Optimal imaging protocol for measuring dynamic expiratory collapse of the central airways.

AIM: To compare measurements of expiratory collapse obtained using multidetector computed tomography (MDCT) of the central airways on routine axial and multiplanar reformatted (MPR) images. MATERIALS AND METHODS: Fifty volunteers with normal pulmonary function and no smoking history were imaged using a 64 MDCT system (40 mAs, 120 kVp, 0.625 mm collimation) with spirometric monitoring at end-inspiration and during forced expiration. Measurements of the trachea, right main (RMB) and left main bronchus (LMB) were obtained on axial and MPR images. Inspiratory and dynamic-expiratory cross-sectional area (CSA) measurements were used to calculate the mean percentage expiratory collapse (%Collapse). A paired t-test was used to assess within-subject differences and a Bland-Altman plot was used to assess agreement between the methods. RESULTS: Among 24 men and 26 women (mean age±standard deviation 50±15 years), CSA values were significantly greater on axial than MPR images (all p<0.001); however, the mean difference in %Collapse values for axial versus MPR were small: trachea ≈1% (55 ±19 versus 56±18, p=0.338); LMB identical (60±20 versus 60±17 p=0.856); and, RMB 4% (62 ±19 versus 66±19 p<0.001). On average, creation of MPR required 12 minutes of additional time per case (range=10-15 min). CONCLUSION: Differences in mean %Collapse for axial versus MPR images were small and unlikely to influence clinical management. This finding suggests that MPR may not be indicated for routine assessment of central airway collapse.

Static end-expiratory and dynamic forced expiratory tracheal collapse in COPD.

AIM: To determine the range of tracheal collapse at end-expiration among chronic obstructive pulmonary disease (COPD) patients and to compare the extent of tracheal collapse between static end-expiratory and dynamic forced-expiratory multidetector-row computed tomography (MDCT). MATERIALS AND METHODS: After institutional review board approval and obtaining informed consent, 67 patients meeting the National Heart, Lung, and Blood Institute (NHLBI)/World Health Organization (WHO) Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria for COPD were sequentially imaged using a 64-detector-row CT machine at end-inspiration, during forced expiration, and at end-expiration. Standardized respiratory coaching and spirometric monitoring were employed. Mean percentage tracheal collapse at end-expiration and forced expiration were compared using correlation analysis, and the power of end-expiratory cross-sectional area to predict excessive forced-expiratory tracheal collapse was computed following construction of receiver operating characteristic (ROC) curves. RESULTS: Mean percentage expiratory collapse among COPD patients was 17 ± 18% at end-expiration compared to 62 ± 16% during forced expiration. Over the observed range of end-expiratory tracheal collapse (approximately 10-50%), the positive predictive value of end-expiratory collapse to predict excessive (≥80%) forced expiratory tracheal collapse was <0.3. CONCLUSION: COPD patients demonstrate a wide range of end-expiratory tracheal collapse. The magnitude of static end-expiratory tracheal collapse does not predict excessive dynamic expiratory tracheal collapse.

Subcarinal collection following mediastinoscopy: a normal post-procedural CT finding.

AIM: To determine the frequency with which a subcarinal collection is present at computed tomography (CT) following mediastinoscopy and to determine the CT features of the collection. MATERIALS AND METHODS: All patients who underwent uncomplicated mediastinoscopy during a 1-year period were retrospectively identified. This list was cross-referenced to determine those patients who also underwent CT within 15 days after the procedure. Each post-mediastinoscopy CT examination was assessed in consensus by three fellowship-trained thoracic radiologists for the presence of subcarinal abnormalities, which were also characterized in terms of their size and density. Additional CT findings were recorded, including tracheobronchial wall thickening, paratracheal collections, mediastinal fat stranding, and mediastinal air. RESULTS: The study cohort included 10 patients (seven men and three women) with mean age of 65 years (range 49-81 years). CT was performed a mean of 11 days following mediastinoscopy. The most common CT finding was an oval subcarinal collection in nine of 10 cases (size 1.1-3.2 cm). In all nine cases, the subcarinal collections were consistently lower in attenuation than the subcarinal lymph node in the same region on the pre-procedure CT examination. Other CT findings included anterior tracheobronchial wall thickening (n=7); paratracheal collection (n=6); mediastinal fat stranding (n=6); and mediastinal air in (n=4) cases. CONCLUSION: A subcarinal collection was identified in 90% of cases following mediastinoscopy. Its rapid development and characteristic appearance help to distinguish it from a lymph node.

