A needle guide device (20/320) configured for releasable mounting on an imaging transducer or on an adaptor on an imaging transducer, the imaging transducer or the adaptor including a coupling member (16/316) comprising a rectangular portion (16A/316A) projecting outwardly from the imaging transducer or the adapter, wherein the rectangular portion includes first and second undercut recesses (16B/316B and 16B/316C) on opposing sides of the rectangular portion (16A/316A), said needle guide device (20/320) comprising: a lockable mounting assembly (24/324); and a needle guide assembly (122/322) coupled to the lockable mounting member (24/324) to retain a needle at a desired trajectory with respect to the imaging transducer, wherein said needle guide assembly (122/322) comprises: a body member (44/304), and a needle holder (46/346), said body member (44/304) comprising a recess (64/302) for receiving the coupling member (16/316) therein, wherein the recess comprises a stop portion (64/306) configured to engage the first undercut recess (16B/316B) in the coupling member (16/316) when the needle guide device (20/320) is locked to the imaging transducer or the adaptor ; wherein said lockable mounting assembly (24/324) comprises: a slidable member (24/310) having an engagement portion (36/310A) configured to engage the second undercut recess (16B/316C) when the needle guide device is locked to the imaging transducer or the adaptor, said lockable mounting assembly (24/324) being configured to be slidably coupled to said body member (44/304) and slidable from an unlocked position to a locked position and vice versa, such that when moved from the unlocked position to the locked position, the stop portion (64/306) of the body member (44/304) engages the first undercut recess (16B/316B) and the engagement portion (36/310A) of the slidable member (24/310) engages the second undercut portion (16B/316C) to clampingly secure the needle guide device (20/320) to the coupling member (16/316). a lockable mounting assembly (24/324); and a needle guide assembly (122/322) coupled to the lockable mounting member (24/324) to retain a needle at a desired trajectory with respect to the imaging transducer, wherein said needle guide assembly (122/322) comprises: a body member (44/304), and a needle holder (46/346), said body member (44/304) comprising a recess (64/302) for receiving the coupling member (16/316) therein, wherein the recess comprises a stop portion (64/306) configured to engage the first undercut recess (16B/316B) in the coupling member (16/316) when the needle guide device (20/320) is locked to the imaging transducer or the adaptor ; a body member (44/304), and a needle holder (46/346), said body member (44/304) comprising a recess (64/302) for receiving the coupling member (16/316) therein, wherein the recess comprises a stop portion (64/306) configured to engage the first undercut recess (16B/316B) in the coupling member (16/316) when the needle guide device (20/320) is locked to the imaging transducer or the adaptor ; wherein said lockable mounting assembly (24/324) comprises: a slidable member (24/310) having an engagement portion (36/310A) configured to engage the second undercut recess (16B/316C) when the needle guide device is locked to the imaging transducer or the adaptor, said lockable mounting assembly (24/324) being configured to be slidably coupled to said body member (44/304) and slidable from an unlocked position to a locked position and vice versa, such that when moved from the unlocked position to the locked position, the stop portion (64/306) of the body member (44/304) engages the first undercut recess (16B/316B) and the engagement portion (36/310A) of the slidable member (24/310) engages the second undercut portion (16B/316C) to clampingly secure the needle guide device (20/320) to the coupling member (16/316). <EOS>