Hybrid Imaging Benign and Malignant MSK Tumors


Professor of Radiology Shahid Beheshti University of Medical Sciences



Tracer uptake pattern s in bone: Focal, multifocal, diffuse, and mixed

Diffuse marrow hyperplasia can be mimic marrow infiltration by myeloma

False-negative F-18 FDG PET/CT: High-dose steroid administration (within 10 days)
Compete F-18 FDG response before stem cell transplant associated with higher overall (92%) and event-free (89%) survival
Assessment of treatment response

Negative F-18 FDG PET 60 days following stem cell transplant associated with excellent prognosis
Persistent F-18 FDG activity following induction therapy associated with early relapse

Early identification of disease recurrence or progression

Patients with relapse often found to have new sites of disease on F-18 FDG PET/CT
Identification of target site for biopsy


Focal hypermetabolic lytic bone lesion or extramedullary site on F-18 FDG PET/CT

Bone (97%)

Diffuse marrow infiltration
Focal lytic bone lesions Breakout lesions: cortical disruption of osseous lesions

o Extramedullary disease (EMD)

Lymph nodes, pleura, testis, skin, nasopharynx, tonsils, paranasal sinuses, liver, lung, spleen, muscle

Useful for initial diagnosis and staging (55- 90% sensitivity) and restaging

Diffuse marrow uptake on F-18 FDG PET/ CT usually indicates elevated plasma cell papulation
Negative whole-body F-18 FDG PET/CT in patients with monoclonal gammopathy reliably identifies stable MGUS

Limited sensitivity in detecting diffuse bone marrow disease; MR more sensitive

More sensitive as compared to MR for EMD (96% sensitivity, 78% specificity)

Associated with advanced disease and poor prognosis
Clinically and radiographically detected in 10-16% of patients, at autopsy in 63% of patients
More common in younger patients
More aggressive myeloma types (nonsecretory myeloma, IgD myeloma, poorly differentiated), rapidly progressive, treatment resistant
Greater frequency with increasing duration if disease