Imaging of the axillary subsegment of the right upper lobe.

The bronchial supply of the lateral or axillary area of the right upper lobe is variable. In 16 percent of normal subjects, an independent ramus of the posterior right upper lobe bronchus supplies an axillary subsegment. Airspace disease in the axillary subsegment has a characteristic appearance on radiographs. The CT appearance of disease in the axillary subsegment correlates closely with classic anatomic studies. Recognizing that disease is located in the axillary subsegment can help in directing bronchoscopy or biopsy.

Radiographic assessment of hyperinflation: correlation with objective chest radiographic measurements and mechanical ventilator parameters.

BACKGROUND: Pulmonary barotrauma is a potentially fatal complication of positive pressure ventilation. We previously found that barotrauma occurred in patients with radiographic hyperinflation, but few objective data define the relationships among hyperinflation, objective chest radiograph (CXR) measurements, ventilator parameters, and development of barotrauma. OBJECTIVES: We sought (1) to assess the relationships among hyperinflation, objective CXR findings, mechanical ventilator parameters, and development of barotrauma. (2) To compare radiographic hyperinflation, ventilator parameters, and incidence of barotrauma in a current group of ICU patients with historical control subjects. SETTING: Medical and surgical ICU patients in a university hospital. DESIGN: Prospective blinded observational study; comparison of current series with historical control subjects. METHODS: One hundred two prospectively enrolled mechanically ventilated medical and surgical ICU patients each received portable supine CXRs that were reviewed independently by three radiologists who made objective measurements and subjectively determined the likelihood of hyperinflation. Ventilator parameters were recorded at the bedside at the time each CXR was obtained. CXR measurements and ventilator parameters were then related to the development of barotrauma during the course of ventilation and compared with findings of a prospective study at our institution 1 year earlier. RESULTS: Radiographically recognizable hyperinflation occurred in 18 of 102 mechanically ventilated ICU patients (18%) and correlated with lung length (24.7 vs 19.8 cm; p<0.05) and the anterior rib number that intersects the hemidiaphragm (5.4 vs 4.7; p<0.05). Patients with hyperinflation were ventilated at higher tidal volume per kilogram (VT/kg) (11.0 vs 9.4; p=0.0081), but peak airway pressure, plateau pressure, and positive end-expiratory pressure were similar. There were significant decreases in VT (810 vs 739 mL; p=0.015) and VT/kg (11.0 vs 10.1 mL/kg; p<0.001) in these mechanically ventilated ICU patients in comparison to hospital control subjects evaluated during the previous year. Paralleling these changes was a decrease in the frequency of CXR hyperinflation (p=0.003) and the incidence of ventilator-associated barotrauma (6.5% vs 0.98%; p=0.048). CONCLUSIONS: Ventilation at higher VT/kg is associated with a higher incidence of CXR hyperinflation. Radiographic hyperinflation is associated with lung length > or =24.7 cm and visualization of the sixth anterior rib. Patients with hyperinflation may be at greater risk for developing barotrauma or volutrauma. Ventilatory strategies utilizing lower volumes are associated with a lower incidence of such trauma in the current sample as compared with historical control subjects.

Evaluation of the portable chest roentgenogram for quantitating extravascular lung water in critically ill adults.

The diagnosis of pulmonary edema is frequently made from characteristic findings on the chest roentgenogram that suggest an increase in lung water. Optimal radiographic technique depends on a cooperative upright patient, which is not possible with most critically ill patients. These patients may also have multiple radiographic abnormalities that make interpretation of the chest roentgenogram difficult. The ability of portable chest roentgenograms to accurately identify the presence of excess lung water and monitor changes in lung water has not previously been evaluated in critically ill adults who are intubated and ventilated and in the supine position when the films are exposed. In 12 patients the pulmonary edema seen on portable chest roentgenograms was given a score (0 to 390 points), which was then compared with a determination of extravascular lung water using the thermal-dye indicator dilution technique. A linear correlation was observed (r = 0.51; p less than 0.05; n = 73). Evaluation of a change in radiographic score vs a change in lung water showed no linear correlation (r = 0.1; p greater than 0.05). While portable chest roentgenograms exposed under the conditions described were a useful technique for demonstrating pulmonary edema, they were not accurate in monitoring modest changes in lung water in critically ill patients.

