a guide catheter having a balloon inflatable via a supply line for occluding the vessel and a device for delivering a liquid or gas to a vascular region to be recorded by an OCT imaging device, wherein the vascular region is located distally to the balloon;

an OCT catheter incorporated within the guide catheter with the OCT imaging device; and

a second inflatable balloon on the guide catheter spaced apart from the first balloon for occluding the vessel,

wherein at least a portion of the section of the guide catheter between the two balloons is transparent to an OCT radiation emittable by the OCT imaging device disposed inside the guide catheter and there is provided at least one pressure sensor for measuring the vascular pressure outside the vascular region occluded between the two balloons and there is provided at least one pressure sensor for measuring the vascular pressure inside the vascular region occluded between the two balloons, and there is provided a closed-loop control device via which the pressure in the occluded vascular region is controllable as a function of the pressure obtained outside the vascular regions.