Methods and apparatuses for positioning within an internal channel
Methods and apparatuses for positioning medical devices onto (or close to) a desired portion of the interior wall of an internal channel, such as for scan imaging, for photodynamic therapy and/or for optical temperature measurement. In one embodiment, a catheter assembly has a distal portion that can be changed from a configuration suitable for traversing the internal channel to another configuration suitable for scan at least a spiral section of the interior wall of an internal channel, such as an artery. In one example, the distal portion spirals into gentle contact with (or close to) a spiral section of the artery wall for Optical Coherence Tomography (OCT) scanning. The spiral radius may be changed through the use of a guidewire, a tendon, a spiral balloon, a tube, or other ways.
1. A method to operate an assembly, the method comprising:
selecting, based on a known radius of a blood vessel, the assembly having a pre-shaped spiral radius wherein a pitch length of spirals is less than ten times the radius of the vessel;
inserting a distal portion of the assembly into the blood vessel, the distal portion of the assembly having a sheath housing a core capable of at least one of: projecting a light onto a portion of the vessel and receiving a light from a portion of the vessel;
operating at a proximal portion of the assembly to expand the spiral radius having a plurality of spirals of the sheath in the vessel; and
optically imaging the portion of the vessel with the core while the core moves through the spirals.
2. The method of claim 1 , wherein said operating comprises:
moving a portion of a guidewire out of the distal portion of the assembly, the portion of the guidewire being substantially straight, the distal portion of the assembly being pre-shaped into spirals in absence of the portion of the guidewire.
3. The method of claim 2 , further comprising:
inserting the portion of the guidewire into the distal portion of the assembly to temporarily straighten the distal portion; and
repositioning the distal portion in the vessel while the guidewire is straightened.
4. The method of claim 2 , further comprising:
moving the portion of the guidewire out of the distal portion of the assembly to allow the distal portion to recover back to a substantially straight shape; and
repositioning the distal portion in the vessel while the guidewire is in the substantially straight shape.
5. A method of scanning a vessel wall of a blood vessel, comprising:
selecting, based on a known radius of the blood vessel, an assembly having a pre-shaped spiral radius wherein a pitch length of spirals is less than ten times the radius of the vessel;
slidably displacing a core in a longitudinally extending spiral pattern having a plurality of spirals within an inner surface of the vessel wall, the core being capable of at least one of projecting and receiving light; and
optically imaging the portion of the vessel with the core while the core moves through the spirals.
6. The method of claim 5 , further comprising:
imaging the inner surface of the vessel wall for the presence of a diseased region;
wherein the core is slidable along a spiral member having an orthogonal distance between adjacent spiral loops which is shorter than a minimum length of diseased regions to be detected plus two times an effective imaging depth of the core.
7. A method of scanning a vessel wall of a blood vessel, comprising:
selecting, based on a known radius of the blood vessel, an assembly having a pre-shaped spiral radius wherein a pitch length of spirals is less than ten times the radius of the vessel;
slidably displacing a core in a longitudinally extending spiral pattern of a sheath having a plurality of spirals within an inner surface of the vessel wall, the core being capable of at least one of projecting and receiving light; and
imaging the inner surface of the vessel wall for the presence of a diseased region while the core slides along the spiral pattern.