High-resolution CT using MDCT: comparison of degree of motion artifact between volumetric and axial methods.

OBJECTIVE: The purpose of this study was to compare the degree of motion artifact on high-resolution CT images obtained using volumetric and axial (nonvolumetric) CT methods. CONCLUSION: Volumetric high-resolution CT is associated with significantly greater motion artifact compared with axial noncontiguous high-resolution imaging.

Frequency and severity of air trapping at dynamic expiratory CT in patients with tracheobronchomalacia.

OBJECTIVE: The purpose of this study was to compare the frequency and severity of air trapping in patients with and without tracheobronchomalacia using dynamic expiratory volumetric CT. MATERIALS AND METHODS: The study group consisted of 20 subjects, including 10 patients with bronchoscopically proven tracheobronchomalacia and 10 control subjects of similar ages without tracheobronchomalacia. All 20 subjects underwent MDCT performed at the end of deep inspiration and during dynamic expiration. The images were analyzed at three lung levels, and the extent of air trapping was assessed visually using a 5-point scale. For each subject, a total air-trapping score was derived by summing the values for the three lung levels (possible range, 0-12). Statistical analysis was performed using the Mann-Whitney U test. RESULTS: In the tracheobronchomalacia group, 10 (100%) of 10 patients showed air trapping, with a median score of 5 (range, 2-12). In the control group, six (60%) of 10 subjects showed air trapping, with a median score of 2 (range, 0-3). The median total air-trapping score was significantly higher (p < 0.001) for the tracheobronchomalacia group compared with the control group. Excessive central airway collapse (expiratory reduction in cross-sectional area of > 50%) was seen on CT scans in all tracheobronchomalacia patients but in none of the control subjects. CONCLUSION: Air trapping was observed with a higher frequency and greater severity in patients with tracheobronchomalacia than in a control group of patients of similar ages without tracheobronchomalacia.

Pulmonary embolism in pregnant patients: a survey of practices and policies for CT pulmonary angiography.

OBJECTIVE: We surveyed the practices and policies of the radiology departments of the Society of Thoracic Radiology members regarding the use of CT pulmonary angiography in pregnant patients suspected of having pulmonary embolism. MATERIALS AND METHODS: Surveys were mailed electronically to the 403 members of the Society of Thoracic Radiology (403 addresses). Respondents were asked to send one response from each institution or department. Information gathered included use of CT angiography in relation to ventilation-perfusion imaging in pregnant patients, written policies, informed consent procedures, and modifications of standard protocols for dose reduction. RESULTS: Fifty-seven members responded; 43 (75%) reported that they perform CT angiography in pregnant patients suspected of having pulmonary embolism. Of the 43 respondents who perform CT angiography in pregnant patients, 23 (53%) generally perform CT angiography as the initial study rather than ventilation-perfusion scanning, 26 (60%) require informed consent from the patient, seven (16%) have a written policy concerning CT angiography in pregnant patients, and 17 (40%) modify standard imaging protocols for pregnant patients. The most common modification for dose reduction is decreasing the scanning area along the z-axis. CONCLUSION: Most respondents perform CT angiography in pregnant patients suspected of having pulmonary embolism, but their policies and practices vary considerably.

Fat attenuation lesions of the mediastinum.

The identification of fat within a focal or diffuse mediastinal lesion significantly narrows the differential diagnosis. In many cases, a specific diagnosis can be suggested on the basis of CT findings. In this article, we illustrate and review the characteristic CT features of common and uncommon fat attenuation lesions of the mediastinum, including focal masses and diffuse abnormalities.

Multi-detector row spiral CT pulmonary angiography: comparison with single-detector row spiral CT.

PURPOSE: To compare vascular conspicuity and ability to connect pulmonary arterial branches on pulmonary angiograms obtained with helical multi-detector row computed tomography (CT) with those on pulmonary angiograms obtained with helical single-detector row CT. MATERIALS AND METHODS: Of 93 consecutive patients suspected of having pulmonary embolism, 48 underwent scanning with multi-detector row CT and 45 with single-detector row CT; scans were obtained in 9 seconds and 28 seconds with 2.5-mm and 3.0-mm collimation, respectively. The lungs were divided into three zones: central, middle, and peripheral. Two independent observers used five-point grading scales. RESULTS: Conspicuity of pulmonary arteries in the central zone was ranked equal (median of 5), but in the middle and peripheral zones it was significantly higher at multi-detector row CT than at single-detector row CT (median 5 vs 4 and 4 vs 3, P < .001, respectively). In addition, multi-detector row CT improved the ability to connect peripheral arteries with their more centrally located pulmonary artery of origin in the peripheral but not the middle zone on transverse images and in both zones on multiplanar images. Viewing with a modified window setting (width, 1,000 HU; level, -100 HU) significantly increased pulmonary arterial conspicuity. Contrast material column in the pulmonary arteries was significantly more homogeneous at multi-detector row CT. CONCLUSION: Use of multi-detector row CT significantly improves pulmonary arterial visualization in the middle and peripheral lung zones.

