A fiducial deployment system comprising: a first handle member attached to an elongate outer sheath, the outer sheath including a sheath lumen longitudinally disposed therethrough; a second handle member disposed longitudinally slidably along the first handle member, the second handle member attached to an elongate needle disposed longitudinally slidably through the sheath lumen, wherein the needle includes a needle lumen disposed longitudinally therethrough; a stylet disposed longitudinally slidably through the needle lumen; and an advancement mechanism configured to attach to a proximal portion of the second handle and to the stylet in a manner configured for effecting longitudinal movement of one of the stylet and the needle relative to the other of the stylet and the needle by predetermined increments: further comprising at least one fiducial; wherein the needle includes a tubular cannula body defining the needle lumen and a distal needle end region, the distal end region comprising a distal needle end opening at a distal end of the needle lumen; characterised by at least one generally longitudinal needle slot extending radially through at least a thickness portion of the cannula body and open to the needle lumen, where the needle slot includes at least one detent; wherein the at least one fiducial comprises a generally columnar body including a central fiducial portion slidably disposed in the needle lumen; and at least one side protuberance projecting into the needle slot; and wherein the stylet is configured to advance the at least one fiducial past the detent and out of the distal needle end opening. a first handle member attached to an elongate outer sheath, the outer sheath including a sheath lumen longitudinally disposed therethrough; a second handle member disposed longitudinally slidably along the first handle member, the second handle member attached to an elongate needle disposed longitudinally slidably through the sheath lumen, wherein the needle includes a needle lumen disposed longitudinally therethrough; a stylet disposed longitudinally slidably through the needle lumen; and an advancement mechanism configured to attach to a proximal portion of the second handle and to the stylet in a manner configured for effecting longitudinal movement of one of the stylet and the needle relative to the other of the stylet and the needle by predetermined increments: further comprising at least one fiducial; wherein the needle includes a tubular cannula body defining the needle lumen and a distal needle end region, the distal end region comprising a distal needle end opening at a distal end of the needle lumen; characterised by at least one generally longitudinal needle slot extending radially through at least a thickness portion of the cannula body and open to the needle lumen, where the needle slot includes at least one detent; wherein the at least one fiducial comprises a generally columnar body including a central fiducial portion slidably disposed in the needle lumen; and at least one side protuberance projecting into the needle slot; and wherein the stylet is configured to advance the at least one fiducial past the detent and out of the distal needle end opening. further comprising at least one fiducial; wherein the needle includes a tubular cannula body defining the needle lumen and a distal needle end region, the distal end region comprising a distal needle end opening at a distal end of the needle lumen; characterised by at least one generally longitudinal needle slot extending radially through at least a thickness portion of the cannula body and open to the needle lumen, where the needle slot includes at least one detent; wherein the at least one fiducial comprises a generally columnar body including a central fiducial portion slidably disposed in the needle lumen; and at least one side protuberance projecting into the needle slot; and wherein the stylet is configured to advance the at least one fiducial past the detent and out of the distal needle end opening.