Purpose: To evaluate the impact of heating-induced frequency drifts on single-voxel spectroscopy and to demonstrate correction strategies based on the interleaved reference scan technique. Materials and Methods:Frequency drifts induced by gradient heating are assessed for two clinical 3 Tesla (T) whole body MR systems. The interleaved reference scan (IRS) method is used for correcting these frequency drifts in 1H spectra in vitro and in vivo. For severely driftaffected spectroscopy experiments, a feedback-based version of the IRS sequence is proposed, which adds the functionality of a frequency lock to prevent a degradation of the water suppression.Results: It is shown that the line widths of the spectral resonances can be largely reduced with the interleaved reference scan method, resulting in considerably improved peak resolution and signal-to-noise ratio. The feedback-based IRS method additionally allows for stable water suppression, even in the presence of very strong frequency drifts. Conclusion:If spectroscopy scans are combined with imaging scans with a high gradient duty cycle such as diffusion-weighted imaging or functional MRI, a drift correction with IRS can considerably improve the validity of data analysis in research studies.

MRS is a promising tool for the non-invasive in vivo assessment of the cerebral neurochemistry in ADHD. More regions of interest (ROI) like amygdala, hippocampus, thalamus and cerebellum should be assessed in future studies. Further methodological improvements of MRS are desirable in order to assess the absolute metabolite concentration of several ROIs at the same time. Such developments will open novel perspectives in spectroscopic investigations of ADHD.

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Motion-induced artefacts in magnetic resonance spectroscopic imaging are much harder to recognize than in imaging experiments and can therefore lead to erroneous interpretation. A method for prospective motion correction based on an optical tracking system has recently been proposed and has already been successfully applied to single voxel spectroscopy. In this work, the utility of prospective motion correction in combination with retrospective phase correction is evaluated for spectroscopic imaging in the human brain. Retrospective phase correction, based on the interleaved reference scan method, is used to correct for motion-induced frequency shifts and ensure correct phasing of the spectra across the whole spectroscopic imaging slice. It is demonstrated that the presented correction methodology can reduce motion-induced degradation of spectroscopic imaging data.

BACKGROUND Non-alcoholic steatohepatitis (NASH) has become one of the leading causes of liver disease in the western world. In obese patients weight reduction is recommended. Up to now there are no specific guidelines for weight loss in order to reduce hepatic fat content. AIM To investigate the effects of a 24-wk guided lifestyle intervention program compared to a meal replacement regimen based on soy protein. METHODS Twenty-six subjects with NASH participated in a randomized single-center study. They were randomly assigned to either meal replacement group (MR-G) with soy-yogurt-honey preparation or to guided lifestyle change group (LC-G) with endurance activity and nutrition counselling. Serum alanine transaminase (ALT), aspartate transaminase (AST), lipid parameters, and adipokines were measured. Liver fat content and lipid composition were determined by magnetic resonance imaging and magnetic resonance spectroscopy. Body fat mass and lean body mass were assessed using Bod Pod ® device. Pre- and post-intervention monitoring of parameters was performed. Statistical analyses were conducted with SPSS software, results were expressed as median (interquartile range). RESULTS Twenty-two subjects (MR-G, n = 11 and LC-G, n = 11) completed the study (9 women, 13 men; age 52.1 (15.0) years, body mass index (BMI) 32.3 (3.3) kg/m²). In both groups a significant weight loss was achieved (MR-G: -6.4 (3.6) kg, P < 0.01; LC-G: -9.1 (10.4) kg, P < 0.01). BMI dropped in both groups (MR-G: -2.3 (1.5) kg/m 2 , P = 0.003; LC-G: -3.0 (3.4) kg/m 2 , P = 0.006). Internal fat and hepatic lipid content were markedly reduced in both groups in comparable amount. There was a strong correlation between reduction in liver fat and decrease in ALT. Likewise, both groups showed an improvement in glycemic control and lipid profile. Changes in adipokines, particularly in adiponectin and leptin were closely related to intrahepatic lipid changes. CONCLUSION Comprehensive lifestyle intervention and meal replacement regimen have comparable effects on body and liver fat, as well as decrease in markers of hepatic inflammation among NASH patients.