Joong Kim, Taeghwan Hyeon, David Brody

Relaxation based MR images have superior spatial resolution compared to other MRI approaches. In addition, structural MRI requires short scan time and yet has high signal to noise ratio. However, the greatest limitation of structural MRI is poor specificity and sensitivity to pathology. Thus a well characterized MR molecular contrast agent would be a major advance. Here we present 3 nm iron oxide nanoparticles (IONP) as a T1 contrast agent. The 3 nm IONP showed strong T1 effects up to 13.5 ms echo time. A fully functionalized 3 nm IONP would be an appropriate component for molecular contrast agents.     

Lindsay Hill, Che Fu Liu, Teeba Jihad, Youssef Wadghiri, Jin Montclare

Our goal is to create protein engineered biomaterials for dual drug delivery and MRI monitoring  to improve the growing field of theranostics. Here we present a drug binding protein that is templated to USPIOs using a biomineralization-inspired biotemplation method. The agent shows promise for T2/T2*-weighted MRI.

Grzegorz Kwiatkowski, Jonas Steinhauser, Patrick Wespi, Matthias Ernst, Sebastian Kozerke

Due to the inherently long relaxation time of ¹³C spins in diamonds, the nuclear polarization enhancement obtained with dynamic nuclear polarization can be preserved for a time on the order of ~1h, opening up a window for a new class of long-lived contrast agents. Up to now, no imaging with hyperpolarized micro and nanodiamonds has been reported. The present communication presents the feasibility of applying directly hyperpolarized diamonds in MR imaging including considerations for potential in-vivo applications.

Andrea Galisova, Marketa Jiratova, Maria Rabyk, Martin Hruby, Milan Hajek, Daniel Jirak

Presented mannan-based polymers have promising properties for tumor and metastasis imaging due to their biocompatibility, nanosize and specificity for the immune cells. In this study, two mannan-based polymers were tested by multimodal imaging (MRI and fluorescence). The polymers showed superior imaging properties compared to a commercially available contrast agent. The polymer modified with oxazoline expressed slower elimination rate from the body. Both probes were visualized by MR and optical imaging modality at the injection sites and in the lymph nodes of the experimental mice suggesting their promising properties for cancer diagnosis.

Eleni Demetriou, Harriet Story, Robin Bofinger, Karin Shmueli, Helen Hailes, Alethea Tabor, Xavier Golay

2-DG has been shown to inhibit tumor growth in vivo; however, it cannot be used as a therapeutic agent in humans due to its toxicity.  Here we show the potential for 2-DG-loaded liposomes to provide detectable Chemical Exchange Saturation Transfer (CEST) contrast, and thereby achieve simultaneous tumour imaging and chemotherapy by targeting areas of greater tumour metabolism. The CEST signal arising from 2-DG was compared to liposome-encapsulated 2-DG and to natural D-glucose, respectively. The results demonstrated an increase in signal for2-DG loaded liposomes when compared to both free 2-DG and glucose possibly due to a decrease in the global exchange rate. 

Jing Wang, Jianxun Qu, Tianyong Xu, Zhenwei Yao

The β-alanine loaded hollow mesoporous silica nanospheres (AMSNs) with a characteristic MRS spectrum are successfully synthesized and used for contrast enhanced magnetic resonance spectroscopy (MRS) imaging of brain glioma. Material characterizations, in vitro and in vivo cytotoxicity studies and contrast enhanced MRS imaging of both subcutaneously transplanted glioma and in situ glioma are conducted with the synthesized AMSNs. 

Zheng Han, Zheng-Rong Lu

Accurate cancer detection and characterization with MRI is hampered by the lack of safe and effective targeted MRI contrast agents. In this work, we have designed and synthesized a high-relaxivity targeted contrast agent by conjugating ZD2 peptide to hydroxylated Gd₃N@C80. ZD2-Gd₃N@C80 has a high T₁ relaxivity of 76.4 mM^-1s^-1 per Gd at 1.5 Tesla and a small diameter of 1 nm on average. At a low dose of 5 µmol Gd/kg, ZD2-Gd₃N@C80 is able to produce prominent contrast enhancement in the highly metastatic MDA-MB-231 triple-negative breast cancer model, but not in the estrogen-dependent MCF-7 tumors. 

Daniel Jirak, Andrea Galisova, Ondrej Sedlacek, Martin Hruby, Milan Hajek

Novel ¹⁹F MR probe with the ability of creation of a depot in the living system is presented. This agent is pH- and termoresponsible with the phase transition point from liquid into the solid state at the temperature above 20 ºC. The MR properties were assessed by relaxometry and ¹⁹F spectroscopy/imaging. In vivo application confirmed efficiency of depot visualization; strong ¹⁹F MR signal was detected in all animals. No adverse effects of the probe to the animals were observed. Sufficient MR sensitivity of the probe and its slow degradation in animals suggest potential for a theranostic use.

Ketan Ghaghada, Saakshi Bhayana, Igor Stupin, Flavia Leao Barbosa, Chandresh Patel, Zbigniew Starosolski, Ananth Annapragada

Heterogeneity in tumor vasculature gives rise to variability in vascular permeability, one of the consequences being non-uniform intra-tumoral uptake and distribution of nanoparticle-based chemotherapeutics. An imaging agent that can assess tumor vascular heterogeneity and monitor uptake and distribution of nanoparticles could be useful for guiding and monitoring nanoparticle-based chemotherapy. In this work, we demonstrate, in orthotopic mouse models of solid tumors, that a high T1 relaxivity liposomal-gadolinium contrast agent (liposomal-Gd) enables MR imaging of nanoparticle uptake and 3D intra-tumoral distribution at clinically-relevant MR field strength.

Puneet Bagga, Mohammad Haris, Kevin D'Aquilla, Francesco Marincola, Hari Hariharan, Ravinder Reddy, Puneet Bagga

We show the use of a sugar alcohol sweetener, maltitol, in cancer MRI studies by exploiting its chemical exchange saturation transfer (malCEST) property. The tumor specific accumulation of maltitol in a rat glioma model provides localized, temporal changes in the CEST contrast, which corroborated the gadolinium-enhanced MRI. These findings illustrate the potential application of maltitol in the diagnosis and monitoring of the therapeutic response of cancers, including gliomas in preclinical studies.

