If you or someone you love has just been told there is a suspicion of multiple myeloma, the imaging question comes up quickly. For most of the last thirty years the answer was a skeletal survey - a set of 12 to 20 plain X-rays of the skull, spine, ribs, pelvis and long bones, looking for the punched-out lytic lesions that myeloma leaves in bone. That is no longer the right answer, and it has not been for some time.
Modern UK guidance from NICE and the International Myeloma Working Group (IMWG) now recommends whole-body MRI, or low-dose whole-body CT, as first-line imaging at diagnosis. This piece explains why - and what a proper myeloma MRI actually looks like, from the protocol on the scanner to the sentence at the end of the report that determines whether you need treatment.
The one-line answer
Whole-body MRI sees myeloma inside the bone marrow before the bone itself breaks. A skeletal survey only sees the damage after roughly 30 per cent of a bone has been eaten away. That is the whole reason the guidelines changed.
Skeletal survey vs whole-body MRI vs low-dose CT
All three are still done somewhere in the UK, and it helps to know which one you are actually being offered. The short version: MRI is the most sensitive, low-dose CT is the fastest and best at showing bone destruction, and skeletal survey is the least sensitive of the three and no longer recommended at baseline.
| Imaging test | What it sees | Sensitivity for myeloma |
|---|---|---|
| Skeletal survey (X-ray) | Lytic (punched-out) lesions after ~30% bone loss | Roughly 40 to 60% |
| Low-dose whole-body CT | Bone destruction, cortical breaches, fractures | Roughly 70 to 80% |
| Whole-body MRI (T1, STIR, DWI) | Marrow infiltration, focal lesions, diffuse disease | Roughly 85 to 95% |
| Full-body MRI (screening context) | Broader survey, non-myeloma incidental findings | Not myeloma-specific |
The clinical point is that MRI picks up disease inside the marrow before any bone has been destroyed. That matters because a single focal marrow lesion larger than 5 mm on MRI is now, on its own, considered a myeloma-defining event in the current IMWG criteria - it can move a patient from "smouldering myeloma, watch and wait" to "active myeloma, treat now".
When myeloma MRI is used
There are four distinct clinical moments when whole-body MRI comes into a myeloma pathway, and it helps to know which one you are in:
- Baseline diagnosis. A new suspicion of myeloma, based on abnormal protein bands, light chains, calcium or kidney function. Whole-body MRI at this point can catch marrow disease that a skeletal survey would miss entirely.
- Initial staging. Once myeloma is confirmed, MRI maps focal lesions, diffuse infiltration and any soft-tissue (extramedullary) disease, feeding into risk scoring.
- Restaging after treatment. After induction, autologous stem-cell transplant or a change of line, MRI helps confirm response - and increasingly, the depth of it.
- MGUS and smouldering myeloma surveillance in high-risk cases. Not every patient with MGUS or smouldering myeloma needs an MRI, but the higher-risk ones (adverse light-chain ratios, high paraprotein, high-risk genetics) are increasingly offered one at diagnosis and then periodically.
If you are not sure which of these four you are in, that is the first question to put to your haematologist - it changes what the scan is looking for and how the report is written.
The MRI protocol: what the scanner actually does
A dedicated myeloma MRI is not a lumbar spine scan or a pelvic MRI. It is a whole-body examination that runs from the top of your head (the vertex) down to the knees, capturing every part of the axial skeleton and the proximal long bones where myeloma cells prefer to live. The lower legs and forearms are usually skipped because myeloma very rarely starts there.
Three sequences do most of the work:
- T1-weighted imaging. Healthy adult marrow contains fat and looks bright on T1. Myeloma cells replace that fat and show up as darker patches.
- STIR (short-tau inversion recovery). Fluid-sensitive, so active marrow lesions, oedema and inflammation stand out.
- Diffusion-weighted imaging (DWI). Highlights areas where cells are densely packed, which is precisely what a focal myeloma lesion is. DWI is the single biggest reason MRI now outperforms every other imaging test for this disease.
Contrast (gadolinium) is not routinely used in myeloma protocols. It is added only in specific situations - suspected extramedullary disease, spinal cord compression, or when the appearance is genuinely unclear. If a clinic tells you contrast is mandatory for every myeloma MRI, it is worth a second opinion.
What the report describes
A good myeloma MRI report is not a paragraph of hedged language. It is a structured read against the IMWG framework and should tell you, in order:
- The pattern of disease. Normal marrow, focal lesions, diffuse infiltration, a mixed focal-and-diffuse pattern, or a "salt-and-pepper" appearance.
- The number and size of focal lesions. Any single focal marrow lesion larger than 5 mm is significant. More than one focal lesion is a myeloma-defining event under IMWG criteria.
- Macrofocal disease. A large focal lesion (often several centimetres) with less diffuse marrow involvement elsewhere - this pattern carries its own prognostic implications.
- Extramedullary disease. Soft-tissue plasmacytomas outside bone, which change treatment intensity.
- Complications. Vertebral collapse, cord compression, cortical breach, impending fracture.
- Response, if it is a follow-up scan. Compared directly to the previous MRI, ideally on the same scanner.
If your report reads more like "marrow signal is heterogeneous, correlate clinically" than the list above, ask your haematologist whether it should be re-reported by a specialist musculoskeletal or haemato-radiologist. This genuinely matters.
The IMWG response criteria and MRI's role
The International Myeloma Working Group updated its response criteria to formally include imaging alongside blood and bone-marrow markers. In practice this means MRI (and PET-CT, in centres that use it) now contributes to whether a patient is judged to have achieved a stringent complete response, complete response, very good partial response, and so on. The clinical implication for you as a patient is straightforward: MRI is no longer just a diagnostic photograph. It is one of the yardsticks by which your treatment is judged to be working.
