Steffen Frank, Hikari Yoshihara, Mor Mishkovsky, Arnaud Comment, Rolf Gruetter

Hyperpolarized 2-keto[1-¹³C]isocaproate (KIC) provides a means to probe brain nitrogen homeostasis and to assess molecular signatures of tumors. The dynamic nuclear polarization process requires a free-radical polarizing agent, and samples are typically doped with persistent radicals. An alternative is to use photo-induced radicals of α-keto acids that recombine upon dissolution. [1-¹³C]KIC hyperpolarized with photo-induced radicals could be used to measure the alterations in amino acid metabolism that are linked to neurodegenerative diseases and cancer, and the aim of the present study is to identify the main features that influence the polarization dynamics.

Andrew Cho, Roozbeh Eskandari, Jason Lewis, Kayvan Keshari

Across most cancer types, increased macrophage infiltration is associated with a worsening prognosis. This is because tumor associated macrophages (TAMs) exhibit a variety of pro-tumor effects ranging from vascular recruitment, cell proliferation, extravasation, and immune suppression. A marker of TAMs is arginase-1 expression, which converts arginine to urea and ornithine. It is thought that arginase expression reduces the amount of arginine available to local T-cells, leading to T-cell receptor dysfunction. In this abstract, we outline the synthesis and characterization of novel compound [6-13C,6-15N3]-Arginine as a hyperpolarized 13C MRS probe to interrogate arginase activity, with the potential for in vivo translation.

James Bankson, Keith Michel, Christopher Walker, Yunyun Chen, Jorge Delacerda, Charles Kingsley, Philip Lorenzi, Lin Tan, Stephen Lai

Dynamic imaging of HP pyruvate shows tremendous promise for offering new insight into tumor metabolism with unprecedented sensitivity, specificity, and spatiotemporal resolution.  Imaging constraints due to the finite, nonstationary, and non-renewable signal pool necessitate the use of complex imaging and reconstruction strategies, but current approaches to validation of complex HP MRI measurements are lacking and new methods are critically needed.  In this work, we investigate a framework for external validation of quantitative HP MRI biomarkers of tumor metabolism using stable isotope tracer analysis (MS-SITA).  We show good agreement between quantitative biomarkers of chemical conversion derived from HP MRI and MS-SITA. 

Rie Hansen, Henrik Gutte, Majbrit Larsen, Annemarie Kristensen, Andreas Kjær, Jan Ardenkjær-Larsen, Adam Hansen

The aim of the present work is to address the challenge of optimal flip angle calibration of ¹³C surface coils in hyperpolarization studies. To this end, we characterize the spatial profile of the flip angle and demonstrate that it allows for a simple calibration improving the signal-to-noise ratio for hyperpolarized ¹³C magnetic resonance spectroscopic imaging.

John Maidens, Jeremy Gordon, Murat Arcak, Hsin-Yu Chen, Ilwoo Park, Mark Van Criekinge, Eugene Milshteyn, Robert Bok, Rahul Aggarwal, Marcus Ferrone, James Slater, John Kurhanewicz, Daniel Vigneron, Peder Larson

We present a method of generating metabolism maps from dynamic hyperpolarized carbon-13 MRI images. By incorporating prior information into our model-based reconstruction via spatial regularization of the parameter maps, we achieve two qualitative benefits: elimination of non-identifiability in unperfused background regions, and denoising. This method is illustrated on a simulated dataset and a clinical prostate cancer dataset.

David Waddington, Thomas Boele, Ewa Rej, Dane McCamey, Torsten Gaebel, David Reilly

Hyperpolarized ¹³C MRI leverages an over 10 000 times increase in the ¹³C polarization of biomolecules, enabling new molecular imaging applications.  However, metabolic applications are limited to processes on the timescale of a minute by the short lifetime of the hyperpolarized signal.  Here, we hyperpolarize nanodiamonds and microdiamonds to achieve large, long-lived ¹³C polarizations.  We then image these particles in phantoms, demonstrating the potential of hyperpolarized nanodiamonds for imaging over long timescales.  As nanodiamond has been established as a biocompatible platform for drug delivery, our results will motivate further research into hyperpolarized MRI for tracking nanoparticles in vivo.

Aaron Coffey, Matthew Feldman, Roman Shchepin, Milton Truong, Wellington Pham, Eduard Chekmenev

We demonstrate murine whole-body MRS and the ability to resolve the ¹³C multiplet of hyperpolarized 1-¹³C-succinate-d₂ in a biplanar magnet with B₀ = 0.0487 T and inhomogeneity <13 ppm over 40 cm DSV. At low magnetic field strength no loss of SNR relative to high field for a well-designed radiofrequency coil occurs, but chemical shift dispersion is potentially insufficient to differentiate hyperpolarized metabolites and contrast agents. However, at sufficiently low field strength, magnetic susceptibility derived B₀ field inhomogeneity in vivo becomes negligible. Consequently, direct spectroscopic resolution of spin-spin couplings or J-couplings, more commonly performed near zero field, becomes feasible.

Kai Buckenmaier, Matthias Rudolph, Christoph Back, Joern Engelmann, Juri Rudin, Tomasz Misztal, Ute Bommerich, Klaus Scheffler, Dieter Koelle, Reinhold Kleiner, Hermann Mayer, Johannes Bernarding, Markus Plaumann

SABRE is a technique to achieve continuous hyperpolarization for MR measurements by the interaction of para-hydrogen and a substrate via steady ligand exchange on a catalyst. Thus, MR-active nuclei can be hyperpolarized more than only once. At field strengths of mT Faraday coils, commonly used in conventional or high field MRI, become insensitive and SQUIDs performing superior. Since SQUIDs are broadband detectors, the static magnetic field B₀ can be changed easily or multiple nuclei can be measured simultaneously. Here, we successfully demonstrate the advantages of a SQUID based system by showing significant signal enhancement (¹H, ¹⁹F) by hyperpolarization of 3-fluoropyridine.

