A modular blood filter device and delivery system, comprising a hollow vessel insertion device with a modular filter apparatus. The insertion device, which can be an introducer, includes a distal end adapted to enter an artery, and a proximal end adapted to receive a modular filter apparatus. When the insertion device is a cannula, the modular filter apparatus is received through a side port. The modular filter apparatus includes a shaft and an adjustable filter device or a removable filter associated with the shaft. The adjustable filter includes filter mesh, an adjustable frame capable of assuming enlarged and contracted conditions and a frame sizing mechanism associated with the frame. Certain embodiments include a filter cartridge, and the shaft is inserted into the cartridge, thereby protecting the adjustable filter device therein. The cartridge may then be removably received by the insertion device. An expandable obturator may be used to ease the entry of the insertion device into the vessel. Indexing and locking mechanisms are described for aligning the cartridge or the obturator to the insertion device. Vessel sizing tools are also described for determining the size of the vessel into which the filter will be introduced. The insertion device may then be introduced into a blood vessel, and the adjustable filter device may be deployed through the device into the vessel. The adjustable frame may be self-adjusting or externally adjusted to fit the vessel and to capture embolic material in the mesh. The frame may be collapsed to the contracted condition, and may be removed from the vessel or embolic debris may be removed by an aspiration tube. The modular filter cartridge may be removed from the cannula, and a new modular filter cartridge may then be received therein.