Abstract: An intravascular sensor device can be used to guide treatment of a diseased blood vessel in the body of a patient. In some examples, the intravascular sensor device includes a pressure sensor and an ultrasound transducer. The intravascular sensor device is used to measure a pressure within the diseased blood vessel and acquire an ultrasound image of the diseased blood vessel. The pressure may be measured during hyperemic blood flow that is caused by a pharmacologic vasodilator drug. The measured pressure can be used to calculate a fractional flow reserve value. The ultrasound image can be used to determine a physical dimension of the blood vessel, such as cross-sectional area. The fractional flow reserve value and physical dimensions of the blood vessel can be used to optimize patient treatment.