Comparison of Fat–Water MRI and Single‐voxel MRS in the Assessment of Hepatic and Pancreatic Fat Fractions in Humans

Hu, Houchun H.; Kim, Hee-Won; Nayak, Krishna S.; Goran, Michael I.

doi:10.1038/oby.2009.352

Cited by 193 publications

(170 citation statements)

References 36 publications

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“…Our study extends the existing works by performing state-of-the-art assessment of the pancreas in a large number of subjects in the general population. Th e IDEAL-MRI allows faster and better measurements of small organs such as the pancreas ( 35 ). We not only provided important epidemiological data, but also defi ned the normal range of pancreatic fat.…”

Section: Fatty Pancreas and Insulin Resistancementioning

confidence: 99%

Fatty Pancreas, Insulin Resistance, and β-Cell Function: A Population Study Using Fat-Water Magnetic Resonance Imaging

Wong

Yeung

et al. 2014

American Journal of Gastroenterology

221

181

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OBJECTIVES:Nonalcoholic fatty liver disease is the most common chronic liver disease. Fatty pancreas has also been described but is diffi cult to assess. It is now possible to measure pancreatic and liver fat accurately with magnetic resonance imaging (MRI). We aimed to defi ne the normal range of pancreatic fat and identify factors associated with fatty pancreas. In addition, the effect of fatty liver and fatty pancreas on insulin resistance (IR) and pancreatic ␤ -cell function was studied. METHODS:Fat-water MRI and proton-magnetic resonance spectroscopy were performed on 685 healthy volunteers from the general population to measure pancreatic and liver fat, respectively. On the basis of fasting plasma glucose and insulin levels, the IR and ␤ -cell function were assessed using the homeostasis model assessment (HOMA). RESULTS:Among subjects without signifi cant alcohol consumption or any component of metabolic syndrome, 90 % had pancreatic fat between 1.8 and 10.4 % . Using the upper limit of normal of 10.4 % , 110 (16.1 % ; 95 % confi dence interval 13.3 -18.8 % ) subjects had fatty pancreas. On multivariable analysis, high serum ferritin, central obesity, and hypertriglyceridemia were independent factors associated with fatty pancreas. Subjects with both fatty pancreas and fatty liver had higher HOMA-IR than did those with either condition alone. Fatty pancreas was not associated with HOMA-β after adjusting for liver fat and body mass index.CONCLUSIONS: In all, 16.1 % of this community cohort of adult Hong Kong Chinese volunteers had a fatty pancreas by our defi nition. Central obesity, hypertriglyceridemia, and hyperferritinemia are associated with fatty pancreas. Individuals with fatty pancreas have increased IR.

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Section: Fatty Pancreas and Insulin Resistancementioning

confidence: 99%

Fatty Pancreas, Insulin Resistance, and β-Cell Function: A Population Study Using Fat-Water Magnetic Resonance Imaging

Wong

Yeung

et al. 2014

American Journal of Gastroenterology

221

181

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“…1, fat is distributed at a low level throughout each pancreas, and localised very high concentrations of fat are rare within the organ. One of the advantages of the three-point Dixon technique is that it is possible to study smaller organs with precise knowledge of boundaries [3]. We have previously reported that the pancreas is 30% smaller in volume and has a more serrated border in type 2 diabetes compared with age-, weight-and sex-matched controls [4].…”

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confidence: 99%

Pancreatic triacylglycerol distribution in type 2 diabetes

et al. 2015

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colleagues concluded that there was no fat in the parenchymal tissue of the pancreas, and hence local release of fatty acids could not influence endocrine function [1]. The authors describe intralobular fat within the pancreas as detected by spectroscopy but then concluded that there was no fat in the parenchyma of the pancreas. This conclusion relied upon magnetic resonance (MR) techniques. We draw attention to three serious errors in the MR methodology employed, and to the sound evidence for the existence of parenchymal fat.First, the imaging method used to measure parenchymal fat yielded negative percentages for pancreas parenchymal fat in approximately half of all individuals, the range of individual parenchymal fat appearing to be from −3% to +4%. Negative fat content of tissue is a concept of no biological validity. The lower limit of detection is stated by the authors as 2%, and from Fig. 2l in their paper it can be seen that this means the majority of their observations cannot yield what they themselves define as a meaningful result. There appears to be a problem of calibration at low fat fraction, possibly caused by the noise performance of fitting too many variables to a twopoint Dixon acquisition, rather than using three or more echoes. Although the authors claim that the technique used has been validated, their supporting reference 29 is an abstract that relates to the simpler matter of measuring liver fat content.Second, it is suggested that there is no fat in the parenchyma of the pancreas but that fat within the pancreas in type 2 diabetes is contained in thick bands of adipose tissue. We have thoroughly assessed over 100 pancreases of people with diabetes and 32 with normal glucose tolerance using our published three-point Dixon method [2]. As illustrated by six examples in our Fig. 1, fat is distributed at a low level throughout each pancreas, and localised very high concentrations of fat are rare within the organ. One of the advantages of the three-point Dixon technique is that it is possible to study smaller organs with precise knowledge of boundaries [3]. We have previously reported that the pancreas is 30% smaller in volume and has a more serrated border in type 2 diabetes compared with age-, weight-and sex-matched controls [4]. Care is indeed required in selecting regions of interest in which to quantify triacylglycerol in the parenchyma of the pancreas and this underscores the value of using an imagingbased method.Third, the authors state that they wanted to assess fat distribution in the pancreas in three supposedly different regions [1]. To do this they employed two very different methods, modified Dixon imaging and spectroscopy. This introduces differences related to the methods. Yet the assessment would more simply be carried out by use of a properly established three-point Dixon technique. Using this method, the region of * Roy Taylor

