Clinical value of thin collimation in the diagnostic workup of pulmonary embolism.

OBJECTIVE: We report our experience with thin-collimation helical CT in a population of patients suspected of having pulmonary embolism. CONCLUSION: Thin-collimation helical CT provided technically acceptable examinations for pulmonary embolism in 360 patients (97%). In this population, CT revealed pulmonary embolism in 104 patients (29%), negative findings in 217 patients (59%), indeterminate findings in 39 patients (10%), and alternative diagnoses in 65% of patients with negative or inconclusive findings. Ventilation-perfusion scanning and Doppler sonography of the lower extremities were performed in 158 (44%) and 133 patients (37%), respectively, whereas pulmonary angiography was performed in 27 patients (7.5%). The estimated false-negative rate of helical CT was 5%.

[The respective role and limitations of pulmonary angiography, thoracic computed tomography, and MRI in the diagnosis of pulmonary embolism]. / Places respectives et limites de l'angiographie pulmonaire, de la tomodensitométrie thoracique, et de l'IRM dans le diagnostic de l'embolie pulmonaire.

Spiral or helical angioscanography for the positive or differential diagnosis of pulmonary emboli has become an emerging technique but remains poorly practised and has been little assessed scientifically. The optimal conditions to perform the test should be understood. The physician should appreciate in view of a large choice of parameters, the diagnostic value of the result and its reliability proximally and distally. Pulmonary angiography is only indicated when the angioscanography is negative according to the degree of clinical and paraclinical suspicion. Angiography magnetic resonance imaging is a diagnostic test full of promise which does not yet have its place in routine practice.

Spiral CT of pulmonary embolism: diagnostic approach, interpretive pitfalls and current indications.

The introduction of spiral CT has recently modified the diagnostic work-up of pulmonary embolism, because it is possible to depict noninvasively 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. Numerous interpretive pitfalls exist in assessing spiral CT images, and certain caveats have to be heeded. However, their recognition becomes increasingly 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.

Volume rendering of the tracheobronchial tree: clinical evaluation of bronchographic images.

PURPOSE: To evaluate the application of the volume-rendering technique to airway disease. MATERIAL AND METHODS: Seventy-four spiral computed tomographic (CT) examination (1- to 5-mm section thickness; pitch, 1.7-20.0) were performed for known or suspected abnormality of the airways, including (a) benign tracheobronchial stenosis (group 1, n = 47), (b) complex airway lesions (group 2, n = 15), and (c) bronchiectasis (group 3, n - 12). Two radiologists independently compared overlapping transverse CT scans and volume-rendered bronchographic images for detection of airway abnormalities and identification of lesion morphology and extent, with bronchoscopic correlation. RESULTS: Bronchographic image quality was graded as excellent (73%) or good (24%), whereas motion-related artifacts led to poor image quality in 3% of cases (trapezoid parameters included window width of -700 to -350 HU, triangular trapezoid shape, parenchymal opacification of 70%, unshaded algorithm). Compared with transverse CT scans, volume-rendered images (a) provided supplemental group 3, even, seven), (b) improved confidence in the interpretation of congenital airway abnormalities in six cases (8%) (all from group 2), and (c) corrected interpretive errors in four cases (5%) (group 1, two cases; group 2, two). CONCLUSION: Volume-rendered images improved the recognition of mild changes in airway caliber and the understand of complex tracheobronchial anomalies.

Tracheobronchial tree: assessment with volume rendering--technical aspects.

A volume-rendering technique was applied at the level of normal airways. Two spiral computed tomographic data sets (central and peripheral bronchi) were selected to evaluate the influence of the technique parameters. Optimal bronchogram-like images were obtained with a continuous rim of peripheral voxels, a 70% opacity value, and the unshaded algorithm. Volume rendering allows creation of airway reconstructions that are very similar to conventional bronchograms.

Multiplanar and three-dimensional reconstruction techniques in CT: impact on chest diseases.

