Multisection CT: scanning techniques and clinical applications.

Multisection computed tomography (CT) was introduced in 1992 with the advent of dual-section-capable scanners and was improved in 1998 following the development of quad-section technology. With a recent increase in gantry speed from one to two revolutions per second, multisection CT scanners are now up to eight times faster than conventional single-section helical CT scanners. The benefits of quad-section CT relative to single-section helical CT are considerable. They include improved temporal resolution, improved spatial resolution in the z axis, increased concentration of intravascular contrast material, decreased image noise, efficient x-ray tube use, and longer anatomic coverage. These factors substantially increase the diagnostic accuracy of the examination. The multisection CT technique has enabled faster and superior evaluation of patients across a wide spectrum of clinical indications. These include isotropic viewing, musculoskeletal applications, use of multiplanar reformation in special situations, CT myelography, long coverage and multiphase studies, CT angiography, cardiac scoring, evaluation of brain perfusion, imaging of large patients, evaluation of acute chest pain or dyspnea, virtual endoscopy, and thin-section scanning with retrospective image fusing. Multisection CT is superior to single-section helical CT for nearly all clinical applications.

Endemic fungal pneumonia in immunocompromised patients.

The endemic fungi Histoplasma capsulatum, Coccidioides immitis, and Blastomyces dermatitidis tend to reside in specific geographic regions. The organisms are pathogenic in that they are able to produce clinical disease in both immunocompromised patients and in patients with normal immunity. These organisms have a variety of clinical presentations, some of which typically are seen in the normal host and others that are primarily encountered in persons with abnormal immunity. Although most of the cases are seen in endemic regions, they may occur in persons who at some time either resided in or traveled to an endemic region.

Noninfectious lung disease in immunocompromised patients.

Immunocompromised hosts have defects in their immune system that make them at risk of developing a variety of infections. In addition, these persons may develop a wide variety of noninfectious disease processes that involve the lung. These disorders may be caused by the underlying disease process. This may be seen with the development of metastatic disease from the underlying neoplasm, or it may represent the development of a malignancy secondary to therapy, as is seen with posttransplant lymphoproliferative disease. The abnormalities may be a result of the therapy used to treat the patients, as is seen with radiation injury to the lung and drug toxicity. Pulmonary edema may occur and be from a wide variety of causes. All of these disease processes may simulate an infectious process and must be differentiated from infection to allow proper therapeutic intervention.

Pulmonary infections in immunocompromised patients who do not have acquired immunodeficiency syndrome: a systematic approach.

Immunocompromised patients are susceptible to infections by organisms that infect individuals with normal immunity and by organisms that affect only those with abnormalities in their immune system. Using the radiographic findings and incorporating clinical information allows for the creation of a useful list differential diagnoses. The nature of the immune defect must be defined because defects in the different parts of the immune system are associated with infections by specific organisms. The time interval since transplantation provides a diagnostic clue because infections tend to occur at certain time intervals after transplantation. An epidemiologic history provides a history of exposure to organisms that may produce pneumonia. Consideration of the therapy the patient has received provides additional clues to the cause of the pneumonia. The physical examination and laboratory studies may provide an indication of the cause of the infection. Organisms tend to produce infections that have a typical rate of clinical development. Classifying the presentation as acute, subacute, or chronic provides additional etiologic clues. Correlating the clinical information with the radiographic findings generates a list of the most likely causative organisms. The list is useful in deciding on additional diagnostic tests and guiding therapy.

Bacterial pneumonia in immunocompromised patients.

Immunocompromised patients develop infections resulting from a wide range of organisms. The most commonly encountered type of infection is bacterial in origin. Many of the infections are community-acquired pneumonias in which most of the infections are caused by organisms that typically produce disease in the healthy person. Hospital-acquired pneumonias are particularly serious, being caused by the highly virulent gram-negative bacilli and Staphylococcus aureus. Immunocompromised patients frequently have indwelling intravascular catheters. These catheters may become infected and seed the lung with septic emboli, producing a hematogenous pneumonia. Underlying conditions and therapy increase the risk for aspiration in the immunocompromised patient. These aspirations can result in the development of an aspiration pneumonia and lung abscess formation. The majority of pneumonias resulting from Legionella and Nocardia occur in immunocompromised patients.

Imaging of lung cancer: old and new.

