US Patent 7384400 Bone marrow biopsy needle

A biopsy needle for removal of tissue from a patient includes an outer tube having a distal end that has an inner diameter (IDtip) and an inner tube within the outer tube and having an inner diameter (IDsc), defined at the distalmost section of the inner tube. The needle also includes a snare having a first end connected to the inner tube and a second end coupled to the outer tube. The snare has a variable diameter that is controlled by rotation of the inner tube with respect to the outer tube in a prescribed direction resulting in the opening and closing, respectively, of the snare. A ratio (R) defined as (IDsc)/(IDtip) is greater than 1.