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Neuroradiology

E3240. Thank Your Lucky T2 Star: Patterns of CNS Pathology on Susceptibility Weighted Imaging

Skalski K,  Kessler A,  Almast J,  Bhatt A. University of Rochester Medical Center, Rochester, NY

Address correspondence to K. Skalski (Kamila_Skalski@urmc.rochester.edu)

Background Information: Susceptibility-weighted imaging (SWI) has become a key component of modern neuroimaging and provides radiologists with a powerful diagnostic tool. This technique creates a visual representation of local magnetic field inhomogeneities by emphasizing intrinsic differences in magnetization and polarization of substances as they interact with the external magnetic field. Materials that disperse the main field are referred to as diamagnetic and comprise most soft tissue in the human body. Materials that concentrate the magnetic field are classified as paramagnetic, superparamagnetic, or ferromagnetic and are most commonly due to substances such as iron, gadolinium, and other metallic ions. The distribution and quantity of substances with these properties alter the appearance of SWI and can help diagnose a wide range of pathology. It is therefore critical that radiologists understand the various SWI sequences available and have a detailed knowledge of the patterns of pathology that can be seen. The purpose of this exhibit is to review the various CNS pathology that can be detected on SWI, with emphasis on a pattern-based approach to diagnosis.

Educational Goals/Teaching Points: After participating in this educational presentation, the learner will be familiar with susceptibility physics, materials that cause susceptibility, and different types of SWI sequences available. Most importantly, the learner will comprehend the role of SWI in pathology and clinical diagnosis and be able to better distinguish between pathology based on common imaging appearances.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Topics to be discussed include physics of susceptibility artifact (ferromagnetic, diamagnetic, paramagnetic, and superparamagnetic materials); specific materials that cause susceptibility artifact (metal, calcifications, hemorrhage, and air); types of SWI available (gradient-recalled echo [GRE], SWAN/SWI, SWAN MIPs, SWI/SWAN-filtered phase images); common imaging appearances of susceptibility and associated pathology—hemorrhage (cortical contusions, subarachnoid hemorrhage, subdural and epidural hemorrhage, diffuse axonal injury, superficial siderosis, arterial thrombus, thrombosed aneurysms, cortical vein thrombosis, cavernoma, cerebral amyloid, and PVNS); other metallic ions (neurodegeneration with brain iron accumulation, Wilson disease, and gadolinium deposition); metal (craniotomy hardware, embolization coils and clips, foreign bodies [bullets], dental braces, etc); and calcification (calcified masses such as meningioma or craniopharyngioma, pineal tumors, calcified aneurysm, Sturge-Weber syndrome, neurocysticercosis, and TORCH infection).

Conclusion: SWI is a valuable tool in clinical diagnosis, and a better understanding of susceptibility physics and patterns of pathology will not only underline the many strengths of SWI but will also lead to better differentiation between common imaging findings and associated pathology.