Tuba Güden-Silber, Jürgen Schrader, Ulrich Flögel

We demonstrate the induction of ¹⁹F photo-chemically induced dynamic nuclear polarization (photo-CIDNP) in ¹⁹F MR imaging experiments. To this end, we made use of laser-induced hyperpolarization in a system consisting of flavin mononucleotide as a photosensitizer and the fluorinated aromatic amino acids tyrosine and tryptophan, respectively. The induction of ¹⁹F photo-CIDNP led to an extensive ¹⁹F signal enhancement which could be exploited for simultaneous imaging of both amino acids by ¹⁹F multi chemical shift-selective imaging within 20 s. Hence, our approach resulted in a substantial improvement of the intrinsically low ¹⁹F MR sensitivity for mono-fluorinated amino acids. 

Thomas Boele, David Waddington, Ewa Rej, Torsten Gaebel, David Reilly

Hyperpolarized ¹³C MRI using nanodiamond (ND) holds the potential for tailored diagnostic imaging combined with targeted drug delivery in the human body. An obstacle to realizing this potential is the transfer of hyperpolarized ND from the hyperpolarizer to the patient without losing the majority of the ¹³C polarization as it travels through low magnetic fields before reaching the MRI scanner. We demonstrate that polarization loss is highly dependent on magnetic field and construct a system of transfer magnets that improves the transfer efficiency of our hyperpolarized ND by more than an order of magnitude.

Rie Hansen, Christian Mariager, Christoffer Laustsen, Rolf Schulte, Jan Ardenkjær-Larsen, Lars Hanson

In this study we demonstrate how reconstruction for IDEAL spiral CSI (spectroscopic imaging scheme developed for hyperpolarized dynamic metabolic MR imaging) can be improved by using regularization with a sparsity constraint. By exploiting sparsity of the spectral domain, IDEAL spiral CSI can achieve chemical shift encoding by acquisition of only few time-shifted echoes. The minimum number of echoes required to avoid noise amplification can be decreased by means of regularization enforcing spectral sparsity, hereby reducing scan time. Improvements achieved by using regularized reconstruction are demonstrated for in vivo data from a hyperpolarized cardiac study of a pig.

Frederike Euchner, Markus Plaumann, Thomas Trantzschel, Joachim Bargon, Ute Bommerich, Johannes Bernarding

Fluorinated amino acids are of high interest in biochemistry and pharmaceutics. The low ¹⁹F MR signal was increased employing hyperpolarization (photo-Chemical Induced Dynamic Nuclear Polarization, photo-CIDNP). 3-Fluoro-tyrosine in physiologic salt solution was hyperpolarized in presence of an albumin derivative using a low cost LED allowing repetitive irradiation and increasing the hyperpolarized signal. A clear ¹⁹F signal enhancement could be observed. In comparison to past examinations with a laser system, only small temperature changes caused by LED light irradiation were measured in the current study.

Hsin-Yu Chen, Jeremy Gordon, Robert Bok, Peng Cao, Cornelius von Morze, Eugene Milshteyn, Ralph Hurd, John Kurhanewicz, Peder Larson, Daniel Vigneron

Hyperpolarized-¹³C MRI has recently enabled imaging of cancer pathophysiology with high spatiotemporal resolution in humans.  Quantitative measure of tumor metabolism can be made possible by estimating conversion rate constants (e.g. k_PL for pyruvate-to-lactate). We have identified 3 systematic sources affecting k_PL estimation that were introduced by MR acquisition and pulse sequences – an RF-spoiling effect, a T₂*-weighting factor, and a crusher flow-suppression phenomenon. These sources were investigated using a transgenic cancer model and simulations.

Stephen DeVience, Graeme Woodworth, Joseph Kao, Dirk Mayer

We performed the first DNP hyperpolarization of ¹³C-labeled 5-aminolevulinic acid (5-ALA), achieving 13% polarization at dissolution and measuring a T₁ of 20 s. 5-ALA is used for fluorescent imaging and photodynamic therapy of glioblastoma, and our results suggest it is also a promising substrate for hyperpolarized metabolic imaging of this cancer.

Markus Plaumann, Frederike Euchner, Rainer Ringleb, Sara Hadjiali, Joachim Bargon, Gerd Buntkowsky, Johannes Bernarding, Ute Bommerich

Nicotinic acid and isonicotinic acid are two derivatives of pyridine carboxylic acids. Both substrates are of high interest in medical chemistry. In the current study seven fluorinated derivatives of these pyridine carboxylic acids were chosen for examination of the ¹H and ¹⁹F hyperpolarizability using the SABRE technique. Influences of the position of the carboxylic group and fluorine as well as the catalyst system concerning the achievable signal enhancements were examined. Furthermore an H/D-exchange could be observed in some cases. The presented data gives important information for future MR imaging studies.

Keith Michel, Christopher Walker, Yunyun Chen, Jorge Delacerda, Stephen Lai, James Bankson

Metabolically inert hyperpolarized tracers can be used for perfusion measurements in vivo. In this work we present a simulation study to compare the performance for measurement of tissue perfusion of a conventional imaging approach to a segmented snapshot acquisition where each segment ends with a 90 degree RF pulse.

Charlie Daniels, Ferdia Gallagher

MRI with hyperpolarized ¹³C-labelled compounds is an emerging clinical technique allowing in vivo metabolic processes to be characterized non-invasively. Accurate quantification of metabolism requires a region-of-interest to be defined, which is usually based on spatial information only. However, as the hyperpolarized data is 5-dimensional (spatial, temporal and spectral), it offers the possibility of applying novel segmentation methods to more accurately define this region-of-interest. A novel solution to the problem of ¹³C image segmentation is proposed here, using a hybrid Markov random field model with fuzzy logic. Performance of the algorithm is demonstrated using in silico and in vivo data.

