Critical reviews in diagnostic imaging最新文献

Esophageal perforation can be a catastrophic event for a patient regardless of the etiology of the perforation. Contrast esophagrams can typically diagnose an esophageal perforation if the clinical symptoms or history suggest the diagnosis. Often, however, the clinical features are atypical and a CT scan is performed early in the patient's workup. It is, therefore, essential to recognize the CT features seen in esophageal perforation. The various etiologies and CT findings of esophageal perforation are reviewed in this article. The CT abnormalities include extraluminal air, periesophageal fluid, esophageal thickening, and extraluminal contrast. These CT findings may be the first clue to the correct diagnosis of esophageal perforation.

High-resolution computed tomography (HRCT) allows a detailed assessment of the anatomy and pathology of the pulmonary parenchyma. However, numerous potential pitfalls exist that can hinder or preclude accurate interpretation of HRCT images. These sources of potential diagnostic error can be systematically evaluated with respect to the major categories of HRCT abnormalities: (1) increased parenchymal attenuation, (2) linear opacities and interstitial disease, (3) nodular lung disease, and (4) holes in the lung. Accurate HRCT interpretation depends on the correct recognition and characterization of imaging abnormalities. Technical factors that enhance or limit scan interpretation, HRCT features of subtle disease, and imaging mimics of commonly observed pathology are addressed in detail with regard to each of the above categories of disease. Common pitfalls are illustrated and explained in an effort to increase general awareness of these sources of real and potential diagnostic confusion.

"Vacuum" phenomena may occur within peripheral joints or in the spine. These phenomena are related to the accumulation of gas, principally nitrogen, under physiologic or pathologic circumstances. Within the spine, vacuums may occur within the intervertebral discs and are useful indicators of intervertebral osteochondrosis , spondylosis deformans, Schmorl's nodes, and limbus vertebrae. In addition, intraosseous vacuum may occur within the vertebral bodies usually related to osteonecrosis. Under physiologic conditions, naturally occurring peripheral vacuums cannot exist in the presence of joint fluid. This is often an easy, inexpensive, noninvasive means of excluding a joint effusion. In this review, the appearance, clinical importance, pathogenesis, and pitfalls of spinal and extra-spinal vacuums are discussed.

The applications of magnetic resonance imaging (MRI) have become numerous for the assessment of disorders involving the knee. Once a technique used nearly exclusively in the evaluation of internal derangement of this joint, it now plays an important role in the diagnosis of processes that affect the bone marrow, including those that occur as a result of trauma, infection, tumor, and rheumatologic disorders. Signal alterations in the bone marrow frequently are present in association with these pathological processes. When the signal is of low intensity on T1-weighted images and becomes heterogeneously increased in intensity on T2-weighted images, it indicates the presence of edema in the bone marrow. Two types of marrow edema are presented in this review: posttraumatic and reactive. In many situations, the area of altered signal intensity is radiographically occult. The distribution of marrow edema often reflects the mechanism of injury in trauma and may correlate with additional injuries to the surrounding soft tissues. Reactive marrow edema occurs either in response to an inflammatory focus in the bone and/or joint or a neoplastic process in or adjacent to the bone.

In 1995, the World Health Organization reported that 18 million people worldwide have been infected with the human immunodeficiency virus (HIV), with projections that this number will increase to 30 to 40 million by the year 2000. Presently, in the U.S. over 1 million persons are infected. Approximately 40,000 people become newly infected each year in the U.S., a number equivalent to those who die from acquired immunodeficiency syndrome (AIDS) yearly. AIDS is now the leading cause of death in young men aged 25 to 44, and the third leading cause of death in women aged 25 to 44. A shift in the demographic profile of those infected has been noted, with an increasing proportion of minorities, heterosexuals, and children affected. The pathogenesis of HIV infection occurs mainly through immunosuppression, which increases the host's susceptibility to numerous infections. The increased incidence of certain neoplasms in this population point to the ability of the virus either to interfere with the host's tumor surveillance ability or to interact with other agents in tumorigenesis. Certain rheumatic diseases, likely with autoimmune etiologies, are increasingly being associated with HIV. The musculoskeletal system is but one of the sites in which the radiologist must always maintain a high index of suspicion for HIV or AIDS-related disease. The spectrum of osteoarticular and soft tissue changes observed in this population is described.

CT has become the primary imaging modality for the evaluation of the patient with clinical symptoms of an acute abdomen and a confusing clinical picture. Because these patients may have a range of various pathologies, CT has been used successfully to define the presence of disease and localize it to a specific organ or organ system. In this article, we review the various processes that resulted in acute abdomen focusing on the small bowel and colon. Specific entities discussed include appendicitis, diverticulitis, Crohn disease, and ulcerative colitis. Other less common processes, including pseudomembranous colitis, intussusception, and bowel ischemia are also discussed. The specific role of CT scanning and specific CT signs are discussed and addressed. The value of CT in relationship to other modalities and clinical evaluation is discussed and key statistics provided.

