Hong Zhang MD, Presenter: Nothing to Disclose

Wen zhu Wang, Abstract Co-Author: Nothing to Disclose

Bo Ma, Abstract Co-Author: Nothing to Disclose

Yun Peng MD, Abstract Co-Author: Nothing to Disclose

Jian Wang, Abstract Co-Author: Nothing to Disclose

Jinyuan Zhou PhD, Abstract Co-Author: Nothing to Disclose

In the TBI, the initial impact includes the primary injury and secondary injury cascades, such as ischemia, progressive neurodegeneration, persistent inflammation, glial hypertrophy and proliferation, and cerebrovascular dysfunctions. APT imaging is a novel molecular MRI method that can non-invasively detect endogenous mobile protein and tissue pH changes. We explored the capabilities of APT imaging for detecting the TBI in rat models.

Six adult male SD rats had craniotomy plus controlled cortical impact (CCI) surgery (3-mm impactor tip, velocity of 5m/sec, deformation depth of 5 mm, and impact duration of 65 msec) under isoflurane anesthesia. MRI data was acquired at 4.7T, using T2w, T2*w, T1w, T2, T1, isotropic ADC, CBF, and APT-weighted (APTw; RF saturation power/time 1.3 μT/4 sec) MRI. APTw images were quantified using the magnetization transfer-ratio asymmetry at 3.5 ppm from water. MRI was performed 1 and 6 hours, as well as 1, 2 and 3 days after TBI.

All APTw images show an ‘ischemia-like’ pattern of hypointensity, unique from all other used MRI sequence, in some areas of the lesion. Average APTw signal intensities decreased significantly and globally at 1 hr (compared to contralateral normal brain tissue), with 84%, 63% and 62% reductions in a contused cortical region, ipsilateral hippocampus and thalamus. There were some areas of intermediate to slightly hyperintense APT signals in the lesion, consistent with the hemorrhage (with abundant mobile proteins), as shown by T2*w and pathology. The low APT-pH MRI signal was gradually recovered after the initial drop. At day 3 after injury, the TBI lesion became heterogeneous with areas of high and low APTw signal intensities. Notably, the APTw signal intensity of the perilesion cortex dramatically increased (3.3% ± 1.5% at 3d vs. -3.2% ± 1.6% at 1 h), due to the secondary inflammatory response, as confirmed by pathology.

This study for the first time demonstrates that APT-MRI can reveal many key TBI features in vivo, such as ischemia, hemorrhage, and inflammatory response.

The APT-MRI signal is a unique, sensitive biomarker for identifying and assessing the TBI in the clinic, which should have considerable influence on the patient care.

Zhang, H, Wang, W, Ma, B, Peng, Y, Wang, J, Zhou, J, Molecular MRI Detection of Traumatic Brain Injury (TBI) with Amide Proton Transfer (APT) Imaging.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018939.html