Chien-Lin Yeh, Courtney Johnson, Ruoyun Ma, Shalmali Dharmadhikari, Sandy Snyder, Ulrike Dydak

While the paramagnetic properties of Mangnaese (Mn) make it useful as a contrast agent for MRI, little is known about the spatial distribution of Mn deposition in the human brain due to occupational Mn exposure. Using a novel approach to analyze and visualize whole brain Mn deposition in welders, Mn was elevated in motor and cognitive associated networks, consistent with respective reports on impaired neuropsychological function. Our Mn maps even reveal the diffusion of Mn along white matter tracts for the first time in humans. These findings help explain how Mn exposure affects the function of particular brain networks. 

Harikrishna Rallapalli, Brian Nieman, Aidin Arbabi, Dulcie Vousden, Jason Lerch, Daniel Turnbull

Imaging the developing mouse brain with conventional MRI is challenging. Manganese-enhanced MRI (MEMRI) has the potential to provide a noninvasive, in vivo approach for analyzing mutant phenotypes in the early postnatal mouse cerebellum. We present preliminary data generated using a CryoProbe (Bruker) suggesting that the primary source of Mn contrast in the mouse cerebellum is the Purkinje cell layer.

Ki-Hye Jung, Ji-Ae Park, Jung Young Kim, Yongmin Chang, Tae-Jeong Kim, Hee-Kyung Kim, Kyo Chul Lee, Joo Hyun Kang, Yong Jin Lee

We have presented a strategy for incorporating low-molecular-weight Gd(III) chelate for dual non-invasive MR contrast agent and NCT, without the necessity of loading individual contrast therapeutic drugs, which is usually required in theranostics. The Gd-DO3A-BTA injected and neutron irradiated group, the tumor growth was significantly suppressed. This information could provide a basis for the prospect of obtaining a synergistic or cumulative action of chemotherapy (ChT) and Gd-NCT. We examined the neutron capture irradiation of MDA-MB-231 mice in the presence of Gd-DO3A-BTA. The results indicate that Gd-DO3A-BTA is suitable neutron capture agent for Gd-NCT.

Soyeon Kim, Hee-Kyung Kim, Eun-Young Jeon, Md. Kamrul Islam, Garam Choi, Au Reum Baek, Bo Kyung Sung, Tae-Jeong Kim, Yongmin Chang

The purpose of the present work is to design and synthesize a new bifunctional complex for use in Mn(II)-based liver-targeting MR imaging. Its r₁ relaxivity in human serum albumin (HSA) solution is 3.21 mM^-1s^-1, similar to MRI CA such as MnDPDP®. In vivo MR image after injection of Mn-DO2A-BTA by tail vein showed that its excretion is made via kidney and also bile duct, confirming hepatobiliary uptake. 

Braedan Prete, Simrun Chahal, Ashvin Fernando, Tao Li, Francis Hane, Brenton DeBoef, Mitchell Albert

Hyperpolarized (HP) 129Xe molecular imaging technology has recently advanced in the detection of biochemically inactive supramolecular cage-molecules within a living mammalian model.  Unfortunately, the natural bio-distribution of these biosensor molecules is non-specific, which makes it difficult to precisely localize them in vivo using HP 129Xe MRI.  With the HyperCEST detection of easily conjugated cyclodextrin-based pseudo-rotaxanes, we have identified a critical advancement in 129Xe biosensor design by uncovering a novel biosensor, which has the potential to precisely detect markers of early disease in a human body with comparable sensitivity to PET but with the spatial resolution of MRI.

Alexia Daoust, Galit Saar, Steven Dodd, Alan Koretsky

MEMRI can be used for different applications such as tracing neuronal connections or functional imaging. However, Mn²⁺ uptake and transport mechanisms are still unclear. These mechanisms were studied in an organotypic hippocampal slice culture. After adding Mn to the medium, MRI contrast changes were affected by Ca channel manipulation and other metals that use divalent metal transporters. Mn cellular uptake was also affected by both, the presence of glutamate receptor antagonist and a neuronal activity inhibitor. Our results establish hippocampal slice as a system to study the cellular mechanisms related to MEMRI.

Eric Gale, Chloe Jones, Ian Ramsay, Christian Farrar, Peter Caravan

Mn-JED is a new biochemically responsive MRI contrast agent that provides 9-fold relaxivity change by switching between the Mn(3+) and Mn(2+) oxidation states. The JED chelator is the only chelator that supports both the Mn(3+) and Mn(2+) oxidation states in biological milieu. Rapid interconversion between oxidation states is achieved by peroxidase activity (oxidation) and cysteine (reduction). Peroxidase activity is drastically elevated during acute inflammation. Thiols such as cysteine are overabundant in the microenvironment of proliferative tumors. Mn-JED provides a new paradigm for the design of biochemically responsive MRI contrast agents.

Gabriela Fernández-Cuervo, Kirsten Tucker, Scott Malm, Kyle Jones, Mark Pagel

We have designed and synthesized new MRI agents that quantitatively detect β-galactosidase and β-glucuronidase activities by measuring changes in chemical exchange saturation transfer (CEST). Based on a modular approach, we incorporated the enzymes’ respective substrates to a salicylate moiety with a spontaneously disassembling, chromogenic spacer via a carbamate linkage. This design furnished highly selective diamagnetic CEST agents that detected and quantified enzyme activities of glycoside hydrolase enzymes. Michaelis-Menten enzyme kinetics studies were performed by monitoring catalyCEST MRI signals, which were validated with UV-vis assays.

