Doppler arteriography, with probes at the fingertips and arms, tests the force and "smoothness" of the blood flow through the radial arteries, with and without having the patient perform various arm maneuvers (which causes compression of the subclavian artery at the thoracic outlet). The movements can elicit symptoms of pain and numbness and produce graphs with diminished arterial blood flow to the fingertips, providing strong evidence of impingement of the subclavian artery at the thoracic outlet. Doppler arteriography does not utilize probes at the fingertips and arms, and in this case is likely being confused with plethysmography, which is a different method that utilizes ultrasound without direct visualization of the affected vessels. It should also be noted that Doppler ultrasound (not really 'arteriography') would not be used at the radial artery in order to make the diagnosis of TOS. Finally, even if a Doppler study of the appropriate artery were to be positive, it would not diagnose neurogenic TOS, by far the most common subtype of TOS. There is plenty of evidence in the medical literature to show that arterial compression does not equate to brachial plexus compression, although they may occur together, in varying degrees. Additionally, arterial compression by itself does not make the diagnosis of arterial TOS (the rarest form of TOS). Lesser degrees of arterial compression have been shown in normal individuals in various arm positions and are thought to be of little significance without the other criteria for arterial TOS.