A guidance system utilizes ultrasound imaging or other suitable imaging technology. In one embodiment, the guidance system includes an imaging device including a probe for producing an image of an internal body portion target, such as a vessel. One or more sensors may be associated with the probe. The system may include a medical device, such as a needle, separate from the probe, the medical device having a magnetic field associated therewith. The system may include a processor that uses data relating to the magnetic field sensed by the one or more sensors to determine a position and/or orientation of the medical device. The system may also include a display that shows an image of the internal body portion target taken by the ultrasound imaging probe and a depiction of the medical device positioned and/or oriented with respect to the image.