Lung cancer is the leading cause of cancer death in the United States. Lung cancer is frequently encountered by the radiologist, whether the lung cancer is detected on a chest radiograph obtained in a symptomatic patient, or is an incidental finding. The radiologic workup of pulmonary lesions suspected of being lung carcinoma has evolved as new technology has become available. Current imaging modalities which are useful in the workup of suspected lung cancers include plain radiography, computed tomography, magnetic resonance imaging, with the recent addition of positron emission tomography and endoscopic ultrasound. The following article discusses the merits of these imaging modalities and their role in the workup of patients with lung cancer.

Pulmonary aspergillosis: a spectrum of disease.

Although many species of the fungus Aspergillus have been identified, the most common human pathogen is A. fumigatus, which has a worldwide distribution. Although any organ may become infected, pulmonary aspergillosis is the most common manifestation. The spectrum of pulmonary aspergillosis includes saprophytic aspergillomas, allergic bronchopulmonary aspergillosis, chronic necrotizing aspergillosis, and invasive aspergillosis. Immune status of the host, and the presence of underlying lung disease are important in determining the type of pulmonary involvement. Thus, the radiographic findings are variable. This article reviews the various manifestations of pulmonary aspergillosis, including the immune status of the patient, the presence of underlying lung disease, and the radiographic appearance of the different entities.

CT evaluation of normal interatrial fat thickness.

PURPOSE: This study was performed to determine the normal thickness of fat in the interatrial septum as demonstrated by CT. METHOD: Eighty-seven subjects underwent helical chest CT examination as part of a separate protocol to compare the quantification of coronary artery calcification by CT to coronary angiographic findings, using a slice width of 3 mm, reconstructed every 1.5 mm. The thickness of the interatrial fat in both groups was measured anterior and posterior to the fossa ovalis. The mean and standard deviation were calculated. RESULTS: The mean thickness of interatrial fat anterior and posterior to the fossa ovalis was 4.6 (SD = 2.5) and 3.7 (SD = 3.1) mm, respectively. CONCLUSION: The normal range of thickness of the interatrial fat is 0-9.6 mm anterior to and 0-9.9 mm posterior to the fossa (2 SD above the mean).

Measurement of coronary artery calcium with dual-slice helical CT compared with coronary angiography: evaluation of CT scoring methods, interobserver variations, and reproducibility.

OBJECTIVE: This study was performed to evaluate new scoring methods for quantitating coronary artery calcifications with helical CT and to compare the results with those of quantitative coronary angiography in patients with suspected coronary artery disease. SUBJECTS AND METHODS: Unenhanced dual-slice helical CT and coronary angiography were performed within 24 hr of each other in 101 patients with symptoms of coronary artery disease. Coronary artery calcifications with a density above 90 H were identified on each slice and, with the same regions of interest, quantitative scoring was performed at thresholds of 90 H (new) 130 H (old). Two mathematical algorithms (one new and one old) were evaluated for both thresholds (yielding four scoring systems). By CT imaging, we defined disease as a score of greater than zero. By angiography, we defined disease as a 50% or greater reduction in the luminal diameter of any major vessel. Interobserver variations in calcification scoring were evaluated. Seventeen of our patients. also underwent a second, consecutive CT scan to determine reproducibility. RESULTS: With the new threshold and the new algorithm, the sensitivity, specificity, and accuracy of helical CT in predicting disease were 88%, 52%, and 76%, respectively. We found a moderate positive association between the total CT calcification score and the number of stenotic coronary arteries at angiography (Pearson's correlation coefficient, .43; p = .05 [analysis of variance]). The accuracy and the area under the receiver operating characteristic curve were higher with the new threshold and the new algorithm. Interobserver agreement in calcification scoring was high (intraclass correlation coefficient, .99 [n = 85]), as was reproducibility (intraclass correlation coefficient, .94 [n = 17]). Reproducibility was higher when scoring was based on the new threshold and the new algorithm. CONCLUSION: The quantity of coronary artery calcifications as measured by helical CT correlated positively with obstructive coronary artery disease as measured by angiography. Interobserver agreement and reproducibility were excellent. A new scoring method showed promise.

Pulmonary histoplasmosis.

