This is a really nice example.
I have seen this several times before and the first time I observed it was the first time I really understood the anatomy of the rotator cuff cable.
The rotator cuss cable is layer 4 of the supraspinatus tendon and is a reflection of the coracohumeral ligament deep to the supraspinatus tendon which then attaches to the joint capsule (layer 5)
In this case the cable anatomy (coracohumeral ligament) has a natural enhancement making it echogenic and really easy to see.
The crystal deposition here will be CPPD as this likes to walk along ligamentous structures whereas hydroxyapatite prefers to aggregate in one 2 and zone 3 of the supraspinatus tendon as it is a bone salt and migrates from the enthesis into the tendon. I will attach a simple diagram of the 5 layers of supraspinatus.
1: coracohumeral ligament
2: supraspinatus collagen heading directly to the enthesis
3: supraspinatus collagen with an oblique interdigitation with the infraspinatus collagen
4: rotator cuff cable made from a reflection of the coracohumeral ligament
5: GH joint capsule
So your patient has CPPD or pseudo gout as it is also known.
Great example, and now you know exactly the shape and position of the mysterious rotator cuff cable!