Niloufar Zarghami, Alexandr Khrapichev, Francisco Perez-Balderas, Manuel Sarmiento-Soto, Nicola Sibson

We have previously reported molecular MRI studies using Microparticles of Iron Oxide (MPIO) coupled to anti-VCAM-1 antibodies. However, Ultrasmall Superparamagnetic Iron Oxide  (USPIO) are more commonly used in MRI applications. Although MPIO provide greater targeting valency and contrast per particle, their advantages over UPSIO for molecular MRI has not been demonstrated empirically. Here, we compared the sensitivity and specificity of VCAM-MPIO and VCAM-USPIO for molecular MRI; VCAM-MPIO, but not VCAM-USPIO, yielded marked and selective contrast in areas of cerebral inflammation. These results confirm the theoretical assumption that MPIO present a more viable platform for molecular MRI than USPIO.

Markus Schreiner, Vladimir Mlynarik, Didier Laurent, Vladimir Juras, Pavol Szomolanyi, Stefan Zbyn, Celeste Scotti, Joerg Goldhahn, Harry Haber, Ewa Kubiak, Ronenn Roubenoff, Stefan Marlovits, Reinhard Windhager, Siegfried Trattnig

To the best of our knowledge, this is the first study that employs gagCEST for the longitudinal evaluation of untreated articular cartilage defects. We demonstrate that gagCEST at 7T has the potential of discriminating between cartilage defects, weight bearing and non-weight bearing femoral cartilage and therefore might serve as a biomarker for the evaluation of novel cartilage therapies. Furthermore, our study implies that proper fixation of the examined knee may help to increase the reliability of gagCEST experiments.

Mirko Hrovat, James Balschi, Mike Dabaghyan, Mark Mattingly, Neal Kalechofsky

A feedback system used in conjunction with a high concentration spin reservoir demonstrates an enhanced MRI signal from a molecular imaging target at low concentration. Enhanced images of a 10mM 19F FDG target obtained by a modified 3D Flash sequence are shown. Detectability curves reveal that for a 100ul voxel size, an imaging time of ~30 min is required to image 1mM 19F FDG with an SNR of 4. 

Nirbhay Yadav, Xing Yang, Yuguo Li, Wenbo Li, Guanshu Liu, Peter van Zijl

Magnetic Resonance Imaging (MRI) is rarely used for molecular binding studies and never without synthetic metallic labels. We designed an MRI approach that can selectively detect substrate-target interaction by exploiting the narrow resonance of protons in free substrate for selective radio-frequency (RF) labeling and, subsequently, the process of immobilisation upon binding to a solid-like target for fast dipolar transfer of this label over the protons in its backbone. This cascade of events is ultimately detected via the water MRI signal with enhanced sensitivity. We demonstrate the principle for caffeine binding in vitro and in vivo.

Shubhangi Agarwal, Nutandev Jayadev, Carlos Renteria, Xiangxing Kong, Yanqing Tian, Landon Inge, Vikram Kodibagkar

Degree of tumor hypoxia and its spatial distribution could impact the therapeutic choices and lead to development of improved treatment plans. This study uses a hypoxia binding T1 contrast agent GdDO3NI, to evaluate the dependence of hypoxia activated pro-drug TPZ (Tirapazamine) on baseline tumor oxygenation and its effect on the oxygenation of two non-small cell lung cancer lines ( NCI-H1975 and patient derived xenograft M112004). GdDO3NI was able to report the changes in hypoxia distribution in the tumor models in response to Tirapazamine therapy and correlation with therapeutic effect.  

Sudath Hapuarachchige, Wenlian Zhu, Yoshinori Kato, Marina Backer, Susanta Sarkar, Joseph Backer, Dmitri Artemov

Noninvasive image-guided drug delivery is important in cancer drug development, and allows visualizing the delivery and predicting the outcome. In this study, the delivery and therapeutic effects of liposomes targeted to tumor vasculature was researched. Intravital microscopy and MRI were used for tracking the drug delivery and therapeutic effects were monitored in MDA-MB-231 mouse tumor model. Our experimental results suggest that targeting liposomes to VEGF receptors (VEGFRs) expressed on tumor endothelium, may inhibit EPR-mediated extravasation and accumulation of VEGFR-targeted liposomes.

Eleni Demetriou, Mohamed Tachrount, Karin Shmueli, Xavier Golay

In this work we propose a novel pulse sequence for measuring chemical exchange rates through a progressive saturation recovery process PRO-QUEST (PROgressive saturation for Quantifying Exchange using Saturation Times).  The water magnetization is sampled under non-steady state conditions and saturation is interleaved with the acquisition of images obtained in a single scan. Unlike previous approaches, it provides maps of T₁ and B₁ , needed for exchange-rate calculations, from the same dataset. The proposed pulse sequence has been successfully applied to obtain exchange rate maps in phantoms and healthy rat brains.

Lale Umutlu, Jasmin Jaeger, Matthias Nittka, Stephan Kannengiesser , Josef Pfeuffer , Gregor Koerzdoerfer , Rainer Kirsch, Florian Meise, Harald Quick, Vikas Gulani, Mark Griswold, Ken Herrmann, Marcel Gratz, Michael Forsting

The successful implementation of integrated PET/MR systems has enabled a unique platform for simultaneous multi-parametric imaging comprising morphologic, functional and metabolic features of pathologic tissue. MR Fingerprinting has been recently presented as a robust and fast framework for simultaneous accurate quantification of multiple MR tissue properties. The results of our study, combining tissue characterization based on PET/MR imaging and MR Fingerprinting, indicate a correlation between tumor grading and changes in tissue features, demonstrating the high diagnostic potential of this novel approach for multi-parametric tissue characterization.    

Sydney Montesi, Rohan Rao, Lloyd Liang, Subba Digumarthy, Amita Sharma, Peter Caravan, Andrew Tager, Ravi Seethamraju

Vascular leak is a cardinal response to injury, and prior assessments of alveolar-capillary permeability suggest that vascular leak is present in the lungs of patients, and that its extent is associated with progression and mortality.  We hypothesized that the degree of vascular leak present reflects the extent of ongoing lung injury, and that measuring lung vascular permeability consequently could provide a much-needed metric for assessing ILD disease activity and predicting disease progression. Using magnetic resonance imaging with the albumin-binding contrast agent gadofosveset, we were able to detect increased vascular permeability in the lung of patients with fibrotic ILD. 

