Author: China Medical Network
Background and Significance
Multiple myeloma (MM) is a hematologic malignancy characterized by clonal plasma cell proliferation.
Whole-body magnetic resonance imaging (WB-MRI) is recognized by the International Myeloma Working Group as the most sensitive imaging technique for detecting bone marrow infiltration in MM.
This consensus aims to standardize the clinical application of WB-MRI for MM in China, integrating international guidelines and addressing domestic clinical needs.
Imaging Techniques
Sequence Selection
- T1-weighted imaging (T1WI): Visualizes bone marrow fat content and anatomical structure. MM lesions typically appear as low signal intensity on T1WI.
- T2-weighted imaging (T2WI) and fat-suppressed T2WI: Detect bone marrow edema and soft tissue lesions. MM lesions often show high signal intensity on T2WI, with fat suppression enhancing lesion visibility.
- Diffusion-weighted imaging (DWI): Reflects water molecule diffusion, aiding early detection of MM lesions and assessment of tumor cell activity. Quantitative analysis via apparent diffusion coefficient (ADC) values is recommended.
- Dynamic contrast-enhanced MRI (DCE-MRI): Evaluates tumor vascularity and perfusion, useful for assessing tumor activity and treatment response.
Scan Range
- Full-body coverage from the skull vertex to the soles of the feet. Minimum coverage should include the skull, spine, pelvis, and proximal bilateral humeri and femora—common MM involvement sites.
Contrast Agent Use
- Non-contrast MRI often suffices for diagnosis. Contrast-enhanced scans are reserved for atypical lesions, soft tissue evaluations, or extramedullary disease assessment.
Image Analysis
Bone Marrow Infiltration Patterns
- Diffuse infiltration: Uniform marrow signal changes—low signal on T1WI, high signal on T2WI/fat-suppressed T2WI, high DWI signal, and reduced ADC values.
- Focal infiltration: Nodular/mass-like low signal on T1WI, high signal on T2WI/fat-suppressed T2WI, marked high DWI signal, and reduced ADC values.
- Mixed infiltration: Combined diffuse and focal patterns.
Bone Destruction
- MRI reveals cortical disruption, trabecular thinning/loss, and adjacent soft tissue masses.
Soft Tissue Lesions
- Detects extramedullary plasmacytomas and soft tissue masses, aiding disease staging.
Spinal and Nerve Root Involvement
- Identifies complications like spinal cord compression or nerve root invasion, critical for treatment planning and prognosis.
Clinical Applications in MM Management
Diagnosis
- WB-MRI detects tumor infiltration before overt bone destruction, enabling early diagnosis.
Risk Stratification
- Based on infiltration patterns, lesion number/size, and bone destruction, guiding treatment strategies.
Treatment Response Evaluation
- Serial WB-MRI tracks changes in lesion signal intensity, size, and number, optimizing therapeutic adjustments.
Prognostic Prediction
- Poor prognosis indicators include diffuse infiltration, multifocal lesions, and soft tissue masses.
Comparison with Other Imaging Modalities
- vs. Whole-body X-ray: WB-MRI is superior for detecting pre-osteolytic lesions and early marrow infiltration.
- vs. Low-dose CT: CT excels in lytic lesion detection, while WB-MRI provides finer marrow and soft tissue detail.
- vs. PET-CT: WB-MRI offers higher sensitivity for marrow infiltration and is radiation-free. PET-CT better evaluates metabolic activity and extramedullary hypermetabolic lesions.
This consensus underscores WB-MRI’s pivotal role in MM diagnosis, staging, and monitoring, advocating its integration into standardized clinical workflows.
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