Image guided catheters and method of use

An interventional medical device is provided that incorporates a forward-directed ultrasound or optical coherence tomography imaging system that is replaceable depending on how close the device is to the target site for a given medical procedure, the device and system integrated into a single minimally invasive device comprising a first probe housing, needle guide assembly and sheath, a sleeve lock for closing a normally open needle channel of a needle guide of the first distal assembly and a second probe and cable housing assembly locked to the first distal probe housing, needle guide assembly and sheath by a locking tab. The probe and cable housing assembly may comprise a linear phased ultrasound array and an accelerometer for orienting an image produced by the device with the gravitational field of the earth. The medical device can be in the form of an image guided catheter or probe, used in a body orifice, externally on skin tissue or subcutaneously. The device comprises a replaceable and reusable ultrasound imaging assembly (and or OCT assembly) and replaceable interventional devices such as a removable introducer needle, hollow biopsy needle, syringe or other medical instrument. The imaging system may comprise one or more small ultrasound or OCT imaging systems that can be replaceably integrated into the device by replacing the reusable second probe and cable housing assembly.