A side-fire ultrasonic probe includes an alignment feature that, when used to connect the probe with a needle guide for intra-cavity medical procedures, enables alignment of a needle in an imaging plane of an ultrasonic transducer. The alignment feature is configured such that alignment of the needle within the imaging plane is accomplished when a protective sheath is disposed between the alignment feature and the needle guide. This configuration can be used with high frequency ultrasonic arrays having frequency distributions centered at about 20 MHz, and for medical procedures, such as biopsying organs or other bodily intra-cavity structures, and delivering intra-cavity therapies.