The purpose of this review is to capture the current state-of-the art of the technical aspects of multiplanar and three-dimensional (3D) images and their thoracic applications. Planimetric and volumetric analysis resulting from volumetric data acquisitions obviates the limitations of segmented transverse images. Among the 3D reconstruction techniques currently available, the most recently introduced technique, i. e., volume rendering, has to be evaluated in comparison with 3D shaded surface display and maximum or minimum intensity projection. Slabs are useful in detecting and localizing micronodular or microtubular patterns and in analyzing mild forms of uneven attenuation of the lungs. Three-dimensional angiography is helpful in the pretherapeutic evaluation and posttreatment follow-up of pulmonary arteriovenous malformations, in the comprehension of the postoperative reorientation of the pulmonary vessels, in the surgical planning of pulmonary tumors, and in the diagnosis of marginated thrombi. The systemic supply to the lung and superior vena cava syndromes are also relevant to these techniques. In acquired or congenital tracheobronchial diseases including stenosis, extraluminal air and complex airway anatomy, multiplanar and 3D reformations have a complementary role to both transaxial images and endoscopy. New developments are also expected in various topics such as 3D conformal radiation therapy, planning of intraluminal bronchoscopic therapy, virtual endoscopy, and functional imaging of the bronchial tree. Miscellaneous clinical applications are promising in the analysis of diaphragmatic morphology and pathophysiology, in the volumetric quantification of the lung parenchyma, and in the vascular components of the thoracic outlet syndromes.

Functional anatomy of the thoracic outlet: evaluation with spiral CT.

PURPOSE: To determine the anatomic characteristics of the thoracic outlet before and after dynamically induced modifications. MATERIALS AND METHODS: Fifty-two volunteers (24 women; 28 men; mean age, 42 years) with no clinical or radiographic indications of thoracic outlet syndrome underwent spiral computed tomography (CT) of the apexes at full inspiration with the arms alongside the body and then with the dominant arm in hyperabduction, with a contralateral rotation of the head. RESULTS: After elevation of the dominant arm, (a) no statistically significant difference was found in median value of the costosubclavian and costoclavicular distances; (b) the median distance between the posterior border of the smaller pectoral muscle and the anterosuperior chest wall was 12 mm in all subjects; (c) the subclavian artery in 18 (75%) women and in 20 (71%) men and/or the subclavian vein in three (12%) women and in three (11%) men were identified in the costoclavicular space. The median angles of rotation, retraction, and upward displacement of the clavicle were 22 degrees, 32 degrees, and 7 degrees, respectively, in women and 25 degrees, 31 degrees, and 11 degrees, respectively, in men. CONCLUSION: Spiral CT is expected to be useful for determining the complex pathophysiologic processes that underlie thoracic outlet syndrome.

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.

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.

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.

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.

Helical CT angiography compared with arteriography in the detection of renal artery stenosis.

OBJECTIVE: The aim of the study was to improve the accuracy and detection rate for renal vascular lesions on helical CT angiography with an improved acquisition protocol and postprocessing. SUBJECTS AND METHODS: Fifty hypertensive patients (man age, 53 years old) referred because of clinical suspicion on renal artery stenosis were prospectively studied with digital renal arteriography and helical CT angiography. A 20-sec helical scan (collimation, 3 mm; pitch, 1) was obtained after injection of contrast medium. Interpretation was base on transverse sections, shaded-surface-display and maximum-intensity-projection reconstructions, and two-dimensional multiplanar reconstruction cuts obtained from shaded-surface-display reconstructions. RESULTS: Arteriography visualized 131 renal arteries (including 32 accessory arteries). Sixteen had significant (greater than 50% in diameter) stenosis. On helical CT angiography, 14 of these 16 stenoses were detected; two were missed (false-negatives), and two additional stenoses (false-positives) were reported. Sensitivity and specificity were 88% and 98%, respectively. Considering only main renal arteries, the sensitivity and the specificity of helical CT angiography were 100% and 98%, respectively. Helical CT angiography detected Conn's syndrome, which was responsible for hypertension, in two other patients. CONCLUSION: The accuracy and detection rate for renal artery stenosis on helical CT angiography compared with arteriography is improved with the described protocol.