Diagnostic procedures are performed to help determine the source or cause of pain. These procedures generally involve introducing a needle at the location of a nerve which supplies a painful area and are usually performed under x-ray guidance to precisely locate the position of the probe or needle. These procedures or "blocks" attempt to briefly numb the nerves or structures thought to be involved in mediating the pain and are performed under local anesthesia. These procedures are most commonly used in the diagnosis of spine-related pain such as low back pain, thoracic or neck pain. The primary goal of diagnostic interventions is to decide if the particular area is involved in the generation of pain.