Systems and methods for assisting the placement of a catheter within the body of a patient through the use of an ultrasound imaging system are disclosed. In particular, the systems and methods described herein enable a clinician to determine, prior to insertion of the medical device, how much of the device will be disposed within the vessel, thus enabling the clinician to choose a catheter with suitable length. In one embodiment, an ultrasound imaging system for assisting with placement of the medical device comprises a console, a probe for producing an image of a target location, and a processor. The processor provides to a user proximity information relating to the anticipated proximity of the medical device to the target location prior to insertion of the medical device. A display is included for depicting the image, target location depth, and the proximity information of the medical device to the target location.