Assessment of renal artery stenosis with CT angiography: Usefulness of multiplanar reformation, quantitative stenosis measurements, and densitometric analysis of renal parenchymal enhancement as adjuncts to MIP film reading

Purpose: Our goal was to evaluate CT angiography (CTA) in diagnosing renal artery stenosis (RAS). Method: Thirty-seven patients underwent digital subtraction angiography (DSA) and CTA. Visual interpretation and stenosis measurements were made from maximum intensity projection (MIP) and multiplanar reformation (MPR) laser film prints of 78 renal arteries. Results: Visual reading of MIP films showed good diagnostic performance by receiver operating characteristic curve analysis, with 100% sensitivity in the assessment of greater than or equal to 50% RAS but only 42-54% specificity (overall accuracy 60-75%). The false-positive rate decreased when MIP and MPR films were read together, but the excess of false negatives among the calcified lesions disabled this diagnostic algorithm. Combining visual interpretation of MIP films with quantitative measurements yielded the best diagnostic performance: 92% sensitivity, 80% specificity, and 84% overall accuracy. Renal cortical enhancement measurements (26 patients) had 81% overall accuracy. Conclusion: The overall accuracy of CTA with MIP film reading can be enhanced by quantitative measurement of stenosis or reviewing MPRs.