Charles T. Lau

Differentiation of Pleural Effusions From Parenchymal Opacities: Accuracy of Bedside Chest Radiography

OBJECTIVE The purpose of this study was to determine, with CT as the reference standard, the ability of radiologists to detect pleural effusions on bedside chest radiographs. MATERIALS AND METHODS Images of 200 hemithoraces in 100 ICU patients undergoing chest radiography and CT within 24 hours were reviewed. Four readers with varying levels of experience reviewed the chest radiographs and predicted the likelihood of the presence of an effusion or parenchymal opacity on independent 5-point scales. The results were compared with the CT findings. RESULTS All readers regardless of experience had similar accuracy in detecting pleural effusions. Among 117 pleural effusions, 66% were detected on chest radiographs (53%, 71%, and 92% of small, moderate, and large effusions) with 89% specificity. Similarly, 65% of all parenchymal opacities were detected on chest radiographs, also with 89% specificity. Most (93%) of the misdiagnosed pulmonary opacities were simply not seen. Meniscus, apical cap, lateral band, and subpulmonic opacity were highly specific findings but had low individual sensitivity for effusions. The finding of homogeneous opacity, including both layering and gradient opacities, was the most sensitive sign of effusion. Atelectasis can occasionally mimic the pleural veil sign of effusion, accounting for most false-positive findings. CONCLUSION Radiologists interpreting bedside chest radiographs of ICU patients detect large pleural effusions 92% of the time and can exclude large effusions with high confidence. However, small and medium effusions often are misdiagnosed as parenchymal opacities (45%) or are not seen (55%). Pulmonary opacities often are missed (34%) but are rarely misdiagnosed as pleural effusions (7%).

High-Pitch ECG-Synchronized Pulmonary CT Angiography Versus Standard CT Pulmonary Angiography: A Prospective Randomized Study

OBJECTIVE The purpose of this study was to compare high-pitch ECG-synchronized pulmonary CT angiography (CTA) with standard pulmonary CTA with regard to radiation dose and image quality in patients with suspected pulmonary embolism. SUBJECTS AND METHODS This prospective study was approved by the institutional review board, and participants provided informed consent. Patients with suspected pulmonary embolism (60% women; mean age, 57 ± 14 years) were randomized to undergo high-pitch ECG-synchronized pulmonary CTA (n = 26) or standard pulmonary CTA (n = 21). Two independent readers assessed subjective image quality of pulmonary arteries, cardiovascular structures, and pulmonary parenchyma. Signal intensity (SI) was measured in one segmental and three central pulmonary arteries. RESULTS High-pitch ECG-synchronized pulmonary CTA showed higher SI (p < 0.001) for pulmonary arteries. Image quality scores indicated improvement in assessment of cardio-vascular structures (p < 0.001), minimization of motion of central (p < 0.001) pulmonary arteries, and an increase in pulmonary arterial enhancement (p = 0.01) with high-pitch ECG-synchronized pulmonary CTA. Image quality scores for lung assessment were higher for standard pulmonary CTA (p < 0.001). The amount of contrast agent administered was similar between techniques (p = 0.86). Radiation dose was lower for high-pitch ECG-synchronized pulmonary CTA (p < 0.001). CONCLUSION High-pitch ECG-synchronized pulmonary CTA provides higher pulmonary arterial SI, decreased motion of central pulmonary arteries, and improved assessment of cardiovascular structures with similar contrast dose and lower radiation compared with standard pulmonary CTA.

Building a Bridge to Save a Failing Ventricle: Radiologic Evaluation of Short- and Long-term Cardiac Assist Devices

Heart failure is recognized with increasing frequency worldwide and often progresses to an advanced refractory state. Although the reference standard for treatment of advanced heart failure remains cardiac transplantation, the increasing shortage of donor organs and the unsuitability of many patients for transplantation surgery has led to a search for alternative therapies. One such therapy is mechanical circulatory support, which helps relieve the load on the ventricle and thereby allows it to recover function. In addition, there is increasing evidence supporting the use of mechanical devices as a bridge to recovery in patients with acute refractory heart failure. In this article, the imaging evaluation of various commonly used short- and long-term cardiac assist devices is discussed, and their relevant mechanisms of action and physiology are described. Imaging, particularly computed tomography (CT), plays a crucial role in preoperative evaluation for assessment of candidacy for implantation of a left ventricular assist device (LVAD) or total artificial heart (TAH). Also, echocardiography and CT are indispensable in assessment of complications associated with cardiac devices. Complications commonly associated with short-term assist devices include bleeding and malpositioning, whereas long-term devices such as LVADs may be associated with infection, pump thrombosis, and cannula malfunction, as well as bleeding. CT is also commonly performed for preoperative planning before LVAD or TAH explantation, replacement of a device or one of its components, and cardiac transplantation. Online supplemental material is available for this article.