Physical principles governing the interrelationships of pressure, flow and volume in collapsible tubes.

Basic principles of fluid mechanics may be used to analyze the relationships of flow, pressure and cross-sectional area of any collapsible tube, including pulmonary blood vessels. The cross-sectional area of a collapsible tube is a direct function of transmural pressure. Alterations in pressure inside the tube may result from changes in fluid velocity, downstream constriction in the tube, or direct increase in internal pressure, as with a manometer. This paper reviews the basic equations applicable to flow in collapsible tubes and illustrates the principles of such flow with a physical model. Depending upon the circumstances, changes in size of the tube may or may not reflect changes in flow or changes in fluid velocity.

Visual skill. Correlation with detection of solitary pulmonary nodules.

A series of visual tests was administered to 65 individuals: 9 Board-certified radiologists, 41 radiology residents, and 15 fourth-year medical students on the senior radiology elective. Results of these visual tests were compared with performance in detection of solitary pulmonary nodules. Among radiology residents or board-certified radiologists, no correlation was found between performance on tests of visual perception and the ability to correctly locate pulmonary nodules. A correlation between visual test scores and nodule detection was evident among medical students. These findings suggest that factors other than skill in visual perception determine a radiologist's ability to correctly identify solitary pulmonary nodules.

Chronic multiple pulmonary emboli. Regional response of the bronchial circulation.

In pulmonary embolism, the bronchial circulation can dramatically increase perfusion to the lung and prevent infarction. The physiology of this response is incompletely understood. The authors studied the regional changes in the bronchial circulation in an animal model after multiple chronic pulmonary emboli to the periphery of one lung. The gross anatomy of the bronchial circulation was studied using Batson's solution to produce vascular casts of the pulmonary and bronchial circulations. These casts were prepared in a normal sheep and in a sheep with multiple chronic microemboli in the periphery of one lung. The normal bronchial arteries are visible as threadlike structures covering the surface of the tracheobronchial tree with ramifications extending to the lung periphery. In a sheep with multiple chronic microemboli, the bronchial arteries supply the pulmonary parenchyma deprived of pulmonary arterial flow. The bronchial arteries following pulmonary arterial embolization markedly dilate and are serpentine.

A method for evaluating the bronchial circulation. Preliminary observations.

Due to the small size of the bronchial arteries, the bronchial circulation is difficult to study and remains poorly understood. We have utilized single photon emission computed tomography (SPECT) as a noninvasive means of studying the bronchial circulation. Imaging studies were performed in sheep before and after the introduction of a single pulmonary embolus. Digital bronchial arteriograms demonstrated the dilatation of the bronchial artery which is present on studies one week after embolization. SPECT bronchial perfusion scans reveal a wedge of increased activity that corresponds to a wedge of decreased activity on SPECT pulmonary perfusion images. Axial images available with SPECT provide information about regional alterations of bronchial perfusion not readily apparent on bronchial arteriograms.

Detection of pulmonary emboli in dogs using digital subtraction angiography.

Digital subtraction angiography (DSA) was performed in six dogs to define the limits of detection of pulmonary emboli. Three angiograms were initially obtained in three normal control animals, two of which were subsequently embolized. A total of ten pulmonary angiograms were then obtained in five dogs that had experimentally produced emboli of Ivalon cubes (2, 3, and 10 mm). The intravenous angiograms were followed by selective arterial angiograms to confirm the presence and location of the emboli. The intravenous angiograms were independently reviewed by two radiologists. The criterion for detection was identification of a vessel cutoff. Perfusion defects were also seen. No intraluminal filling defects were seen. This study indicates that pulmonary emboli greater than 2 mm in diameter may be detected in dogs by DSA.

Anterior chest wall mass in an elderly male.

