Gordon Gamsu

CT-determined pulmonary artery diameters in predicting pulmonary hypertension.

This study was to determine if the diameters of pulmonary arteries measured from computed tomographic (CT) scans could be used 1) as indicators of pulmonary artery hypertension and 2) as a reliable base for calculating mean pulmonary artery pressure. The diameters of the main, left, proximal right, distal right, interlobar, and left descending pulmonary arteries were measured from CT scans in 32 patients with cardiopulmonary disease and in 26 age- and sex-matched control subjects. Diameters were measured using a special computer program that could display a CT density profile of the artery and its adjacent tissues. The upper limit of normal diameter for the main pulmonary artery was found to be 28.6 mm (mean + 2 SD). In the patient group, the diameters were correlated with data from cardiac catheterization. In these patients, a diameter of the main pulmonary artery above 28.6 mm readily predicted the presence of pulmonary hypertension. The calculated cross-sectional areas of the main and interlobar pulmonary arteries (normalized for body surface area [BAS]) were found to give the best estimates of mean pulmonary artery pressure (r = 0.89, P less than 0.001 and r = 0.66, P less than 0.001). Multiple regression analysis gave the useful equation: mean pulmonary artery pressure = -10.92 + 0.07646 X area of main pulmonary artery/BSA + 0.08084 X area of the right interlobar pulmonary artery/BSA (r = 0.93, P less than 0.0001). Because CT allows precise, noninvasive measurement of the diameter of pulmonary arteries, it can be of value in detecting pulmonary hypertension and estimating mean pulmonary artery pressure.

A consensus statement of the Society of Thoracic Radiology: screening for lung cancer with helical computed tomography.

This consensus statement by the Society of Thoracic Radiology is a summary of the current understanding of low dose computed tomography (CT) for screening for lung cancer. Lung cancer is the most common fatal malignancy in the industrialized world. Unlike the next three most common cancers, screening for lung cancer is not currently recommended by cancer organizations. Improvements in CT technology make lung screening feasible. Early prevalence data indicate that about two-thirds of lung cancers that are detected by CT screening are at an early stage. Other data support the postulate that patients with lung cancers detected at this early stage have better rates of survival. Whether this will translate into an improved disease specific mortality is yet to be demonstrated. The suggested technical protocols, selection criteria, and method of handling the numerous benign nodules that are detected are discussed. It is the consensus of this committee that mass screening for lung cancer with CT is not currently advocated. Suitable subjects who wish to participate should be encouraged to do so in controlled trials, so that the value of CT screening can be ascertained as soon as possible.

Ct of a Bronchial Phantom: Factors Affecting Appearance and Size Measurements

In order to determine the most appropriate window settings for viewing CT of the bronchial tree, we performed CT of a bronchial phantom consisting of air-filled tubes measuring from 3.1 to 12.7 mm, oriented at varying angles relative to the scan plane, surrounded by water or air, and with scan collimation of 10 mm, 5 mm, and 1.5 mm. Using a computer program to graphically display CT number relative to the distance across the tubes lumen, it was found that a window mean of -150 H accurately estimated the internal diameter of tubes surrounded by water, at all angles, when collimation was 5 mm or 1.5 mm. With 10-mm collimation, tube diameter was slightly underestimated for tubes 9.5 mm or less when oriented 30 degrees or more from perpendicular to the plane of scan. At lower window settings and window widths of 500 H or less, all tubes diameters were significantly underestimated. At -150 H, with tubes parallel to and centered in the scan plane, 5-mm and 1.5-mm collimation were most accurate; with decentering of 4 mm, 10-mm collimation better showed the tubes lumen. When surrounded by air, tube wall thickness was best estimated using a window mean of -450 H.

