An effective blood vessel diameter at a deployment site within a blood vessel may be determined using a measurement apparatus that includes an inflatable balloon. The measurement apparatus may be advanced to the deployment site and the inflatable balloon may be inflated in order to temporarily reshape the blood vessel at the deployment site to a more circular cross-sectional profile. A measurement pertaining to the effective vessel diameter may be obtained while the inflatable balloon remains inflated. The measurement may be obtained using an ultrasound catheter. The measurement may be obtained using fluoroscopy, for example.