Evaluating Childhood Obesity: Magnetic Resonance-Based Quantification of Abdominal Adipose Tissue and Liver Fat in Children

Abstract

Purpose: The purpose of this study is to establish and validate a magnetic resonance (MR)-based fat quantification package that provides an accurate assessment of abdominal adipose tissue and liver fat in children.

Materials and Methods: Ex vivo trials with a torso model and water-oil mixtures are conducted. Abdominal adipose tissue (AAT) is covered by magnetic resonance imaging (MRI) using a fat-selective sequence and is analyzed by a plug-in based on the open source software ImageJ. Liver fat (LF) is measured with localized ¹H Magnetic Resonance Spectroscopy (¹H MRS) and the jMRUI (java-based Magnetic Resonance User Interface) software package. Evaluation of the clinical methodology involved a study of 10 children in this feasibility study (mean age and body mass index: 13.3 yr; 33.3 kg/m²). To evaluate the method’s validity, reference measurements were performed.

Results: Ex vivo trials with the torso model showed that adipose tissue was measured appropriately with a systematic underestimation by 9.3 ± 0.2 % (0.32 ± 0.064 kg). Coefficients of variation for both intra- and inter-observer measurements ranged between 0 – 2.7 % and repeated analyses showed significant equivalent results (p < 0.01). The lipid content obtained by ¹H MRS ex vivo revealed significant equivalence with the predefined fat content in water-oil mixtures (p < 0.01). In vivo, the homemade plug-in significantly overestimated the AAT, with the visceral adipose tissue being most affected (+ 15.7 ± 8.4 %).

Conclusion: Although an overestimation of the AAT by the presented plug-in should be taken into consideration, this children-friendly package enables the quantification of both LF and AAT within 30 min on a freeware-based platform.

Zusammenfassung

Ziel: Ziel war, ein Magnetresonanz(MR)-basiertes Fettquantifizierungspaket zu entwickeln und zu validieren, welches die Beurteilung von abdominellem Fettgewebe (AF) und Leberfett (LF) in Kindern erlaubt.

Material und Methoden: Es wurden Ex-vivo-Versuche anhand eines Bauchmodells sowie Wasser-Öl-Phantomen durchgeführt. AF wurde mittels Magnetresonanztomografie unter Anwendung einer fettselektiven Sequenz erfasst und mithilfe eines Plug-Ins auf Basis der open-source Software ImageJ analysiert. LF wurde mittels ¹H-Magnetresonanzspektroskopie (¹H MRS) erfasst und innerhalb der jMRUI-Software berechnet. Um die klinische Durchführbarkeit zu beurteilen, wurden 10 Kinder untersucht (mittleres Alter und Body-Mass-Index: 13,3 Jahre; 33,3 kg/m²). Zur Methodenevaluierung wurden Referenzmessungen durchgeführt.

Ergebnisse: Die Ex-vivo-Versuche mit dem Bauchmodell zeigten, dass AF mit einer systematischen Unterschätzung von 9,3 ± 0,2 % (0,32 ± 0,064 kg) adäquat erfasst wurde. Die Variationskoeffizienten für die Analysen eines und die Analysen verschiedener Untersucher bewegten sich zwischen null und 2,7 %. Wiederholte Analysen zeigten signifikant gleiche Ergebnisse (p < 0,01). Hinsichtlich eines minimal-relevanten Unterschieds von δ = 1 /10 belegten die ex vivo mittels ¹H MRS erfassten Fettkonzentrationen signifikante Gleichheit mit den vordefinierten Fettkonzentrationen in den Wasser-Öl-Phantomen (p < 0,01). In vivo überschätzte das Plug-In signifikant AF, wobei Viszeralfett am stärksten betroffen war ( + 15,7 ± 8,4 %).

Schlussfolgerung: Obwohl eine Überschätzung des AF bei der Interpretation der Daten berücksichtigt werden sollte, erlaubt dieses Paket die Quantifizierung von LF und AF in Kindern und Jugendlichen innerhalb von 30 min mittels frei verfügbarer Software.

Key words

abdomen - MR spectroscopy - MR imaging - technology assessment - segmentation

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