VC 1. Black-Blood Venous Imaging with Phase Contrast: A Contrast-Free Cardiovascular Magnetic Resonance Approach for the Diagnosis of May-Thurner Syndrome

May-Thurner syndrome (MTS) is a venous compression syndrome in which the left common iliac vein is compressed between the lower lumbar spine and the right common iliac artery. The objective of this study was to determine whether black-blood venous imaging (BBVI) technique can diagnose May-Thurner syndrome. This is a prospective, single-center study. All patients were admitted to the cardiovascular surgery division for MTS and screened for study eligibility; 46 patients received BBVI with phase contrast (BBVI + PC), computed tomography venography (CTV), and digital subtraction angiography (DSA). Two blinded readers assessed the randomized BBVI + PC images from all participants and made independent decisions about the presence or absence of iliac vein compression. Images obtained by CTV and DSA were also randomized and assessed by the two readers. Using the consensus diagnosis of DSA as the reference, the sensitivity, specificity, positive and negative predictive values, and accuracy of BBVI + PC and CTV as well as their diagnostic agreement with DSA were calculated. In addition, diagnostic confidence and inter-reader diagnostic agreement were evaluated for all three techniques. BBVI + PC with optimized parameters effectively allowed visualization of iliac venous compression directly. High sensitivity (92.4% vs 88.6%), specificity(99.0% vs 96.7%), positive predictive values (96.5% vs 89.8%), negative predictive values (98.7% vs 93.3%), and accuracy (98.2% vs 97.6%) were obtained by BBVI + PC in comparison with CTV. Good diagnostic confidence and excellent diagnostic and inter-reader agreements were achieved by BBVI + PC, which were superior to CTV in detecting MTS. BBVI + PC allows direct visualization of iliac venous compression and has the potential to be a reliable diagnostic method without the use of contrast agent.