The Diagnostic Utility of Cardiac-Gated Magnetic Resonance Imaging for Assessing Surgical Resectability of Mediastinal Tumors

Abstract

Objective: To evaluate the diagnostic utility of cardiac-gated magnetic resonance imaging (MRI) for assessing surgical resectability of mediastinal tumours. Materials and Methods:We searched our database for cardiac-gated MRI scans [cine steady-state free precession (SSFP), T1-weighted spin-echo sequences] performed for mediastinal tumor staging. Nine patients underwent both cardiac-gated MRI and non-cardiac-gated computed tomography (CT) scans with subsequent surgical confirmation. Pathological diagnoses were germ cell tumors (n=4) and thymic tumors (n=5). The criteria for mediastinal invasion on CT included tumor abutment of mediastinal structures (>90 degrees) with loss of the intervening fat plane or direct vascular invasion, while those for MRI included absence of sliding motion between tumor and mediastinal structure or direct vascular invasion. Imaging findings were compared and correlated to surgical/histopathological findings.Results: CT showed 48 mediastinal structures with tumor abutment (>90 degrees), with 19 structures confirmed to be involved intraoperatively. MRI showed 38 structures with tumor abutment (>90 degrees), with 18 structures confirmed to be involved intraoperatively. The accuracy, sensitivity, and specificity in determining mediastinal invasion using the presence of tumor abutment of mediastinal structures (>90 degrees) on CT were 50.8 (31/61), 95 (19/20), and 29.3% (12/41), respectively, and those for MRI were 63.9 (39/61), 90 (18/20), and 51.2% (21/41). Cardiac-gated cine SSFP images showed loss of sliding motion in 15 structures, with 14 confirmed to be involved intraoperatively. The accuracy, sensitivity, and specificity in determining mediastinal invasion using absence of sliding motion were 88.5 (54/61), 70 (14/20), and 97.6% (40/41), respectively. Conclusion:This study shows that cardiac-gated MRI is more accurate than non-cardiac-gated CT in mediastinal tumor staging. However, because of higher cost, cardiac-gated MRI may be used to detect mediastinal invasion when findings are equivocal on CT.