1. A grid adapted to be arranged on a patient's skin to provide positioning information in a medical imaging procedure, comprising: a) a frame comprising a top and bottom surface and a central opening; and b) hydrogel strips comprising a hydrogel layer formed from a mixture of a hydrogel and a contrast agent, the hydrogel strips attaching to opposite sides of the frame and extending across the central opening, wherein the hydrogel strips are flexibly movable or removable so as to permit a technician to move a strip to a side, when the frame is attached to a patient, so that an area underneath the strip may be accessed.