Experimental MR Imaging of the Rabbit Brain: How to Perform It Better

Rabbits are among the most widely used animals in experimental studies in basic and clinical medical sciences. MR images may also be coupled with the studies of rabbits and may provide important clues to the researchers.

Several coils and parameters may be implemented for experimental MR imaging of the rabbit brain, but because of the small size of this brain, the image quality may not be satisfactory. This letter briefly describes our efforts to improve the quality of MR images of the rabbit brain by using different coils and varying technical parameters.

We retrospectively evaluated the MR imaging of 87 male New Zealand white rabbits used in cranial experimental studies between 1994 and 2003 on a 1T system. Experiments had been conducted in conformity with the Guide for the Care and Use of Laboratory Animals¹ and were approved by the local ethics committee. A circularly polarized head coil, a quadrature extremity coil, or a 3-inch (7.62-cm) circular surface coil and fast spin-echo images were used. The images were reviewed by 2 experienced neuroradiologists and classified as not acceptable, poor, intermediate, and high quality with regard to the gray/white matter differentiation.

Among the 87 rabbits, 8 were in the group with the head coil; 56 in the group with the extremity coil; and 23 in the group with the 3-inch surface coil. The 3-inch surface coil was found to be superior to other coils because of its higher image quality, permitting a smaller field of view and a thinner section thickness–intersection gap in a shorter imaging time.

The use of high-powered MR imaging scanners and specifically designed surface coils for different body parts of the animals is preferred to obtain high image resolution and increased signal-to-noise ratio (SNR).²–⁴ Despite their advantages, these devices are not widespread and in common use. Also, a radiofrequency coil fitted to the animal size is crucial because the SNR scales linearly with the filling factor of the coil.⁵ The 3-inch surface coil was found to have the most suitable size for the rabbit brain in our study.

In summary, we recommend that in experimental MR imaging of the rabbit brain, a 3-inch surface coil may provide a more acceptable image quality than other coils in everyday practice.

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