Peripheral pulmonary arteries: optimization of the spiral CT acquisition protocol.

PURPOSE: To analyze the influence of collimation on identification of segmental and subsegmental pulmonary arteries on spiral computed tomographic (CT) scans. MATERIAL AND METHODS: Contrast material-enhanced spiral CT scans were retrospectively analyzed. Patients in group A (n = 20) underwent CT with 3-mm collimation, 1.00 second per revolution, and pitch of 1.7; those in group B (n = 20) underwent CT with 2-mm collimation, 0.75 second per revolution, and pitch of 2.0. A total of 800 segmental (20 arteries per patient) and 1,600 subsegmental (40 arteries per patient) arteries were assessed. RESULTS: The mean number of analyzable segmental arteries per patient was greater in group B patients (18.6 of 20.0 [93%]) than that in group A patients (17.0 of 20.0 [85%]) (P < .001). The mean number of analyzable subsegmental arteries per patient was greater in group B patients (24.6 of 40.0 [61%]) than that in group A patients (14.8 of 40.0 [37%]) (P < .0001). Frequency of identification on CT scans of 13 of the 40 subsegmental arteries was improved in group B compared with group A patients (P < .0001). CONCLUSION: Spiral CT with 2-mm collimation at 0.75 second per revolution enables marked improvement in the analysis of segmental and subsegmental pulmonary arteries.

Airway changes in chronic pulmonary embolism: CT findings in 33 patients.

PURPOSE: To evaluate airway changes in chronic pulmonary embolism with computed tomography (CT). MATERIALS AND METHODS: CT findings in 33 patients with chronic pulmonary embolism (group 1) were retrospectively compared with those in a control group of 19 patients with acute pulmonary embolism (group 2). Bronchial abnormalities were analyzed on thin-section CT scans; vascular signs of pulmonary embolism were evaluated on spiral CT angiograms obtained at the same session. In group 1, pulmonary function test results were available in 15 patients and serial CT scans were obtained in nine patients (mean follow-up, 17.7 months). RESULTS: In group 1, cylindric bronchial dilatation was found in 21 (64%) patients versus two (11%) patients in group 2 (P < .001) at the level of segmental and/or subsegmental bronchi and in the absence of obstructive syndrome. Bronchial wall thickening was identified in four (12%) patients in group 1 and in two (11%) patients in group 2 (P = .6). In group 1, concordance was found between the location of bronchial dilatation and that of completely obstructed and retracted pulmonary arteries (kappa = 0.70), with a lower lobe predomina for bronchial dilatation. Follow-up CT scans demonstrated no changes in airway caliber over time. CONCLUSION: Chronic pulmonary embolism may lead to ipsilateral proximal bronchial dilatation.

Spiral CT of pulmonary embolism: technical considerations and interpretive pitfalls.

The diagnostic work-up of pulmonary embolism has been recently modified by the introduction of spiral computed tomography (CT), which enables noninvasive depiction of endoluminal clots in second-to fourth-division pulmonary arteries. If this technique is currently considered a powerful imaging alternative for the detection of acute central emboli, it is mainly related to the possibility to obtain a uniform and high degree of arterial enhancement of pulmonary arteries down to 2-3 mm in diameter. Minimal experience in spiral CT angiography is necessary to achieve this goal and requires familiarity with both data acquisition and contrast medium injection. A number of interpretive pitfalls exist in assessing spiral CT images, and certain caveats have to be heeded. However, it is important to keep in mind that their recognition becomes less and less problematic as the radiologist gains experience with spiral CT of the pulmonary vasculature. Therefore, the purpose of this article is to review the diagnostic approach to pulmonary embolism with spiral CT, with special emphasis on protocol parameters and scan interpretation.

Bronchial arteries in the pig before and after permanent pulmonary artery occlusion.

RATIONALE AND OBJECTIVES: The authors study the bronchial arteries in the adult pig before and after pulmonary artery occlusion. METHODS: The bronchial artery anatomy was analyzed on postmortem aortograms in six pigs in group 1. In 20 animals in group 2, the left diaphragmatic lobar pulmonary artery (DLPA) was proximally (n = 12), medially (n = 5), or distally (n = 3) occluded via angiographic procedures; an unintentional embolization of coils in the right DLPA led to an incomplete pulmonary arterial occlusion. Eight to 12 weeks later, postmortem bronchial angiograms and pathologic studies were performed systematically in group 2. RESULTS: Outcomes in group 1 were: (A) a common trunk to the right and left bronchial arteries found in five animals, and (B) bronchopulmonary anastomoses found in the five lungs optimally injected. Outcomes in group 2 were: (A) the absence of pulmonary infarct and the development of a collateral bronchial supply were constant in the left lung; (B) the left DLPAs were patent beyond the coils and opacified via bronchopulmonary anastomoses; (C) dilated subpleural bronchial arteries were constant in the interlobular septa of the lung parenchyma devoid of pulmonary arterial perfusion; (D) the right bronchial arteries were normal after incomplete pulmonary artery occlusion. CONCLUSIONS: Because of an anastomosed dual circulation, the pig is a reliable experimental model for interventional and surgical procedures.

Acute central thromboembolic disease: posttherapeutic follow-up with spiral CT angiography.

