Biomedical subjects
Publications and source records attributed to G Gamsu.
Magnetic resonance imaging (MRI) of an angiographically confirmed pulmonary embolus was performed. The thrombus appeared as an intense intraluminal signal within the left descending pulmonary artery; this signal was absent on repeat examination after clot lysis. Because MR will not image flowing blood, it provides a potential method of non-invasive identification of stationary emboli within the pulmonary vascular tree.
The clinical presentation and radiographic progression of Legionnaires' disease is described in 10 renal transplant patients, the majority undergoing treatment for rejection. Presentation with pleuritic chest pain, fever, hypoxia, and hemoptysis was typical and in some cases led to confusion with pulmonary embolism. The radiographic appearance was that of rapidly progressive, dense, sublobar consolidation, occasionally showing patchy spread to other areas and usually accompanied by pleural effusion. Cavitation occurred in seven of 10 patients.
In order to determine the value of coronal magnetic resonance (MR) in diagnosing thoracic abnormalities, the multisection coronal spin echo MR images were reviewed of 10 normal subjects and 20 patients with thoracic abnormalities. In the abnormal patients, coronal images were compared with transaxial MR images obtained with TR values of 0.5 and 2.0 sec. In general, coronal imaging was of value in several situations. It allowed structures oriented in the coronal plane to be imaged along their longitudinal axes, provided an additional perspective and increased the confidence of diagnosis, and helped clarify anatomic relationships difficult or impossible to resolve on transaxial images because of volume averaging. Specifically, coronal images were sometimes superior to transaxial images in evaluating the aorticopulmonary window and masses at the lung apex or base. Transaxial images were often superior in evaluating the pretracheal space, subcarinal space, and hili. Within the pulmonary hili, lateral hilar masses were better defined on coronal images than were anterior or posterior hilar masses. Coronal images obtained with a TR of 1.0 sec (10 sections) allow evaluation of most node-bearing mediastinal compartments and provide adequate mass/fat contrast.
The presence of mediastinal and/or hilar adenopathy was assessed from the chest radiographs of two groups of homosexual men: 30 with diffuse, persistent lymphadenopathy syndrome and 45 with acquired immunodeficiency syndrome (AIDS). Intrathoracic adenopathy was not seen on the chest radiographs of the 30 men having diffuse, persistent lymphadenopathy and is therefore not a manifestation of that syndrome. Nine of the 45 men with AIDS demonstrated intrathoracic adenopathy. In each instance, adenopathy was indicative of serious intrathoracic disease. Seven of the nine had minimal or no respiratory symptoms. In four of the nine, the intrathoracic adenopathy detected from the chest radiographs was the first indication of AIDS. In six of the nine patients, one or more opportunistic infections were diagnosed from material obtained at bronchoscopy. Two patients had Hodgkin disease, diagnosed by lymph-node biopsy. The ninth patient, who died, had an immunoblastic sarcoma. Mediastinal and/or hilar adenopathy in patients with AIDS, or in patients at high risk for AIDS, necessitates immediate investigation, including bronchoscopy or lymph-node biopsy.
The posterior wall of the bronchus intermedius (PWBI) is visible on lateral chest radiographs and computed tomographic (CT) scans and can become abnormally thickened in the presence of right hilar disease. The appearances of the PWBI on plain radiographs and CT were correlated in groups of 20 normal patients and 20 patients with a right hilar abnormality. Among 10 patients with an abnormal hilum who had thickening of the PWBI on CT, the lateral radiograph showed thickening of similar degrees in seven. However, in two of the 10, the lateral chest radiograph significantly underestimated the degree of thickening of the PWBI, and in one the PWBI was not visible. Among 10 patients with an abnormal right hilum who had no thickening of the PWBI on CT, the PWBI appeared to be abnormal on lateral chest radiographs in four because of adenopathy in the lateral or medial hilum. One other finding of note was the presence in one patient of an anomalous pulmonary vein passing posterior to the bronchus intermedius, simulating a small posterior hilar mass.
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Ten patients having a mediastinal tumor were studied with magnetic resonance imaging (MRI) using from two to four imaging sequences. Seven had bronchial carcinoma and three had benign lesions. The sequences included the spin-echo technique with repetition time (TR) values of 0.5, 1.0, and 2.0 sec and echo time (TE) values of 28 and 56 msec, and the inversion-recovery technique. The signal-intensity ratios of the mediastinal mass and mediastinal fat, which are a measure of image contrast, were compared for the different imaging sequences. Also signal-to-noise ratios were measured relative to both mediastinal fat and mediastinal mass. With spin-echo imaging, decreasing the TR value resulted in an increase in mass/fat contrast in all patients, making the masses easier to detect, but this also resulted in decreased signal-to-noise ratios. Inversion-recovery imaging with the sequence used resulted in a greatly increased mass/fat contrast, because of a relative decrease in signal from the mass. However, in two of four patients studied with this technique, the mass was so low in intensity that it could not be distinguished from the trachea or mediastinal vessels, and in one of these four, a lung nodule was also invisible. Spin-echo imaging with both short and long TR values provides good tissue contrast and good signal-to-noise ratios.
