Ultrasound devices and guidance systems for ultrasound devices for subdermal devices (e.g., needles) used in conjunction with the ultrasound devices are described. The guidance systems can include features for easy release of a device from the system following targeting to a subdermal site. A guidance system can be ambidextrous such that a needle can be released by use of either the left or right hand and by use of either a thumb or a finger of an operator. Embodiments that include guidance tracks and slidable guidance cartridges that grasp the hub of a subdermal device are also described.
