An ultrasonic imaging system includes an imaging catheter and an imaging apparatus. The imaging catheter has an insert for being inserted into a blood vessel, a transducer disposed in the insert, and at least one temperature sensor disposed in the insert. The temperature sensor measures the intravascular temperature in a radial direction of the blood vessel and rotates to measure an intravascular temperature distribution in a transverse cross section of the blood vessel. The diagnostic imaging apparatus has an ultrasonic signal receiver for receiving an ultrasonic signal measured by the transducer, a temperature signal receiver for receiving an intravascular temperature signal measured by the temperature sensor, and an image constructing unit for constructing an image to be displayed from a tomographic vascular image generated from the ultrasonic signal and intravascular temperature information generated from the intravascular temperature signal, in relation to positional information of the ultrasonic signal and the intravascular temperature signal.