PURPOSE: To evaluate the resolution of acute central pulmonary embolism (PE). MATERIALS AND METHODS: Sixty-two patients with angiographic (n = 43) or spiral computed tomographic (CT; n = 19) diagnosis of acute central PE underwent spiral CT after a mean of 11 months. CT signs of unresolved acute or chronic PE at the level of the central pulmonary arteries were recorded. A scoring system enabled quantification of endoluminal abnormalities at the time of diagnosis and follow-up. RESULTS: At follow-up, 30 patients (group 1; 48%) had complete resolution of acute PE; 32 patients (group 2; 52%) showed endovascular abnormalities (mean follow-up in both groups, 10.5 months). Whereas clinical presentation, risk factors at diagnosis, and therapeutic modalities did not differ statistically significantly between the two groups, group 2 had more extensive acute PE at diagnosis than did group 1. In group 2, CT showed an incomplete resolution of acute PE in 24 patients (group 2a; 39%) and development of chronic PE in eight patients (group 2b; 13%). Six patients had exertional dyspnea (five group 2a patients and one group 2b patient); five patients had echocardiographically demonstrated pulmonary hypertension (all group 2a patients). CONCLUSION: Spiral CT enabled noninvasive detection of unresolved PE and of newly developed chronic PE.

Diagnosis of pulmonary embolism with spiral CT: comparison with pulmonary angiography and scintigraphy.

PURPOSE: To evaluate the accuracy of spiral computed tomography (CT) in the noninvasive diagnosis of pulmonary embolism (PE). MATERIALS AND METHODS: A prospective study was performed in 75 patients who were evaluated with spiral CT and pulmonary angiography of each lung to detect central PE; 25 of the patients also underwent ventilation-perfusion (V-P) scanning. RESULTS: Spiral CT scans were technically suboptimal in three patients. CT and angiographic findings were negative for PE in 25 patients; one patient had false-negative CT findings. Findings from both studies were positive in 39 patients. CT findings of 188 central emboli corresponded exactly to those of angiography. Ten emboli were depicted only on CT scans, whereas seven emboli were identified only on angiograms because of inadequate depiction of the pulmonary arteries in the plane of the CT scans (n = 5) or because of misinterpretation of CT findings (n = 2). The prospective sensitivity of CT was 91%, the specificity was 78%, the positive predictive value was 100%, and the negative predictive value was 89%. Technical failures (n = 3) and inconclusive CT findings (n = 7) were the major limitations of spiral CT. Spiral CT enabled accurate classification of PE in 16 patients with indeterminate (n = 7) and low (n = 9) probability of PE on V-P scans. CT demonstrated central PE in two patients with normal V-P scans. CONCLUSION: Spiral CT can reliably depict central PE and may be introduced into the classic diagnostic algorithms.

Diffuse infiltrative lung disease: clinical value of sliding-thin-slab maximum intensity projection CT scans in the detection of mild micronodular patterns.

PURPOSE: To evaluate sliding-thin-slab maximum intensity projection (MIP) reconstructions in the assessment of micronodular patterns of low profusion in diffuse infiltrative lung disease. MATERIALS AND METHODS: Eighty-one adult patients (mean age, 48 years) with suspicion of pneumo-coniosis (n = 25), sarcoidosis (n = 19), smoker bronchiolitis (n = 17), and bronchiolitis of miscellaneous causes (n = 20) underwent 1- and 8-mm-thick conventional computed tomography (CT) and focal spiral CT with generation of 3-, 5- and 8-mm-thick MIP reconstructions. The presence and characterization of micronodular infiltration were analyzed on the two sets of conventional CT scans and on the three sets of MIPs. RESULTS: When conventional CT findings were normal (n = 18 [22%]), MIPs did not demonstrate additional abnormalities. When conventional CT findings were inconclusive (n = 17 [21%]), MIPs enabled detection of micronodules that involved less than 25% of the lung surface. When conventional CT scans depicted micronodules (n = 46 [57%]), MIPs showed the profusion and distribution of micronodules and associated bronchiolar abnormalities better. The sensitivity of MIP (3-mm-thick MIP, 94%; 5-mm-thick MIP, 100%; 8-mm-thick MIP, 92%) was significantly higher than that of conventional CT (8 mm thick, 57%; 1 mm thick, 73%) in the detection of micronodules (P < .001). CONCLUSION: Sliding-thin-slab MIP helps detect mild forms of micronodular infiltration and should be considered a valuable additional tool in the evaluation of diffuse infiltrative lung diseases.

Obstructive lesions of the central airways: evaluation by using spiral CT with multiplanar and three-dimensional reformations.

The purpose of this study was to assess the accuracy of transverse CT scans as well as multiplanar (MPR) and three-dimensional (3D) reconstructions in the evaluation of obstructive lesions of the central airways. A total of 64 patients were evaluated for the presence of obstructive lesions of the central tracheobronchial tree with transverse spiral CT scans, multiplanar reformations (MPRs), 3D shaded surface displays (3D SSDs) and minimum intensity projections (MIPs). The findings of these modalities were then compared with those obtained at bronchoscopy. The severity, length, and shape of airway narrowing were analyzed comparatively on the four sets of images. Transverse CT scans and MPRs had a similar accuracy (99%) in detecting obstructive airway lesions. The accuracy of both was significantly higher than that of 3DSSDs (90%, p < 0.05) and MIPs (81%; p < 0.01). There was no statistically significant difference between the four imaging modalities in the analysis of the morphology of airway stenoses. Symmetric stenoses were similarly analyzed on the four sets of images, whereas MPRs and MIPs failed to depict accurately simple and complex asymmetric stenoses. Transverse CT scans are accurate in the depiction of obstructive lesions of the central airways and may be complemented by MPRs and/or 3DSSDs in their morphologic evaluation.