Learning Points 1. SWI-Phase can be used to identify calcifications on MRI. 2. Certain SWI patterns can correlate with tumor histologic type. 3. SWI can discriminate mature from immature components of desmoid tumors. 4. SWI patterns can help assess treatment response in soft tissue sarcomas. 5. SWI patterns can help characterize post-surgical changes.

Susceptibility-weighted imaging (SWI)is a full velocity compensated high-resolution 3D gradient echo MRI sequence that uses magnitude and filtered-phase information, both separately and in combination with each other, to create new sources of contrast. The susceptibility effect demonstrated on SWI occurs when substances interact with the local magnetic field, resulting in loss of signal, arising from molecules that have: Paramagnetic(deoxyhemoglobin, ferritin, and hemosiderin), Diamagnetic(bone minerals, dystrophic calcifications, and oxyhemoglobin), or Ferromagnetic(iron, nickel, and cobalt) properties.

Calcifications: Distinguishing between calcification and blood products is impossible on the post-processed SWI images because both demonstrate signal dropout and blooming. Nevertheless, the filtered phase images (SWI-Phase) can distinguish between the two because diamagnetic and paramagnetic compounds will affect phase differently, causing hemorrhage and calcification to appear of opposite signal intensity from each other. SWI-Phase can characterize "hair-on-end" bone osteosarcoma and Soft-Tissue Low-grade Liposarcoma calcifications. Soft-Tissue Abscess: An abscess shows concentric enhancement on the post-contrast series. It displays a non-enhancing central necrotic component with central...

SWI is making inroads in musculoskeletal oncologic imaging due to its sensitivity for displaying blood products and ability to recognize soft-tissue calcifications and collagenization. SWI-CE shows superior differentiation between mature fibrotic T2* dark components and active enhancing elements in desmoid fibromatosis, compared with conventional T2-WI. SWI-CE can demonstrate the viable, enhancing portions of soft tissue sarcomas separately from hemorrhagic/necrotic components, suggesting its utility as a biomarker of tumor grade and treatment response. Becoming familiar with the differences between the hemorrhage patterns that occur spontaneously in...

R. F. Valenzuela: Nothing to disclose B. Amini: Nothing to disclose E. Duran-Sierra: Nothing to disclose M. Canjirathinkal: Nothing to disclose H. Idrees: Nothing to disclose J. Madewell: Nothing to disclose C. Costelloe: Nothing to disclose W. Murphy: Nothing to disclose

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