MRI application and molecular imaging during the course of restenosis / 中华放射学杂志

ABSTRACT

Objective To observe the formation process with 3.0 T MRI dynamically, and to discuss the feasibility of molecular imaging studies on restenosis. Methods The models were built with balloon (2.0 F) injury which were separated into restenosis group (n=48) and control group (n=48). Zero h, 24 h, 1 week, 2 week, 4 week and 8 week after surgery, 3.0 T MRI scanning (T1WI, T2WI, PDWI) was performed respectively, the vascular of injured side were obtained for HE staining to observe the pathological changes, to analyze the measurement of neointimal area (IA), intimal proliferation index (IHI), lumen area (LA) and stenosis rates, correlation between HE staining measurements and MR images were analyzed. Two weeks after the injury, the restenosis model of rats (n=8) and control rats (n=8) were injected ultrasmall superparamagntiec iron oxide (USPIO,1 mmol/kg) by tail vein, respectively. 3.0 T MRI scanning (T2WI) was underwent at 0 h and 24 h after injection, the change of the arterial wall T2 signal was quantitatively analyzed and the relative signal intensity (rSI) and relative change rate (rSIC) of the vessel wall were calculated. Reference to MRI images, corresponding line segments were taken for Perl's blue staining and immunohistochemically staining of macrophages. One-way ANOVA, Pearson and t test were used for statistical analysis. Results In the early?term (0 h,24 h), the wall and surrounding high signal organization boundary was not clear, there was no obvious morphological change of the lumen. In the medium?term (1, 2 week), signal of the injured wall increased with different extents, wall thickening and luminal narrowing was progressive, the inwall was coarse. In the later?term (4, 8 week) wall signal got slightly lower, wall thickness, lumen change were not significant, the wall area and LA were significantly associated with pathologic measurement result (r value were 0.978, 0.732; P0.05). rSI was 1.582±0.051 after the injection of USPIO, then 24 h after injection of USPIO, T2 signal of the vessel wall was reduced significantly, rSI was 1.260 ± 0.088, rSIC was (-20.249 ± 6.489) % with statistical difference (t value was 8.924,P0.05). Perl's staining combined with immunohistochemical staining confirmed that the iron particles were taken by the macrophage's phagocytosis just in the neointimal. Conclusion 3.0 T MRI is capable of demonstrating the vessel wall and lumen changes dynamically, and the measurements are correlated with pathological results. USPIO can be consumed by macrophages in the neointimal, resulting in T2 signal of the vessel wall decreased significantly.