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

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.

The application of Silenz MR angiography in the follow-up assessment of intracranial aneurysms embolization / 中华放射学杂志

Objectives To explore the value of Silenz MRA in the follow-up assessment of intracranial aneurysms embolization. Methods Fifteen patients underwent coiled embolization were prospectively collected. Silenz and time of flight MRA (TOF MRA) were performed on the same day as DSA examination. Two neuro-radiologists scored the structures of peripheral vascular with a 4-score grading system and evaluate embolism status (two-grade montreal scale). The scores of vascular structures were compared using Wilcoxon signed rank tests. Weighted Kappa statistics was used to assess the inter-observer agreement on each MRA scoring, the inter-modality agreement between MRA and DSA, the inter-modality agreement between the MRA methods. Results There were 11 cases with complete occlusion, 4 cases with residual aneurysm revealed by DSA. For depiction, Silenz MRA was significantly better than TOF MRA [(3.50 ± 0.62) vs. (3.00 ± 0.63), Z=-3.12, P=0.002]. Inter-modality agreement of Silenz MRA and DSA was excellent (Kappa=0.82), while the agreement of TOF MRA and DSA was moderate(Kappa=0.60). Inter-modality agreement between Silenz MRA and TOF MRA was good (Kappa=0.76). Conclusions Silenz MRA is superior to TOF MRA for depiction of vascular structures and evaluation of embolism status, which is highly related with DSA. It has the value in the postoperative follow-up evaluation.

MR imaging of tropomyosin-4 antibody targeting synthetic phenotype vascular smooth muscle cells in vitro / 中华放射学杂志

Objective To isolate,culture,and identify the synthetic phenotype vascular smooth muscle cells (VSMC) and identify the specific marker protein (tropomyosin-4,TPM-4) of synthetic phenotype.To employ the immune molecular imaging technique to develop MRI of probe targeted with TPM-4 antibody VSMC in vitro.Methods The synthetic phenotype VSMC and endothelial cells (EC) were isolated and cultured in vitro,respectively.Immunocytochemistry (ICC) staining for α-smooth muscle actin (SMA) and Ⅷ factor was performed for cell identification,respectively.The high expression level of TPM-4 protein was tested by immunofluorescence double staining.The MRI molecular probe was built by chemical cross-linking,TPM-4 conjuncted probe (TPM4-USPIO) as the experimental group,IgG conjuncted probe (IgG-USPIO) as the negative group,unconjuncted probe (USPIO) as the control group,and PBS as the blank group.The synthetic VSMC were incubated with probes within experimental group,negative group,control group,respectively,and EC were incubated with experimental group as another control group.Prussian blue staining was employed to analyze the specific-targeting and MTT assay was used to test bioactivity of the probe under different concentrations (0,5,10,20,40 μg/ml) in vitro.7.0 T MRI scanner was used to detect the magnetic properties.With 7.0 T MRI scanner,the T2WI images of different probes labeled synthetic VSMC and different concentration gradient (1 × 103,5 × 103,1 × 104,5 × 104)TPM4-USPIO labeled cells were obtained and analyzed.T2 signal and MTT data among groups were compared using single factor analysis of variance (ANOVA) and LSD test.Results The synthetic phenotype of VSMC were isolated and cultured successfully,and the VSMC could express the TPM-4 protein.The synthetic phenotype VSMC had a high level of the protein expression.The probe was made successfully.The T2 relaxivity of TPM4-USPIO and IgG-USPIO were 0.0350 × 106,0.0316 × 106 mol/s,respectively,with high stability as USPIO (0.0292 × 106 mol/s).Prussian blue staining results showed that the experimental group probe could specifically bind to the synthetic VSMC.MTT results showed that iron concentration within 40 μg/ml or less had no effect on VSMC proliferation activity.The T2 WI of experimental group showed lower signal than the control group.The T2 relaxivity was (116.67 ± 2.08) ms,which was less than the control group [(217.67 ±2.52),(219.33 ±2.08)ms,respectively] and the blank group [(205.33 ± 1.53)ms](F =1670.43,P ＜ 0.01).The T2 relaxivity of the different concentration gradient labeled cells (1 × 103 、1 × 104 、1 × 105) were (184.33 ± 2.08),(169.67 ± 1.15),(116.67 ± 2.08) ms,respectively (F =684.35,P ＜0.01).No significant difference of the T2WI gradual signal dim was found between cells with the same order concentration(P ＞ 0.05).Conclusions The synthetic phenotype of VSMC can be obtained by PDGF-BB treatment.TPM4-USPIO probe is efficient,specific and targeted at combination with synthetic VSMC.The T2WI signal changed obviously under high field MRI scanner,which provides a new way for molecular imaging research.