Ashish Chawla

Hepatitis C virus replication is directly inhibited by IFN-α in a full-length binary expression system

Hepatitis C virus (HCV) is a leading cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. The absence of culture systems permissive for HCV replication has presented a major bottleneck to antiviral development. We sought to recapitulate the early steps in the life cycle of HCV by means of DNA-based expression of viral genomic sequences. Here we report expression of replicating HCV RNA by using a, to our knowledge, novel binary expression system in which cells were transfected with a T7 polymerase-driven full-length HCV cDNA plasmid containing a cis-acting hepatitis Δ ribozyme to control 3′ cleavage, and infected with vaccinia-T7 polymerase. HCV genomic and replicative strand synthesis, in addition to protein synthesis, was detectable and depended on full-length HCV sequences. Moreover, the system was capable of generating HCV RNA quasispecies, consistent with the action of the low-fidelity HCV NS5B RNA polymerase. IFN-α, but not ribavirin, directly inhibited the viral replicative cycle in these cells, identifying the virus itself and not solely the immune system as a direct target of IFN action. The availability of a cell-based test for viral replication will facilitate screening of inhibitory compounds, analysis of IFN-resistance mechanisms, and analysis of virus–host cell interactions.

Primary leiomyosarcoma of inferior vena cava, a rare entity: Imaging features

Leiomyosarcoma of the inferior vena cava (IVC) is an uncommon neoplasm, most frequently seen in the sixth decade with a female predominance. Imaging modalities allow an early and accurate preoperative diagnosis resulting in a higher rate of surgical resection and improved survival. Imaging findings in a 65-year-old woman with leiomyosarcoma of IVC are described. Computed tomography and MRI typically showed a non-fatty, necrotic intraluminal IVC mass with extension to retroperitoneal compartments. Cavography was useful to evaluate the collateral circulation associated with the extensive intraluminal mass. The lesion was biopsied under ultrasound guidance.

Imaging findings of swallowed dentures: a case series

Dental prosthesis is an uncommon ingested non-food foreign body in adults. Once swallowed, it can lead to serious complications and morbidity. Hence, early localization of the offending foreign body is crucial for timely management. As the dentures are usually made up of non-metallic material and often impacted at or below the level of C7 vertebra, conventional radiograph has limited role in their evaluation. We describe the clinical history and imaging findings of swallowed partial dentures in four patients who presented to the emergency department. The dentures were localized using unenhanced CT of the neck that showed the characteristic mildly hyperdense curvilinear or irregular appearance of the dentures within the upper esophagus. Multiplanar CT reconstructions provide an orientation of the ingested denture within the esophagus, thus guiding the endoscopist.

Imaging Features of Sinonasal Inverted Papilloma: A Pictorial Review

Computed tomography and magnetic resonance imaging are widely used for evaluation of patients with nasal masses, playing an integral role in their diagnosis and treatment. Inverted papilloma is a rare tumor of the sinonasal region that demonstrates characteristic imaging appearances. Preoperative diagnosis and precise tumor extent are essential for surgical planning as this tumor grows centrifugally and has high potential to recur following incomplete surgery. This pictorial review aims to illustrate the spectrum of imaging features of inverted papilloma and highlight the key features that are useful for making an accurate diagnosis of this condition. Common differential diagnoses are also discussed.

Imaging of acute cholecystitis and cholecystitis-associated complications in the emergency setting.

Acute cholecystitis is a common cause of right upper quadrant pain in patients presenting at the emergency department. Early diagnosis and recognition of associated complications, though challenging, are essential for timely management. Imaging studies, including ultrasonography, computed tomography and magnetic resonance imaging, are increasingly utilised for the evaluation of suspected cases of cholecystitis. These investigations help in diagnosis, identification of complications and surgical planning. Imaging features of acute cholecystitis have been described in the literature and are variable, depending on the stage of inflammation. This article discusses the spectrum of cholecystitis-associated complications and their imaging manifestations. We also suggest a checklist for the prompt and accurate identification of complications in acute cholecystitis.

Dual-energy CT applications in salivary gland lesions

The increasing availability of dual-energy CT (DECT) has set the stage for an exciting era in CT technology. This technique is extensively used throughout the world with numerous centres working on the applications of DECT in various radiology subspeciality areas. DECT provides many advantages over the conventional single-energy scan. Instead of a single set of images, radiologists have access to multiple sets of images from a single acquisition. The DECT workstation enables the reader to generate images, according to the clinical setting, in order to answer a specific clinical question. Radiologists should be aware of the basic concepts of DECT and the usefulness of each image data set. This article aimed to describe the basic principles, techniques and applications of DECT in the imaging of salivary gland lesions. The specific roles of each image data set, in the context of salivary gland lesions, are also discussed.

Schematic interpretation of lateral neck radiographs of adults in the emergency department: a pictorial review

The lateral neck radiograph is widely utilized for the evaluation of common neck conditions in the emergency department. The anatomy of the neck is complex and it can be difficult to differentiate between soft tissue structures on a lateral radiograph. We suggest a schematic pattern of interpreting the lateral neck radiograph with case images of various pathologies that can present in the emergency setting.

An Approach to Various Gastric Pathologies Using an “Image Appearance−Based Classification” on Computed Tomography

Although pathologies affecting stomach are commonly encountered in computed tomography imaging of the abdomen, they are frequently overlooked. Their etiologies are often diverse; however, most of them have certain well-documented imaging characteristics. Conventionally the stomach abnormalities were classified according to their etiopathogenesis. This article aims at providing the readers with an easy approach by categorizing abnormalities of stomach using a novel image appearance-based classification. An attempt to illustrate various gastric pathologies using this new classification by means of pictorial examples is made. Basic computed tomography imaging anatomy of the stomach and imaging techniques that need to be adapted are also emphasized in the outset of the discussion.

Computed Tomography Features of External Auditory Canal Cholesteatoma: A Pictorial Review

Computed tomography (CT) is widely used for evaluation of patients with otologic conditions. External auditory canal cholesteatoma (EACC), although rare, demonstrates characteristic CT appearance. Moreover, the accurate extent of involvement cannot be accurately assessed clinically. This pictorial review aims to illustrate the spectrum of CT features of EACC and highlight the key features that are useful for making an accurate diagnosis of this condition. We have also discussed the radiological and clinical differential diagnoses of external auditory canal lesions that can be mistaken for an EACC.

Clinics in diagnostic imaging (173)

A 56-year-old Chinese man presented with giddiness and vertigo. Subsequent chest radiography showed the classic scimitar sign of an abnormal pulmonary venous return. Further evaluation with non-contrast computed tomography substantiated the finding of a partial anomalous venous drainage pattern and identified an associated rare lung anomaly, horseshoe lung. The imaging findings of scimitar syndrome and its association with horseshoe lung are reviewed.