J Korean Soc Radiol.  2017 Nov;77(5):317-326. 10.3348/jksr.2017.77.5.317.

A Study of Feasibility of Brain Imaging in Medium- and Small-Sized Animals: Using a Clinical 3T MR System with Three Surface Coils

• Park SY
• Jeong MR
• Cho BM
• Kim KS
• Kim HJ

• KMID: 2394046
• DOI: http://doi.org/10.3348/jksr.2017.77.5.317

Abstract

PURPOSE
To evaluate which brain MR images obtained with a clinical 3T MR system using surface coils less than 15.4 cm in diameter are best in rabbit and rat models, and to assess the feasibility of the clinical 3T MR machine in the study of morphologic brain in a preclinical study using medium- and small-sized animal models.
MATERIALS AND METHODS
Brain T2-weighted image (T2WI), T1-weighted image (T1WI), diffusion-weighted image (DWI), and susceptibility-weighted image (SWI) were obtained, and MR angiography was performed with a clinical 3T MR system using a rat, a cat, and a knee coil (5, 12, and 15.4 cm in diameter, respectively) in normal rabbits (n = 3) and using a rat and a cat coil in normal rats (n = 3). MR images were assessed qualitatively by consensus of two neuroradiologists and quantitatively using signal-to-noise ratio (SNR) and statistical analysis (using analysis of variance or t-test) in terms of which images obtained with different coils were the best. Brain T2WI, DWI, SWI, and Gd-T1WI MR images were obtained 2 hours after embolization with triolein emulsion infused into the carotid artery in rabbits (n = 3) and rats (n = 3) using the coil which showed highest SNR in the above study, and the images were assessed in terms of abnormal findings and image quality.
RESULTS
Brain MR images obtained with the rat coil revealed better image quality and higher SNR compared with those obtained with other coils, and they showed statistical significance (p < 0.05) in rabbits. In rats, brain MR images obtained with the rat coil were better than those obtained with the cat coil in qualitative analysis; however, they revealed no statistical significance except for DWI in quantitative analysis. MR images obtained after triolein emulsion showed T2 hyperintensity and lesional contrast enhancement on Gd-T1WI without evidence of infarction or hemorrhage.
CONCLUSION
The clinical 3T MR system using surface coils for animals enabled us to obtain good quality brain images in medium- and small-sized animal models in the present study. Brain MR images seem to be feasible for the morphologic evaluation in animal models.

MeSH Terms

Angiography
Animal Experimentation
Animals*
Brain*
Carotid Arteries
Cats
Consensus
Embolism, Fat
Hemorrhage
Infarction
Knee
Magnetic Resonance Imaging
Models, Animal
Neuroimaging*
Rabbits
Rats
Signal-To-Noise Ratio
Triolein
Triolein

Figure

• 

  Fig. 1. Surface coils used in the present study. Rat coil (5 cm in diameter) with a rabbit (A) and a rat (B) within the coil. Cat coil (C, 12 cm in di-ameter) and knee coil (D, 15.4 cm in diameter) with a rabbit within the coils.

• 

  Fig. 2. Brain MR images of a normal rabbit obtained with a rat coil (1), a cat coil (2) and a knee coil (3). T2WI (a), T1WI (b), DWI (c), ADC map image (d), SWI (e) and MRA (f). All MR images obtained with the rat coil reveal good differentiation of the gray/white matter and smoothness of the parenchyma. However, images obtained with the rat coil (1) show better quality compared to those obtained with the cat (2) or knee coil (3). The sharpness of MRA is best on the image obtained with the rat coil (1f) compared to the image obtained with the cat (2f) or knee coil (3f). ADC = apparent diffusion coefficient, DWI = diffusion-weighted image, MRA = MR angiography image, SWI = susceptibility-weighted image, T1WI = T1-weighted image, T2WI = T2-weighted image

• 

  Fig. 3. Brain MR images of a normal rat obtained with the rat coil (1) and with the cat coil (2). T2WI (a), T1WI (b), DWI (c), ADC map image (d), SWI (e) and MRA (f). MR images obtained with the rat coil (1) reveal better quality in terms of gray/white matter differentiation and smooth-ness compared to those obtained with the cat coil (2). MRA image obtained with the rat coil (1f) shows better sharpness compared to that ob-tained with the cat coil (2f). ADC = apparent diffusion coefficient, DWI = diffusion-weighted image, MRA = MR angiography image, SWI = susceptibility-weighted image, T1WI = T1-weighted image, T2WI = T2-weighted image

• 

  Fig. 4. MR images of a rabbit (1) and a rat (2) obtained with the rat coil 2 hours after embolization of triolein emulsion into the carotid artery. Embolized hemispheres show mild hyperintensity on T2WI (a), no evidence of diffusion restriction (b, c), no hemorrhage on SWI (d) and diffuse contrast enhancement on Gd-T1WI (e). Lesion conspicuity is better on images obtained from the rabbit (1) compared with those obtained from the rat (2). SWI = susceptibility-weighted image, T1WI = T1-weighted image, T2WI = T2-weighted image

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