A catheter apparatus may have a flexible shaft, guidewire lumens passing through the shaft, and a positioning device for positioning the guidewires relative to an external lumen. The positioning device may be an expansible scaffold covered with a retractable sheath. The positioning device may also be one or more balloons that are inflated through an inflation port in the shaft. The catheter apparatus may be operated by inserting a guide catheter into a vasculature with a chronic total occlusion, inserting the catheter apparatus into the guide catheter, and advancing the guidewires through the guidewire lumens and into contact with a chronic total occlusion. The positioning device may be activated before and/or between attempts to pass the guidewires through the chronic total occlusion to interrogate various parts of the chronic total occlusion.