Christiane Mallett, Matthew Latourette, Jeremy Hix, Alexander Wolf, Erik Shapiro

We are developing an MRI method to measure acetaminophen toxicity in the liver. We obtained dynamic T1 weighted images of the liver and T1 maps using the clinically approved contrast agent gadoxetate disodium (Eovist). After acetaminophen overdose, the uptake of contrast was decreased in the liver and increased in the kidney. T1 and variation in T1 were higher after acetaminophen. T1 was correlated with ALT, a serum measure of liver damage. This is a promising method for quantifying drug induced liver damage in vivo.

Hyunseung Lee, Eun-jung Kim, Hyun Min Kim, Kwan Soo Hong

A novel dual imaging probe for in vivo magnetic resonance imaging (MRI) and optical imaging was developed by combining gadolinium (Gd)-chelating MR probe and a near-infrared (NIR) fluorophore, aza-BODIPY (AB; BODIPY = borondipyrromethene). This aza-BODIPY-based bimodal contrast agent (AB-BCA) showed a significant fluorescence emission around the NIR range and an enhanced longitudinal relaxivity in MR modality. The probe was easily delivered to phagocytic cells of the innate immune system, together with macrophages and dendritic cells (DCs), and presented high-performance fluorescence and MR imaging without obvious cytotoxicity.

Hyla Allouche-Arnon, Amnon Bar-Shir

Non-invasive imaging of inflammation is crucial for understanding both inflammatory processes and immunotherapy. We propose a non-invasive and non-radioactive approach for longitudinal imaging of activated immune cells. We show that the use of the natural nucleoside cytidine as CEST imaging probe enable the monitoring of specific activated T-cells population with MRI. By using fluorescent analog of cytidine it is shown that CD8 T-cells are in situ labeled, underlying the specificity of nucleosides as potential probes for monitoring activated immune cells. We conclude that by using cytidine as a MRI-based probe one could monitor specific activated T-cells population during inflammation. 

Xiaoyong Zhang, Ximei Qian, Sha Wang, Xiaoping Hu

Iron oxide nanoparticles (IONPs) are widely used as labels for noninvasive cell tracking using magnetic resonance imaging (MRI). However, IONP induced contrast dilutes rapidly over time due to cell growth and division, limiting its applications in long-term cellular visualization. In the present work, unlike techniques focusing on modification of IONPs, we established a novel transgenic approach to increase IONP retention, significantly prolonging the tracking time of IONP labeled cells. In addition, this approach could be generalized to other cell types and magnetic nanoparticles, making it attractive for long-term cell tracking or tumor progression monitoring.  

Lesley Foley, James DeMar, Andrew Batuure, William Rittase, John Rosenberger, Donna Wilder, Patrick Kochanek, Joseph Long, T Hitchens

Our objective is to longitudinally monitor the nature and timing of immune cell guided inflammatory processes following multiple blasts in an animal model, in an effort to discern potential therapeutic windows. Blast, results in a heterogeneous whole-body inflammatory response that can be observed with a perfluorocarbon contrast agent and ¹⁹F MRI. A second closely timed blast increased the amount of fluorine signal in injured rats, which most likely represents increased macrophage accumulation. Despite having potent anti-inflammatory properties, we did not observe that a diet rich in omega-3 fatty acids has a significant impact on the inflammatory response to blast injuries. 

Rachelle Crescenzi, Adriana Marton, Paula Donahue, Helen Mahany, Ping Wang, Joshua Beckman, Manus Donahue, Jens Titze

Sodium MRI is a molecular imaging tool that may be sensitive to the impact of lymphatic impairment on tissue homeostasis, yet has not been evaluated in a clinical population with a lymphatic disorder. Lipedema is a lymphatic fat-disorder that is under-recognized due to a need for further advanced MR imaging to diagnosis and assess treatment efficacy of the condition. Here, we apply quantitative 3T sodium imaging for the first time in a lipedema cohort to quantify tissue sodium levels and found elevated sodium concentration in the skin and muscle of patients with lipedema compared to BMI- and age-matched controls.

Bashar Issa

Theories describing T2 enhancement due to the presence of superparamagnetic particles agree well with experimental and Monte Carlo simulation data under the condition that the particles are monodisperse both in size and magnetization. We present a T2 distributed model that takes into account the particle size and magnetization distributions. The results shown confirm the ability of the distributed relaxation model to correctly predict T2 values for a mixed MAR and SDR sample of MNP under a wide range of values of size, magnetization, volume fraction, etc. The new model will reduce the error in calculating T2 values using the mean size and mean magnetization values when a distribution of MNP exists.

Qun Zhao, Forrest Goodfellow, Gregory Simchick, Thomas Hodge, Melinda Brindley, Steven Stice

A chicken embryo is the developmental biology’s oldest model organism. In ovo development of the chicken embryo closely mirrors human embryo development. The relatively large size, ease of access, and lack of maternal motion generated in pregnant mammals are distinct advantages the chicken embryo model provides. The chicken embryo provides an excellent platform for monitoring morphology and metabolism of central neural system (CNS) by using MRI or NMR spectroscopy over the course of development. In this presentation our recent work on monitoring Zika virus induced microcephaly and tracking stem cells are presented.

Anna Ulyanova, Jadegoud Yaligar, Anantharaj Rengaraj, Tian Xianfeng, Venkatesh Gopalan, Sanjay K Verma, Christiani Jeyakumar Henry, S Sendhil Velan

The lack of dietary essential amino acid leucine influences energy metabolism via hypothalamic leptin signaling pathway. However, these neural circuits and its relationship with pathogenesis of obesity still remain unclear. In this work we investigated the hypothalamic neural pathway, abdominal fat and liver fat by multi-parametric imaging in leucine deficient diet fed mice. MEMRI results indicated that leu deficiency triggers neuronal inhibition in certain hypothalamic regions suggesting POMC neuronal pathway involvement in enhanced energy expenditure through leptin signaling pathway. Combined with systemic metabolic changes this may facilitate in understanding of amino acid sensing and metabolic regulatory network of energy homeostasis. 
 

