An apparatus for carrying out diagnostic and/or therapeutic procedures and/or diagnosis, said apparatus comprising a hollow tubular catheter for insertion into the venous or arterial system or other body cavity of a patient, said catheter having a tip, an imaging device being associated with the tip of the catheter, said imaging device being adapted to provide an image of the tissue ahead of and lateral to the catheter tip, wherein the imaging device is provided at a distal end of an elongate guide member guided within a guide passage to be axially translatable within the guide passage, a portion of the guide passage at or adjacent the tip of the catheter extending in a substantially helical and/or circumferential configuration around a distal region of the catheter whereby the imaging device can be reciprocated around the tip of the catheter to produce a toroidal or substantially toroidal image of the tissue immediately around and ahead of the catheter tip.