The authors review their experience with magnetic resonance imaging (MRI) of the thymus and discuss the appearance of thymic epithelial tumors where MRI is clinically useful. Detailed descriptions of MRI findings in benign thymomas, invasive thymomas, and thymic carcinomas are provided. Most benign (noninvasive) thymomas appear with a slightly higher signal intensity than that of muscle on T1-weighted images. On T2-weighted images, thymomas have an increase in signal intensity on both T1- and T2-weighted images. Neither fibrous septa nor lobulated internal architecture can be detected on MRI. Gd-DTPA-enhanced MR images show homogeneous enhancement. On the other hand, invasive thymomas show the same signal intensity as benign thymomas, both on T1- and T2-weighted images. However, invasive thymomas appear inhomogeneous in signal intensity on T2-weighted images. T2-weighted images also show a lobulated border, fibrous septa, and lobulated internal architecture, characteristic of most invasive thymomas. Irregularity of tumor margins indicating invasion into surrounding structures is noted in some cases of invasive thymomas. Exceptionally minute thymomas (< 1 cm in diameter) show a different signal intensity on MRI as compared to those of usual thymomas: both T1- and T2-weighted MR images show a low signal intensity mass with irregular or unclear borders. Histopathologically, these minute thymomas contain numerous tiny cysts and/or abundant collagenous tissues. Generally, thymic carcinomas, except carcinoid tumors, appear with a relatively low signal intensity on T1- and T2-weighted MR images in comparison to those of thymomas. In particular, well-differentiated squamous cell carcinomas appear with a low signal intensity on both T1- and T2-weighted images. Abundant collagenous tissue may be a causative factor for the low signal intensity on T2-weighted MR images. Thymic carcinomas appear slightly inhomogeneous on both T1- and T2-weighted images. Neither fibrous septa nor lobulated internal architecture can be detected in any thymic carcinoma. If MRI is performed on a patient with anterior mediastinal tumors, thymic carcinoma may be precisely diagnosed when characteristic MR findings are demonstrated.

Sonography can be used for the accurate differentiation of many benign and malignant solid breast lesions. However, considerable experience, and close correlation with the physical examination and the mammogram, are required to do so. Sixteen sonographic signs useful in this differentiation are reviewed. The specific sonographic appearances of the most common being entities are described. Primary breast malignancies are divided into five categories according to their sonographic presentations: (1) classic neoplasms with irregular borders, echoic rims, and usually posterior shadowing, (2) small, round neoplasms with no echoic rim or posterior shadowing, (3) neoplasms with mixed or increased echogenicity, (4) cystic or intracystic carcinomas, and (5) colloid carcinomas. Methods for identification of these different types of invasive malignancy, and of in situ carcinomas, are presented. The usefulness of sonomammography is considered in specific circumstances, including evaluation of mammographic or physical findings, dense breasts, post-radiation breasts, and women under 35 years of age.

The recent progress of CT technology, such as spiral and ultrafast CT, has made it possible to obtain contiguous thin-section CT images of the pulmonary hilum during rapid injection of contrast material. These CT images consistently provide clear images of the pulmonary hilum, including normal peribronchovascular interstitium, bronchi, and pulmonary vessels, enabling a more precise and detailed evaluation of various pathological conditions than CT previously allowed. This article illustrates high-quality CT images in normal and abnormal conditions occurring in the pulmonary hilum and discusses the present CT diagnosis of various pulmonary hilar diseases.

The clinical and radiologic manifestations of pulmonary aspergillosis depend on the underlying status of the patients' lung parenchyma and the patients' immunologic response to the infecting agent, most commonly Aspergillus fumigatus. Thus, many different manifestations of pulmonary aspergillosis have been described, with distinct clinical, pathological, and radiological characteristics. Aspergillomas (mycetomas) result from Aspergillus colonization of preexisting lung cavities. Allergic bronchopulmonary aspergillosis results from a hypersensitivity reaction to the fungus in asthmatic patients. Invasive aspergillosis occurs in immunocompromised patients and can take one of many forms, depending on the degree and etiology of the patients' immunosuppression. CT is currently the best imaging modality for the assessment of pulmonary parenchymal disease. In the correct clinical setting, the CT findings frequently suggest a specific diagnosis. The aim of this review is to discuss and illustrate the various CT manifestations of pulmonary aspergillus infection.