Ray Zhang, Christinna Brunnquell, Reinier Hernandez, Alan McMillan, Anatoly Pinchuk, Paul Clark, Vincent Cryns, John Kuo, Jamey Weichert

Extensive structure-activity relationships studies have previously shown that alkylphosphocholine (APC) analogs selectively deliver radioiodine and larger fluorophores to a variety of tumor types in rodent models and humans^1-3.  To further explore the payload capacity of APCs, we synthesized several new APC-chelates and assessed their ability to deliver Gd (MRI) and ⁶⁴Cu (PET) selectively to tumors in vivo.  Prolonged T1-weighted signal enhancement following Gd-DOTA-APC injection was observed in all tumor models.  Clinical PET/MR imaging of U87 flank xenograft at 24h and 48h post-administration of Gd-DOTA-APC and ⁶⁴Cu-DOTA-APC demonstrated co-localization of T1-weighted signal enhancement and PET activity in the tumor.

Hye Sun Park, Mi Young Cho, Hyunseung Lee, Kwan Soo Hong

We proposed the phase transferring method of hydrophobic magnetic nanoparticles without any chemical modifications, for use as a magnetic resonance (MR)/near-infrared (NIR) fluorescence bimodal imaging contrast agent. Indocyanine green (ICG) was used both as an optical component and a surfactant for phase transfer with no superfluous moiety. ICG-MNP-labeled dendritic cells presented MR/NIR dual-modal imaging properties with high and sensitive detection ability for a long time. We expect that this novel MR/NIR contrast agent with sensitive detection and simultaneous imaging capability can be used in the imaging and tracking of immune cells to confirm immunotherapeutic efficacy.

Xi Huang, Shizhen Chen, Yaping Yuan, Lianhua Liu, Xin Zhou

In this abstract, multifunctional Fe₃O₄@SiO₂@PAA-cRGD nanocomposites were designed and synthesized to load water soluble Mn-porphyrin and anticancer drug doxorubicin, which could realize both pH-responsive drug release and T1/T2 dual-mode MRI capability. In vitro cell fluorescent imagings showed that c(RGDyk)-modified nanocomposites can effectively target A549 cells. Furthermore, in vitro T1-weighted and T2-weighted MR images of A549 cells were observed. For in vivo MRI, T1 and T2 relaxation was significantly accelerated in the tumor after i.v. injection of nanocomposites. These evidences showed that the nanocomposites could be used as pH-responsive T1/T2 dual-mode contrast agent, and have the potential for the tumor-targeted MRI and drug delivery.

Christian Gösweiner, Danuta Kruk, Per-Olof Westlund, Fischer Roland, Schlögl Martin, Markus Bödenler, Andreas Petrovic, Hermann Scharfetter, Stefan Spirk

Quadrupole Relaxation Enhancement is a quantum mechanical effect that can be exploited to create a new generation of extrinsic contrast agents for usage in MRI. In this work we have investigated the physical requirements of such contrast agents have to meet to be useful. Based on our findings concerning nuclear quadrupole resonance-properties, spin relaxation behavior and toxicity we suggest a variety of ²⁰⁹Bi-aryl compounds. The sensitivity of these compounds onto chemical or magnetic field changes equip them with smart properties such as on/off switching of the contrast or molecular imaging.

Aurora Rodriguez-Rodriguez, Nicholas Rotile, Julian Goding, Clemens Probst, Andrew Tager, Alexei Bogdanov, Jr, Peter Caravan

We report the synthesis of a new amplifiable MR probe that combines the stability of the macrocyclic Gd-DOTA core with the myeloperoxidase-reactive 5-hydroxytryptamide (5-HT) moiety. The relaxivity of Gd-5-HT-DOTAGA is increased 60% in the presence of myeloperoxidase activity.  In a mouse model of bleomycin induced lung injury, the change in lung-to-muscle contrast to noise ratio is increased 50% compared to naïve animals, consistent with 3-fold higher Gd lung concentrations measured ex vivo.

Heekyung Kim, Garam Choi, Md. Kamrul Islam, Soyeon Kim, Ah Rum Baek, Bo Kyung Sung, Eunyoung Jeon, Tae-Jeong Kim, Yongmin Chang

Novel manganese (II) complex based on EDTA coordination cage bearing benzothiazole aniline (BTA) moiety with high chelation stability was designed and synthesized for use as a liver-specific MRI contrast agent. In addition to forming a hydrophilic, this new hepatobiliary Mn(II) chelate is rapidly taken up by hepatocyte of liver. The magnetic and kinetic properties of Mn(II) complex are higher than commercially available analogue, Mn-DPDP, which was clinically approved MR liver contrast agent. The complex, Mn-EDTA-BTA, was evaluated via in vivo MR imaging to prove high tumor detection sensitivity using animal liver tumor model.

Sanhita Sinharay, Gabriela Fernández-Cuervo, Jasmine Acfalle, Mark Pagel

CatalyCEST MRI with a diamagnetic CEST agent, 4-acedamido-2-(sulfoxy)benzoic acid, can detect the activity of sulfatase.  An enzyme-responsive CEST signal was compared to an unresponsive CEST signal to determine a reaction coordinate of contrast agent cleavage by sulfatase.  This imaging method produced parametric maps of CEST signal amplitudes and the reaction coordinates.  Three isoforms of the enzyme were tested in biochemical solutions.  catalyCEST MRI with the agent detected sulfatase activity in the media from sulfatase-expressing HEK293 cells but not in the media of sulfatase-deficient BT529 cells.  

Sha Li, Shizhen Chen, Yaping Yuan, Lili Ren, Yuqing Yang, Xin Zhou

In this study, we have designed a one-pot microwave strategy for facile and rapid synthesis of blue-emitting ¹⁹F-SiNPs. The as prepared ¹⁹F-SiNPs significantly exhibited ultral small sizes, excellent water solubility and strong fluorescence. Besides, The chemically and magnetically equivalent trifluoromethyl groups grafted on the prepared nanoparticles displayed a single NMR signal, which offered advantages to maximize the generated magnetic resonance signal. In summary, such resultant ¹⁹F-SiNPs are particularly suitable for real-time ¹⁹F-MRI and fluorescence dual modality imaging.

