, pseudo-continuous ASL (pCASL) has been successfully applied to study cerebral and renal perfusion by labeling the carotid arteries and abdominal aorta. The high blood velocity in these anatomies enabled high labeling efficiency. However, the extension of pCASL to study pulmonary perfusion has been non-trivial due to the complex anatomy of the lungs. In this work, we demonstrate pulmonary perfusion using pCASL, specifically targeting the inferior vena cava and optimizing the labeling parameters to achieve high labeling efficiency. This provided higher SNR, reduced pulmonary vasculature signal and more homogeneous perfusion compared to the established pulsed ASL approach (e.g. 2D FAIRER).

Hao Song¹, Wenyang Liu², Dan Ruan^2,3, Sungkyu Jung⁴, and H Michael Gach^1,5
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States, ²Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States,³Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, United States, ⁴Statistics, University of Pittsburgh, Pittsburgh, PA, United States, ⁵Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States

A respiratory motion predictor (RMP) was implemented to prospectively correct respiratory motion for arterial spin labeling (ASL) in the abdomen. An artificial neural network (ANN) algorithm predicted the position of the image slices at the time of acquisition. The ASL sequence adjusted the image acquisition in real-time based on the RMP data obtained during the transit delay. The ANN algorithm accurately predicted the diaphragm motion during the ASL acquisition with an error of 0.8 mm. Renal perfusion maps were consistent with maps acquired using breathhold with respiratory feedback, while requiring much less effort from the subject and less exam time.

Dong Xing¹, Yunfei Zha¹, Lei Hu¹, Jiao Wang¹, Yuan Lin¹, and Hui Lin^2
1Department of Radiology, Renmin Hospital of Wuhan University, Wuhan, Hubei, China, ²MR Research, GE Healthcare China, Shanghai, China

Arterial spin labeling (ASL) has been a preliminary application in musculoskeletal perfusion analysis. However, it has not been applied to the spinal bone marrow (SBM) lesions in the literature up to date. First, this study investigate the effects of inversion time(TI) on flow-sensitive alternating inversion recovery(FAIR) perfusion imaging of SBM to find the optimized TI, then the correlation between ASL and dynamic contrast enhanced (DCE) magnetic resonance (MR) imaging in the measurement of SBM perfusion were assessed to analyse the feasibility of ASL SBM perfusion.

Mohamed Tachrount¹, Andrew Davies², Roshni Desai², Kenneth Smith², David Thomas³, Xavier Golay¹, and Roshni Desai^2
1Department of brain repair and rehabilitation, UCL Institute of Neurology, London, London, United Kingdom, ²Department of Neuroinflammation, UCL Institute of Neurology, London, United Kingdom, ³UCL Institute of Neurology, London, United Kingdom

A new multi-slice ASL technique is detailed and applied to the study of rat spinal cord at 9.4T. The quantification of the spinal cord blood flow was performed using a pre-saturation FAIR Q2TIPS ASL technique based on the use of adiabatic RF pulses with a reduced FOV. The averaged perfusion within the GM (95.1±4.6ml/100g/min) was higher than within the WM (39.7±3.2ml/100g/min).

Charlotte E Buchanan¹, Eleanor F Cox¹, Claire Grant², Nick M Selby², Chris W McIntyre³, Maarten W Taal², and Susan T Francis^1
1SPMIC, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom, ²Division of Medical Sciences and Graduate Entry Medicine, Royal Derby Hospital, Nottingham, United Kingdom, ³Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada

A modified look locker inversion (MOLLI) recovery arterial spin labelling (ASL) technique is used to measure myocardial blood flow (MBF) in humans. Cardiac triggering was used with a ‘Trigger-delay’ (TD) prior to the label module to allow data to be collected at a range of post-label delay times. 8 TD values were collected (0 - 350 ms), with 3 readout pulses per Look-Locker set. MBF was 1.25 ± 0.45 and 1.34 ± 0.42 ml/g/min in healthy controls and chronic kidney disease patients. On exercise, the mean increase in MBF was 85 ± 24 % for patients.

Weiying Dai¹, Lauren S. Weiner², David C. Alsop¹, and Aaron M. Cypess^2
1Radiology, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA, United States, ²2Section of Integrative Physiology and Metabolism, Joslin Diabetes Center, Boston, MA, United States

Brown adipose tissue (BAT) can improve insulin sensitivity and hence may prove to be an important anti-diabetic tissue. The volume and activity of BAT have previously been measured using 18F-FDG PET/CT. Here, we demonstrate the feasibility and repeatability of using Dixon water/fat imaging and ASL imaging to assess BAT volume and perfusion responses to mild cold stimulation in the cervical area of adult humans. The Dixon method can provide a quantitative measurement of the BAT volume. ASL shows great promise for measuring perfusion activity within BAT and can be successful if the vessel signals near the BAT are well suppressed.

Jeff L Zhang¹, Christopher J Hanrahan¹, Jason Mendes¹, Gwenael Layec², Corey Hart², Kristi Carlston¹, Michelle Mueller³, Russell S Richardson², and Vivian S Lee^1
1Radiology, University of Utah, Salt Lake City, Utah, United States, ²Division of Geriatrics, University of Utah, Utah, United States, ³Vascular Surgery, University of Utah, Utah, United States

Capable of measuring perfusion rapidly, ASL is suitable for monitoring muscle perfusion during exercise recovery. However, ASL estimated perfusion could be severely erroneous for tissue voxels containing large blood vessels. Inclusion of large-vessel voxels in a muscle ROI could change the magnitude and the temporal pattern of the averaged perfusion dramatically. In this study, we studied ASL signals of blood vessel simulated by a flow phantom, and using the obtained velocity-perfusion relationship, developed a velocity selective method for excluding the large-vessel voxels. The method was shown to be effective for our healthy subjects, and improved the perfusion accuracy.

Céline Giraudeau^1,2, Benjamin R. Knowles³, Thomas Lange³, Michael Herbst^3,4, Maxim Zaitsev³, and Pierre Carlier^1,2
1NMR Laboratory, Institute of Myology, Paris, France, ²NMR Laboratory, CEA, I2BM, MIRCen, Fontenay-aux-Roses, France, ³Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, ⁴John A. Burns School of Medicine, Uni Hawaii, Honolulu, Hawaii, United States

Acquiring clean ASL perfusion data in exercising skeletal muscle is highly desirable and would have significant impact for the pathophysiological mechanisms of many conditions affecting the skeletal muscle, primarily or secondarily. However, studies have been limited to post-exercise data due to motion that dramatically impairs perfusion curves. Recently, real-time prospective motion correction (PMC) with optical tracking has been proposed for brain and knee MRI. In this work we investigated the potential of PMC-augmented ASL to improve the quality of perfusion curves acquired during calf muscle exercise.