Various portable systems, devices and methods for imaging or visualizing blood vessels or other body tissue to facilitate accurate placement of a needle or other elongate instrument in blood vessels or other body tissue are described herein. In certain variations an imaging system for aiding needle insertion in a patient may include a mountable unit having an illumination source, an image sensor, and a display for displaying an image based on image information from the image sensor. The mountable unit may be configured for attachment to a hand of a user such that the users hand on which the unit is mounted remains free to hold an object. The display may be positioned next to a needle insertion site during needle insertion by the user such that the needle insertion site and an image of the blood vessel and/or needle are simultaneously within the users field of view.