Ten cardiac and paracardiac masses were studied with magnetic resonance imaging (MRI) to evaluate the utility of this new method for determining the nature, location, and extent of such masses. The masses were intramural lesions (two cases), left atrial thrombus (one case), pericardial cysts (three cases), and mediastinal masses deforming and displacing the left atrium (two cases). ECG-gated images were obtained in all patients. In each of nine cases, MRI determined the location of the mass as intracavitary, intramural, or paracardiac, without the need for exogenous contrast material. It excluded the clinical diagnosis of cardiac tumor in one case. A combination of multislice transaxial, coronal, and sagittal images established the extent of the masses and the degree of impingement on cardiac structures. This initial experience suggests that MRI can provide as much information as echocardiography, computed tomography, and angiography combined in the evaluation of cardiac and paracardiac masses.
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Nuclear magnetic resonance (NMR) imaging, using the spin-echo and inversion recovery techniques, provides an excellent demonstration of normal intrathoracic anatomy, and has proven useful in the diagnosis of a number of chest diseases. Because of the absence of NMR signal from rapidly flowing blood, vascular lesions can be easily diagnosed without the use of contrast agents, and mediastinal and hilar masses can be easily distinguished from normal or abnormal vessels. On the basis of T1 values, mediastinal masses can be distinguished from normal mediastinal tissues, and using T1 and T2 values, fluid within masses can be detected. Although NMR appears to offer no great advantage relative to CT in the diagnosis of mediastinal mass, small hilar masses are much more easily distinguished from normal hilar structures using NMR. Another significant advantage of NMR is its ability to directly image in the sagittal and coronal planes with good spatial resolution. In some patients, this can be helpful in the assessment of mediastinal masses. NMR may prove helpful in the evaluation of blood flow, the noninvasive diagnosis of pulmonary embolism, and in the quantitation of lung water.
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NMR promises great advances in diagnosis and has delivered so much already that it is expected that in the future it will replace many applications of the currently used imaging modalities. Although x-ray computed tomography is continuing to advance in speed of scanning and resolving power, NMR will most likely soon eliminate its use in many studies of the central nervous system and also in many other areas of the body. The promise of combining topical spectroscopy with imaging is also exciting and should provide further information about metabolic processes of various organs. Progress in NMR is so rapid and the future is so bright that one of the great problems will be to develop a new breed of radiologists who are versatile in biochemistry, mathematics, and computers, as well as competent in morphologic anatomy and pathologic physiology. As time goes on, advances in NMR will be achieved only by teams of clinical and basic scientists encompassing multiple disciplines.
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Posterior to the left hilum, lung contacts and outlines the posterior wall of the left main bronchus, producing a stripe of density (left retrobronchial stripe) visible using computed tomography. Thickening or nodularity of the stripe, resulting in separation of air in lung from air in the bronchial lumen often reflects tumor infiltration of the bronchial wall, or lymphadenopathy. Consolidation of the lower lobe can obliterate the stripe, but, because the pleural space does not extend posterior to the bronchial wall, pleural effusion generally will not.
Computed tomography (CT) is generally superior to plain chest radiographs in differentiating pleural and pulmonary parenchymal lesions. We report a patient with asbestos exposure who had a rare interlobar pleural plaque involving the major fissure. In this patient CT suggested the presence of a lung nodule but the lateral chest radiograph indicated the correct diagnosis.
In 30 patients with histologically proven bronchogenic carcinoma, computed tomographic (CT) scans of the pulmonary hila, plain radiographs, and medical records were reviewed. All had abnormal plain radiographs. The CT findings included (a) a local alteration in hilar contour; (b) thickening of the posterior wall of the right upper lobe bronchus, bronchus intermedius, or left main bronchus; and (c) narrowing, displacement, or obstruction of bronchi. In 24 patients having fiberoptic bronchoscopy, CT findings of bronchial abnormality correlated closely with bronchoscopic findings. In two patients, CT showed a bronchial abnormality invisible at bronchoscopy, leading to a positive biopsy. In one patient, a bronchial abnormality invisible at CT was visible at bronchoscopy and positive on biopsy.
Computed tomography in a man with recurrent right lower lobe pneumonias showed an endobronchial mass associated with hilar lymph node enlargement. Because of this combination of findings, bronchogenic carcinoma with hilar node involvement was suggested as likely. Surgery revealed a carcinoid bronchial adenoma limited to the bronchus, with hyperplastic lymph node enlargement resulting from pneumonia. Care must be taken not to assume that hilar lymph node enlargement represents tumor, even when associated with an endobronchial lesion.