| abstract |
A medical filter has a double-basket design, in which the two filter baskets have balanced filtering efficiencies, so that both filter baskets tend to collect or capture amounts of material that are approximately equivalent. In other words, a second or “downstream” filter basket may be designed to have a filter efficiency greater than that of a first or “upstream” filter basket. There are a variety of ways in which this tailored filter basket performance can be achieved. Some examples include increasing the number of struts or decreasing the size of the filter cells or other filter elements of the second or “downstream” filter basket. Likewise, a similar result may be reached by decreasing the number of struts or increasing the size of the filter cells or other filter elements of the first or “upstream” filter basket. In some cases, such a filter may be used in a blood vessel, for the purpose of intercepting thrombus. Where the filter is implanted in a blood vessel, it may be retrievable for a longer period of time. |