I am really only keen to scan for arterial TOS with ultrasound.
My technique is simple. Scan the affected subclavian artery from its origin to the axillary artery.
Follow it medially to where it disappears under the medial head of the clavicle. At this level scan the subclavian artery in long axis with the colour Doppler going and watch the flow in the vessel. Then ask the patient to slowly raise their arm into a stop sign position looking for compression of the vessel and associated high velocity jet or occlusion of the vessel.
Then ask the patient to raise the arm further checking for the same.
Then back to stop sign and pull the elbow / humerus posteriorly (this is the Adsons provocative test) Some normal volunteers will get compression / occlusion during a strong Adsons test but people with symptomatic arterial TOS usually stenos tightly or occlude even with just a simple passive stop sign position.