Magnetic resonance imaging of amyloid plaques in transgenic mice

Transgenic mice are used increasingly to model brain amyloidosis, mimicking the pathogenic processes involved in Alzheimer's disease (AD). In this chapter, a strategy is described that has been successfully used to map amyloid deposits in transgenic mouse models of AD with magnetic resonance imaging (MRI), utilizing molecular targeting vectors labeled with MRI contrast agents to enhance selectively the signal from amyloid plaques. To obtain sufficient spatial resolution for effective and sensitive mouse brain imaging, magnetic fields of 7-Tesla (T) or more are required. These are higher than the 1.5-T field strength routinely used for human brain imaging. The higher magnetic fields affect contrast agent efficiency, and determine the choice of pulse sequence parameters for in vivo MRI, all addressed in this chapter. Ex vivo imaging is also described as an important step to test and optimize protocols prior to in vivo studies. The experimental setup required for mouse brain imaging is explained in detail, including anesthesia, immobilization of the mouse head to reduce motion artifacts, and anatomical landmarks to use for the slice alignment procedure to improve image co-registration during longitudinal studies, and for subsequent matching of MRI with histology.