A guidance system for guiding an intervention device such as a needle to a target location such as a vessel while remaining within a field of view of an imaging device such as an ultrasound. The guidance system may include an attachment mechanism for removable attachment to a specific ultrasound probe or which is adaptable to multiple different probes. A guidance mechanism may extend outwardly from the attachment mechanism for guiding the angle and depth of the intervention device. The guidance mechanism may include a plurality of openings through which the intervention device may be selectively inserted, with each opening being configured for a different angle and/or depth. Alternatively, the guidance mechanism may include a single opening that is adjustable along an arcuate path. A release mechanism may be included to allow the intervention device to be safely removed from the guidance mechanism without undue movement of the intervention device.