In vivo Messung der ω-3 Fettsäurenfraction mittels 1H MR Bildgebung bei 3 Tesla
Zusammenfassung der Projektergebnisse
Omega-3 fatty acids are a major substrate in the synthesis of anti-inflammatory prostaglandins, thromboxanes and leukotrienes. The study of omega-3 fatty acid metabolism and expressed storage patterns in adipose tissue is therefore of interest in the context of the metabolic syndrome and insulin resistance. Due to the lack of enzymes in mammals, omega-3 fatty acids cannot be synthesized but have to be absorbed through diet. Currently omega-3 levels can only be assessed in adipose tissue using highly invasive tissue biopsies or in the serum using blood testing. Consequently, the study in various adipose tissue depots, especially visceral depots which are in general not easily accessible for drawing biopsies, appears to be infeasible on a larger scale. Furthermore, the study of omega-3 levels in the serum cannot be considered as optimal as it may not adequately represent the local tissue-specific inflammation status. A non-invasive method allowing the characterization of the omega-3 fatty acid fraction in adipose tissue is therefore needed to allow for the study of macroscopic patterns of omega- 3 fatty acid patterns and related metabolic processes. Core of the present project was the development and evaluation of a non-invasive MR imaging-based method that is capable of measuring the omega-3 fatty acid fraction in human adipose tissues using a clinical 3T MR scanner. Therefore, a chemical shift encoding-based magnetic resonance imaging technique was combined with an omega-3 fatty acid resolving triglyceride signal decomposition model. This approach allowed the extraction of spatially resolved information in a clinically feasible scan time. The general feasibility of the aforementioned MR imaging-based approach for the extraction of the omega-3 fatty acid fraction was demonstrated in controlled phantom validation experiments as well as in vitro in adipose tissue samples. Finally, the applicability of this technique was demonstrated in adipose tissue of healthy volunteers. First preliminary results, presented at the ISMRM 2021 conference, showed pronounced difficulties in terms of overestimation for low omega-3 fatty acid fractions and the observed non-linear relationship of the MR measures. Based on these preliminary results, further methodological improvements were implemented (refinement of the signal model, processing pipeline, and switch to a non-linear least square solver (NL2SOL)) and are described in detail in the journal publication of J. Honecker et al. Major challenges encountered throughout the project included overcoming the rather low signal-to-noise ratio (SNR) during long signal readouts, accurately measuring signal phase, and defining a robust yet accurate omega-3 fatty acid signal model. In addition, the in vivo assessment of the omega-3 fatty acid fraction in particular demonstrated the need for good shimming and a homogeneous B0 field to maintain an acceptable T2* relaxation required for signal deconvolution. In conclusion, the extraction of the omega-3 fatty acid fraction was demonstrated to be feasible using a non-invasive MR imaging technique. It is anticipated that this technique will be of great value in future research, e.g. in the context of metabolic syndrome cohort studies investigating the effect of macroscopic omega-3 fatty acid storage patterns.
Projektbezogene Publikationen (Auswahl)
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“Feasibility of model-based omega-3 fatty acid fraction mapping using multi-echo gradient-echo imaging at 3T,” in Proceedings International Society for Magnetic Resonance in Medicine, Virtual, 2021, vol. 29, p. 1271. [Online].
D. Weidlich & al.
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Feasibility of omega‐3 fatty acid fraction mapping using chemical shift encoding‐based imaging at 3 T. NMR in Biomedicine, 37(10).
Honecker, Julius; Prokopchuk, Olga; Seeliger, Claudine; Hauner, Hans; Junker, Daniela; Karampinos, Dimitrios C. & Ruschke, Stefan
