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In magnetic resonance imaging (MRI), arrays of small loop antennas/coils are extensively used for signal reception. In such arrays, the loop current must be suppressed to prevent transmit antennas or other elements in a receive array from being detuned, thereby preserving image quality. While suppressing the current in conventional loop antennas/coils is straightforward, achieving effective suppression in shielded loops has remained an unresolved challenge. In this article, we derive theoretical principles for optimally suppressing the loop current of shielded loops at fundamental resonance and verify them experimentally. Maximal current suppression is achieved by carefully selecting the electrical load at the antenna outputs. We identify a critical relationship between loop inductance and load inductance specific to shielded loops. Our results demonstrate that the optimal suppression method reduces loop current by an additional 31–36 dB compared with the straightforward yet suboptimal approach of shorting the antenna outputs. These findings can facilitate the development of more robust antenna/coil arrays for MRI applications.

Hyperpolarized 13 C Magnetic Resonance Spectroscopic Imaging (HP 13 C-MRSI) has the potential to transform diagnostic radiology thanks to its unique ability to noninvasively detect a broad range of diseases entailing aberrant metabolism. However, clinical adoption has been hindered by the short lifetime of 13 C-hyperpolarization and the resulting need for on-site polarizer near the MR scanner. In this work, we present a solution for long-lived transportable HP molecular contrast agents that uses dissolution Dynamic Nuclear Polarization (dDNP) combined with UV-induced labile radicals. This approach allows centralized pre-polarization and transport under hours-long storage T 1 conditions. We validate this concept through the first across-cities HP 13 C-MRSI experiments in vivo, injecting healthy female rats with both a perfusion/angiography ([1- 13 C]HP001) and a metabolic ([U- 13 C, d 7 ]glucose) contrast agent. Our findings advance the feasibility of decentralized, scalable HP MRI workflows, removing the barrier of on-site infrastructure. A method using UV-generated radicals allows hyperpolarized 13 C MRI agents to be produced centrally and transported for hours while preserving polarization, enabling in-vivo imaging off-site after long-distance transport.

Good glycemic control is crucial to prevent the onset and progression of late diabetic complications, but insulin treatment often fails to achieve normalization of glycemic control to the level seen in healthy controls. In fact, recent experimental studies indicate that insufficient treatment with insulin, resulting in poor glycemic control, has an additional effect on progression of late diabetic complications, than poor glycemic control on its own. We therefore compared renal metabolic alterations during conditions of poor glycemic control with and without suboptimal insulin administration, which did not restore glycemic control, to streptozotocin (STZ)‐diabetic rats using noninvasive hyperpolarized 13C‐pyruvate magnetic resonance imaging (MRI) and blood oxygenation level–dependent (BOLD) 1H‐MRI to determine renal metabolic flux and oxygen availability, respectively. Suboptimal insulin administration increased pyruvate utilization and metabolic flux via both anaerobic and aerobic pathways in diabetic rats even though insulin did not affect kidney oxygen availability, HbA1c, or oxidative stress. These results imply direct effects of insulin in the regulation of cellular substrate utilization and metabolic fluxes during conditions of poor glycemic control. The study demonstrates that poor glycemic control in combination with suboptimal insulin administration accelerates metabolic alterations by increasing both anaerobic and aerobic metabolism resulting in increased utilization of energy substrates. The results demonstrate the importance of tight glycemic control in insulinopenic diabetes, and that insulin, when administered insufficiently, adds an additional burden on top of poor glycemic control. e12233 This work describes the metabolic changes associated with insufficient insulin administration in the type 1 diabetic rat kidney, showing that poor glycemic control with insufficient insulin administration, has an cumulative effect on the development of late diabetic complications.

Magnetic Resonance Imaging combined with hyperpolarized 13 C-labelled metabolic contrast agents produced via dissolution Dynamic Nuclear Polarization can, non-invasively and in real-time, report on tissue specific aberrant metabolism. However, hyperpolarization equipment is expensive, technically demanding and needs to be installed on-site for the end-user. In this work, we provide a robust methodology that allows remote production of the hyperpolarized 13 C-labelled metabolic contrast agents. The methodology, built on photo-induced thermally labile radicals, allows solid sample extraction from the hyperpolarization equipment and several hours’ lifetime of the 13 C-labelled metabolic contrast agents at appropriate storage/transport conditions. Exemplified with [U- 13 C, d 7 ]-D-glucose, we remotely produce hyperpolarized 13 C-labelled metabolic contrast agents and generate above 10,000-fold liquid-state Magnetic Resonance signal enhancement at 9.4 T, keeping on-site only a simple dissolution device. Hyperpolarized metabolic contrast agents for magnetic resonance imaging can provide non-invasive and realtime information on tissue specific aberrant metabolism, but producing and handling them is highly demanding because of their short lifetime. Here a solid sample extraction, storage, and transport technique allows disconnecting production from end-user sites handling, as well as hour-long lifetimes of the agents.