A case of chondrosarcoma arising from the right anterior second rib in an 84-year-old man is described. Radiographic features include amorphous calcification within a chest wall mass. CT findings include calcification and necrosis within the 8 X 8 X 10 cm tumor, and extension into the adjacent lung. The presence of zones of dedifferentiation into fibrosarcoma in the surgically resected tumor indicates a poor prognosis, with a high likelihood of early recurrence and pulmonary metastasis.

Digital synthesis of lung nodules.

Studies evaluating observer accuracy and visual perception of pulmonary nodules usually are based upon test films obtained from clinical practice in patients with proven pulmonary nodules. Unfortunately, such nodules do not always occur in the optimal size and location to facilitate testing. Such studies would be enhanced by the ability to place nodules of desired size and location on chest radiographs. This report describes a method of placing a computer-generated (synthesized) nodule on a digitized chest radiograph. To demonstrate the similarity of these synthesized nodules to real nodules, each digitized radiograph with a computer-generated nodule was paired with a digitized chest radiograph of a patient with a clinically proven pulmonary nodule. A total of 22 pairs of chest radiographs were then shown to 13 radiologists, who were asked to distinguish the synthesized nodule from the real nodule. With this two alternative forced-choice test, the radiologists were only able to distinguish the synthesized nodule in 51% of the cases, strongly suggesting that computer generated nodules may be used to simulate real pulmonary nodules in future tests of nodule detection.

Distribution of 15- and 137-mu diameter microspheres in the dog lung in the axial plane.

Oleic acid infusion, as a model of fat embolism, produces a predominantly peripheral lesion in the dog lung. The lung injury corresponds to the peripheral distribution of labeled oleic acid. The basis for this distribution of oleic acid is not known. Our hypothesis for this nonuniform distribution is that particle diameter plays a role in the subsequent distribution of infused oleic acid and the resulting lung injury. We injected 15-mu microspheres 85Sr and then 137-mu microspheres (141Ce) into the right atria of seven dogs, which were killed and the lungs removed. Analysis of the distribution of the two different diameter microspheres within axial slices from the left caudal lobe of each dog revealed a peripheral distribution of the larger diameter microspheres not seen with the smaller microspheres.

CT of the pulmonary hilum.

Histologic examination of the lymph nodes is the only 100% accurate method of detecting metastatic disease. Even the pathologist encountering a lymph node cannot predict from the macroscopic appearance whether a lymph node is involved with tumor. Because enlarged lymph nodes may be free of tumor, and nodes of normal size may contain metastases, the accuracy of CT in the detection of hilar involvement by tumor is limited. The primary role of imaging procedures in the preoperative staging of patients with bronchogenic carcinoma is to determine the need for further prethoracotomy assessment. Decisions regarding operability of lung cancer should be based on tissue verification. Recognition of hilar abnormality requires a thorough understanding of normal bronchial and pulmonary vascular anatomy. The administration of intravenous contrast material can facilitate the distinction on a CT scan image of enhancing pulmonary vessels from nonenhancing hilar lymph nodes.

A radiographic approach to diffuse lung disease.

The chest radiograph remains the first and foremost imaging modality used in the assessment of patients who have diffuse lung disease. An optimal approach to the radiograph requires an understanding of pulmonary anatomy and pathophysiology of disease. The assessment of the radiograph can be based on an anatomic or a descriptive approach. Associated abnormalities, including pleural effusion, pneumothorax, lymphadenopathy, and so forth, also influence the differential diagnosis. This article presents a basic radiologic approach to diffuse lung diseases.

Intrathoracic metastasis from an extrathoracic malignancy: a radiographic approach to patient evaluation.

The likelihood of metastatic spread of an extrathoracic primary tumor to the thorax depends on a number of factors, most importantly, the site and nature of the primary tumor. Although the plain chest radiography remains the first-line screening procedure, understanding the pattern of spread of various tumors and the frequency with which such spread occurs enables one to develop a rational approach to the use of other imaging modalities, particularly computed tomography, in evaluation of patients with known extrathoracic primary tumors.

Bronchogenic carcinoma: a survey of CT protocols for staging disease.

