In radiology, venous access generally refers to central venous access, which is the insertion of a specially made thin, flexible tube, known as a catheter, into a central vein. The central veins are the large veins within the chest and abdomen.

With a catheter in place, treatments such as chemotherapy or antibiotics can be given through the catheter over a period of time without the need for repeated injections. A catheter can also be used when regular blood samples need to be taken for blood transfusions and other medical conditions that need access to a vein over days, weeks or months.