A needle guide device (20/320) configured for releasable mounting on an imaging transducer or on an adaptor on an imaging transducer, the needle guide device comprising: a needle guide assembly (122/322) for retaining a needle at a desired trajectory with respect to the imaging transducer, wherein the needle guide assembly (122/322) comprises: a planar body member (44/304), a needle holder subassembly (46/346) that includes a needle holder (74/374), and a slide member (48/348), wherein the needle holder subassembly (46/346) is pivotally and adjustably mounted on the planar body member (44/304) to enable the needle holder (74/374) to be oriented to various selected orientations with respect to the planar body member (44/304) to establish various angled trajectories for the needle holder (74/374), and wherein the slide member (48/348) is slidable along a plane of the planar body member (44/304) and coupled to the needle holder subassembly (46/346) to cause the needle holder subassembly (46/346) to pivot with respect to the plane of the planar body member (44/304) to a first angular orientation when the slide member (48/348) is moved to a first position, and to pivot the needle holder subassembly (46/346) with respect to the plane of the planar body member (44/304) to a second angular orientation when the slide member (48/348) is moved to a second position. a needle guide assembly (122/322) for retaining a needle at a desired trajectory with respect to the imaging transducer, wherein the needle guide assembly (122/322) comprises: a planar body member (44/304), a needle holder subassembly (46/346) that includes a needle holder (74/374), and a slide member (48/348), wherein the needle holder subassembly (46/346) is pivotally and adjustably mounted on the planar body member (44/304) to enable the needle holder (74/374) to be oriented to various selected orientations with respect to the planar body member (44/304) to establish various angled trajectories for the needle holder (74/374), and wherein the slide member (48/348) is slidable along a plane of the planar body member (44/304) and coupled to the needle holder subassembly (46/346) to cause the needle holder subassembly (46/346) to pivot with respect to the plane of the planar body member (44/304) to a first angular orientation when the slide member (48/348) is moved to a first position, and to pivot the needle holder subassembly (46/346) with respect to the plane of the planar body member (44/304) to a second angular orientation when the slide member (48/348) is moved to a second position. a planar body member (44/304), a needle holder subassembly (46/346) that includes a needle holder (74/374), and a slide member (48/348), wherein the needle holder subassembly (46/346) is pivotally and adjustably mounted on the planar body member (44/304) to enable the needle holder (74/374) to be oriented to various selected orientations with respect to the planar body member (44/304) to establish various angled trajectories for the needle holder (74/374), and wherein the slide member (48/348) is slidable along a plane of the planar body member (44/304) and coupled to the needle holder subassembly (46/346) to cause the needle holder subassembly (46/346) to pivot with respect to the plane of the planar body member (44/304) to a first angular orientation when the slide member (48/348) is moved to a first position, and to pivot the needle holder subassembly (46/346) with respect to the plane of the planar body member (44/304) to a second angular orientation when the slide member (48/348) is moved to a second position.