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Postirradiation Vertebral Marrow
KEY FACTS
Terminology
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Transformation of cellular vertebral marrow into fatty marrow following therapeutic irradiation
Imaging
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Sharp demarcation between irradiated and untreated marrow (margins of radiation port)
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Corresponds to site of irradiation and extent of radiation field
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Marrow signal intensity within radiotherapy portal similar to subcutaneous fat on T1WI
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May demonstrate associated compression fractures
Top Differential Diagnoses
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Normal fatty marrow
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Vertebral hemangioma
Pathology
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Marrow changes on MR dependent on radiation dose, fractionation, and time elapsed after treatment
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Complications include osteopenia, osteoporotic compression fracture, osteonecrosis, residual/recurrent metastases, and postradiation myelitis
Clinical Issues
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Usually asymptomatic
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Development or worsening of pain and neurologic complaints worrisome for radiation necrosis, insufficiency fracture, or tumor recurrence or progression
Diagnostic Checklist
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Homogeneous fatty marrow sharply delineated from untreated vertebral marrow diagnostic of postirradiation change
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MR is modality of choice for marrow imaging
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T2WI FS MR or STIR and T1WI C+ FS MR to evaluate for residual or recurrent marrow disease
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Sagittal T1WI (for metastatic intracranial glioblastoma with “drop metastases”) shows typical postradiation “bright” fatty marrow conversion following whole-spine radiation
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Sagittal T2WI in the same case again demonstrates diffuse postradiation fatty marrow replacement with uniformly “bright” vertebral bodies
. Multiple metastatic nodules can be seen within the cauda equina
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. Multiple metastatic nodules can be seen within the cauda equina .
TERMINOLOGY
Definitions
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Transformation of cellular vertebral marrow into fatty marrow following therapeutic irradiation
IMAGING
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