Histoplasmosis is a common infection in the central United States and is acquired through inhalation of airborne spores. The majority of infected persons have an asymptomatic, self-limiting illness. Clinical pneumonia occurs in those with exposure to a large number of infecting spores. Resolution of the pneumonia often leaves calcified pulmonary nodules, calcified mediastinal lymph nodes, or splenic calcifications. Chronic disease, which mimics tuberculosis, may develop in those with underlying emphysema. In patients with deficient cell-mediated immunity, Histoplasma capsulatum may disseminate throughout the body; this often is fatal. Delayed manifestations arise months or years after the primary infection. Broncholithiasis occurs when peribronchial calcific nodes produce bronchial obstruction. Mediastinal granuloma is the continued proliferation of fibrous tissue in draining mediastinal lymph nodes. These granulomas may obstruct adjacent veins, arteries, or airways and lead to various clinical symptoms.

Reexpansion pulmonary edema.

Reexpansion pulmonary edema is a rare complication attending the rapid reexpansion of a chronically collapsed lung, such as occurs after evacuation of a large amount of air or fluid from the pleural space. The condition usually appears unexpectedly and dramatically-immediately or within 1 h in 64% of patients and within 24 h in the remainder. The clinical manifestations are varied; they range from roentgenographic findings alone in asymptomatic patients to severe cardiorespiratory insufficiency. The radiographic evidence of reexpansion pulmonary edema is a unilateral alveolar filling pattern, seen within a few hours of reexpansion of the lung. The edema may progress for 24-48 h and persist for 4-5 days. Human data on the pathophysiology of reexpansion pulmonary edema derive from small series of patients, case reports, and reviews of the literature. On the other hand, a larger body of data exists on experimental reexpansion pulmonary edema in cats, monkeys, rabbits, sheep, and goats. This review examines the clinical and experimental evidence for reexpansion pulmonary edema. In addition, we detail the historical background, clinical setting, treatment, and outcome of reexpansion pulmonary edema.

Surgical management of pulmonary carcinoma secondary to recurrent respiratory papillomatosis.

Recurrent respiratory papillomatosis is a rare, but acknowledged, risk factor for pulmonary squamous cell carcinoma. Although previous reports suggest a poor prognosis for lung cancer associated with papillomatosis, we have successfully treated 1 such patient, who presented with three synchronous pulmonary malignancies, using parenchyma-sparing resection techniques.

Tracheoesophageal fistula due to Wegener granulomatosis.

Most acquired tracheoesophageal fistulas (TEFs) are due to malignant disease processes, with nonmalignant causes infrequently encountered. We report a patient with a TEF caused by Wegener granulomatosis. The radiographic findings of this rare cause of TEF are described.

Spiral CT evaluation of the trachea and bronchi.

OBJECTIVE: We report two cases in which spiral CT with three-dimensional (3D) reconstruction was used to evaluate abnormalities of the trachea and bronchi. MATERIALS AND METHODS: Two patients with known airway abnormalities, one with a carinal tumor and the other with a postoperative bronchial stenosis, had spiral CT of the chest performed. Images were reconstructed in the coronal plane as well as using a curved planar reformat and shaded surface display. RESULTS: Spiral CT with 3D reconstruction provided excellent anatomic definition of the central airway abnormalities. In our two cases the information provided was used in both the clinical assessment and treatment planning of the patients. CONCLUSION: Spiral CT was useful in the evaluation of two patients with central airway abnormalities. Further investigation into applications of spiral CT for the evaluation of the central airways appears warranted.

Interventional chest radiology.

Interventional radiology has important applications for the diagnosis and treatment of chest diseases. Fine-needle aspiration biopsy of a lung nodule is the most commonly performed procedure, but lesions in the mediastinum, hilum, and chest wall also can be biopsied. Needle aspiration and catheter drainage help in treating pleural effusion, empyema, and lung and mediastinal abscesses. Emphasis on teamwork and patient care is essential. In this article, the authors offer practical advice on how and when to undertake these procedures and how to manage any associated complications.

Painful transthoracic needle biopsy: a sign of neurogenic tumor.

Neurogenic tumors most commonly appear initially as posterior mediastinal masses. These tumors, however, may occur in other intrathoracic locations and present a diagnostic challenge. In such cases transthoracic fine-needle aspiration (FNA) often is used to make a definitive diagnosis. This procedure usually does not result in severe pain. We report two patients who experienced severe pain during transthoracic FNA of neurogenic tumors. We believe that severe pain associated with transthoracic needle biopsy of an intrathoracic mass is suggestive of a neurogenic tumor. When pain accompanies this procedure, a cytopathologist should be notified so that specific immunostaining techniques can be performed to confirm the diagnosis.