How Far Can We Take Vessel Wall MRI for Intracranial Atherosclerosis? The Tissue is Still the Issue

Rabbit models of intracranial atherosclerotic disease for pathological validation of vessel wall MRI

INTRODUCTION

Vessel wall magnetic resonance imaging can improve the evaluation of intracranial atherosclerotic disease. However, pathological validation is needed to improve vessel wall magnetic resonance imaging techniques. Human pathology samples are not practical for such analysis, so an animal model is therefore needed.

MATERIALS AND METHODS

Watanabe heritable hyperlipidemic rabbits and apolipoprotein E knockout rabbits were evaluated against New Zealand white wild-type rabbits. Evaluation of intracranial arteries was performed with vessel wall magnetic resonance imaging and pathological analysis, rating the presence and severity of disease in each segment. Two-tailed t-tests were performed to compare disease occurrence and severity prevalence among rabbit subtypes. Sensitivity and specificity were calculated to assess the diagnostic accuracy of vessel wall magnetic resonance imaging.

RESULTS

Seventeen rabbits (five Watanabe heritable hyperlipidemic, four apolipoprotein E knockout and eight New Zealand white) were analysed for a total of 51 artery segments. Eleven segments (five Watanabe heritable hyperlipidemic and six apolipoprotein E knockout) demonstrated intracranial atherosclerotic disease on pathology. Disease model animals had lesions more frequently than New Zealand white animals (P<0.001). The sensitivity and specificity of vessel wall magnetic resonance imaging for the detection of intracranial atherosclerotic disease were 68.8% and 95.2%, respectively. When excluding mild cases to assess vessel wall magnetic resonance imaging accuracy for detecting moderate to severe intracranial atherosclerotic disease lesions, sensitivity improved to 100% with unchanged specificity.

CONCLUSION

Intracranial atherosclerotic disease can be reliably produced and detected using 3T vessel wall magnetic resonance imaging-compatible Watanabe heritable hyperlipidemic and ApoE rabbit models. Further analysis is needed to characterize better the development and progression of the disease to correlate tissue-validated animal findings with those in human vessel wall magnetic resonance imaging studies.

Quantification of intracranial arterial stenotic degree evaluated by high-resolution vessel wall imaging and time-of-flight MR angiography: reproducibility, and diagnostic agreement with DSA

OBJECTIVES

The purpose of this study was to compare the reproducibility and diagnostic agreement of high-resolution vessel wall imaging (HR-VWI) and time-of-flight magnetic resonance angiography (TOF-MRA) with digital subtraction angiography (DSA) to evaluate intracranial arterial stenosis.

METHODS

We retrospectively enrolled patients who underwent HR-VWI and TOF-MRA with suspected intracranial artery disease and had DSA results from our institutional imaging database. Two neuroradiologists separately and independently evaluated anonymous image data for the stenotic lesions. DSA was analyzed by two neurointerventionalists and it served as a standard criterion. The reproducibility of these two MR techniques was determined by the intraclass correlation coefficients (ICCs). The diagnostic agreement to DSA was assessed by the concordance correlation coefficients (CCCs).

RESULTS

A total of 246 lesions from 106 individuals were analyzed for stenotic degrees. The total intra-observer and inter-observer reproducibility of HR-VWI was excellent for identifying stenosis and better than of TOF-MRA. The overall concordance of HR-VWI with DSA was excellent with CCC = 0.932, whereas TOF-MRA was 0.694. In addition, HR-VWI could provide additional vessel wall information.

CONCLUSIONS

HR-VWI has more advantages over TOF-MRA, such as better reproducibilities and diagnostic agreements with DSA to analyze intracranial arterial stenosis. It provides additional information that helps in clinical diagnosis and management.

KEY POINTS

• High-resolution vessel wall imaging can assess intracranial arterial stenosis with a better reproducibility than TOF-MRA and has a higher diagnostic agreement with DSA. • High-resolution vessel wall imaging had a higher diagnostic agreement with DSA compared with TOF-MRA. • Apart from evaluating vascular stenosis, HR-VWI provided additional vessel wall information to help in clinical diagnosis.

Apolipoprotein E knockout rabbit model of intracranial atherosclerotic disease

Intracranial atherosclerotic disease (ICAD) is the most common cause of ischemic stroke. Poor understanding of the disease due to limited human data leads to imprecise treatment. Apolipoprotein E knockout (ApoE-KO) rabbits were compared to an existing model, the Watanabe heritable hyperlipidemic (WHHL) rabbit, and wild-type New Zealand white (NZW) rabbit controls. Intracranial artery samples were assessed on histopathology for the presence of ICAD. Logistic and ordinal regression analyses were performed to assess for disease presence and severity, respectively. Eighteen rabbits and 54 artery segments were analyzed. Univariate logistic analysis confirmed the presence of ICAD in model rabbits (P < .001), while no difference was found between WHHL and ApoE-KO rabbits (P = .178). In multivariate analysis, only classification as a model vs wild-type animal (P < .001) was associated with the presence of ICAD. Univariate ordinal regression analysis demonstrated an association between ICAD severity and model animals (P = .001), with no difference was noted between WHHL and ApoE-KO rabbits (P = .528). In multivariate ordinal regression analysis, only classification as a model retained significance (P < .001). ICAD can be reliably produced in ApoE-KO rabbits, developing the disease comparably to the older WHHL model. Further analysis is warranted to optimize accelerated development of ICAD in ApoE-KO rabbits to more efficiently study this disease.