Hyperpolarized [1-13C]pyruvate (Pyr) has been used to assess metabolism in healthy and diseased states, focusing on downstream labeling of lactate (Lac), bicarbonate (Bic), and alanine. Whereas hyperpolarized [2-13C]Pyr, which retains the labeled carbon when Pyr is converted to acetyl-coenzyme A (acetyl-CoA), has been successfully used to assess mitochondrial metabolism in the heart, the application of [2-13C]Pyr in the study of brain metabolism has been limited to date, with Lac being the only downstream metabolic product previously reported. In this study, single time-point chemical shift imaging data were acquired from rat brain in vivo. [5-13C]Glu, [1-13C]ALCAR, and [1-13C]Cit were detected in addition to resonances from [2-13C]Pyr and [2-13C]Lac. Brain metabolism was further investigated by infusing dichloroacetate (DCA), which upregulates Pyr flux to acetyl-CoA. After the DCA administration, a 40 % increase of [5-13C]Glu from 0.014 ± 0.004 to 0.020 ± 0.006 (p = 0.02) primarily from brain and a trend to higher citrate (0.002 ± 0.001 to 0.004 ± 0.002) was detected, whereas [1-13C]ALCAR was increased in peripheral tissues. This study demonstrates, for the first time, that hyperpolarized [2-13C]Pyr can be used for the in vivo investigation of mitochondrial function and TCA cycle metabolism in brain.

Purpose To deploy clinically, a combined parallel imaging compressed sensing method with coil compression that achieves a rapid image reconstruction, and assess its clinical performance in contrast-enhanced abdominal pediatric MRI. Materials and Methods With IRB approval and informed patient consent/assent, 29 consecutive pediatric patients were recruited. Dynamic contrast-enhanced MRI was acquired on a 3T scanner using a dedicated 32-channel pediatric coil and a 3D SPGR sequence, with pseudo-random undersampling at a high acceleration (R=7.2). Undersampled data were reconstructed with three methods: a traditional parallel imaging method and a combined parallel imaging compressed sensing method with and without coil compression. The three sets of images were evaluated independently and blindly by two radiologists at one siting, for overall image quality and delineation of anatomical structures. Wilcoxon tests were performed to test the hypothesis that there was no significant difference in the evaluations, and inter-observer agreement was analyzed. Results Fast reconstruction with coil compression did not deteriorate image quality. The mean score of structural delineation of the fast reconstruction was 4.1 on a 5-point scale, significantly better (P<0.05) than traditional parallel imaging (mean score 3.1). Fair to substantial inter-observer agreement was reached in structural delineation assessment. Conclusion A fast combined parallel imaging compressed sensing method is feasible in a pediatric clinical setting. Preliminary results suggest it may improve structural delineation over parallel imaging.

We report metabolic images of 13C, following injection of a bolus of of hyperpolarized [1-13C] pyruvate in a live rat. The data were acquired on a clinical scanner, using custom coils for volume transmission and array reception. Proton blocking of all carbon resonators enabled proton anatomic imaging with the system body coil, to allow for registration of anatomic and metabolic images, for which good correlation was achieved, with some anatomic features (kidney and heart) clearly visible in a carbon image, without reference to the corresponding proton image. Parallel imaging with sensitivity encoding was used to increase the spatial resolution in the SI direction of the rat. The signal to noise ratio in was in some instances unexpectedly high in the parallel images; variability of the polarization among different trials, plus partial volume effects, are noted as a possible cause of this.

Purpose: To compare signal-to-noise ratios (SNRs) and T* 2 maps at 3 T and 7 T using 3D cones from in vivo sodium images of the human knee. Materials and Methods:Sodium concentration has been shown to correlate with glycosaminoglycan content of cartilage and is a possible biomarker of osteoarthritis. Using a 3D cones trajectory, 17 subjects were scanned at 3 T and 12 at 7 T using custom-made sodium-only and dualtuned sodium/proton surface coils, at a standard resolution (1.3 Â 1.3 Â 4.0 mm 3 ) and a high resolution (1.0 Â 1.0 Â 2.0 mm 3 ). We measured the SNR of the images and the T* 2 of cartilage at both 3 T and 7 T.Results: The average normalized SNR values of standardresolution images were 27.1 and 11.3 at 7 T and 3 T. At high resolution, these average SNR values were 16.5 and 7.3. Image quality was sufficient to show spatial variations of sodium content. The average T* 2 of cartilage was measured as 13.2 6 1.5 msec at 7 T and 15.5 6 1.3 msec at 3 T. Conclusion:We acquired sodium images of patellar cartilage at 3 T and 7 T in under 26 minutes using 3D cones with high resolution and acceptable SNR. The SNR improvement at 7 T over 3 T was within the expected range based on the increase in field strength. The measured T* 2 values were also consistent with previously published values.

We describe the electronics for controlling the independently pulsed polarizing coil in a prepolarized magnetic resonance imaging (PMRI) system and demonstrate performance with free induction decay measurements and in vivo imaging experiments. A PMRI scanner retains all the benefits of acquiring MRI data at low field, but with the higher signal of the polarizing field. Rapidly and efficiently ramping the polarizing coil without disturbing the data acquisition is one of the major challenges of PMRI. With our modular hardware design, we successfully ramp the 0.4-T polarizing coil of a wrist-sized PMRI scanner at up to 100 T/s without causing image artifacts or otherwise degrading data acquisition.