Systems and methods are provided for removal of clot material from a treatment site in a blood vessel, particularly in venous vasculature. A treatment device (101) can include a core member (115) having a distal portion (109) and an inner coil (111) surrounding the distal portion of the core member. A helical outer member (113) surrounds at least a portion of the inner coil, and a sheet of flexible material (117) extends between the inner coil and the helical outer member, such that the sheet extends helically around the inner coil to provide a surface for clot engagement at the treatment site.
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