Samuel Maritim, Daniel Coman, Yuegao Huang, Jyotsna Rao, John Walsh, Fahmeed Hyder

Since acidification of the extracellular environment is a hallmark of cancer pathogenesis, successful therapy may manifest as normalization of pHe. We have shown that quantitative pHe measurement is possible with BIRDS is possible even in the presence of superparamagnetic iron oxide nanoparticles (SPIO-NPs). Because SPIO-NPs have been used to image and track drug delivery, we envisage co-injection of BIRDS agents and NPs, containing drugs and SPIO, as a new protocol that can track drug delivery to tumors, concurrently map tumor location and size (by MRI), and at the same time measure therapeutic efficacy through changes in tumor pH (by BIRDS).

Max Senders, Calvin Yeang, Hannah Groenen, Francois Fay, Claudia Calcagno, Simone Green, Phuong Miu, Thomas Reiner, Joseph Witztum, Zahi Fayad, Willem Mulder, Carlos Perez-Medina, Sotirios Tsimikas

Atherosclerotic plaques that rupture can cause stroke or myocardial infarction. Oxidation specific epitopes (OSE), as present in oxidized LDL (OxLDL), are hallmarks of vulnerable plaques?. We have developed the PET radiotracer ⁸⁹Zr-LA25 that targets OSE. Integration of ⁸⁹Zr-LA25 PET imaging with previous validated techniques enables ?‘’vulnerable’’ plaque phenotyping by PET/MRI

Heekyung Kim, Ah Rum Baek, Soyeon Kim, Eun-Young Jeon, MD. Kamrul Islam, Garam Choi, Bo Kyung Sung, Tae-Jeong Kim, Yongmin Chang

Gd-EOB-DO3A is prepared according to the general synthetic methods, and characterized by spectroscopic analysis. The relaxivities are r1 = 8.07, r2 = 8.57 mM-1s-1. From in vivo T1-weighted MR images, we observe good liver-specific enhancement that can be compared with commercial liver targeting agents, and confirm the biliary excretion via gallbladder. Also the kinetic stability of the gadolinium complex was determined with time-dependent longitudinal relaxation rate (R1,p(t)/R1,p(0)) and the relaxation was maintained above 70% against to initial value during the measurement.

Dan Heo, Jaemoon Yang, Jin-Suck Suh

ErbB2, which belongs to the epidermal growth factor receptor (EGFR) family, plays a key role in human malignancies. ErbB2 is overexpressed in approximately 30% of human breast cancers and in many other cancer types, including stomach, bladder, ovarian and lung carcinomas. The objective of this study is the development of anti-ErbB2 aptamer-modified T2 contrast agent based on magnetic nanoprobe (Apt_ErbB2-MNP) having high-specificity onto Erbb2-expressing cancer.  For confirmation of Apt_ErbB2-MNP as T2 contrast agent, T2 relaxivity and hydrodynamic diameter was measured. in vitro binding affinity tests were conducted not only recombinant ErbB2 proteins but also the live cells. in vivo targeting ability was verified by in vivo MRI analysis. 

Reggie Taylor, Irina Rachinsky, Zahra Kassam, William Pavlosky, Ashley Lozanski, John Butler, Stephen Pautler, Aaron Ward, Joseph Chin, Ting-Yim Lee, Glenn Bauman, Jonathan Thiessen

PET data with the [¹⁸F]-DCFPyL PSMA-targeted probe to examine prostate cancer in patients scheduled for radical prostatectomy was acquired concurrently with diffusion weighted imaging and chemical shift imaging using a 3T PET-MRI.  Standard uptake values (SUV) were compared to apparent diffusion coefficients (ADC) and choline plus creatine over citrate ratios (CC/C).  Positive correlations existed between the SUV and CC/C in voxels with low ADC. Negative correlations existed between the ADC and SUV in voxels with high CC/C, and negative correlations also existed between the ADC and CC/C in voxels with high SUV.

Osamu Togao, Akihiro Nishie, Chihiro Tamura, Mayumi Yamato, Kazuhiro Ichikawa, Satoshi Nohara, Yoshio Ito, Naoki Kato, Satoshi Yoshise, Hiroshi Honda

Apoptosis is involved in many pathological processes. Early detection of treatment-induced apoptosis in malignant tumors is clinically useful for a decision making in therapeutic strategy. Phosphatidylserine (PS) expressed on the cell membrane is known to be a marker of apoptosis which can be detected by probes with Annexin V. In this study, we newly synthesized USPIO-conjugated Annexin V and investigated its potential in the use in apoptosis imaging in both in vitro and in vivo studies.

Daniel Szulc, Tameshwar Ganesh, Maryam Abdinejad, Hanlin Liu, Xiao-an Zhang, Hai-Ling Cheng

Tissue engineered biomaterials have the potential to regenerate almost every tissue type. One difficult aspect to advancing this technology is determining the properties and fate of these materials once introduced in vivo. Non-invasive imaging technology such as MRI holds significant potential for monitoring implanted biomaterials.  Few novel approaches to directly image biomaterials have recently been developed; however, most are designed for specific materials or utilize iron oxides with limited specificity. In this study, we investigate a novel approach to labelling biomaterials with a highly efficient T1 agent and a biologically derived adhesive, which allows for accurate and sensitive detection in vivo.

Xiaoli Liu, A. B. Madhankumar, Patti Miller, Becky Slagle-Webb, Oliver Mrowczynski, Akiva Mintz, Qing X. Yang, James R. Connor

There is a clinical need for targeted MRI-contrast agents that are more sensitive and specific in detection of glioma than conventional MRI contrast. We use interleukin-13 (IL-13) as targeting ligand because 75% of glioma cells overexpress IL-13Rα2 significantly1. We investigated the relative efficacy of liposomes conjugated with wild type IL-13 to a variant of IL-13, known as Targeted Quadruple Mutant13 (TQM-13) that has been shown to be more selective for the IL-13Rα2 and binds with higher affinity than the  wide type. Our targeted MRI agent, TQM-13-liposomes-Gd, produced specific MRI contrast, delineating tumor, inflamed and normal tissues.