Sternal dehiscence in patients with and without mediastinitis.

The authors compared patients with sternal dehiscence (SD) with and without mediastinitis with respect to: 1) time interval from surgery to diagnosis; and 2) frequency of sternal wire abnormalities on chest radiographs (CXR). Using a hospital information system to identify all patients with a diagnosis of SD from January 1993 through April 1999, the authors obtained clinical data by performing a retrospective chart review. For each patient, a CXR from the date of diagnosis of SD was retrospectively compared with the first postoperative CXR to assess for sternal wire displacement, rotation, and disruption. The timing of sternal wire alterations was correlated with clinical findings of SD or mediastinitis. The authors found that sternal wire abnormalities are evident radiographically in the majority of SD patients with and without mediastinitis; there is no significant difference in the frequency of sternal wire abnormalities between these two subgroups. Patients with SD and mediastinitis generally present later in the postoperative period than patients with isolated dehiscence.

Gemcitabine pulmonary toxicity: CT features.

The purpose of this case report is to describe the CT imaging features of pulmonary toxicity from gemcitabine, a relatively new chemotherapeutic agent, in three patients. CT features of gemcitabine pulmonary toxicity include ground glass opacity (n = 3), thickened septal lines (n = 3), and reticular opacities (n = 3). Distribution is diffuse and bilateral, and may be symmetric (n = 2) or asymmetric (n = 1). Clinical symptoms and imaging findings are potentially reversible with steroid therapy.

Mediastinal lymphadenopathy: diagnostic yield of transbronchial mediastinal lymph node biopsy with CT fluoroscopic guidance-initial experience.

PURPOSE: To determine whether the use of computed tomographic (CT) fluoroscopy to guide transbronchial needle aspiration (TBNA) of mediastinal lymph nodes can improve the diagnostic yield. MATERIALS AND METHODS: CT fluoroscopy was used to guide TBNA in 12 consecutive patients with mediastinal lymphadenopathy who had previously undergone nondiagnostic conventional TBNA. CT fluoroscopy was used to confirm the location of the biopsy needle by using a "quick-check" technique (ie, fluoroscopy was performed sparingly after needle insertion). The location of each needle, the total procedural and fluoroscopic times, and any complications were recorded. RESULTS: All CT fluoroscopic procedures were performed in less than 1 hour, and a tissue diagnosis was established in all patients. Eighteen lymph nodes with a diameter of 0.8-2.4 cm were sampled with 116 needle passes. CT fluoroscopy documented inadequate positioning in 48 of the 116 (41.3%) needle passes. Eighteen (15.5%) needles did not fully penetrate the tracheobronchial tree. Six needles (5.2%) were placed into the great vessels. Malignant disease was diagnosed in nine patients, and benign disease was diagnosed in three. The mean fluoroscopic exposure time was 20.5 seconds +/- 12.7. No pneumothoraces or substantial hemorrhage were observed. CONCLUSION: CT fluoroscopic guidance for TBNA procedures is a safe and efficient means of providing diagnostic material and should be considered for patients who have previously undergone nondiagnostic blinded TBNA.

MR imaging of thoracic lymph nodes. A comparison of computed tomography and positron emission tomography.

CT scanning has traditionally been the preferred imaging modality for the assessment of patients with non-small-cell lung cancer. The low sensitivity and specificity of CT scanning, however, has limited its usefulness in assessing nodal status. Despite this limitation, CT scanning still plays an important role by aiding the selection of the most appropriate procedure for staging purposes, guiding biopsy procedures, and providing anatomic information for visual correlation with FDG-PET images. Anatomic imaging with MR imaging has been shown to have accuracy comparable with CT scanning in assessing mediastinal lymph nodes. MR imaging, however, is more accurate than CT in the assessment of hilar lymph nodes. At present, anatomic imaging of lymph nodes with MR imaging should be considered a secondary, problem-solving tool for cases in which CT scanning is inconclusive. Advances in physiologic imaging of mediastinal lymph nodes with FDG-PET imaging have resulted in better diagnostic accuracy than obtained with anatomic imaging with CT scans or MR imaging. At present, an imaging strategy that employs both FDG-PET imaging and CT scanning appears to be the most accurate, noninvasive, and cost-effective means available for assessing nodal status in patients with non-small-cell lung cancer. Physiologic MR imaging with iron oxide is currently being assessed in clinical trials. Future studies are necessary to determine the clinical efficacy, accuracy, and cost effectiveness of this technique.

