A system for deploying a device to a distal location across a diseased vessel, comprising: a railed expandable sheath defining a lumen therethrough and comprising two or more longitudinal rail structures coupled to a sheetlike member, the sheath having a collapsed configuration, wherein the sheath has a first cross sectional outer diameter and a first lumen inner diameter, and an expanded configuration, wherein the sheath has a second cross sectional outer diameter and a second lumen inner diameter; a proximal control assembly with an elongate obturator coupling member which is movable and positioned within the lumen; wherein the collapsed railed sheath is removably coupled to a distal obturator-jacket assembly; wherein the distal obturator-jacket assembly is coupled to the elongate obturator coupling member; the distal obturator jacket assembly having an atraumatic tip; wherein in the collapsed configuration, the sheath is configured to be advanced across at least a portion of the diseased vessel to a position adjacent the distal location without substantial size interference between the first cross sectional outer diameter of the sheath and an inner diameter profile of a lumen of the diseased vessel; and wherein upon positioning the collapsed configuration to the desired position relative to the distal location, the sheath is configured to be expanded to the expanded configuration, such expanded configuration having a diameter greater than said first inner lumen diameter, with incremental pushing of a device, longitudinally through the lumen; wherein the distal obturator jacket assembly is configured to assist in temporarily maintaining a collapsed configuration of a distal portion of the sheath; and wherein the two or more longitudinal rail structures are configured to self-expand upon removal of the distal obturator jacket assembly, the two more longitudinal rail structures expanding to an expanded configuration to support a tubular or frustoconical porous filter mesh surface configured to capture particles that enter it. a railed expandable sheath defining a lumen therethrough and comprising two or more longitudinal rail structures coupled to a sheetlike member, the sheath having a collapsed configuration, wherein the sheath has a first cross sectional outer diameter and a first lumen inner diameter, and an expanded configuration, wherein the sheath has a second cross sectional outer diameter and a second lumen inner diameter; a proximal control assembly with an elongate obturator coupling member which is movable and positioned within the lumen; wherein the collapsed railed sheath is removably coupled to a distal obturator-jacket assembly; wherein the distal obturator-jacket assembly is coupled to the elongate obturator coupling member; the distal obturator jacket assembly having an atraumatic tip; wherein in the collapsed configuration, the sheath is configured to be advanced across at least a portion of the diseased vessel to a position adjacent the distal location without substantial size interference between the first cross sectional outer diameter of the sheath and an inner diameter profile of a lumen of the diseased vessel; and wherein upon positioning the collapsed configuration to the desired position relative to the distal location, the sheath is configured to be expanded to the expanded configuration, such expanded configuration having a diameter greater than said first inner lumen diameter, with incremental pushing of a device, longitudinally through the lumen; wherein the distal obturator jacket assembly is configured to assist in temporarily maintaining a collapsed configuration of a distal portion of the sheath; and wherein the two or more longitudinal rail structures are configured to self-expand upon removal of the distal obturator jacket assembly, the two more longitudinal rail structures expanding to an expanded configuration to support a tubular or frustoconical porous filter mesh surface configured to capture particles that enter it.