Whole-body low-dose CT has replaced the skeletal survey: count lytic lesions ≥ 5 mm, look for fractures at risk and extramedullary disease; whole-body MRI finds focal marrow lesions (> 1 lesion ≥ 5 mm) that define disease needing treatment.
Orient first
- IMWG: ≥ 1 osteolytic lesion on CT (≥ 5 mm) or > 1 focal lesion on MRI (≥ 5 mm) is a myeloma-defining event (verify).
- Diffuse marrow infiltration can be invisible on CT.
- Pathological fractures of the spine and long bones — the report flags lesions at risk.
Acquire the study
- Whole-body low-dose CT, bone window, sagittal spine reformats.
The manoeuvre
- Bone window: count lytic lesions ≥ 5 mm; largest size in mm.
- Cortical destruction in long bones (fracture risk — Mirels score if applicable).
- Vertebral fractures and retropulsion on sagittal reformats.
- Extramedullary soft-tissue masses.
What confirms it
- Lytic or focal lesions meeting IMWG criteria with clonal plasma cells.
What licenses you to exclude it
- A normal whole-body MRI makes bone disease unlikely.
The classic misread
- Calling osteoporotic mottling in the elderly lytic lesions.