Whole body diffusion weighted MRI--a new view of myeloma

Abstract

The recent consensus statement from the International Myeloma Working Group has introduced the role of whole body (WB) magnetic resonance imaging (MRI) into the management pathway for patients with multiple myeloma. The speed, coverage and high sensitivity of WB diffusion weighted (DW)-MRI and the unique capability to quantify both burden of disease and response to treatment has led to increasing implementation at leading centres worldwide for imaging malignant marrow disease, both primary and metastatic. WB DW-MRI is likely to have a significant impact on management decisions and pathways for patients with multiple myeloma. This review will introduce the basic principles of DW-MRI, present current evidence for patients with myeloma and will discuss practicalities and exciting future applications.

Keywords: MRI; MRI myeloma; functional studies; imaging; myeloma.

Figure 1

Diffusion weighted magnetic resonance imaging (DW‐MRI) shows increased sensitivity for diffuse marrow infiltration. Sagittal ¹⁸F‐fluorodeoxyglucose positron emission tomography (¹⁸F‐FDG PET)/computerized tomography (CT) (A) and b900 whole body DW‐MRI Maximum Intensity Projection image in a 52‐year‐old male with multiple myeloma. (A) ¹⁸F‐FDG PET/CT was reported as normal with no areas of increased FDG uptake and no lytic lesions on the CT component. (B) Inverted greyscale WB DW‐MRI demonstrated diffuse marrow infiltration. Marrow trephine confirmed 80–90% infiltration with plasma cells.

Figure 2

Whole body diffusion weighted magnetic resonance imaging (WB DW‐MRI) provides excellent contrast between normal bone marrow and focal lesions. b900 WB DW‐MRI Maximum Intensity Projection image in a 55‐year‐old male with multiple myeloma demonstrates multiple focal lesions that appear low signal on the inverted grey scale image (examples indicated by arrows) with excellent contrast against normal marrow, which does not return signal (block arrow).

Figure 3

Diffusion weighted magnetic resonance imaging (DW‐MRI) is highly sensitive for detection of focal rib lesions. Left: Inverted greyscale b900 whole body DW‐MRI Maximum Intensity Projection of the chest in a 53‐year‐old female with multiple myeloma shows numerous sites of disease in the ribs (examples indicated by arrows). Right: A chest radiograph in the same patient shows rib fractures (block arrow) but no lytic lesions.

Figure 4

Subjective assessment of response on whole body diffusion weighted magnetic resonance imaging (WB DW‐MRI). Inverted greyscale b900 WB DW‐MRI Maximum Intensity Projection pre‐ (A) and 98 d post‐CVD (cyclophosphamide, bortezomib and dexamethasone) (B) in a 63‐year‐old male with multiple myeloma demonstrates multiple focal lesions reducing in size and number. Small volume sites of disease persist (B, example shown by arrow). International Myeloma Working Group (IMWG) response status was very good partial response. Inverted greyscale b900 WB DW‐MRI Maximum Intensity Projection pre‐ (C) and 92 d post‐DT‐PACE (dexamethasone, thalidomide, cisplatin, doxorubicin, cyclophosphamide and etoposide) (D) in a 67‐year‐old male with multiple myeloma demonstrates diffuse marrow infiltration which normalizes after treatment. IMWG response status was complete response.

Figure 5

The extremely high sensitivity of diffusion weighted magnetic resonance imaging (DW‐MRI) allows detection of tiny foci of residual disease post‐autograft. b900 whole body DW‐MRI Maximum Intensity Projection images of a 70‐year‐old female with multiple myeloma before (A), 3 months post‐ (B) and 8 months post‐ (C) autograft. At baseline there is widespread marrow disease including a focal lesion in the right iliac bone (A, arrow). At 3 months post‐autograft, the marrow signal has normalized apart from a tiny residual focus of abnormal signal at a site of original disease in the right iliac bone (B, arrow). WB DW‐MRI 8 months post‐autograft shows progression of the residual disease (C, arrow) and development of new sites (example shown by block arrow). Ill‐defined distortion overlying the left hip (dashed arrow) represents artefact from a metal hip prosthesis.

Figure 6

Whole body MRI protocol. Diffusion weighted magnetic resonance imaging (DW‐MRI) is performed axially using b values of 50 (A) and 900 (B). The system software automatically generates an apparent diffusion coefficient map (C) for each slice using the b 50 and 900 data. Axial images through the head demonstrate abnormal signal in the skull vault indicating infiltration (arrows). Radiographers post‐process the data to produce the 3‐dimensional inverse grey scale Maximum Intensity Projection image (d). Whole body DW‐MRI is supplemented by sagittal T2 (e) and T1 (f) weighted images of the spine. Total imaging time 45 min.

Figure 7

Whole body diffusion weighted magnetic resonance imaging (WB DW‐MRI) can differentiate active from inactive sites and reveals unexpected additional sites of disease. A 53‐year‐old female with a previous history of solitary rib plasmacytoma treated with radiotherapy, with rising paraproteins. Weighted T1 (T1W) MRI of the spine (A) was normal. WB DW‐MRI [axial b900 B, apparent diffusion coefficient (ADC) map, C] demonstrated a 3 mm focal nodule of restricted diffusion (arrows, B and C) within the treated rib bone defect (block arrow, C), in keeping with local recurrence. In addition WB DW‐MRI showed a 5 cm expansile focus of disease arising from the left iliac bone [arrows on b900 (D) and ADC map (E)].

Figure 8

False positive whole body diffusion weighted magnetic resonance imaging (WB DW‐MRI) following granulocyte colony‐stimulating factor (GCSF) administration. b900 WB DW‐MRI Maximum Intensity Projection images in a 67‐year‐old female with relapsed multiple myeloma (A) show diffuse abnormal marrow signal indicating infiltration which was confirmed by 20% plasma cell infiltration on trephine. b900 WB DW‐MRI Maximum Intensity Projection images 6 months later following treatment (B) show stable appearances; however; trephine showed regenerating marrow and no plasma cells. The patients had received GCSF 3 d prior to the MRI (B), which caused a false positive MRI secondary to marrow hypercellularity.