Historical Evolution of Imaging Techniques for the Evaluation of Pulmonary Embolism: RSNA Centennial Article

As we celebrate the 100th anniversary of the founding of the Radiological Society of North America (RSNA), it seems fitting to look back at the major accomplishments of the radiology community in the diagnosis of pulmonary embolism. Few diseases have so consistently captured the attention of the medical community. Since the first description of pulmonary embolism by Virchow in the 1850s, clinicians have struggled to reach a timely diagnosis of this common condition because of its nonspecific and often confusing clinical picture. As imaging tests started to gain importance in the 1900s, the approach to diagnosing pulmonary embolism also began to change. Rapid improvements in angiography, ventilation-perfusion imaging, and cross-sectional imaging modalities such as computed tomography (CT) and magnetic resonance imaging have constantly forced health care professionals to rethink how they diagnose pulmonary embolism. Needless to say, the way pulmonary embolism is diagnosed today is distinctly different from how it was diagnosed in Virchows era; and imaging, particularly CT, now forms the cornerstone of diagnostic evaluation. Currently, radiology offers a variety of tests that are fast and accurate and can provide anatomic and functional information, thus allowing early diagnosis and triage of cases. This review provides a historical journey into the evolution of these imaging tests and highlights some of the major breakthroughs achieved by the radiology community and RSNA in this process. Also highlighted are areas of ongoing research and development in this field of imaging as radiologists seek to combat some of the newer challenges faced by modern medicine, such as rising health care costs and radiation dose hazards.

Imaging in Chronic Thromboembolic Pulmonary Hypertension.

Chronic thromboembolic pulmonary hypertension (CTEPH) is one of the potentially curable causes of pulmonary hypertension and is definitively treated with pulmonary thromboendartectomy. CTEPH can be overlooked, as its symptoms are nonspecific and can be mimicked by a wide range of diseases that can cause pulmonary hypertension. Early diagnosis of CTEPH and prompt evaluation for surgical candidacy are paramount factors in determining future outcomes. Imaging plays a central role in the diagnosis of CTEPH and patient selection for pulmonary thromboendartectomy and balloon pulmonary angioplasty. Currently, various imaging tools are used in concert, with techniques such as computed tomography (CT) and conventional pulmonary angiography providing detailed structural information, tests such as ventilation-perfusion (V/Q) scanning providing functional data, and magnetic resonance imaging providing a combination of morphologic and functional information. Emerging techniques such as dual-energy CT and single photon emission computed tomography-CT V/Q scanning promise to provide both anatomic and functional information in a single test and may change the way we image these patients in the near future. In this review, we discuss the roles of various imaging techniques and discuss their merits, limitations, and relative strengths in depicting the structural and functional changes of CTEPH. We also explore newer imaging techniques and the potential value they may offer.

Staging Lung Cancer: Regional Lymph Node Classification

This article reviews regional lymph node assessment in lung cancer. In the absence of a distant metastasis, the absence or location of lung cancer spread to a regional mediastinal lymph node affects treatment options and prognosis. Regional lymph node maps have been created to standardize assessment of the N descriptor. The International Association for the Study of Lung Cancer lymph node map is used for the standardization of N descriptor assessment. CT, PET/CT with fluorodeoxyglucose, endobronchial ultrasound-guided and/or esophageal ultrasound-guided biopsy, and mediastinoscopy are common modalities used to determine the N descriptor.

Radiologic review of acquired pulmonary vein stenosis in adults

Acquired pulmonary vein stenosis (PVS) is an uncommon occurrence in adults, but one that carries significant morbidity/mortality. PVS can be secondary to neoplastic infiltration/extrinsic compression, non-neoplastic infiltration/extrinsic compression, or iatrogenic intervention. This article: (I) reviews the common causes of acquired PVS; (II) illustrates direct and indirect cross-sectional imaging findings in acquired PVS (in order to avoid misinterpretation of these imaging findings); and (III) details the role of imaging before and after the treatment of acquired PVS.