An arterial or venous single-lumen vascular catheter for being inserted into a blood flow channel for injecting a bolus product as a fluid by venous or arterial pathway, including a tube with a hollow longitudinal body with a longitudinal axis, a given length and having a lumen with a given total surface area and a given radius R, the lumen extending all along the tube and for enabling the injection of a product given volume, according to a prescribed flow rate, the tube having symmetric lateral ports enabling exit of the volume radially to the tube, of an identical size, which are symmetrically disposed with respect to the longitudinal axis in the longitudinal body, only in proximity to and before a distal end of the tube along the direction of the longitudinal axis, and characterised in that: - an end surface located from the distal end of the tube along the direction of the longitudinal axis, reduces a total surface area of the lumen from the distal end of the tube, to an endoluminal frustoconical shape pierced with a central port, - the central port being configured to receive a guide, the central port being of the size of the guide and being only used to: place the guide and enable the distal end of the tube to be rinsed, the vascular catheter being referred to as a nearly closed-end catheter; - the central port having a fixed size which is not to be elastically deformed during the passage of the bolus, - the side ports of the catheter have a dimension calculated so that, according to a prescribed flow rate of a same fluid, the difference between: - a total hydraulic resistance calculated over the whole given length of the catheter, and - a reference total hydraulic resistance calculated with a reference catheter with an open end for being open when the channel is full, having at the end only a fluid outlet longitudinal port corresponding to the lumen, and a length equal to the given length, is lower than 5% of the reference total hydraulic resistance, - the lateral ports have a longitudinal dimension along the axis X, calculated so that a sum of the individual surface areas of the lateral ports is at least equal to the given total surface area of the lumen, - the lateral ports and the end surface area are arranged and sized so that at least 90% of the volume exits from the catheter through the lateral ports according to a fluid prescribed flow rate. - an end surface located from the distal end of the tube along the direction of the longitudinal axis, reduces a total surface area of the lumen from the distal end of the tube, to an endoluminal frustoconical shape pierced with a central port, - the central port being configured to receive a guide, the central port being of the size of the guide and being only used to: place the guide and enable the distal end of the tube to be rinsed, the vascular catheter being referred to as a nearly closed-end catheter; - the central port having a fixed size which is not to be elastically deformed during the passage of the bolus, - the side ports of the catheter have a dimension calculated so that, according to a prescribed flow rate of a same fluid, the difference between: - a total hydraulic resistance calculated over the whole given length of the catheter, and - a reference total hydraulic resistance calculated with a reference catheter with an open end for being open when the channel is full, having at the end only a fluid outlet longitudinal port corresponding to the lumen, and a length equal to the given length, is lower than 5% of the reference total hydraulic resistance, - the lateral ports have a longitudinal dimension along the axis X, calculated so that a sum of the individual surface areas of the lateral ports is at least equal to the given total surface area of the lumen, - the lateral ports and the end surface area are arranged and sized so that at least 90% of the volume exits from the catheter through the lateral ports according to a fluid prescribed flow rate.