Patency of the inferior vena cava after placement of Simon nitinol filter

This paper reports on Simon nitinol filters (SNFs) placed in 33 patients (11 male, 22 female; mean age, 67 years; range, 38-88 years) since February 1988. MR imaging and US were performed in 18 of these patients to evaluate patency of the inferior vena cava (IVC) 2-9 months after SNF placement. Six patients were imaged twice with MR and US, for a total of 24 studies. Duplex Doppler US was used. For MR imaging, spin-echo sequences were used for six examinations in five patients, and fast low-angle shot sequences in the remaining 18. The results were as follows for MR imaging versus US: adequate visualization of the IVC, 23 versus 10 studies; partial visualization, one versus five; nonvisualization, zero versus nine; normal IVC, 16 versus 10; occlusions of IVC, five (three patients) versus zero; partial occlusion, two (asymptomatic patients) versus zero; and nondiagnostic findings, one versus 14