Sebastian Temme, Christoph Jacoby, Christoph Grapentin, Jürgen Schrader, Ulrich Flögel

Exact localization of acute thrombi is still a serious problem in the clinical setting. Here we show the feasibility of artefact-free ¹⁹F MR-imaging using clinically relevant PFOB-nanoemulsions functionalized with an α2-antiplasmin peptide, specific for early thrombi. Utilizing the isolated CF₃-peak of PFOB in combination with a conventional ¹⁹F RARE sequence is suitable for specific and artefact-free imaging of acute thrombi in vitro and also in vivo.       

Hyun Min Kim, Hyunseung Lee, Kwan Soo Hong

Reported here is a new theranostic agent, 1, which consists of a Gd³⁺-texaphyrin core conjugated to a doxorubicin prodrug via a disulfide bond undergoing cleavage in the presence of glutathione, a species typically upregulated in cancer cells. To improve the solubility and tumor targeting of 1, it was loaded into folate receptor-targeted liposomes to produce FL-1. FL-1 was found to selectively produce a greater anti-proliferative effect in the case of the KB and CT26 cell lines as compared to the HepG2 and NIH3T3 cell lines. FL-1 was also found to provide enhanced MR imaging in vivo under conditions of T1 contrast in the early stage of metastatic cancer progression. 

Emeline Darçot, Jerome Yerly, Tom Hilbert, Roberto Colotti, Maxime Pellegrin, Elena Najdenovska, Tobias Kober, Matthias Stuber, Ruud van Heeswijk

In addition to conventional signal averaging, compressed sensing (CS) can be applied to fluorine-19 MRI to improve its low signal-to-noise ratio. For a given acquisition time and CS algorithm, an N-averages N-fold-undersampled dataset results in higher sensitivity than a fully sampled non-averaged dataset. However, it is still unclear whether averaging changes the sensitivity to motion artifacts for an undersampled acquisition.We therefore tested the hypothesis that an N-averages N-fold undersampled acquisition is more robust against motion artifacts than a fully sampled non-averaged acquisition when both are reconstructed with CS.

Zoe O'Brien-Moran, Marie-Laurence Tremblay, Christa Davis, James Rioux, Kimberly Brewer

Understanding immune cell behaviour is important for evaluating therapeutic response in pre-clinical models. We monitor cell migration in a mouse model of cervical cancer by labeling cells with superparamagnetic iron oxide (SPIO). Simultaneous pre-clinical PET/MRI confirmed that the balanced steady-state free precession (bSSFP) sequence lacks specificity to SPIO-labeled cells within the tumor. We tested TurboSPI, a multi-echo single point imaging technique with compressed sensing that provides high temporal resolution 3D R₂* mapping in under 45 minutes. These maps exhibit superior SPIO specificity compared to bSSFP images and enabled us to do both qualitative and quantitative cell tracking.

Alessandro Scotti, Rongwen Tain, Weiguo Li, Xiaohong Zhou, Kejia Cai

Detection of the elusive Reactive Oxygen Species is pivotal for understanding and diagnosis of many diseases. Recently ROS has been imaged with endogenous MRI contrasts in biological system by reduction in CEST trough combined T₁ shortening and proton exchange enhancing effects. We here show potential confounding factors such as H₂O₂, molecular oxygen, iron oxidation, pH, and temperature to be negligible in phantom studies. In addition, for the first time, we have imaged ROS by endogenous MRI contrasts under physiological conditions, at clinical MRI field strength and on ex vivo brain tissue, paving the path for clinical translation. 

Sebastian Temme, Guang Yang , Christoph Jacoby, Stegbauer Johannes , Flögel Ulrich

Abdominal aortic aneurysms (AAA) are a relatively common disease, with still unclear etiology that is associated with high mortality due to aortic rupture. Here we show that mice deficient for the Mas-receptor show aggravated AAA formation upon Ang-II treatment and that accumulation of macrophages in bulk aneurysms can be non-invasively visualized by ¹H/¹⁹F MRI using intravenously applied perfluorocarbon nanoemulsions which are efficiently phagocytosed by macrophages. We conclude that Mas-receptor deficiency leads to increased inflammation with enhanced AAA formation and that ¹⁹F MRI-based inflammation imaging will help to further unravel the role of monocytes/macrophages in the course of AAA progression.    

Kavindra Nath, Jeffrey Roman, David Nelson, Mary Putt, Kevin Muriuki, Stepan Orlovskiy, Dennis Leeper, Jerry Glickson

Using ³¹P magnetic resonance spectroscopy, we have shown that LND selectively lowers the intracellular pH and decreases ATP levels in human melanoma xenografts. Tumor acidification results from inhibition of lactate export via the monocarboxylic acid transporters and inhibition of pyruvate transport and oxidation via the mitochondrial pyruvate carrier. Energetics is further attenuated by inhibition of electron transport at complex II. Under these conditions, temozolomide accumulates in the tumor as a result of decreases in intracellular pH, which inhibits DNA repair by O⁶-alkyltransferase via conversion to dacarbazine and formation of diazomethane, and also inhibits glutathione-S-transferase that deactivates the reactive alkylating intermediate.  

Ashley Makela, Paula Foster

The escape and invasion of cancer cells and the growth of metastatic tumors is in part due to the role of tumor associated macrophages. The macrophages present in these metastatic sites are called metastasis associated macrophages. This study used ¹⁹F-based cellular MRI to detect lymph node, lung and brain metastases arising from breast cancer. A custom built ¹H/¹⁹F birdcage coil allowed for ‘head to toe’ mouse imaging, allowing for detection of ¹⁹F agent accumulation, with ¹H images verifying anatomical location. This information may be useful in understanding the timing and role of macrophages in the metastatic process.

