PURPOSE: To investigate the value of magnetization transfer (MT) measurements for assessment of acute rejection (AR) in a murine lung transplantation model.
MATERIALS AND METHODS: Thirty mice including 15 C57BL/10 mice serving as donors and 15 C57BL/6 mice as recipients were examined in this study. MT imaging datasets were acquired on a 4.7 Tesla small animal MR scanner using a three-dimensional zero echo time sequence with a Gaussian-shaped MT prepulse with 1000° or 3000° flip angle and systematic variation of off-resonance frequencies between 1000 and 15,000 Hz. After image acquisition, the images were qualitatively assessed, magnetization transfer ratio (MTR) values were calculated and lungs were taken for histologic examination including staining with hematoxylin/eosin, Masson's trichrome (collagen), and α-smooth muscle (fibroproliferative tissue) staining.
RESULTS: Lung transplantation was successfully performed in all 15 mice. All animals showed AR characterized by the presence of interstitial mononuclear cell infiltrates. There were significant differences of MTR in lungs with and without AR (P = 0.007). With a flip angle of 1000°, the largest differences between the MTR of healthy lungs and lungs with AR were observed for an off-resonance frequency of 10,000 Hz (difference MTR 1.80%) and 15,000 Hz (1.91%) and with a flip angle of 3000° at off-resonance frequencies of 6000 Hz (1.37%) and 8000 Hz (1.70%).
CONCLUSION: MT measurements may provide a tool for the quantitative assessment of AR.