A medical imaging system for conducting an image-guided medical procedure on a subject, the system comprising: a medical imaging apparatus for obtaining volumetric images of the subject; means for planning an interventional procedure on a subject using the volumetric images; a mechanical arm assembly disposed in proximity to the medical imaging apparatus, the mechanical arm assembly comprising a base support, a distal end, a plurality of arm segments (50, 54, 58, 62), and a plurality of joints (48, 52, 58, 60, 64) between the arm segments (50, 54, 58, 62) for carrying out the interventional procedure; and an end-effector disposed at the distal end of the mechanical arm assembly, the end-effector comprising gripping means for selectively gripping and releasing a surgical instrument during the interventional procedure,wherein the end-effector further comprises: a first finger portion having a first gripping surface; a second finger portion having a second gripping surface, the first and second gripping surfaces (104, 106) being opposed to one another for applying a gripping force to the surgical instrument; characterized in that the end-effector further comprises: a first surgical instrument guide removeably fastened to the first finger portion and extending perpendicularly to the first gripping surface; and a second surgical instrument guide removeably fastened to the second finger portion and extending perpendicularly to the second gripping surface, wherein the first and the second surgical instrument guides (110, 112) provide stability to the surgical instrument. a medical imaging apparatus for obtaining volumetric images of the subject; means for planning an interventional procedure on a subject using the volumetric images; a mechanical arm assembly disposed in proximity to the medical imaging apparatus, the mechanical arm assembly comprising a base support, a distal end, a plurality of arm segments (50, 54, 58, 62), and a plurality of joints (48, 52, 58, 60, 64) between the arm segments (50, 54, 58, 62) for carrying out the interventional procedure; and an end-effector disposed at the distal end of the mechanical arm assembly, the end-effector comprising gripping means for selectively gripping and releasing a surgical instrument during the interventional procedure,wherein the end-effector further comprises: a first finger portion having a first gripping surface; a second finger portion having a second gripping surface, the first and second gripping surfaces (104, 106) being opposed to one another for applying a gripping force to the surgical instrument; characterized in that the end-effector further comprises: a first surgical instrument guide removeably fastened to the first finger portion and extending perpendicularly to the first gripping surface; and a second surgical instrument guide removeably fastened to the second finger portion and extending perpendicularly to the second gripping surface, wherein the first and the second surgical instrument guides (110, 112) provide stability to the surgical instrument. a first finger portion having a first gripping surface; a second finger portion having a second gripping surface, the first and second gripping surfaces (104, 106) being opposed to one another for applying a gripping force to the surgical instrument; characterized in that the end-effector further comprises: a first surgical instrument guide removeably fastened to the first finger portion and extending perpendicularly to the first gripping surface; and a second surgical instrument guide removeably fastened to the second finger portion and extending perpendicularly to the second gripping surface, wherein the first and the second surgical instrument guides (110, 112) provide stability to the surgical instrument.