Improved preparation of chick embryonic samples for magnetic resonance microscopy

Previous work demonstrated the power of three-dimensional (3D) magnetic resonance microscopy (MRM) to follow complicated morphologic development in the embryonic cardiovascular system. In this study we describe a new dual-contrast method for specimen preparation that combines perfusion fixation and immersion in fixative with macro- and small molecular gadolinium agents to provide enhanced definition of both the heart wall and chamber. MRM was performed at 9.4 T with image resolutions of 25, 31, and 50 microm isotropic voxels for three stages of chick embryos (day 4, day 5.5, and day 9), and compared to histological sections of the same embryos. The results show considerable improvement of image quality over previous efforts, with better signal-to-noise ratio (SNR) and contrast between the cardiac chamber and myocardial wall. Excellent correlation was shown between the MRM images and histological sections. Thus, 3D high-resolution MRM in combination with the dual-contrast technique is useful for acquiring quantitative 3D morphologic data regarding heart development.