Meng-Syuan Lin, Ying-Jui Ho, Jun-Cheng Weng

Dementia with Lewy bodies (DLB) is thought to be the second commonest cause of neurodegenerative dementia in older people, accounting 15 to 25% cases at autopsy. However, to date there are no reliable methods of instrumental and laboratory diagnosis of this disease while its treatment is based on reducing the symptoms. The drug X has been shown to have neuroprotective effects in neurodegenerative diseases. Therefore, we aimed to clarify the medicinal effectiveness of drug X through manganese-enhanced magnetic resonance imaging (MEMRI). Our results indicated that drug X may have clinical potential in the treatment of DLB.

Begona Lavin Plaza, Alkystis Phinikaridou, Marcelo Andia Kohnenkampf, Rene Botnar

The deleterious impact of atherosclerosis on other cardiovascular diseases has recently been shown, but the effect of vascular alterations on plaque formation at a distal site, including the underlying mechanisms of this systemic response, has not been elucidated. In this study, we used an albumin-binding contrast agent to assess whether (1) endothelial injury in the abdominal aorta accelerates plaque progression in the brachiocephalic artery located distally to the site of injury and (2) whether monocytes can be the link between acute and systemic response. 
 

Isabel Ramos, Markus Henningsson, Maryam Nezafat, Begoña Lavin, Silvia Lorrio, Alkystis Phinikaridou, Ulrich Flögel, Ajay Shah, René Botnar

After a myocardial infarction (MI) the degree of inflammation and its timely resolution, together with the degradation and deposition of extracellular matrix proteins are key processes in post-MI healing. Monocyte chemoattractant protein-1 (MCP1) plays an important role in the recruitment of monocytes/macrophages and its absence has revealed a significant reduction of inflammatory cell recruitment and subsequent ECM protein production in the infarcted area. Here, we explored the merits of multinuclear ¹H/¹⁹F MRI for the simultaneous assessment of myocardial inflammation and remodelling in a murine model of MI. ¹⁹F containing nanoparticle that is avidly taken up by macrophages was used to investigate inflammatory cell recruitment into injured myocardium², and a small molecular weight gadolinium-based elastin-specific MR contrast agent was used to evaluate changes of elastin content post-MI³.

Sushanta Mishra, Subash Khushu, Gurudutta Gangenahalli

Stem cells transplantation has emerged as a promising alternative therapeutic due to its potency at injury site. Thus, tracking of stem cells is very essential. Here, we have described a serial in vivo tracking of implanted stem cells through 7T MRI and its differentiation potential into neuronal precursors. T2*-weighted images and relaxation study demonstrated a significant signal loss and effective decrease in T2* relaxation time on day-3 at injury site. Expression of neuronal markers like GFAP, MAP2 and NeuN were observed in transplanted MSCs. The proposed procedure could be extrapolated for stem cell tracking and therapies in various neurodegenerative diseases.

Christakis Constantinides, Ricardo Carnicer, Ayman Al Haj Zen, Mahon Maguire, Eileen McNeil, Edyta Swider, Mangala Srinivas, Carolyn Carr, Jurgen Schneider

Stem cell (SC) technologies constitute a potential new therapeutic approach aiming to achieve tissue regeneration. Despite advances in the visualization of pre-labeled SCs with SPIOs (¹H MRI), and of nanoparticles (NPs) containing perfluoro-crown-ethers (PFCE) [2-4] in ¹⁹F MRI, there have been no prior reports on cardiac ¹⁹F imaging with direct SC injections. We report herein the implementation of a fast acquisition protocol for cardiac and skeletal muscle ¹⁹F imaging of the C57BL/6 mouse post-mortem, and identify the minimum cellular load for PFCE labels to achieve visualization following direct SC cell injections.

Samata Kakkad, Balaji Krishnamachary, Marie-France Penet, Yelena Mironchik, Flonne Wildes, Zaver Bhujwalla

Total choline in tumors is associated with increased aggressiveness.  Since the distribution of total choline in tumors is usually heterogenous, here we have examined the relationship between high and low total choline, obtained with 1H MRSI, with hypoxia and necrosis in a human breast cancer xenograft model engineered to express red fluorescence protein under hypoxic conditions.  We found that the highest total choline regions were associated with hypoxia.  We also observed that overall total choline in tumors inversely correlated with the necrotic fraction, suggesting that reduced total choline may reflect increased cell death in tumors. 

Ashley Makela, Jeffrey Gaudet, Paula Foster

Tumour associated macrophages (TAMs) have been associated with tumour aggressiveness, including tumour growth and metastatic potential. ¹⁹F-based MRI is used in this study to track these cells in vivo, revealing the ability to differentiate TAM content between 3 murine models of breast cancer. Highly aggressive tumours had significantly higher ¹⁹F signal when compared to the low and non aggressive variants. This information may be of use as a biomarker, to differentiate between tumours with high infiltration of TAMs, which have the propensity to metastasize and progress quicker, versus tumours with less TAMs, which may not advance as quickly.

Renuka Sriram, Justin DeLos Santos, Julia Nguyen, Mark Van Criekinge, Seth Vigneron, John Kurhanewicz, John MacKenzie

Carbon-13 magnetic resonance with dynamic nuclear polarization is a potential molecular imaging strategy to detect and monitor inflammation. In this study we investigated hyperpolarized 13C-pyruvate and alterations in its conversion to 13C-lactate as an imaging biomarker for disease severity and monitoring treatment response in inflammatory disorders.

Eul Hyun Suh, Weijun Ou, Ian Corbin, Dean Sherry, Jae Mo Park

Upregulated branched-chain amino transaminase 1 (BCAT1) expression is a common metabolic feature of most primary cancers with wild-type isocitrate dehydrogenase (IDH), including glioblastoma. In this study, ¹³C-labeled a-ketoisocaproate (KIC) metabolism was investigated in a brain tumor-bearing rat to assess BCAT1 and branched-chain α-ketoacid dehydrogenase (BCKDH) activities in the tumor. Following an intravenous bolus injection of hyperpolarized [1-¹³C]KIC, both [1-¹³C]leucine and ¹³C-bicarbonate were observed in the brain. We observed less [1-¹³C]leucine but greater bicarbonate production in the tumor compared to normal, healthy brain tissue, suggesting downregulated chemical exchange of [1-¹³C]KIC with leucine catalyzed by BCAT1 and upregulated BCKDH activity, respectively.