Imaging features of Pneumocystis carinii pneumonia.

Despite a declining prevalence secondary to improved prophylaxis, Pneumocystis carinii remains an important pulmonary pathogen in the immunocompromised host. Because the radiologist is often the first to suggest the diagnosis of PCP, an awareness of the entire spectrum of imaging features associated with this organism is important. The classic presentation of PCP is a bilateral interstitial pattern, which may be characterized as finely granular, reticular, or ground-glass opacities. When chest radiographic findings are normal or equivocal, high-resolution CT may be helpful, because it is more sensitive than chest radiographs for detecting PCP. The classic CT finding is extensive ground glass attenuation. Increasingly recognized characteristic patterns of PCP in AIDS patients include cystic lung disease, spontaneous pneumothorax, and an upper lobe distribution of parenchymal opacities. Although the radiographic findings in PCP are similar for AIDS and non-AIDS immunosuppressed patients, cystic lung disease has not been described in the latter patient population.

Wandering wires: frequency of sternal wire abnormalities in patients with sternal dehiscence.

OBJECTIVE: The purpose of this study is to assess the frequency of various sternal wire abnormalities on chest radiographs of patients with sternal dehiscence and to determine the role of radiography in detecting or confirming this complication. MATERIALS AND METHODS: We used our computerized hospital information system to identify all patients with a diagnosis of sternal dehiscence from January 1993 through June 1998. Clinical data were obtained by retrospective chart review. A chest radiograph from the date of diagnosis was compared with the first postoperative radiograph obtained after median sternotomy. Each radiograph was retrospectively reviewed by two radiologists who assessed three sternotomy wire abnormalities: displacement (offset of one or more wires in relation to others in the vertical row), rotation (alteration in the axis of a wire compared with its orientation on a baseline radiograph), and disruption (unraveling or fracture of a wire). We also reviewed a series of postoperative radiographs in a group of matched controls who had an uneventful postoperative course with no clinical evidence of dehiscence. RESULTS: The study cohort included 19 patients, 13 men and six women, who were 49-84 years old (mean, 66 years). The chest radiographs revealed sternal wire abnormalities in 17 (89%) of 19 patients with sternal dehiscence, including displacement in 16 (84%) of 19 patients, rotation in 10 (53%) of 19 patients, and disruption in four (21%) of 19 patients. The mean number of displaced wires per patient was 2.3 (range, 1-5). The mean distance of maximal displacement was 20 mm (range, 6-45 mm). Radiographic abnormalities preceded the clinical diagnosis in 13 (68%) of 19 patients. We observed no case of sternal wire displacement, rotation, or disruption in the control group. CONCLUSION: Sternal wire abnormalities, most notably displacement, are present in most patients with sternal dehiscence; radiographic abnormalities precede the clinical diagnosis in most cases.

The changing face of Pneumocystis carinii pneumonia in AIDS patients.

The classic presentation of PCP is a bilateral interstitial pattern, which may be characterized as finely granular, reticular, or ground-glass opacities. When chest radiographic findings are normal or equivocal, high-resolution CT may be helpful because it is more sensitive than chest radiography for detecting PCP. The typical CT finding is extensive ground-glass attenuation. The face of PCP is changing. The classic radiographic presentation is being encountered less frequently. Increasingly recognized characteristic patterns of PCP include cystic lung disease, spontaneous pneumothorax, and an upper lobe distribution of parenchymal opacities. The spectrum of abnormalities associated with PCP is broadening and now includes abnormalities of the lung parenchyma, airways, lymph nodes, and pleura. An awareness of the varied presentations of PCP is important because the radiologist is often the first to suggest the diagnosis of PCP.

Effect of lung volume reduction surgery on diaphragm length in severe chronic obstructive pulmonary disease.