Lucia Salamanca-Cardona, Alex Poot, Valentina Di Gialleonardo, Fabian Correa, Hardik Shah, Hui Liu, Vesselin Miloushev, Kristin Granlund, Justin Cross, Craig Thompson, Kayvan Keshari

2-hydroxyglutarate (2-HG) is an oncometabolite that accumulates in various cancers as a result of mutations in the isocitrate dehydrogenase (IDH1/2) genes and can be used as a biomarker for diagnosis. In this work, we demonstrate the fast conversion of glutamine to 2-HG and use it as a basis for developing a 2-HG in-vivo detection method. Using hyperpolarized [1-¹³C] glutamine and magnetic resonance imaging (MRI), we present the non-invasive unambiguous detection of 2-HG formation with high specificity from glutamine in-vivo and real-time in IDH1 and IDH2 mutant tumors.

Nobu Oshima, Shun Kishimoto, Keita Saito, Dan Crooks, Kristin Beebe, Kazutoshi Yamamoto, Jeffery Brender, Ganesha Rai, Bryan Mott, David Maloney, James Mitchell, Murali Cherukuri, Leonard Neckers

This study aimed to monitor the impact on metabolic flux in vivo of a newly developed Lactate Dehydrogenase A Inhibitor (LDHI), using hyperpolarized 13C Magnetic Resonance (MR) technology. Using hyperpolarized 13C MR Spectroscopy and Chemical Shift imaging, we found that the LDHI significantly and rapidly suppressed the [1-13C]lactate to [1-13C]pyruvate ratio after single dose administration to mice harboring a MiaPaca (a glycolytic pancreatic cancer cell line)  xenograft. These results indicate that the LDHI suppressed lactate production in the tumors. Thus, using Hyperpolarized 13C MRI provides a very useful technology to evaluate in vivo on-target efficacy of LDH inhibitors. 

Jonas Steinhauser, Grzegorz Kwiatkowski , Patrick Wespi, Sebastian Kozerke

Isoflurane is frequently used in hyperpolarized [1-13C]pyruvate studies. Even though literature suggests direct interaction with mitochondrial metabolism, the influence of the compound on cardiac metabolism has not been assessed in detail yet. In the present study the impact of low versus high isoflurane concentration is examined in a cross-over experiment. Results reveal that cardiac metabolism is modulated by isoflurane concentration showing increased lactate and reduced bicarbonate production during high isoflurane dose relative to low dose.

Jonas Steinhauser, Grzegorz Kwiatkowski , Patrick Wespi, Sebastian Kozerke

Lithium is the first-line drug used in bipolar disorder, a chronic psychiatric illness characterized by severe biphasic changes in mood. Lithium has a narrow therapeutic window and has shown cardiac side effects. The present work demonstrates the detectability of lithium induced changes of mitochondrial metabolism in cardiomyocytes by employing hyperpolarized [1-13C]pyruvate magnetic resonance imaging of the in-vivo heart. In healthy rats, lithium is shown to increase mitochondrial metabolism and decrease glycolytic lactate production indicating a potential role of lithium in the heart.

Haiyun Qi, Per Nielsen, Marie Schroeder, Lotte Bertelsen, Fredrik Palm, Christoffer Laustsen

Metformin is the primary anti-diabetic drug in type-2 diabetes.However, controversy exists on its use in patients with renal impairment.Here we investigated the acute metabolic effects of metformin treatment in rat kidneys,with hyperpolarized ¹³Cpyruvate and Clark-electrodes.A significantly altered metabolic phenotype was observed 30min post metformin treatment.Anaerobic metabolism was elevated in the cytosol,indicated by increased lactate/pyruvate ratio,and mitochondrial aerobic metabolism was reduced,indicated by decreased bicarbonate/pyruvate ratio.Acute metformin treatment increased renal blood flow with higher O₂ saturation and did not change tubular O₂ consumption.These results indicate that metformin reduces mitochondrial respiration and enhances anaerobic metabolism,even with enough oxygen supply,within only 30min of treatment.

Stefan Markovic, Anne Fages, Tangi Roussel, Ron Hadas, Michal Neeman, Lucio Frydman

Monitoring placental metabolism is of particular interest for the early-detection of complications during pregnancy. This study discusses the use of dynamic nuclear polarization (DNP) enhanced ¹³C MRSI of hyperpolarized pyruvate, that has been injected into pregnant rats. The enzymatic conversion of pyruvate to lactate was followed in real-time in maternal and fetal compartments –including placentas. Lactate ¹³C signals in placentas could be observed; they peaked significantly later and were longer-lived than both placental ¹³C pyruvate and ¹³C signals in maternal organs. Single-voxel analyses for both metabolites in different organs revealed the T₁ relaxation times and kinetics of the Pyr -> Lac transformation.

Per Nielsen, Rolf Schulte, Hayuin Qi, Christoffer Laustsen

Renal IRI is a leading cause of AKI in several disease states; currently there are several methods to measure renal perfusion in the clinic, but all suffer under specific drawbacks. Here we present a pilot study using the hyperpolarized perfusion marker α-trideuteromethyl[15N]glutamine in a 40 min unilateral ischemia reperfusion rat model. A reduction of 51% in perfusion was observed in the animal. We therefore believe that α-trideuteromethyl[15N]glutamine is a highly promising molecule in renal perfusion studies.

Stephen DeVience, Xin Lu, Julie Proctor, Parisa Rangghran, Juliana Medina, Elias Melhem, Rao Gullapalli, Gary Fiskum, Dirk Mayer

We investigated the use of dichloroacetate (DCA) in ¹³C-pyruvate imaging of traumatic brain injury as a way to improve bicarbonate signal strength and to elucidate changes in pyruvate dehydrogenase activity. Rats were injured with a controlled cortical impact and then injected with ¹³C-pyruvate before and after administration of DCA. Spectrally-resolved imaging was performed on the brain to quantify the resulting pyruvate, lactate, and bicarbonate signals. The bicarbonate signal and bicarbonate-to-lactate ratio were found to be sensitive to traumatic brain injury, and were affected equally by DCA in injured and uninjured hemispheres of the brain.