Rasmus Tougaard, Esben Hansen, Christoffer Laustsen, Jakob Lindhardt, Marie Schroeder, Hans Erik Bøtker, Won Yong Kim, Henrik Wiggers, Hans Stødkilde-Jørgensen

Deranged metabolism is now considered a key causal factor in heart failure and has therefore gained considerable scientific interest. The novel technique hyperpolarized MR has emerged as a leading methodological candidate to study these derangements. We employed a clinically relevant, large animal model of angiotensin-II-mediated acute hypertension to study cardiac metabolism in the setting of elevated afterload using hyperpolarized [1-¹³C]Pyruvate MR. The method was able to detect acute increases in both anaerobic and aerobic cardiac metabolism, which, in the future could mean a useful way of monitoring a possible treatment response to afterload reduction by using hyperpolarized MR.

Kerstin Timm, Jack Miller, Dragana Savic, Vicky Ball, Lucia Giles, Cher-Rin Chong, Michael Dodd, Damian Tyler

Chemotherapeutic agents such as doxorubicin can cause serious adverse effects on the heart, leading to decreased left ventricular function and heart failure.  The biochemical mechanisms for this are not fully understood, however, increased oxidative stress in cardiomyocytes as well as bioenergetic changes to the heart have been suggested as primary triggers for the functional decline.  Here we show that hyperpolarized ¹³C magnetic resonance spectroscopy and CINE magnetic resonance imaging of the heart can detect metabolic as well as functional changes in a clinically relevant rat model of doxorubicin-induced cardiotoxicity, and that metabolic changes may precede functional abnormalities. 

Rasmus Tougaard, Esben Hansen, Christoffer Laustsen, Thomas Nørlinger, Emmeli Mikkelsen, Jakob Lindhardt, Marie Schroeder, Per Nielsen, Lotte Bertelsen, Hans Erik Bøtker, Won Yong Kim, Henrik Wiggers, Hans Stødkilde-Jørgensen

Standardized large animal models for cardiac hyperpolarized MR metabolic studies are becoming increasingly important as translation into human trials progresses. We employed a porcine (n=17) model of fasting/feeding to study these two states and to examine normal feeding as a standardized model for increasing hyperpolarized [1-¹³C]Pyruvate signal in the heart. All metabolic ratios were higher in fed animals with no additional variance. This indicates the role of pyruvate uptake to be more important in pigs than in rodents, underlining the need for large animals in metabolic research, and also suggests feeding to be a feasible, standardized model for increasing signal.

Esben Hansen, Rasmus Tougaard, Per Nielsen, Jakob Lindhardt, Hans Jørgensen, Christoffer Laustsen

Hyperpolarized MR may be a key tool for investigation cardiac metabolism and cardiac treatment response. [1,4-¹³C₂]Fumarate is an emerging and interesting candidate for measuring and visualizing cardiac injury after ischemia. In this study we showed an initial step for imaging cardiac cell death in a large animal model with [1,4-¹³C₂]malate. The [1,4-¹³C₂]malate signal correlated well with increased ¹³C-lactate signal and ¹³C-alanine absence. Overall, this shows increased metabolism in the infarcted area and ongoing necrosis.

Dmitry Kurzhunov, Robert Borowiak, Marco Reisert, Axel Krafft, Ali Özen, Michael Bock

This study presents a comparative analysis of different reconstruction techniques for quantification of 3D maps of the cerebral metabolic rate of oxygen consumption (CMRO₂) in human brain. CMRO₂ maps were calculated from a direct ¹⁷O-MRI experiment at 3T in which ¹⁷O gas was inhaled. Conventional Kaiser-Bessel reconstruction of ¹⁷O MR images was compared to two iterative reconstruction methods using total variation (TV) and anisotropic diffusion (AD) of coregistered proton data as constraints. AD-constraint reconstruction, which acts as a non-homogeneous edge-preserving smoothing filter, enabled CMRO₂ mapping at clinical field strengths by increasing the SNR, and reducing partial volume effects.

Mehrdad Pourfathi, Hooman Hamedani, Yi Xin, Stephen Kadlecek, Maurizio Cereda, Harrilla Profka, Ian Duncan, Nicholas Drachman, Sarmad Siddiqui, Kai Ruppert, Joe Naji, Rahim Rizi

In this hyperpolarized pyruvate imaging study of acute lung injury, we assessed alterations of regional lactate-to-pyruvate ratio during the progression of lung inflammation caused by acid aspiration. The study shows that posterior lactate-to-pyruvate ratio changes more significantly after injury compared to the anterior ratio. This is consistent with the pattern observed with proton MRI. We report good correlation between increased lactate-to-pyruvate ratio due to inflammation and increased proton image intensity as a result of formation of edema, especially in the posterior regions.

Christian Hundshammer, Miriam Braeuer, Müller Christoph, Adam Hansen, Jorge Cabello, Mathias Schillmaier, Benedikt Feuerecker, Stephan Duewel, Schachoff Sylvia, Birgit Blechert, Michael Michalik, Jan-Bernd Hövener, Steffen Glaser, Axel Haase, Franz Schilling, Andreas Kjaer, Stephan Nekolla, Schwaiger Markus

In order to understand complex mechanisms of the tumor biology, multimodal imaging approaches are useful. Here we present a workflow to characterize subcutaneous MAT-B-III tumors in rats on a clinical 3T PET/MR. Proton imaging was used for tumor localization and to characterize tumor cellularity by diffusion-weighted imaging. Glucose uptake and downstream glucose metabolism of pyruvate by lactate dehydrogenase (LDH) was addressed by [¹⁸F]FDG-PET and hyperpolarized [¹³C]pyruvate metabolic imaging. The [¹⁸F]FDG standard uptake values and the LDH activity were consistently and reproducibly higher compared to normal tissue.