Determination of obstructive site in obstructive sleep apnea

Patients with obstructive sleep apnea syndrome (OSAS) may have airway obstruction at various levels, including the uvula‐soft palate complex, base of tongue, and/or possibly other sites. For patients with tongue base and/or laryngeal obstruction, uvulopalatopharyngoplasty (UPPP, ppp) will not alleviate the obstruction. Prior authors have proposed that the hyoid bone position as determined by cephalometric x‐rays can predict which patients have obstruction at a lower site than the soft palate.

Computed tomography in pulmonary sarcoidosis.

We studied the high resolution CT (HRCT) scans of 15 patients with biopsy-proven sarcoidosis and correlated the findings with pulmonary function tests (12 patients), 67Ga scans (10 patients), bronchoalveolar lavage (five patients), recent transbronchial biopsy (six patients), and recent open lung biopsy (three patients). The HRCT features included small nodules, thickened interlobular septa, patchy focal increase in lung density, honeycombing, and central conglomeration of vessels and bronchi. Active alveolitis was present by gallium scanning criteria in 5 of 10 cases. By bronchoalveolar lavage criteria, activity was present in three of five cases. Patchy increase in density may correlate with active alveolitis as seen on 67Ga scanning. High resolution CT was better than chest X-radiography for demonstration of patchy increase in density and for distinguishing nodules from septal thickening. Both nodules and patchy density were partly reversible following therapy. Nodular densities seen on CT correlated with the presence of granulomata on histology. Resting pulmonary function tests correlated poorly with presence and extent of lung disease on HRCT. The presence on HRCT of focal fine nodules, patchy focal increase in lung density, and central crowding of bronchi and vessels should suggest the diagnosis of sarcoidosis. In some patients, HRCT can identify unsuspected parenchymal lung disease and document the reversible components of sarcoid lung disease.

Tree-in-bud pattern: frequency and significance on thin section CT.

PURPOSE Our goal was to describe those diseases of the airways that manifest the tree-in-bud (TIB) pattern on CT scan and to establish a differential diagnosis for this CT scan finding. METHOD We prospectively collected cases with the TIB pattern on CT and reviewed the scans of patients with histories pertaining to small airway disease. CT scans were performed at 1 to 3 mm collimation. RESULTS Twenty-six of 27 cases with the TIB pattern had associated bronchiectasis or proximal airway wall thickening. One case with normal proximal airways had an acute aspiration. In addition, we reviewed 141 scans of patients with emphysema, respiratory bronchiolitis (RB), bronchiolitis obliterans (BO), bronchiolitis obliterans organizing pneumonia (BOOP), extrinsic allergic alveolitis (EAA), bronchiectasis, bronchitis, and pneumonia. Of the CT scans with bronchiectasis, 25.6% had TIB, and 17.6% of CT scans with acute infectious bronchitis or pneumonia had this pattern. None of the patients with emphysema, BO, BOOP, EAA, or RB had this pattern. CONCLUSION The TIB pattern on CT scan is mostly associated with pulmonary infections that commonly involve the large airways. This pattern was present in 17.6% of cases with acute bronchitis or pneumonia and 25.6% of cases with bronchiectasis.

Dynamic quantitative computed tomography. A predictor of pulmonary function in obstructive lung diseases.

Stern EJ, Webb WR, Gamsu G. Dynamic quantitative computed tomography: a predictor of pulmonary function in obstructive lung diseases. Invest Radiol 1994;29:564-569. RATIONALE AND OBJECTIVES.Nine patients were examined using dynamic electron beam computed tomography to assess the utility of this technique in detecting airway obstruction and air trapping, and to compare this technique with pulmonary physiologic testing. METHODS.Dynamic computed tomography (C-100 Ultrafast CT scanner, Imatron Inc., South San Francisco, CA) was performed, with a series of ten, 100-msec images obtained in a 6-second period during forced inhalation and exhalation. Time-attenuation curves were calculated from the observed changes in lung attenuation. Estimates of the percentage of each lung that showed air trapping were made at each level scanned, using a 5-point scale. Specific correlations were made for pulmonary function test results and air-trapping score. RESULTS.In all nine patients, dynamic computed tomography demonstrated one or more sites that failed to show a normal increase in lung attenuation during forced exhalation. Four of these 9 patients showed a paradoxical decrease in lung attenuation during exhalation in at least one region of the lung. Extent of air-trapping correlated well with forced expiratory volume in one second (r = –.92). CONCLUSIONS.Based on this small sample, the authors believe that this technique will prove sensitive for detecting abnormalities of ventilation and may be a useful adjunct to conventional diagnostic procedures in the management of disorders of airway obstruction.

