A system for injection of a fluid into a body includes: a source of a first fluid, a source of a second fluid; the first fluid being less toxic than the second fluid; at least one pressurizing system in operative connection with the source of the first fluid and with the source of the second fluid; at least one controller in operative connection with the pressurizing system; and at least a first sensor in communicative connection with the controller. The first sensor is adapted to transmit a signal of a detected change in fluid level in tissue indicative of extravasation to the controller. The controller is adapted to cause injection of the first fluid into the body to determine if extravasation of the first fluid occurs using the sensor in an administration phase before injection of the second fluid.