Gaurav Sharma, Cheng Yang Wu, R. Max Wynn, David Chuang, Craig R. Malloy, Chalermchai Khemtong, A. Dean Sherry

The Pyruvate Dehydrogenase Complex (PDC) plays a critical role in the regulation of carbohydrate metabolism. Pyruvate Dehydrogenase Kinase (PDK) inhibits PDC via phosphorylation making it a novel therapeutic target for metabolic diseases. The present study aimed to evaluate whether the metabolism of HP-13C pyruvate is sensitive to PDK inhibition. Our results showed that higher production of HP-bicarbonate via PDC in PDK deficient livers. ¹³C NMR isotopomer analysis of tissue extracts confirms higher 13C-enrichment of AcCo-A in the DKO livers than the control group. The result suggested that the appearance of HP-bicarbonate  is a sensitive biomarker for monitoring the consequences of PDK inhibition.

Sarmad Siddiqui, Mehrdad Pourfathi, Andreas Habertheuer, Yi Xin, Harrilla Profka, Hooman Hamedani, Stephen Kadlecek, Ali Naji, Prashanth Vallabhajosyula, Rahim Rizi

Orthotopic rat lung transplantation is a well-established animal model used for elucidating the mechanics of lung transplant surgery. However, most lung function assessment is conducted via invasive techniques. In this study, we demonstrated that hyperpolarized pyruvate MRI can be used to generate metabolic biomarkers that can be used for non-invasive lung function assessment after transplantation. In successful syngeneic lung transplants, the lactate-to-pyruvate ratio remains low in both lungs after transplant. However, in allogeneic or failed syngeneic lung transplantation, the native lung returns to baseline one week after surgery, whereas the transplanted lung shows a significant(~3-fold) increase in the lactate-to-pyruvate ratio.

Hooman Hamedani, Mehrdad Pourfathi, Yi Xin, Stephen Kadlecek, Maurizio Cereda, Harrilla Profka, Ian Duncan, Sarmad Siddiqui, Nicholas Drachman, Kai Ruppert, Rahim Rizi

In this study we seek to investigate the dependency of the changes of lactate-to-pyruvate ratio on various covariates in the settings of experimental acute lung injury using a random-effect model.

Jae Mo Park, Ralph Hurd, Daniel Spielman

In this study, we demonstrated the strategies of increasing signal sensitivities of ¹³C-pyruvate and ¹³C-lactate generated from an injection of hyperpolarized ¹³C-alanine by (1) adjusting the alanine dose and (2) co-injecting unlabeled pyruvate. 120-mM alanine produced larger amount of labeled pyruvate and lactate as compared to when 80-mM or 40-mM alanine was injected. The co-injection of 7-mM unlabeled pyruvate showed up to 49% SNR increase in pyruvate and lactate peaks.

Eugene Milshteyn, Cornelius von Morze, Jeremy Gordon, Zihan Zhu, Peder Larson, Daniel Vigneron

The bSSFP sequence provides high spatial and temporal resolution capabilities, but has a difficult to manage frequency response at 3T with regards to hyperpolarized [1-¹³C]pyruvate and its products. The purpose of this project was to integrate a spectral suppression pulse, designed to suppress alanine and pyruvate-hydrate, with the bSSFP sequence to image [1-¹³C]pyruvate and its conversion to [1-¹³C]lactate. The results showed no significant effect on quantitative analysis of lactate-to-pyruvate ratios or k_pl after suppression of alanine and pyruvate-hydrate. Subsequently, dynamic imaging of [1-¹³C]pyruvate and [1-¹³C]lactate at high in-plane spatial resolution was achieved with the bSSFP sequence.

Eleonora Cavallari, Carla Carrera, Silvio Aime, Francesca Reineri

Hyperpolarization (HP) of the 13C magnetic resonance signal of [1-13C]-lactate has been obtained using the ParaHydrogen Induced Polarization by means of Side Arm Hydrogenation (PHIP-SAH). Different ester derivatives of lactate have been tested in order to optimize the hydrogenation kinetics and the polarization level on the product. The metabolic transformation of hyperpolarized [1-13C]-lactate into pyruvate has been observed in vitro. The bio-compatibility of the aqueous solution and the good polarization level (7.9±0.4%) make the hyperpolarized metabolite thus obtained a good candidate for metabolic imaging studies. 

Grzegorz Kwiatkowski, Jonas Steinhauser, Patrick Wespi, Matthias Ernst, Sebastian Kozerke

Hyperpolarized silicon particles have been shown to exhibit enormously long T₁ relaxation at room temperature, making them favourable as novel imaging MR probes. To date, only large particles (average particle size (APS)=2.2 μm) could be efficiently polarized, restricting their in-vivo applicability.

The objective of the present work was to develop nanometre size hyperpolarized silicon-29  particles (APS= 55+/-12 nm) with superior MR properties. A maximum achievable polarization of 12.6% is reported with relaxation time of 42 min at room temperature. Applications of imaging of both solid and colloidal dispersion of silicon particles are demonstrated.  

Justin Lau, Benjamin Geraghty, Yiping Gu, Albert Chen, Charles Cunningham

An interleaved multi-echo imaging sequence is proposed to improve off-resonance robustness for spectral-spatial excitation and echo-planar imaging of hyperpolarized [1-¹³C]pyruvate. A non-iterative pointwise k-space signal decomposition approach for removing pyruvate hydrate contamination from lactate images is presented. Performance of the sequence and reconstruction pipeline was evaluated using an ethylene glycol phantom and a catalyzing enzyme system. Minimal signal loss and successful removal of pyruvate hydrate contamination were demonstrated in vivo for realistic cases of off-resonance.

Thomas Theis, Zijian Zhou, Jin Yu, Johannes Colell, Warren Warren

Current hyperpolarization methods used in preclinical research are limited by high cost (>$2M) and short hyperpolarization lifetimes (<1 min). Here we demonstrate hyperpolarization of long-lived states with inexpensive equipment. Specifically, we use parahydrogen which is simple to produce (<$10k in equipment costs) and transfer its singlet hyperpolarization by non-reactive polarization transfer to long-lived singlet states on 13C spin pairs in molecular substrates. We detail polarization transfer mechanisms and obtain hyperpolarization lifetimes in excess of two minutes. Moving forward, we expect to achieve hyperpolarization lifetimes of hours as has been demonstrated on thermally polarized 13C spin pairs.     

