Abstract: The present application concerns detecting catheter proximity to a blood-vessel wall and blood-vessel wall artifacts associated therewith. In one embodiment, a light source, in a catheter, can be used to project light into the blood vessel. An intensity associated with at least one light wavelength that interacted with blood can be measured. Based on the measured intensity, a determination can be made regarding blood-vessel wall artifacts due to the catheter tip proximity to a blood-vessel wall. Feedback can be provided to the clinician in order to assist the clinician in adjusting the catheter to optimize signal quality and minimize artifacts due to the blood-vessel wall.