Radiographics : a review publication of the Radiological Society of North America, Inc
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Review
Transthoracic Echocardiography: Pitfalls and Limitations as Delineated at Cardiac CT and MR Imaging.
Transthoracic echocardiography ( TTE transthoracic echocardiography ) is a critical tool in the field of clinical cardiology. It often serves as one of the first-line imaging modalities in the evaluation of cardiac disease owing to its low cost, portability, widespread availability, lack of ionizing radiation, and ability to evaluate both anatomy and function of the heart. Consequently, a large majority of patients undergoing a cardiac computed tomography (CT) or magnetic resonance (MR) imaging examination will have a TTE transthoracic echocardiography available for review. ⋯ Common pitfalls and limitations of TTE transthoracic echocardiography will be highlighted using cardiac CT and MR imaging as the problem-solving modality. In this article, we have categorized the relevant pitfalls and limitations of TTE transthoracic echocardiography into four broad categories: (a) masses and mass mimics (crista terminalis, eustachian valve, right ventricle moderator band, atrioventricular groove fat, left ventricular band [or left ventricular false tendon], hiatal hernia, caseous calcification of the mitral annulus, lipomatous hypertrophy of the interatrial septum, cardiac tumors), (b) poorly visualized apical lesions (aneurysm, thrombus, infarct, and hypertrophic and other nonischemic cardiomyopathies), (c) evaluation for ascending thoracic aortic dissections (false positive, false negative, dissecting aneurysms), and (d) pericardial disease (acute and chronic/constrictive pericarditis, pericardial tamponade, pericardial cysts and diverticula, congenital absence of the pericardium). Online supplemental material is available for this article. ©RSNA, 2017.
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Advances in imaging and the development of injection techniques have enabled spinal intervention to become an important tool in managing chronic spinal pain. Epidural steroid injection (ESI) is one of the most widely used spinal interventions; it directly delivers drugs into the epidural space to relieve pain originating from degenerative spine disorders-central canal stenoses and neural foraminal stenoses-or disk herniations. Knowledge of the normal anatomy of the epidural space is essential to perform an effective and safe ESI and to recognize possible complications. ⋯ Familiarity with the findings on a typical "true" epidurogram (demonstrating correct needle placement in the epidural space) permits proper performance of ESI. Findings on "false" epidurograms (demonstrating incorrect needle placement) include muscular staining and evidence of intravascular injection, inadvertent facet joint injection, dural puncture, subdural injection, and intraneural or intradiscal injection. ©RSNA, 2016 An earlier incorrect version of this article appeared online. This article was corrected on December 22, 2016.
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Optimal treatment of thyroid cancer is highly dependent on accurate staging of the extent of disease at presentation. Preoperative ultrasonography (US) is the most sensitive method for detecting metastatic lymph nodes and is recommended as part of the standard preoperative workup. Missed findings on preoperative scans may lead to understaging and inadequate surgical management, which subsequently predispose these patients to residual disease postoperatively and a higher risk for recurrence, possibly requiring repeat surgery. ⋯ This review highlights the importance of accurate preoperative US for patients with differentiated thyroid cancer, with specific attention to deficiencies that exist in general radiology department thyroid US reports. We present a standardized approach to neck US reporting that incorporates the newly updated 2015 recommendations from the American Thyroid Association and also addresses the pertinent questions for thyroid surgeons. By ensuring comprehensive preoperative assessment and improving thyroid US reporting, we seek to improve patient access to optimized care. ©RSNA, 2016.
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Dual-energy computed tomography (CT) is a powerful diagnostic tool that is becoming more widely clinically available. Dual-energy CT has the potential to aid in the detection or add diagnostic confidence in the evaluation of a variety of emergent neurologic conditions with use of postprocessing techniques that allow one to take advantage of the different x-ray energy-dependent absorption behaviors of different materials. Differentiating iodine from hemorrhage may help in delineating CT angiographic spot signs, which are small foci of intracranial hemorrhage seen on CT angiograms in cases of acute hemorrhage. ⋯ Bone subtraction may also be helpful for improving the conspicuity of small extra-axial fluid collections and extra-axial masses. Material characterization can be helpful for clarifying whether small foci of intermediate attenuation represent hemorrhage, calcification, or a foreign material, and it may also be useful for quantifying the amount of hemorrhage or iodine in preexisting or incidentally detected lesions. Virtual monochromatic imaging also can be used to problem solve in challenging cases. (©)RSNA, 2016.
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Single-source dual-energy (DE) computed tomography (CT) with fast switching of tube voltage allows projection-based image reconstruction, substantial reduction of beam-hardening effects, reconstruction of accurate monochromatic images and material decomposition images (MDIs), and detailing of material composition by using x-ray spectral information. In vascular applications, DE CT is expected to overcome limitations of standard single-energy CT angiography, including patient exposure to nephrotoxic contrast medium and carcinogenic radiation, insufficient contrast vascular enhancement, interference from metallic and beam-hardening artifacts and severe vessel calcification, and limited tissue characterization and perfusion assessment. Acquisition of low-energy monochromatic images and iodine/water MDIs can reasonably reduce contrast agent dose and improve vessel enhancement. ⋯ Various MDIs are useful for accurate differentiation among materials with high attenuation values, including contrast medium, calcification, and fresh hematoma. Iodine/water MDIs are used to assess organ perfusion, such as in the lungs and myocardium. Understanding these DE CT techniques enhances the value of CT for vascular applications. (©)RSNA, 2016.