Jeremy Gordon, Yesu Feng, Peter Shin, Daniel Vigneron, Peder Larson

With the translation of hyperpolarized ¹³C to the clinic, imaging approaches will require large volumetric FOVs to support clinical applications. Parallel imaging techniques will be crucial to increasing volumetric scan coverage while minimizing RF requirements and temporal resolution. Calibrationless parallel imaging approaches are well-suited for this application because they eliminate the need to acquire coil profile maps or auto-calibration data. In this work, we explored the application of calibrationless parallel imaging (SAKE) and corresponding sampling strategies to accelerate and undersample hyperpolarized ¹³C data using 3D blipped EPI acquisitions and multichannel receive coils.

Jae Eun Song, Hansol Lee, Eunhae Joe, Jaewook Shin, Dong-Hyun Kim

In this study, using high spatial and/or spectral resolution CSI technique in 1H, the SPICE (SPectroscopic Imaging by exploiting spatiospectral CorrElation), we investigated the feasibility of using SPICE in hyperpolarized ¹³C through numerical simulations for applications targeted for K_p estimation and high resolution studies. The error of the fitted K_p were within ±20% of the true value and the high spatial resolution rat brain image was reconstructed. It is seen that this method can be transferred to a hyperpolarized ¹³C situation where due to the T1 decay and metabolite exchange the temporal basis can change dynamically.

Tom Peeters, Thiele Kobus, Andor Veltien, Arend Heerschap, Tom Scheenen

The delivery of targeted metabolic compounds can be hindered by a natural barrier in the brain. Nowadays, focused ultrasound techniques allow temporarily opening of this blood-brain barrier (BBB). Here we investigated the feasibility to combine this technique with dynamic imaging of hyperpolarized (HP) pyruvate. After opening the BBB in a focal spot, we acquired in vivoHP pyruvate images of the mouse brain using a dynamic gradient-echo imaging acquisition scheme at 7T. This approach eventually allows  investigations with hyperpolarized compounds in the brain that are usually hindered by the BBB or suffer from a too slow uptake for DNP-imaging.

Angus Lau, Albert Chen, Justin Lau, Charles Cunningham

Recently we proposed using simultaneous multislice (SMS) acceleration to improve spatial coverage in the hyperpolarized ¹³C experiment, and demonstrated that controlled aliasing improves conditioning of the inverse problem. For single-shot experiments this requires gradient modulation along z, which can be sensitive to gradient imperfections. Here, we show that inherent coil sensitivity variations can be sufficient for SMS acceleration in hyperpolarized ¹³C experiments, without additional readout gradient modification. Two-fold acceleration with a 8 cm slice gap can be obtained with less than 20% SNR loss. We anticipate that this strategy will enable multiple organ ¹³C imaging of in vivo metabolism.

Thomas Theis, Johannes Colell, David Waddington, Warren Warren, Matthew Rosen

Hyperpolarized MRI is a powerful approach to non-invasisve biomolecular imaging because of high sensitivity and excellent molecular specificity. However, current methods are limited by high cost (>$5M) and short hyperpolarized signal lifetimes (<1 min). We overcome both limitations by low field (6.5 mT) imaging of molecules polarized by non-reactive transfer of spin order from parahydrogen. Both, parahydrogen polarizers and low-field MRI hardware are simple technologies affordable on a modest budget (<$200k). At low fields, we establish hyperpolarization decay time constants of above 20 min, greatly exceeding current markers. This suggests highly sensitive biomolecular MR imaging could be done at the cost of an X-Ray.

Hansol Lee, Jae Eun Song, Jaewook Shin, Eunhae Joe, Young-suk Choi, Ho-Taek Song, Dong-Hyun Kim

Hyperpolarized ¹³C technique might be a practical challenge to achieve both high spatial and spectral resolution in spectroscopic images due to the amount of required data. Recently, an emerging technique called to SPectroscopic Imaging by exploiting spatiospectral CorrElation (SPICE) has been introduced for high spatiotemporal resolution in ¹H magnetic resonance spectroscopic image (MRSI). In this study, by applying this technique to hyperpolarized ¹³C MRSI, a high resolution spectroscopic image was acquired.

Xucheng Zhu, Jeremy Gordon, Peder Larson

Due to limited transmit coil volume, refocusing pulses spoil magnetization located around the edge of the coil even with adiabatic pulses.  This is a major problem for hyperpolarized 13C MRI, as this can destroy precious magnetization. To overcome this drawback, we propose to use a high bandwidth slice-selective adiabatic pulse to replace the original non-selective pulse. We designed and optimized the pulse via simulation. Then the slice-selective double spin echo sequence was tested on both phantom and in vivo studies.

Eduardo Coello, Esben Hansen, Christoffer Laustsen, Bjoern Menze, Axel Haase, Rolf Schulte

The overdiscrete reconstruction, originally proposed for ¹H MR Spectroscopic Imaging (MRSI), is adapted and applied to hyperpolarized ¹³C MRSI. The method is demonstrated for in-vivo hyperpolarized [1-13C]-pyruvate scans of a pig’s kidneys using phase encoded 2D-MRS. Linewidth and spectral separation were improved in addition to a significant signal enhancement for low concentrated downstream metabolites such as lactate, alanine and pyruvate-hydrate.

Patrick Wespi, Jonas Steinhauser, Grzegorz Kwiatkowski, Sebastian Kozerke

In this work dynamic shimming was implemented for multi-slice hyperpolarized metabolic imaging of the rat heart at 9.4T. Phantom experiments were carried out to test the switching between different shim sets and eddy current effects. The method was subsequently applied to assess cardiac metabolism in healthy rats after injecting hyperpolarized [1-13C] pyruvate. It is demonstrated that B₀ inhomogeneity induced signal variations could be reduced with dynamic shimming when compared to static shimming.

