IC‐P1‐008: Comparison of amyloid plaque contrast generated by T2‐, T2*, and susceptibility‐weighted magnetic resonance imaging methods in transgenic mice

Magnetic resonance imaging has been used to visualize amyloid plaques in transgenic mouse specimens. Plaques appear hypointense relative to background tissue; however, there has not been a systematic comparison of T2- and T2*-weighted methods. The purpose of this study was to compare plaque contrast generated by T2-, T2*- and susceptibility-weighted imaging methods. The nine imaging methods compared were: spin-echo (SE), multi-spin-echo (mSE), gradient-echo (GRE), multi-gradient-echo (mGRE), fast spin-echo (FSE), multi-asymmetric spin-echo (mASE), gradient-echo with susceptibility weighted imaging (GRE-SWI), multi-gradient-echo with SWI (mGRE-SWI), and mASE with SWI (mASE-SWI). The multi-echo methods summed the echoes from an echo train to increase the signal-to-noise ratio. Imaging parameters for each method were optimized to produce maximal plaque contrast in a 1 hr 45 min total scan time. The imaging methods were compared quantitatively on plaque to background contrast to noise ratio (CNR). Four 9-month old ex vivo APP/PS1 specimens and one 22-month old ex vivo PS1 specimen were scanned. Two 13-month old in vivo APP/PS1 mice were used to compare the asymmetric spin-echo and gradient-echo sequences in living mice. In the ex vivo specimens, the CNR was greater for the SE than the FSE method. Contrast was greater for sequences that summed the echoes of an echo train compared to a single echo sequence in the analogous pulse sequence family. The T2*-weighted sequences provided greater contrast than the T2-weighted sequences, and the SWI images gave the greatest contrast. However, the in vivo susceptibility artifacts caused the gradient-echo and SWI images to degrade before plaque contrast could develop. Therefore, the mASE sequence gave the largest contrast in vivo. Based on these experiments, we recommend a mASE sequence with initial TE = 30 ms, echo train length = 5, and an echo offset = 8ms for in vivo imaging of amyloid plaques in transgenic AD mice.