A medical guidewire assembly comprises a guidewire having a flexible tip. A medical device such as a collapsible filter for use as an embolic protection device is mounted on the guidewire. The filter is advanced through a body lumen with the guidewire tip extending distally. A variable thickness guidewire (having a recess or thinner segment between thicker segments) can be employed. At a first location the filter is advanced relative to the tip to a location which is distally advanced from the first location. Placement of the filter in an optimal distal location is thereby achieved.
