At 6-months post-implant, if a study subject's filter had not been converted, no further conversion assessments were to be performed and no attempts were to be made to convert the filter as part of the study. The 6-month post filter implant visit was the final follow-up for nonconverted subjects, which also included imaging (KUB or spot film and Doppler or CT). The study protocol allowed the investigators flexibility as to the best IVC imaging modality based on the condition and anatomy of the subject.