In recent years, hyperpolarization of water protons via dissolution Dynamic Nuclear Polarization (dDNP) has attracted increasing interest in the magnetic resonance community. Hyperpolarized water may provide an alternative to Gd-based contrast agents for angiographic and perfusion Magnetic Resonance Imaging (MRI) examinations, and it may report on chemical and biochemical reactions and proton exchange while perfoming Nuclear Magnetic Resonance (NMR) investigations. However, hyperpolarizing water protons is challenging. The main reason is the presence of radicals, required to create the hyperpolarized nuclear spin state. Indeed, the radicals will also be the main source of relaxation during the dissolution and transfer to the NMR or MRI system. In this work, we report water magnetizations otherwise requiring a field of 10,000 T at room temperature on a sample of pure water, by employing dDNP via UV-generated, labile radicals. We demonstrate the potential of our methodology by acquiring a 15 N spectrum from natural abundance urea with a single scan, after spontaneous magnetization transfer from water protons to nitrogen nuclei. Hyperpolarised water is an attractive alternative to metal-containing contrast agents in magnetic resonance imaging, but generating usefully persistent hyperpolarised water protons is challenging. Here dissolution dynamic nuclear polarisation using UV-generated radicals is used to obtain substantial water signal enhancement.

Six four-element balun topologies are introduced that enable complex impedance matching in addition to common-mode rejection. Design equations for these topologies are presented. Three of these networks are universal, while the other three are capable of performing only specific impedance transformations. Examples of these networks were designed and fabricated along with a traditional lattice balun network for an operating frequency of 300 MHz. These networks were verified through extensive electromagnetic simulations and by measuring the fabricated networks. The fabricated novel network examples were able to achieve common-mode rejection ratios above 20 dB, power wave reflection coefficients below −20 dB, and insertion losses of approximately 0.1 dB; these results were similar to or better than the performance of the fabricated traditional lattice balun. The design example networks also provided power matching and low insertion loss over a greater bandwidth compared to the fabricated traditional network. These networks will allow for the footprints of lumped-element balun circuitry to be reduced, which is particularly useful in integrated circuit design. These topologies are also expected to further increase radio-frequency (RF) circuit design flexibility by offering more alternative realizations.

Polarisation transfer schemes and indirect detection are central to magnetic resonance. Using the trityl radical OX063 and a pulse electron paramagnetic resonance spectrometer operating in the Q-band (35 GHz, 1.2 T), we show here that it is possible to use pulsed dynamic nuclear polarisation (DNP) to transfer polarisation from electrons to protons and back. The latter is achieved by first saturating the electrons and then simply using a reverse DNP step. A variable mixing time between DNP and reverse DNP allows us to investigate the decay of polarisation on protons in the vicinity of the electrons. We qualitatively investigate the influence of solvent deuteration, temperature, and electron concentration. We expect reverse DNP to be useful in the investigation of nuclear spin diffusion and envisage its use in electron–nuclear double-resonance (ENDOR) experiments.

PurposeCancer has a multitude of phenotypic expressions and identifying these are important for correct diagnosis and treatment selection. Clinical molecular imaging such as positron emission tomography can access several of these hallmarks of cancer non-invasively. Recently, hyperpolarized magnetic resonance spectroscopy with [1-13C] pyruvate has shown great potential to probe metabolic pathways. Here, we investigate simultaneous dual modality clinical molecular imaging of angiogenesis and deregulated energy metabolism in canine cancer patients.MethodsCanine cancer patients (n = 11) underwent simultaneous [68Ga]Ga-NODAGA-E[(cRGDyK)]2 (RGD) PET and hyperpolarized [1-13C]pyruvate-MRSI (hyperPET). Standardized uptake values and [1-13C]lactate to total 13C ratio were quantified and compared generally and voxel-wise.ResultsTen out of 11 patients showed clear tumor uptake of [68Ga]Ga-NODAGA-RGD at both 20 and 60 min after injection, with an average SUVmean of 1.36 ± 0.23 g/mL and 1.13 ± 0.21 g/mL, respectively. A similar pattern was seen for SUVmax values, which were 2.74 ± 0.41 g/mL and 2.37 ± 0.45 g/mL. The [1-13C]lactate generation followed patterns previously reported. We found no obvious pattern or consistent correlation between the two modalities. Voxel-wise tumor values of RGD uptake and lactate generation analysis revealed a tendency for each canine cancer patient to cluster in separated groups.ConclusionWe demonstrated combined imaging of [68Ga]Ga-NODAGA-RGD-PET for angiogenesis and hyperpolarized [1-13C]pyruvate-MRSI for probing energy metabolism. The results suggest that [68Ga]Ga-NODAGA-RGD-PET and [1-13C]pyruvate-MRSI may provide complementary information, indicating that hyperPET imaging of angiogenesis and energy metabolism is able to aid in cancer phenotyping, leading to improved therapy planning.

Renal ischemia/reperfusion injury (IRI) is a leading cause of acute kidney injury (AKI), and at present, there is a lack of reliable biomarkers that can diagnose AKI and measure early progression because the commonly used methods cannot evaluate single-kidney IRI. Hyperpolarized [1,4- 13 C 2 ]fumarate conversion to [1,4- 13 C 2 ]malate by fumarase has been proposed as a measure of necrosis in rat tumor models and in chemically induced AKI rats. Here we show that the degradation of cell membranes in connection with necrosis leads to elevated fumarase activity in plasma and urine and secondly that hyperpolarized [1,4- 13 C 2 ]malate production 24 h after reperfusion correlates with renal necrosis in a 40-min unilateral ischemic rat model. Fumarase activity screening on bio-fluids can detect injury severity, in bilateral as well as unilateral AKI models, differentiating moderate and severe AKI as well as short- and long-term AKI. Furthermore after verification of renal injury by bio-fluid analysis the precise injury location can be monitored by in vivo measurements of the fumarase activity non-invasively by hyperpolarized [1,4- 13 C]fumarate MR imaging. The combined in vitro and in vivo biomarker of AKI responds to the essential requirements for a new reliable biomarker of AKI.