Pyruvate is included in the energy production of the heart muscle and is metabolized into lactate, alanine, and CO 2 in equilibrium with HCO 3 ؊ . The aim of this study was to evaluate the feasibility of using 13 C hyperpolarization enhanced MRI to monitor pyruvate metabolism in the heart during an ischemic episode. The left circumflex artery of pigs (4 months, male, 29 -34 kg) was occluded for 15 or 45 min followed by 2 hr of reperfusion. Pigs were examined by 13 C chemical shift imaging following intravenous injection of 1-13 C pyruvate. 13 C chemical shift MR imaging was used in order to visualize the local concentrations of the metabolites. After a 15-min occlusion (no infarct) the bicarbonate signal level in the affected area was reduced (25-44%) compared with the normal myocardium. Alanine signal level was normal. After a 45-min occlusion (infarction) the bicarbonate signal was almost absent (0.2-11%) and the alanine signal was reduced (27-51%). Due to image-folding artifacts the data obtained for lactate were inconclusive. These studies demonstrate that cardiac metabolic imaging with hyperpolarized 1-13 C-pyruvate is feasible. The changes in concentrations of the metabolites within a minute after injection can be detected and metabolic maps constructed. Magn Reson Med 59:1005-1013, 2008.

A new strategy for a quantitative measurement of regional pulmonary ventilation using hyperpolarized helium-3 (

The evolution of magnetic resonance imaging (MRI) has been astounding since the early 1980s, and a broad range of applications has emerged. To date, clinical imaging of nuclei other than protons has been precluded for reasons of sensitivity. However, with the recent development of hyperpolarization techniques, the signal from a given number of nuclei can be increased as much as 100 000 times, sufficient to enable imaging of non-proton nuclei.Technically, imaging of hyperpolarized nuclei offers several unique properties, such as complete lack of background signal and possibility for local and permanent destruction of the signal by means of radio frequency (RF) pulses. These properties allow for improved as well as new techniques within several application areas. Diagnostically, the injected compounds can visualize information about flow, perfusion, excretory function, and metabolic status. In this review article, we explain the concept of hyperpolarization and the techniques to hyperpolarize 13 C. An overview of results obtained within angiography, perfusion, and catheter tracking is given, together with a discussion of the particular advantages and limitations. Finally, possible future directions of hyperpolarized 13 C MRI are pointed out.

BACKGROUND: Electroconvulsive therapy (ECT) is associated with volumetric enlargements of corticolimbic brain regions. However, the pattern of whole-brain structural alterations following ECT remains unresolved. Here, we examined the longitudinal effects of ECT on global and local variations in gray matter, white matter, and ventricle volumes in patients with major depressive disorder as well as predictors of ECT-related clinical response. METHODS: Longitudinal magnetic resonance imaging and clinical data from the Global ECT-MRI Research Collaboration (GEMRIC) were used to investigate changes in white matter, gray matter, and ventricle volumes before and after ECT in 328 patients experiencing a major depressive episode. In addition, 95 nondepressed control subjects were scanned twice. We performed a mega-analysis of single subject data from 14 independent GEMRIC sites. RESULTS: Volumetric increases occurred in 79 of 84 gray matter regions of interest. In total, the cortical volume increased by mean 6 SD of 1.04 6 1.03% (Cohen's d = 1.01, p , .001) and the subcortical gray matter volume increased by 1.47 6 1.05% (d = 1.40, p , .001) in patients. The subcortical gray matter increase was negatively associated with total ventricle volume (Spearman's rank correlation r = 2.44, p , .001), while total white matter volume remained unchanged (d = 20.05, p = .41). The changes were modulated by number of ECTs and mode of electrode placements. However, the gray matter volumetric enlargements were not associated with clinical outcome. CONCLUSIONS: The findings suggest that ECT induces gray matter volumetric increases that are broadly distributed. However, gross volumetric increases of specific anatomically defined regions may not serve as feasible biomarkers of clinical response.

Purpose:To measure the apparent diffusion coefficient (ADC) of hyperpolarized (HP) 3 He gas using diffusion weighted MRI in healthy volunteers and patients with emphysema and examine the reproducibility and volume dependency. Materials and Methods:A total of eight healthy volunteers and 16 patients with emphysema were examined after inhalation of HP 3 He gas mixed with nitrogen (N 2 ) during breathhold starting from functional residual capacity (FRC) in supine position. Coronal diffusion-sensitized MR images were acquired. Each subject was imaged on three separate days over a seven-day period and received two different volumes (6% and 15% of total lung capacity [TLC]) of HP 3 He each day. ADC maps and histograms were calculated. The mean and standard deviation (SD) of the ADC at different days and volumes were compared. Results:The reproducibility of the mean ADC and SD over several days was good in both healthy volunteers and patients (SD range of 0.003-0.013 cm 2 /second and 0.001-0.009 cm 2 /second at 6% and 15% of TLC for healthy volunteers, and a SD range of 0.001-0.041 cm 2 /second and 0.001-0.011 cm 2 /second, respectively, for patients). A minor but significant increase in mean ADC with increased inhaled gas volume was observed in both groups. Conclusion:Mean ADC and SD of HP 3 He MRI is reproducible and discriminates well between healthy controls and patients with emphysema at the higher gas volume. This method is robust and may be useful to gain new insights into the pathophysiology and course of emphysema. THE HABIT OF SMOKING is increasing worldwide and so is one of its direct consequences, i.e., the chronic obstructive pulmonary disease (COPD). By the year 2020, COPD is expected to rank third as a cause of mortality and fifth of morbidity (1). A validated imaging technique that is sensitive to very early structural changes in the lungs could be helpful in the design of therapy and management of emphysema.MRI using hyperpolarized (HP) gases as helium ( 3 He) have emerged as a promising technique for studies of the structure and function of the lungs. Inhalation of HP 3 He can be used not only to derive information related to regional ventilation but also to the size of the alveoli. This is accomplished by measurement of the apparent diffusion coefficient (ADC) of inhaled HP 3 He. When HP 3 He is inhaled, diffusion of the gas is restricted by the boundaries of the alveoli and if restricted diffusion measurement conditions are met, the measured ADC will reflect the size of the peripheral airway spaces (2-4). It could thereby allow quantification of the structural changes (of the lungs) in emphysema. The ADC has been shown to increase in animals with elastase-induced emphysema (5). Studies have also been performed in small numbers of healthy adult subjects and subjects with lung disease (6 -12). In these studies, the ADC values in emphysematous lungs were increased relative to ADC values obtained in subjects with healthy lungs.