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“…In this study, when IDEAL is based on a single lipid resonance, we refer to it as single-peak IDEAL (SP-IDEAL), and when it is based on multiple lipid resonances, it is referred to as multipeak IDEAL (MP-IDEAL). Even though the in vivo accuracy of IDEAL in the estimation of fat fractions has been adequately characterized for the measurement of hepatic fat fractions (16)(17)20), the in vivo accuracy of the technique for BM has not as yet been determined.…”

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confidence: 99%

“…If we assume that the fat content of hematopoietic cells is negligible in comparison to that of adipocytes, and that the water content of adipocytes is negligible compared with that of the remainder of softmarrow tissues, CF is also equivalent to 1 minus the volume fat fraction. Both MRI and proton magnetic resonance spectroscopy (H-MRS) have been used to measure fat fractions in BM (12-13) and liver (14)(15)(16)(17). Hence, it is possible to measure CF noninvasively in a patient using MRI or H-MRS.…”

mentioning

confidence: 99%

MRI Measurement of Bone Marrow Cellularity for Radiation Dosimetry

Pichardo

Milner²,

Bolch³

2011

J Nucl Med

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The current gold standard for measuring marrow cellularity is the bone marrow (BM) biopsy of the iliac crest. This measure is not predictive of total marrow cellularity, because the biopsy volume is typically small and fat fraction varies across the skeleton. MRI and localized MR spectroscopy have been demonstrated as noninvasive means for measuring BM cellularity in patients. The accuracy of these methods has been well established in phantom studies and in the determination of in vivo hepatic fat fractions but not for in vivo measurement of BM cellularity. Methods: Spoiled gradient-echo in vivo images of the femur, humerus, upper spine, and lower spine were acquired for 2 dogs using a clinical 3-T MRI scanner. Single-peak iterative decomposition of water and fat with echo asymmetry and least squares (SP-IDEAL) was used to derive BM fat fractions. Stimulated-echo acquisition mode spectra were acquired in order to perform multipeak IDEAL with precalibration (MP-IDEAL). In vivo accuracy was validated by comparison with histology measurements. Histologic fat fractions were derived from adipocyte segmentation. Results: Bland-Altman plots demonstrated excellent agreement between SP-IDEAL and histology, with a mean difference of 20.52% cellularity and most differences within 62% cellularity, but agreement between MP-IDEAL and histology was not as good (mean difference, 27% cellularity, and differences between 5% and 220%). Conclusion: Adipocyte segmentation of histology slides provides a measure of volumetric fat fraction (i.e., adipocyte volume fraction [AVF]) and not chemical fat fraction, because fat fraction measured from histology is invariant to the relative abundances of lipid chemical species. In contrast, MP-IDEAL provides a measure of chemical fat fraction, thus explaining the poor agreement of this method with histology. SP-IDEAL measures the relative abundance of methylene lipids, and this measure is shown to be equivalent to AVF. AVF provides the appropriate parameter to account for patient-specific cellularity in BM mass predictive equations and is consistent with current micro-CTbased models of skeletal dosimetry.

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Comparison of Fat–Water MRI and Single‐voxel MRS in the Assessment of Hepatic and Pancreatic Fat Fractions in Humans

Cited by 193 publications

References 36 publications

Fatty Pancreas, Insulin Resistance, and β-Cell Function: A Population Study Using Fat-Water Magnetic Resonance Imaging

Fatty Pancreas, Insulin Resistance, and β-Cell Function: A Population Study Using Fat-Water Magnetic Resonance Imaging

Pancreatic triacylglycerol distribution in type 2 diabetes

MRI Measurement of Bone Marrow Cellularity for Radiation Dosimetry

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