A method to assist an operator of an interactive measurement system for determining flow related parameters based upon physiological signals obtained by a measurement unit that comprises a catheter adapted to be inserted into a vessel inside a body of a human or an animal, a wire adapted to be inserted into the catheter and provided with a temperature sensor at its distal end, and a computer means adapted to receive and store detected temperature signals received from said sensor and said wire. The system further comprises a graphical user interface on a display screen connected to said computer means, wherein the method comprises the steps of: determine if a valid activation command is received from the operator, and upon receipt of a valid activation command activate a continuous analysis of detected temperature signals, display on said graphical user interface an operator instruction in an instruction window instructing the operator to perform steps in a measurement procedure to obtain said flow related parameters, detect steps performed by the operator during the measurement procedure and display on said user interface the current status of said performed steps, display on said user interface, in real-time, temperature curves related to the measurement procedure, determine at least one flow related parameter based upon the temperature measurements obtained during said measurement procedure, display on said user interface said at least one determined flow related parameter.