Whole-Body Low-Dose CT Protocol for Multiple Myeloma
Whole-body low-dose CT (WBLDCT) is the recommended primary imaging modality for initial diagnosis and follow-up of multiple myeloma, extending from skull vertex to knees without intravenous contrast, with radiation doses of 3.2-4.8 mSv. 1
Technical Parameters for WBLDCT Protocol
- Detector configuration: 80×0.5 mm 2
- Scanning range: Single spiral acquisition from skull to proximal femoral bones 2
- Tube voltage: 120 kVp 2, 3
- Tube current time product: 40-86 mAs (can be adjusted based on patient size) 2, 3
- Slice thickness: 1 mm 2
- No intravenous contrast (should be avoided in myeloma patients) 1
- Expected radiation dose: 4.1-4.8 mSv (compared to 2.4 mSv for conventional skeletal survey) 1, 3
Image Reconstruction Parameters
- Two sets of axial images should be reconstructed 2, 3:
- Bone assessment (high-resolution algorithm)
- Soft tissue assessment (standard algorithm)
- Secondary coronal and sagittal reconstructions should be generated 2
- Middle-frequency reconstruction algorithm (B50f kernel) is beneficial for all energy protocols 3
Clinical Application in Multiple Myeloma
- WBLDCT is designated as "obligatory" for initial diagnosis of multiple myeloma according to EHA-ESMO guidelines 4
- WBLDCT detects 25.5% more lesions than conventional skeletal surveys, particularly in spine and pelvis 1
- For follow-up after treatment, WBLDCT is recommended when patients become symptomatic 4
- NCCN guidelines recommend either WBLDCT or FDG-PET/CT for initial diagnostic workup 4, 1
Advantages Over Conventional Skeletal Survey
- Superior detection of osteolytic lesions in areas difficult to visualize with skeletal surveys (skull, ribs, spine, pelvis) 1, 5
- Prospective studies show WBLDCT identifies more bone lesions per patient (8.2 vs 3.6 with skeletal survey) 5
- Faster scanning time and higher resolution images for proper management of MM patients 6
- Can detect extraosseous findings including pleuro-pulmonary lesions 6
Comparison with Other Imaging Modalities
- If PET/CT is used instead of WBLDCT, the CT component should have imaging quality equivalent to WBLDCT 1
- MRI is particularly useful when WBLDCT is negative, especially for discerning smoldering myeloma from active disease 1
- WBMRI has higher sensitivity for detecting focal and diffuse plasma cell infiltration patterns before osteolytic destruction 7
Follow-up Recommendations
- The same imaging modality used during initial workup should be used for follow-up assessments for consistency 1
- Assessment frequency should be at minimum every 3 months during active treatment 1
- For relapse assessment, WBLDCT is recommended when patients become symptomatic 4
Common Pitfalls and Caveats
- Image quality may be reduced in patients with diffuse skeletal infiltration or concurrent osteoporosis 3
- Non-isotropic voxel size may limit the quality of multiplanar reformatted images compared to axial images 3
- Small arachnoid granulations can be misinterpreted as lytic lesions on skull radiographs but are correctly identified with CT 2