a preferred embodiment struts 32 are comprised of an alloy of titanium and nickel known in the art as nitinol the shape memory material construction of struts 32 enable struts 32 to change shape in response to a change in temperature at about body temperature struts 32 assume an extended shape as shown in fig1 at a selected temperature other than body temperature struts 32 assume a contracted shape as shown in fig2 in fig2 struts 32 have partially contracted inside apertures 30 of body portion 24 as a result of the contraction of struts 32 anchors 52 have retracted from walls 23 of blood vessel 22 various techniques can be used to alter the temperature of struts 32 suitable techniques for warming struts 32 include applying electromagnetic energy to body portion 24 e g laser light delivered by an optical fiber and applying electrical energy to thrombosis filter 20 e g inducing a current through struts 32 a process which may be used to remove thrombosis filter 20 from lumen 21 of blood vessel 22 is illustrated in fig3 a removal catheter 110 with a lumen 112 and a distal end 114 is disposed in lumen 21 of blood vessel 22 removal catheter 110 enters the patients vascular system at a point which is readily accessible to the physician once in the vascular system.