Review of high-resolution CT of the lung.

High-resolution computed tomography (HRCT) of the lung provides detailed visualization of the lung parenchyma and is being used to evaluate chronic interstitial lung disease. The technique of HRCT involves use of 1-2-mm-thick collimation scans with a high spatial frequency algorithm. To fully appreciate the HRCT findings, one should understand the anatomy of the secondary pulmonary lobule. Lung disease can be classified according to pattern (linear areas, nodular areas, areas of decreased attenuation, and areas of ground-glass attenuation) and distribution (peripheral, axial, and parenchymal). Identifying the pattern and distribution of disease helps in formulating a differential diagnosis. Furthermore, when biopsy is necessary, distribution of lung disease, as seen on HRCT scans, can help in planning the approach.

CT demonstration of calcification in carcinoma of the lung.

Radiologic visualization of calcification within lung cancer is uncommon and may cause confusion and misdiagnosis. For this reason, we reviewed CT records of 353 patients undergoing initial evaluation of lung cancer for the presence of calcification within the tumor, both to document this finding and to estimate its prevalence. Twenty patients (6%) whose records indicated that CT showed calcification were identified, and their chest radiographs and CT scans were analyzed. Patients were included in the study if calcium was seen within the tumor on noncontrast pretreatment CT scans and if pathologic data were available. There were 15 lung and five mediastinal tumors. Fourteen were 5 cm or greater in diameter; three were between 3 and 5 cm, and three were 2 cm or smaller. Cell types of the tumors included small-cell carcinoma (eight patients), squamous cell carcinoma (seven patients), adenocarcinoma (four patients), and undifferentiated carcinoma (one patient). Patterns of calcification were amorphous (eight patients), punctate (10 patients), and reticular (two patients). Extent of tumor calcification and distribution (central, peripheral, or diffuse) did not correlate with cell type or size of the lesion. The visualization of calcium on chest radiographs and CT scans does not alone exclude the diagnosis of bronchogenic carcinoma.

The left paratracheal reflection.

The left paratracheal reflection, which is found medial to the left subclavian artery reflection, was sought in 302 normal posteroanterior (PA) chest radiographs, 93 conventional chest tomograms, and 113 thoracic computed tomographic (CT) scans. The left paratracheal reflection was visible on 31% of normal PA chest radiographs. Conventional tomography and CT showed that this finding is produced by contact of the lung with the mediastinum anterior to the left subclavian artery. The CT scans studied showed that the left paratracheal reflection actually represents contact of the lung with left paratracheal mediastinal fat 94% of the time, with the proximal 1-2 cm of the lateral wall of the left common carotid artery 5% of the time, and with the left tracheal wall 1% of the time. A variety of entities may alter the left paratracheal reflection.

Orthotopic cardiac transplantation: evaluation with CT.

As cardiac transplantation has become widely available, computed tomography (CT) of the chest has played a useful role in the examination of patients after heart transplantation. To determine anatomic features related to the procedure, the authors evaluated 59 scans in 46 patients who had undergone orthotopic cardiac transplantation. Aortic anastomosis (seen in 98% of scans) and altered spacing between the great vessels (83%) proved to be the most common and most reliable findings. Other features including atrial anastomosis, high main pulmonary artery segment, remnant superior vena cava, and cardiac reorientation were also seen. Accurate interpretation of adenopathy, mediastinal abscess, and pericardial effusion will be enhanced in these patients through a better understanding of the cardiovascular-pericardial complex, which is afforded by CT.

Diagnosis of anemia on computed tomography scans of the thorax.

Scans of 14 patients with hemoglobin levels of 7.6 to 10.2 grams/deciliter (gm/dL) were positive for the diagnosis of anemia. All demonstrated the interventricular septum and ascending and descending aortic walls. Scans of 23 patients with hemoglobin levels of 10.5 to 12.8 gm/dL were positive for the diagnosis of anemia in 11 and negative in 12. The ascending and descending aortic walls were seen 39% and 48% of the time, respectively. Scans of 13 patients with hemoglobin levels of 12.9 to 16.0 gm/dL were negative for the diagnosis of anemia.