The main differences between a PICC line and a midline are the length of the lines and the duration the catheters can stay in the vein (referred to as "dwell time"). A midline is three to eight inches long and the tip lies in the upper arm ending before the shoulder. This type of catheter is generally used for therapies lasting two to four weeks such as antibiotic therapy. A PICC (peripherally inserted central catheter) is also inserted in the upper arm but its tip goes past the shoulder and stops just outside the heart. The dwell time for a PICC is longer than the dwell time for a midline. PICCs can stay in the patient for a year or more, as long as there are no complications with the insertion site or the catheter. A PICC line requires a chest X-ray after insertion to make sure that the tip is in the correct place. PICCs are commonly used for TPN (total parenteral nutrition), chemotherapy, and any other therapies lasting longer than four weeks.