Radiation-induced MRI signal changes in bone are the earliest detectable changes in bone. They increase with increase in the radiation dose.
- 1st week: decreased marrow cellularity with oedema and haemorrhage
- 2nd week: increased marrow cellularity due to influx from unirradiated areas
- 1-3 months: marrow sinusoids and cellularity is decreased
- after 6 months: regenration of hematopoetic tissue and sinusoids
Little changes in signal intensity during first 3 weeks of radiation therapy on spin echo sequences. STIR shows increased signal intensity during this period .
After 3 weeks heterogenous mottled appearance of marrow is seen.
During 3-6 weeks marrow cellularity is replaced by central fat predominantly surrounding the basivertebral veins.
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