ThanQ Baker !
They did an MRI with a dye contrast. Reason Myelopathy (swollen area on cord). They MRI the middle and lower back. Lumbar 4 and 5 are the level of iliac (hip) crest. Sounds like S1 (Sacral or tail bone vertebra) transitioned to Lumbar ? Not familiar with that. Your cord ends and becomes horsetail of nerves near L2-3. Slightly prominent creeping vessels front and back to the far end of the Thoracic (middle section) to near end of Lumbar (lower back) - T9-L1. They think this is your spinal arteries. Similar to a previous MRI. Mild chronic height loss toward bottom of you Thoracic area. No bone fragments poking inward in that area. No evidence of fracture.
I am not a Dr., just anon that has had lots of MRI's and learned to understand some of their bullshit.
Do your own research, just like here ! Do not let this report scare you to death. Different Drs can look at the same MRIs and produce different reports. I don't know what kind of symptoms you are having. Ask lots of questions and make them explain it to you. Always get digital copies of your MRI's in case you end up with a different Dr./Hospital. Just take each word you don't understand and look it up. That will help you understand the situation better and be a better patient.
God Bless You Anon.