RATIONALE AND OBJECTIVES: To determine whether a standard computed tomographic (CT) protocol is used in the staging of lung cancer. MATERIALS AND METHODS: A questionnaire was designed to determine what type of CT scanner is used, whether intravenous contrast material is used, how often the abdomen is scanned and at what level, and the section thicknesses used in scanning the chest and abdomen in patients with lung cancer. A total of 1,118 survey forms were mailed to members of the Society of Thoracic Radiology and to all community hospitals in the United States with at least 300 beds. RESULTS: The authors received 520 responses (47%) to the 1,118 questionnaires mailed. Of these 520 responses, 140 were from society members, 256 were from hospitals with 300-500 beds, and 124 were from hospitals with more than 500 beds. One-half of hospital respondents used helical CT scanners. Significantly more society members used helical CT scanners (P < .001). Intravenous contrast material was used to opacify mediastinal blood vessels at 449 (86%) of 520 hospitals. Intravenous contrast material was used for liver scanning at 363 (82%) of 444 hospitals, but it was used less often at hospitals in the northeast region and by society members than at hospitals in other regions (P < .001). A mixture of section thicknesses was commonly used (252 [48%] of 520 responses) for scanning the chest; a thickness of 8-10 mm was used in scanning the abdomen at most hospitals (348 [78%] of 445 responses). CONCLUSION: No CT protocol is consistently used for the examination of patients with lung cancer. Use of intravenous contrast material during chest or liver CT also is not uniform.

Incidence of pulmonary edema after tracheotomy for obstructive sleep apnea.

OBJECTIVE: The phenomenon of postobstructive pulmonary edema (POPE) has been associated with the relief of upper airway obstruction, which itself is fundamental to the pathophysiology of obstructive sleep apnea (OSA). A review of patients with OSA undergoing tracheotomy was performed to characterize this process. STUDY DESIGN: Retrospective chart review of study patients with OSA undergoing tracheotomy and of control patients without OSA undergoing tracheotomy for unrelated problems. Chest radiographs were reviewed in a double-blind fashion to score posttracheotomy changes in pulmonary status. SETTING: Academic tertiary referral center. RESULTS: Thirty (67%) of 45 OSA patients treated by tracheotomy had evidence of POPE, whereas only 5 (20%) of 25 control group patients had increased pulmonary edema. The remaining 15 (33%) of 45 OSA patients and 20 (80%) of 25 control patients had either no change or an improved pulmonary status. Those with OSA that developed POPE were mostly graded as having mild pulmonary edema (22/30, 73%). Far fewer were graded as having moderate pulmonary edema (6/30, 20%), and fewer still with severe pulmonary edema (2/30, 7%). Two (7%) of 45 patients with severe POPE died of complications related to cor pulmonale in the postoperative period. CONCLUSION: Results support maintaining a high index of suspicion for the development of postobstructive pulmonary edema in patients treated for OSA. Treatment options, such as positive pressure ventilation and diuresis, and an increased awareness of this condition may help reduce the morbidity and mortality associated with treatment of this disease.

Analysis of the solitary pulmonary nodule by means of digital techniques.

Currently the radiographic determination of the benign or malignant nature of solitary pulmonary nodules relies on growth characteristics determined by comparison radiographs or the detection of calcification in the nodule with either low-peak kilovoltage fluoroscopy or CT of the chest. An alternative approach is analysis of the optical densities within the nodules by means of digital radiography. Two techniques have been described: histogram analysis of chest radiographs digitized with a laser scanner and dual-energy digital radiography. Although both techniques remain experimental, they offer a potential advantage over CT in that a single radiographic exposure is sufficient, thus decreasing the radiation dose to the patient and providing the patient with a less complex work-up.

Epithelioid hemangioendothelioma of the superior vena cava: computed tomography demonstration and review of the literature.

A case is reported of a 79-year-old man with rapid onset of superior vena cava syndrome caused by an epithelioid hemangioendothelioma. Contrast-enhanced helical computed tomography showed a soft-tissue mass with punctate calcifications obstructing the superior vena cava and infiltrating adjacent fat. Epithelioid hemangioendothelioma is a very rare primary mesenchymal tumor of the superior vena cava that often presents with calcifications. It should to be added to the differential diagnosis of tumors of the anterior mediastinum.