Lung volume reduction surgery (LVRS) has been suggested as improving respiratory mechanics in patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that LVRS might lengthen the diaphragm, increase its area of apposition with the chest wall, and thereby improve its mechanical function. To determine the effect of bilateral LVRS on diaphragm length, we measured diaphragm length at TLC, using plain chest roentgenograms (CXRs), in 25 patients (11 males and 14 females) before LVRS and 3 to 6 mo after LVRS. A subgroup of seven patients (reference data) also had diaphragm length measurements made with CXRs, using films made within a year before their presurgical evaluation. Right hemidiaphragm silhouette length (PADL) and the length of the most vertically oriented portion of the right hemidiaphragm muscle (VDML) were measured. Diaphragm dome height was determined from the: (1) distance between the dome and transverse diameter at the manubrium; and (2) highest point of the dome referenced horizontally to the vertebral column. Patients also underwent spirometry, measurements of lung volumes and diffusion capacity, an incremental symptom-limited maximum exercise test, and measurements of 6 min walk distance (6MWD) and transdiaphragmatic pressures during maximum static inspiratory efforts (Pdimax sniff) and bilateral supramaximal electrophrenic twitch stimulation (Pditwitch) both before and 3 mo after LVRS. Patients were 58 +/- 8 yr of age, with severe COPD and hyperinflation (FEV1 = 0.68 +/- 0.23 L, FVC = 2.56 +/- 7.3 L, and TLC = 143 +/- 22% predicted). Following LVRS, PADL increased by 4% (from 13.9 +/- 1.9 cm to 14.5 +/- 1.7 cm; p = 0.02), VDML increased by 44% (from 2.08 +/- 1.5 cm to 3.00 +/- 1.6 cm, p = 0.01), and diaphragm dome height increased by more than 10%. In contrast, diaphragm lengths were similar in subjects with CXRs made before LVRS and within 1 yr before evaluation. The increase in diaphragm length correlated directly with postoperative reductions in TLC and RV, and also with increases in transdiaphragmatic pressure with maximal sniff (Pdimax sniff), maximal oxygen consumption (V O2max), maximal minute ventilation (V Emax), and maximum voluntary ventilation following LVRS. We conclude that LVRS leads to a significant increase in diaphragm length, especially in the area of apposition of the diaphragm with the rib cage. Diaphragm lengthening after LVRS is most likely the result of a reduction in lung volume. Increases in diaphragm length after LVRS correlate with postoperative improvements in diaphragm strength, exercise capacity, and maximum voluntary ventilation.

Acute pulmonary embolism: assessment of helical CT for diagnosis.

PURPOSE: To determine the sensitivity and specificity of helical computed tomography (CT) for the diagnosis of acute pulmonary embolism. MATERIALS AND METHODS: This prospective study included 47 patients who underwent pulmonary arteriography for evaluation for possible acute pulmonary embolism. Tailored helical CT and pulmonary arteriography were performed within 24 hours of each other. Each CT scan was interpreted by two chest radiologists, blinded to arteriographic results, at two institutions. CT scan interpretations were compared with findings on bilateral selective pulmonary arteriograms interpreted by two vascular radiologists at one institution. RESULTS: Fifteen (32%) of 47 patients had angiographically proved pulmonary embolism. For the readers at the first institution, helical CT had 60% sensitivity, 81% specificity, 60% positive predictive value, 81% negative predictive value, and 75% overall accuracy. For the readers at the second institution, helical CT had 53% sensitivity, 97% specificity, 89% positive predictive value, 82% negative predictive value, and 83% accuracy. CONCLUSION: Detection of pulmonary embolism with helical CT may be less accurate than previously reported. Given its high specificity but relatively low sensitivity, helical CT may not have the ideal attributes of a first-line imaging study for the diagnosis of pulmonary embolism.

Imaging of mediastinal lymph nodes: CT, MR, and FDG PET.

The evaluation of mediastinal lymph nodes is an important aspect of staging in patients with non-small cell lung cancer. Anatomic imaging of lymph nodes with computed tomography (CT) and magnetic resonance (MR) imaging has been limited by the relatively low sensitivity and specificity of these techniques. Advances in physiologic imaging of mediastinal lymph nodes with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) have resulted in improved diagnostic accuracy in the determination of nodal status. Despite the limitations of CT, this technique still plays an important role by aiding in the selection of the most appropriate procedure for staging, by guiding biopsy, and by providing anatomic information for visual correlation with FDG PET images. At present, anatomic MR imaging of lymph nodes is primarily a problem-solving tool for cases with inconclusive CT results. Physiologic MR imaging with iron oxide is an exciting area of investigation, and the accuracy of this technique is being assessed in clinical trials. Anatomic and physiologic imaging techniques should be considered complementary rather than competitive imaging strategies.