Abstract
In experimental models of pancreatic growth and recovery, changes in pancreatic size are assessed by euthanizing a large cohort of animals at varying time points and measuring organ mass. However, to ascertain this information in clinical practice, patients with pancreatic disorders routinely undergo non-invasive cross-sectional imaging of the pancreas using magnetic resonance imaging (MRI) or computed tomography (CT). The aim of the current study was to develop a thin-sliced, optimized sequence protocol using a high field MRI to accurately calculate pancreatic volumes in the most common experimental animal, the mouse. Using a 7 Telsa Bruker micro-MRI system, we performed abdominal imaging in whole-fixed mice in three standard planes: axial, sagittal, and coronal. The contour of the pancreas was traced using Vitrea software and then transformed into a 3-dimensional (3D) reconstruction, from which volumetric measurements were calculated. Images were optimized using heart perfusion-fixation, T1 sequence analysis, and 0.2 to 0.4 mm thick slices. As proof of principle, increases in pancreatic volume among mice of different ages correlated tightly with increasing body weight. In summary, this is the first study to measure pancreatic volumes in mice, using a high field 7 Tesla micro-MRI and a thin-sliced, optimized sequence protocol. We anticipate that micro-MRI will improve the ability to non-invasively quantify changes in pancreatic size and will dramatically reduce the number of animals required to serially assess pancreatic growth and recovery.
Highlights
Pancreas size is a key parameter that is used in the experimental setting to assess pancreatic growth, development, and recovery following injury [1,2,3,4,5]
We optimized a method for accurately quantifying pancreatic volume in mice using a 7 Tesla micro-magnetic resonance imaging (MRI) and a thin-sliced RARE sequence protocol
To test the ability of the optimized MRI protocol to differentiate in situ differences in pancreatic volume, we examined growth of the pancreas with advancing age (Fig. 6)
Summary
Pancreas size is a key parameter that is used in the experimental setting to assess pancreatic growth, development, and recovery following injury [1,2,3,4,5]. Many studies in pancreas development and regeneration use mouse models that exploit sophisticated transgenic technology, most of these studies only qualitatively describe changes in pancreatic size or are forced to weigh out the pancreas ex vivo. There are several published protocols in humans to calculate pancreatic volume using CT [8,9] and MRI [10,11,12,13,14], methods in animals models are limited to large animals [10]. We optimized a method for accurately quantifying pancreatic volume in mice using a 7 Tesla micro-MRI and a thin-sliced RARE sequence protocol
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