Bone metastases G.P. Schmidt, Schmidt, Munich/DE OIC 2012 Oncologic Imaging Course | June 28-30, 2012 | Dubrovnik, Croatia
Based on morphologic criteria in X-ray and CT, skeletal metastases are classified into osteolytic (50%), osteoblastic (35%) and mixed type (15%). The clinical algorithm for clarification of bone metastases includes X-ray studies, skeletal scintigraphy, CT and MRI. Yet, only pronounced destructions (>50%) of bone mineral content are readily visible in radiographic studies. CT is more sensitive than radiography and modality of choice to evaluate the extent of bone destruction and assess fracture risk. MRI allows visualization of bone marrow with high spatial resolution, is more sensitive than X-ray, CT or scintigraphy and provides precise assessment of marrow infiltration into adjacent paraosseous structures. Noncontrasted T1-w-TSE- and Turbo-STIR-sequences proved most sensitive for discrimination of the benign from malignant marrow disorders. Osteolytic lesions are iso-/hypointense on T1-w-TSEand hyperintense on STIR-sequences. Osteoblastic metastases may often show isointense signal patterns on STIR. Diagnostic problems in MRI may arise in younger patients with highly cellular hematopoietic marrow, where knowledge of age-dependent conversion patterns is required. Furthermore, avital bone metastases after therapy can remain virtually unchanged in morphology/signal, thus complicating evaluation of response. Technological improvements have introduced whole-body MRI (WB-MRI) as new tool for bone marrow screening. Parallel imaging (PAT) and matrix coil concepts significantly reduced acquisition times without compromises in spatial resolution. High diagnostic accuracy for WB-MRI bone marrow screening has been reported with relevant additional findings outside the axial skeleton or within parenchymal organs. The proposed protocol at 1.5 T consists of coronal whole-body T1w-TSE- / STIR-imaging, including sagittal imaging of the spine, with 42 minutes total imaging time. This lecture summarises the radiographic and CT patterns of bone metastases, illustrates potentials and limits of different imaging procedures for the detection of skeletal metastases and discusses the added value of whole-body imaging techniques.
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