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The purpose of this review article is to review the process of developing optimal computed tomography (CT) protocols for quantitative lung CT (QCT). In this review, we discuss the following important topics: QCT-derived metrics of lung disease; QCT scanning protocols; quality control; and QCT image processing software. We will briefly discuss several QCT-derived metrics of lung disease that have been developed for the assessment of emphysema, small airway disease, and large airway disease. The CT scanning protocol is one of the most important elements in a successful QCT. We will provide a detailed description of the current move toward optimizing the QCT protocol for the assessment of chronic obstructive pulmonary disorder and asthma. Quality control of CT images is also a very important part of the QCT process. We will discuss why it is necessary to use CT scanner test objects (phantoms) to provide frequent periodic checks on the CT scanner calibration to ensure precise and accurate CT numbers. We will discuss the use of QCT image processing software to segment the lung and extract the desired QCT metrics of lung disease. We will discuss the practical issues of using this software. The data obtained from the image processing software are then combined with those from other clinical examinations, health status questionnaires, pulmonary physiology, and genomics to increase our understanding of obstructive lung disease and improve our ability to design new therapies for these diseases.

Computed tomography has facilitated recognition that chronic obstructive pulmonary disease is not a single disease but encompasses several overlapping entities, including emphysema, bronchitis, and small airways disease. Quantitative computed tomography can effectively characterize and quantify the extent of emphysema, airway wall thickening, and air trapping related to small airways disease.

Summary Inflammatory airways disease is an uncommon but recognized complication of ulcerative colitis (UC). The present study was undertaken to determine the computed tomographic (CT) and high-resolution CT appearances of this entity. A retrospective review was performed of the radiographs and CT scans of seven patients (ages 24 to 54 years) with UC who presented with cough and recurrent respiratory infections. Four patients had total colectomies, and one had sigmoid colectomy. Fiberoptic bronchoscopy in six subjects showed diffuse mucosal erythema and edema that was most severe in the proximal airways. Sinus radiographs revealed maxillary sinus mucosal thickening in four patients and ethmoid sinus involvement in two. Chest radiographs showed bronchiectasis in two patients and bronchial wall thickening in three; radiographs were normal in two patients. CT features included bronchiectasis in six patients, peripheral airways involvement in four, and airway stenosis in three.

Extrapleural pneumonectomy, which usually requires placement of a prosthetic hemidiaphragm, can be offered to approximately 24% of patients with malignant mesothelioma. Expanded polytetrafluoroethylene (Gore-Tex) has superior physical characteristics for diaphragmatic grafting and is the material of choice at the authors' institutions. This article describes conventional radiography and computed tomography findings in three patients who underwent extrapleural pneumonectomy. A freshly placed Gore-Tex prosthetic diaphragm appears as a radiolucent crescent-shaped band at the inferior border of the hemithorax and could be confused with a pneumoperitoneum. With time, the lucent crescent becomes thinner and eventually becomes radiopaque; it may be confused with a calcified diaphragm.

In reviewing the medical records of ten patients with Lennert's lymphoma, we found chest radiographic abnormalities in five cases. Two cases had hilar and mediastinal adenopathy without associated parenchymal or pleural disease, and three cases had isolated pulmonary parenchymal abnormalities. In one patient, both the chest radiograph and the histologic findings, obtained by open lung biopsy, mimicked miliary granulomatous disease. This article emphasizes the need to be alert to this aggressive T-cell neoplasm, since its clinical course differs significantly from some of the diseases it tends to imitate. By being aware of the entity and by using thorough pathologic and immunopathologic techniques, difficult cases of Lennert's lymphoma can be successfully diagnosed.