Quantitative susceptibility mapping (QSM) is a novel MRI method for quantifying tissue magnetic property. In the brain, it reflects the molecular composition and microstructure of the local tissue. However, susceptibility maps reconstructed from single-orientation data still suffer from streaking artifacts which obscure structural details and small lesions. We propose and have developed a general method for estimating streaking artifacts and subtracting them from susceptibility maps. Specifically, this method uses a sparse linear equation and least-squares (LSQR)-algorithm-based method to derive an initial estimation of magnetic susceptibility, a fast quantitative susceptibility mapping method to estimate the susceptibility boundaries, and an iterative approach to estimate the susceptibility artifact from ill-conditioned k-space regions only. With a fixed set of parameters for the initial susceptibility estimation and subsequent streaking artifact estimation and removal, the method provides an unbiased estimate of tissue susceptibility with negligible streaking artifacts, as compared to multi-orientation QSM reconstruction. This method allows for improved delineation of white matter lesions in patients with multiple sclerosis and small structures of the human brain with excellent anatomical details. The proposed methodology can be extended to other existing QSM algorithms.

Multidetector computed tomography (CT) is the modality of choice for the evaluation of facial trauma because it helps accurately identify and characterize fractures and associated complications, thereby aiding timely clinical management and surgical planning. In particular, CT clearly depicts clinically relevant fractures in the eight osseous struts or buttresses that function as an underlying scaffold for facial structures. Information about the involvement of specific facial buttresses in a complex fracture is helpful for determining the type of fracture present and for identifying associated soft-tissue injuries that may require urgent care or surgery. Various kinds of complications can be expected to occur in Le Fort fractures, which affect the full thickness of the pterygoid plates, with resultant dissociation of part or all of the maxilla from the skull base; naso-orbitoethmoid complex fractures, which involve the medial orbital wall, nasal bone, ethmoid sinuses, and, often, the attachment site of the medial canthal tendon; zygomaticomaxillary complex fractures, which disrupt all four zygomatic sutures and may lead to enophthalmos due to increased orbital volume because of angulation of the lateral orbital wall; orbital "blowout" fractures, which may result in extraocular muscle herniation or entrapment and injuries to the globe or the infraorbital nerve; and fractures of the alveolar process, which are treated as open fractures because of their extension through the gingiva to the oral cavity and their resultant vulnerability to infection. Similarly, extension of a frontal sinus fracture through the posterior sinus wall creates a portal to the anterior cranial fossa and may lead to cerebrospinal fluid leakage, intracranial hemorrhage, or intracranial infection.

Background and PurposeAccurate diagnosis of Atypical Parkinsonian Syndromes (APS) is important due to differences in prognosis and management, but remains a challenge in the clinical setting. The purpose of our meta-analysis was to identify characteristic patterns of gray matter atrophy in Corticobasal Degeneration (CBD), Progressive Supranuclear Palsy (PSP), Multisystem-Atrophy Parkinsonian type (MSA-P), and Idiopathic Parkinson's Disease (IPD).Materials and MethodsWhole-brain meta-analysis was performed on 39 published voxel-based morphometry (VBM) articles (consisting of 404 IPD, 87 MSA-P, 165 CBD, and 176 PSP subjects) using the modified Anatomic Likelihood Estimation method. Based on these results, contrast analyses were then utilized to determine areas of atrophy shared by as well as unique to each disorder.ResultsCBD was characterized by asymmetric gray matter atrophy in multiple cortical regions, while the thalamus-midbrain and insula were predominantly involved in PSP. The striatum and superior cerebellum were affected in MSA-P, while IPD demonstrated an anterior cerebral pattern. Although there was a mild overlap among PSP, CBD, and MSA-P, significant regions of atrophy unique to each disorder were identified, including (1) the superior parietal lobule in CBD (2) putamen in MSA-P (3) insula and medial dorsal nucleus in PSP.ConclusionOur results suggest that there are characteristic patterns of atrophy in APS. Guided by these findings, future studies on the individual subject level may lead to the development of robust imaging biomarkers.

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Imaging of the orbit plays an important role in the workup of orbital emergencies. Orbital imaging is particularly useful in the emergency department, where clinical history and physical examination may be limited or delayed until the exclusion or treatment of more life-threatening conditions. Cross-sectional orbital imaging with multidetector computed tomography (CT) and magnetic resonance (MR) imaging is commonly performed in addition to ultrasonography. In an emergent setting, CT is the preferred modality when evaluating for intraorbital foreign bodies, fractures, or calcifications within a mass lesion. MR imaging is typically the modality of choice for orbital pathologic conditions, owing to its superior ability to delineate the orbital soft tissues and visual pathways. CT and MR imaging together may supplement clinical evaluation by helping establish an accurate diagnosis, providing an objective assessment of disease extent and progression, and assisting in pretreatment planning. Orbital emergencies have a spectrum of cross-sectional imaging findings in four major categories: infection, trauma, vascular disease, and inflammation. Use of a systematic approach to these entities will assist the radiologist with identifying immediate threats to vision and thereby facilitate prompt clinical management. Familiarity with the clinical presentations also improves the radiologist's diagnostic confidence and role in guiding patient care. This article reviews imaging protocols, relevant orbital anatomy, the role of CT and MR imaging, and key imaging findings of orbital emergencies that the radiologist must know. RSNA, 2017.