Erin Adamson, Kai Ludwig, Benjamin Cox, Sean Fain

Real-time quantification of in vivo metabolism with hyperpolarized ¹³C magnetic resonance spectroscopic imaging (MRSI) is currently limited by partial volume effects from intense vascular signal. Flow-sensitive, bipolar gradients are an attractive option for suppressing vascular signal due to their minimal influence on static spins. This work looks at the impact of incorporating bipolar gradients on the quantification and repeatability of hyperpolarized ¹³C MRSI metabolic measures of lactate-to-pyruvate area-under-the-curve ratios (AUC_ratio). The results suggest that incorporating bipolar gradients mitigates vascular partial voluming, increasing measured AUC_ratio, while reducing measurement repeatability, indicated by the larger repeatability coefficients.

Jiazheng Wang, Alan Wright, Richard Hesketh, De-en Hu, Kevin Brindle

We have developed a workflow for hyperpolarized ¹³C EPI phase correction that requires no reference scan. The workflow provides ghost-free images on phantoms with large or tight fields of view and where there are multiple signal sources. Dynamic images acquired from hyperpolarized [1-¹³C]pyruvate and [1-¹³C]lactate in a tumor showed comparable image quality to those corrected using a separate ¹³C reference scan.

Patrick Wespi, Jonas Steinhauser, Grzegorz Kwiatkowski, Sebastian Kozerke

The effect of B₀ inhomogeneity on the quantification of hyperpolarized metabolic data is studied using simulations based on B₀ maps acquired in-vivo in rat hearts at 9.4T. Kinetic modelling is compared to area-under-the-curve analysis and both methods are applied to average signals over myocardial segments and individual voxels, respectively.

Christian Mariager, Mette Riis-Vestergaard, Haiyun Qi, Steffen Ringgaard, Christoffer Laustsen

Hyperpolarized (HP) [1-¹³C]-pyruvate imaging has gained increasing attention, as its ability to monitor metabolic changes in real-time is expected to have a great clinical impact. In this work we investigate the use of a fast multi-echo balanced steady state free precession (BSSFP) sequence to acquire spectroscopic images at 9.4T. We show that this technique, in combination with the iterative Dixon type reconstruction technique (IDEAL), yields dynamic high resolution spectroscopic maps in a ¹H phantom as well as for preliminary in vivo HP [1-¹³C]-pyruvate experiments in rat kidneys.

Nicholas Whiting, Jingzhe Hu, Julie Liu, Klaramari Gellci, Pamela Constantinou, Jennifer Davis, Niki Millward, David Menter, Daniel Carson, Pratip Bhattacharya

Hyperpolarized silicon nano- and microparticles hold great promise as targeted molecular imaging agents due to their overall biocompatibility and long-lasting enhanced MRI signals. We performed dynamic nuclear polarization on silicon microparticles that were functionalized with an antibody that targets Mucin overexpression in colorectal cancer. Conjugation of the antibody to the particle surface did not affect the ²⁹Si hyperpolarization characteristics, and in vivo imaging was attained 20 minutes after particle injection into a colorectal cancer mouse model. The goal is to develop these targeted particles as a platform technology that will allow non-invasive screening of colorectal cancer using ²⁹Si MRI.

Christopher Walker, Keith Michel, Rafal Zielinski, Waldemar Priebe, Dawid Schellingerhout, James Bankson

Hyperpolarized pyruvate can be used to noninvasively probe metabolism in vivo. However, quantitative measurement of metabolic processes is frequently complicated by tissue perfusion. Metabolic inert compounds such as hyperpolarized urea have been used to measure tissue perfusion. This work shows a strong correlation between hyperpolarized urea signal and the sum of hyperpolarized pyruvate and lactate signal, suggesting that the combination of pyruvate and lactate signals can be used to estimate tissue perfusion.

Mor Mishkovsky, Brian Anderson, Magnus Karlsson, Mathilde Lerche, A Dean Sherry, Rolf Gruetter, Zoltan Kovacs, Arnaud Comment

Real-time glucose metabolism was observed in healthy mice brain following infusion of hyperpolarized [U-²H, U-¹³C]glucose and [U-²H, 3,4-¹³C]glucose. The evolution of lactate formation was readily observed. In addition, two glycolysis metabolites, namely 3-phosphoglycerate and pyruvate, were identified. Abnormalities in cerebral glucose metabolism is associated with large number of diseases so implementation of this method may prove useful in imaging brain metabolism in various animal models.

Benjamin Geraghty, Justin Lau, Logi Vidarsson, William Dominguez-Viqueira, Albert Chen, Charles Cunningham

A platform consisting of a dual-echo 3D echo-planar pulse sequence and a custom coil system was implemented and tested for metabolic imaging of breast cancer.  A two-channel unilateral breast ¹³C receive array was designed for integration with the Sentinelle Vanguard Breast MRI system. A single-loop coil was designed for RF excitation. The highly ergonomic design enables the operator to swap between proton and ¹³C breast coils without moving the patient, providing intrinsically registered anatomical and metabolic data. Phantom data and hyperpolarized ¹³C pre-clinical rat images were obtained and are presented. The proposed coil system represents important progress towards a viable breast cancer patient study.

Jonas Steinhauser, Grzegorz Kwiatkowski , Patrick Wespi, Sebastian Kozerke

In this work rapid decarboxylation of [1,2-13C]pyruvate using hydrogen peroxide was employed to obtain hyperpolarized [1-13C]acetate. 13C polarization was transferred completely and reproducibly. The application of the concept is demonstrated for detecting [1-13C]acetate and [1-13C]acetylcarnitine in the in-vivo heart.

Abubakr Eldirdiri, Stefan Posse, Lars Hanson, Rie Hansen, Adam Hansen, Jan Ardenkjær-Larsen

Fast and robust symmetric echo planar spectroscopic imaging sequence for hyperpolarized ¹³C in a clinical system is presented. The sequence employs a reconstruction algorithm that re-grids the sampled data in the spatio-temporal frequency space to compensate for the chemical shift artifacts and achieve an improved reconstruction within a limited bandwidth. The sequence was tested on a clinical 3 T whole body scanner using dedicated ¹³C coils and was compared with the conventional chemical shift imaging. Good tradeoff between speed, efficiency and SNR was achieved and the reconstruction was superior compared to the commonly used FFT reconstruction.