An elongate probe comprising: a probe head including a transducer array; a shaft; a handle affixed to the shaft; an articulating member located between the probe head and the shaft, the articulating member being configured to articulate between a position in which the probe head extends along a longitudinal axis of the probe and at least one articulated position in which the probe head extends at a non-zero angle from the longitudinal axis of the probe; and a stiffener (224; 602) configured to controllably move from a retracted position to an extended position at which the stiffener (224; 602) inhibits articulation of the articulating member, the stiffener including an elongate rod (302; 602); characterized in that the probe head further includes: an elongate channel; and a pre-loaded elastic device, which is affixed to one end of the elongate rod and which holds the elongate rod in the elongate channel in the retracted position, where it does not inhibit articulation of the articulating member; and in that the probe further comprises: an element affixed to the other end of the elongate rod and extending through the articulating member, the shaft and the handle, the element being configured to be moved in a direction from the probe head towards the handle, thereby pulling the elongate rod into the articulating member into the extended position against the pre-loading of the pre-loaded elastic device thereby inhibiting articulation of the articulating member. a probe head including a transducer array; a shaft; a handle affixed to the shaft; an articulating member located between the probe head and the shaft, the articulating member being configured to articulate between a position in which the probe head extends along a longitudinal axis of the probe and at least one articulated position in which the probe head extends at a non-zero angle from the longitudinal axis of the probe; and a stiffener (224; 602) configured to controllably move from a retracted position to an extended position at which the stiffener (224; 602) inhibits articulation of the articulating member, the stiffener including an elongate rod (302; 602); characterized in that the probe head further includes: an elongate channel; and a pre-loaded elastic device, which is affixed to one end of the elongate rod and which holds the elongate rod in the elongate channel in the retracted position, where it does not inhibit articulation of the articulating member; and in that the probe further comprises: an element affixed to the other end of the elongate rod and extending through the articulating member, the shaft and the handle, the element being configured to be moved in a direction from the probe head towards the handle, thereby pulling the elongate rod into the articulating member into the extended position against the pre-loading of the pre-loaded elastic device thereby inhibiting articulation of the articulating member. a stiffener (224; 602) configured to controllably move from a retracted position to an extended position at which the stiffener (224; 602) inhibits articulation of the articulating member, the stiffener including an elongate rod (302; 602); characterized in that the probe head further includes: an elongate channel; and a pre-loaded elastic device, which is affixed to one end of the elongate rod and which holds the elongate rod in the elongate channel in the retracted position, where it does not inhibit articulation of the articulating member; and in that the probe further comprises: an element affixed to the other end of the elongate rod and extending through the articulating member, the shaft and the handle, the element being configured to be moved in a direction from the probe head towards the handle, thereby pulling the elongate rod into the articulating member into the extended position against the pre-loading of the pre-loaded elastic device thereby inhibiting articulation of the articulating member. an elongate channel; and a pre-loaded elastic device, which is affixed to one end of the elongate rod and which holds the elongate rod in the elongate channel in the retracted position, where it does not inhibit articulation of the articulating member; and in that the probe further comprises: an element affixed to the other end of the elongate rod and extending through the articulating member, the shaft and the handle, the element being configured to be moved in a direction from the probe head towards the handle, thereby pulling the elongate rod into the articulating member into the extended position against the pre-loading of the pre-loaded elastic device thereby inhibiting articulation of the articulating member.