Computed tomography in the diagnosis of asbestos-related thoracic disease.

High-resolution computed tomography (HRCT) has improved the radiologists ability to detect and potentially quantify the abnormalities of asbestos exposure. It has proved to be more sensitive than chest radiography for detecting pleural plaques and for discriminating between pleural fibrosis and extrapleural fat. HRCT is also more sensitive than chest radiography or conventional CT for detecting parenchymal abnormalities in asbestos-exposed persons. The HRCT findings that correlate with other parameters of asbestosis include (1) septal and centrilobular thickening, (2) parenchymal fibrous bands, (3) honeycomb patterns, (4) subpleural density persisting in the prone position, and (5) subpleural curvilinear lines that persist in the prone position. CT has an important role in evaluating benign and malignant lung and pleural masses in asbestosis.

Diagnostic value of chest radiography for pericardial effusion

OBJECTIVES This study was designed to determine the diagnostic value of chest radiography for pericardial effusion. BACKGROUND Pericardial effusions may cause life-threatening cardiac complications, yet they are often difficult to diagnose. METHODS In a blinded manner, we reviewed the chest radiographs of 83 patients with echocardiographically diagnosed pericardial effusions (5 large, 18 moderate, 60 small) and those of 17 control subjects without effusions. We examined four radiographic signs: an enlarged cardiac silhouette, a pericardial fat stripe, a predominant left-sided pleural effusion and an increase in transverse cardiac diameter compared with the diameter on a previous chest radiograph. RESULTS An enlarged cardiac silhouette was moderately sensitive (71%) but not specific (41%) for pericardial effusion. A pericardial fat stripe, a predominant left-sided pleural effusion and an increase in transverse cardiac diameter were all specific (94%, 100% and 80%, respectively) but not sensitive (12%, 20% and 46%, respectively). A predominant left-sided pleural effusion was associated with pericardial effusions of all sizes (odds ratio = 1.3, 95% confidence interval [CI] = 1.0-1.6, p = 0.04) and with large and moderate pericardial effusions alone (odds ratio = 7.7, 95% CI = 2.5-24.0, p = 0.0004). In contrast, a pericardial fat stripe was associated only with large and moderate pericardial effusions (odds ratio = 3.3, 95% CI = 0.9-12.0, p = 0.07), and an enlarged cardiac silhouette and an increase in cardiac diameter were not associated with pericardial effusion at all. CONCLUSIONS A predominant left-sided pleural effusion and a pericardial fat stripe are chest radiographic signs that are suggestive, but not diagnostic, of pericardial effusion. Because these signs cannot reliably confirm or exclude the presence of pericardial effusion, we conclude that chest radiography is poorly diagnostic of this condition.

Pulmonary artery dissection: MR findings.

We report a case of pulmonary artery dissection imaged by MR. Dissection of a markedly dilated pulmonary artery is a rare and usually fatal complication of chronic pulmonary arterial hypertension. The diagnosis is made at autopsy, with only two cases having previously been documented (by Doppler echocardiography) during life. The hallmark of an arterial dissection is the finding of an intimal flap and a false lumen. In our case, spin echo MR imaging failed to show either the intimal flap or any intraluminal signal defects. The dissection was presumably obscured by nonhomogeneous intraluminal signal caused by the slow blood flow associated with severe pulmonary arterial hypertension. Cine MR imaging, however, demonstrated different signal intensity within the true and false lumens of the dissection, thereby outlining the intimal flap between the two channels.