Patent ID: 7364567

Claim:
A method of detecting tissue contact and a needle penetration depth of a needle used internally to deliver a therapeutic agent to a patient comprising: dispensing a measured amount of therapeutic agent through a lumen of a needle and from a second end of the needle to a first end of the needle at a predetermined flow rate, wherein the second end of the needle is connected to a pressure measurement assembly; measuring a pressure of the therapeutic agent in the needle wherein measuring the pressure includes; measuring a first change in pressure by measuring a change in the flow rate of the therapeutic agent dispensed through the lumen of the needle when the first end of the needle contacts a tissue and the first end of the needle becomes occluded; and measuring a second change in pressure when the needle penetrates the tissue further and when a first aperture located a predetermined distance from the first end of the needle becomes occluded by measuring another change in the flow rate of the therapeutic agent dispensed through the lumen of the needle, wherein said predetermined distance is used to specify a depth of the needle.