Eugen Kubala, Laura Jacobs, Julia Kempf, Kim Muñoz Alvarez, Rolf Schulte, Steffen Glaser, Markus Schwaiger, Marion Menzel, Ulrich Keller

We proved that the transcriptional activation of c-Myc expression controlled by tetracycline has a direct influence on lactate dehydrogenase-A (LDH-A) activity in B-cell line P493-6 in vitro. Using hyperpolarized [1-¹³C]pyruvate and ¹³C magnetic resonance spectroscopy we were able to monitor a reduction of pyruvate to lactate reaction catalyzed by LDH-A. Incubation of the P493-6 cells in a media with 0.1 μg/mL tetracycline for 24 hours reduced the kinetic value of the reaction by 41.8±10.5 %. This proves that the control of c-myc has a significant influence on LDH-A activity and can be measured using ¹³C magnetic resonance spectroscopy with hyperpolarized [1-¹³C]pyruvate.

Kasper Hansen, Per Nielsen, Esben Hansen, Cathrine Williams, William Joyce, Michael Pedersen, Tobias Wang, Christoffer Laustsen

Many non-mammalian vertebrates hold enormous potential as “model animals” for various fields of basic physiological and biomedical research. Hyperpolarized magnetic resonance imaging (MRI) can provide quantitative in vivo information about metabolic processes including major pathways of the citric acid cycle and glycolysis via spectral differences of pyruvate intermediates. The combination of [1-¹³C]-MRI and model animals exhibiting “selected physiological traits” may be a strong tool for gaining novel insights into relevant metabolic mechanisms. In this pilot study we test, for the first time, the application of [1-¹³C]-MRI in an ectothermic reptile.

Keita Saito, Deepak Sail, Burchelle Blackman, Hellmut Merkle, Rolf Swenson, James Mitchell, Murali Krishna

5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) is used to detect reactive oxygen species in vitro, and N-acetyl-L-cysteine (NAC) is an antioxidant. We synthesized ¹³C-labeled DMPO and NAC, and investigated feasibility of hyperpolarized ¹³C-DMPO and ¹³C-NAC for evaluating oxidative stress in mice. Hyperpolarized ¹³C-DMPO and ¹³C-NAC provided a single peak at 76 ppm and 174 ppm, respectively, and the T₁ relaxation time was sufficiently long to apply them for mouse imaging. The signals ¹³C-DMPO and ¹³C-NAC were also detected in a mouse body after intravenous injection. The results showed ¹³C-DMPO and ¹³C-NAC can be applied to some disease models to evaluate oxidative stress in vivo. 

Per Nielsen, Hayuin Qi, Christoffer Laustsen

Renal IRI is a leading cause of AKI in several disease states; there is a current lack of precise methods to directly assess success of kidney transplant after reperfusion. We here showed how we can measure metabolic function in both the contralateral kidney and post-ischemic 2 min after reperfusion and again after 1 hour of reperfusion. We here saw a very different response compared to metabolic data collected from animals after 24 hours of reperfusion. In this study we induced mild/moderate ischema and it looks like we captured metabolic images in a phase of repair and salvage to maintain normal kidney filtration function in the animals. It seems that severe injury has not yet occurred, or maybe won’t occur. Together with perfusion measurements or kidney filtration measurements this method might hold some clinical value.

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

In this study, hyperpolarized [1-¹³C]-pyruvate imaging was used to investigate the effect of positive-end expiratory pressure (PEEP) on the stabilization of lung metabolism after injury. Results demonstrated significantly lower lactate-to-pyruvate ratio in rats ventilated with PEEP.

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

We assess gas exchange in healthy and acutely injured rat lungs by measuring the difference between bicarbonate-to-pyruvate signal-ratio in the right vs. left ventricle of the heart following co-administration of hyperpolarized [1-¹³C] pyruvate and ¹³C-bicarbonate.

Renuka Sriram, Celine Baligand, Hecong Qin, Justin DeLos Santos, Robert Bok, John Kurhanewicz, Zhen Wang

The incidence of renal cell carcinomas (RCCs) has increased significantly over time due to the widespread use of cross-sectional imaging with incidental cancer detection. RCCs vary widely in histological grade and risk of metastasis. However, current imaging techniques cannot reliably differentiate low grade, indolent RCCs from localized but potentially aggressive RCCs, resulting in the over-treatment of many indolent cancers. Increasing evidence has shown that increased glycolysis with lactate production is a dominant metabolic feature of RCCs. In particular, lactate dehydrogenase expression is positively correlated with RCC grade, and a strong predictor of tumor progression and poor prognosis. Hyperpolarized ¹³C MR allows real time investigation of cellular metabolism, and provides time-resolved metabolic kinetics that reflects flux through enzyme-catalyzed reactions. The purpose of this study is to investigate whether hypeprolarized ¹³C pyruvate MR can inform on the LDH activity in orthotopic RCC tumor models.  

Joseph Weygand, Prasanta Dutta, Jessica Molkentine, Yeonju Lee, Travis Salzillo, Meifang Yu, Jaehyuk Lee, Eugene Koay, Cullen Taniguchi, Pratip Bhattacharya

Although immunotherapy presents an attractive new treatment option for patients with pancreatic cancer, its implementation has been underwhelming. As a critical first step in understanding this failure, we have applied hyperpolarized pyruvate spectroscopic imaging and NMR spectroscopy to interrogate the metabolic properties of pancreatic tumors cultivated in the presence of different immune environments. We observed that the immune environment in which a pancreatic tumor is harvested significantly alters metabolic function and that these metabolic differences exhibit a temporal dependence with respect to tumor development.