A catheter assembly for sensing the temperature of an arterial wall or other body lumen includes a blood-flow-occluding feature to increase the accuracy of the temperature measurements. In addition to the flow-occluding feature, the catheter includes a distal end with a temperature sensing structure and a proximal end including a manually operated expansion control. The temperature sensing structure including one or more presentation elements in the form of a basket or braided structure having at least one temperature sensor supported thereon, each sensor being operative to generate an electrical signal indicative of temperature. The presentation elements are physically coupled to the manually operated expansion control, such that operation of the control causes the structure to move between a collapsed state, enabling the temperature sensing structure to be positioned in a section of the vessel to be measured, and an expanded state, wherein the sensor is in contact with, or immediately proximate to, the vessel wall.