MRI Radiation Spine
What happens to vertebral body signal post radiation and how to spot a post radiation spine and tumour recurrence easily .
What Happens: The effect of radiation on the spine is cell death of both tumour and normal marrow. And over time the dead cells are replaced with fat.
What Does it look like: When we image the spine post radiation, because the marrow has become fatty replaced, its fairly uniformly bright on T1 sequences. We see two things on MRI
- Diffuse increase in T1 fatty signal in the area that has been irradiated.
- Straight Lines. Because the radiation beam has defined, sharp margins it produces straight lines at the bottom and top of the radiation field. Between the lines the marrow has been radiated and there is fatty replacement, above and below the lines where there hasnt been radiation, there is normal marrow. As a rule, nature doesn’t like straight lines, so when you see a sharp straight demarcation in signal, with fatty marrow on one side and normal marrow signal on the other, you should be suspicious that the patient has had radiation.
What happens when there is recurrence of tumour post radiation?
- When you have replacement of radiated marrow with tumour it becomes easy to see. The radiated marrow is bright T1 fatty signal, however the new tumour infiltration is low T1 signal so it stands out.