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A N Leung

Publications and source records attributed to A N Leung.

18 recordsLinked to original sources
PubMed1998

Bronchiolitis obliterans after lung transplantation: detection using expiratory HRCT.

OBJECTIVE: The objective of this study was to determine if air trapping, as detected on expiratory high-resolution CT (HRCT), is useful as an indicator of bronchiolitis obliterans (BO) in lung transplant recipients. MATERIALS AND METHODS: Corresponding inspiratory and expiratory HRCT images at five different levels and spirometry were obtained in 21 lung transplant recipients. Eleven patients had BO proved by transbronchial biopsy specimens; the remaining 10 patients had no pathologic or functional evidence of airways disease. Two "blinded" observers assessed the inspiratory images for the presence of bronchiectasis and mosaic pattern of lung attenuation, and the expiratory images for presence and extent of air trapping. Statistical comparison of the frequency of HRCT findings between patients with and without BO was performed using Fisher's Exact Test. RESULTS: On inspiratory images, bronchiectasis and mosaic pattern of lung attenuation were present in 4 (36%) and 7 (64%) of 11 patients with BO, and 2 (20%) and 1 (10%) of 10 patients without BO (p>0.05 and p<0.05), respectively. The sensitivity, specificity, and accuracy of bronchiectasis and mosaic pattern for BO were 36%, 80%, and 57%, and 64%, 90%, and 70%, respectively. On expiratory images, air trapping was found in 10 of 11 (91%) patients with BO compared to 2 of 10 (20%) patients without BO (p<0.002). Air trapping was found to have a sensitivity of 91%, specificity of 80%, and accuracy of 86% for BO. Air trapping was identified in one patient with BO who had normal results of baseline spirometric function tests. CONCLUSION: Air trapping, as detected on expiratory HRCT, was the most sensitive and accurate radiologic indicator of BO in the lung transplant population.

Adult↗
PubMed1997

MRI of pulmonary embolism using Gd-DTPA-polyethylene glycol polymer enhanced 3D fast gradient echo technique in a canine model.

This study was to evaluate the accuracy of MR angiography (MRA) using a Gd-DTPA-polyethylene glycol polymer (Gd-DTPA-PEG) with a 3D fast gradient echo (3D fgre) technique in diagnosing pulmonary embolism in a canine model. Pulmonary emboli were created in six mongrel dogs (20-30 kg) by injecting tantalum oxide-doped autologous blood clots into the femoral veins via cutdowns. MRI was performed with a 1.5 T GE Signa imager using a 3D fgre sequence (11.9/2.3/15 degrees) following intravenous injection of 0.06 mmol Gd/kg of Gd-DTPA-PEG. The dogs were euthanized and spiral CT of the lungs were then obtained on the deceased dogs. The MRI images were reviewed independently and receiver-operating-characteristic (ROC) curves were used for statistical analysis using spiral CT results as the gold standard. The pulmonary emboli were well visualized on spiral CT. Out of 108 pulmonary segments in the six dogs, 24 contained emboli >2 mm and 27 contained emboli < or = 2 mm. With unblinded review, MRI detected 79% of emboli >2 mm and only 48% of emboli < or = 2 mm. The blinded review results were significantly worse. Gd-DTPA-PEG enhanced 3D fgre MRI is potentially able to demonstrate pulmonary embolism with fairly high degree of accuracy, but specialized training for the interpretations will be required.

Animals↗
PubMed1997

Spiral CT of the thorax in daily practice: optimization of technique.

Effective utilization of spiral computed tomography (CT) technology in imaging of the thorax requires an understanding of technical parameters that affect image and scan quality. This article discusses how operator-controlled scan parameters can be optimized to achieve diagnostic and cost-effective examinations appropriate for daily clinical practice.

Contrast Media↗
PubMed1997

Simulated dose reduction in conventional chest CT: validation study.

PURPOSE: To validate a technique of computer-simulated dose reduction for conventional chest computed tomography (CT). MATERIALS AND METHODS: In 27 patients, CT scans were obtained at 200, 100, and 40 mAs at two levels. The raw data from the 200-mAs scan were modified on a computer workstation to simulate the increased noise present on 100- and 40-mAs scans. Real and simulated 100- and 40-mAs images were independently assessed in random order for overall image quality and radiologic findings by four subspecialty-trained chest radiologists who were blinded to the technique. The four observers were given paired real and simulated images. They were asked to identify the real image and note any difference in diagnostic quality. RESULTS: No difference was seen in overall image quality or radiologic findings between real and simulated images (P > .05). In the paired comparison, 433 of 864 (50.1%) real images were correctly identified. CONCLUSION: Computer modification of 200-mAs raw scan data to simulate 100- and 40-mAs noise levels produces reconstructed images indistinguishable from real 100- and 40-mAs scans. This technique provides realistic reduced-dose images without patient radiation exposure and with identical image registration and motion artifact.

Adult↗
PubMed1997

Clinics in diagnostic imaging (27). Sarcoidosis.

A 44-year-old Caucasian man presented with third-degree heart block. Chest radiograph and high-resolution computed tomography (HRCT) of the thorax showed mediastinal and bilateral hilar lymphadenopathy associated with a diffuse, bilateral micronodular pattern. The HRCT findings and differential diagnosis of sarcoidosis are reviewed.

Adult↗
PubMed1996

Abnormalities of the airways and lung parenchyma in asthmatics: CT observations in 50 patients and inter- and intraobserver variability.

The purpose of the study was to evaluate the CT abnormalities of airways and lung parenchyma in asthmatic patients and to assess inter- and intraobserver variability for these abnormalities. The CT scans of 50 asthmatic patients and 10 healthy volunteers were assessed independently by four independent chest radiologists who were masked with respect to the clinical information. Bronchiectasis involving mostly subsegmental and distal bronchi was noted in 28.5% of the asthmatic subjects and none of the non-asthmatics. Bronchial wall thickening, small centrilobular opacities and decreased lung attenuation were observed in 82%, 21% and 31% of asthmatic patients respectively, compared with 7%, 5% and 7% of healthy subjects. The intra- and inter-observer agreements for these four CT abnormalities were measured by the kappa statistic and ranged from 0.60 to 0.79 and from 0.40 to 0.64, respectively. It is concluded that asthmatic patients may exhibit bronchial wall thickening, bronchiectasis and morphological abnormalities suggestive of distal airways disease that can be assessed on CT scans with a clinically acceptable observer variability.

Adult↗
PubMed1996

Pulmonary tuberculosis: comparison of CT findings in HIV-seropositive and HIV-seronegative patients.

PURPOSE: To determine the differences in the computed tomographic (CT) appearance of pulmonary tuberculosis (TB) between patients with and patients without human immunodeficiency virus (HIV) infection. MATERIALS AND METHODS: CT scans and chest radiographs of 42 HIV-seropositive and 42 HIV-seronegative patients with pulmonary TB were reviewed. CD4 T-lymphocyte counts, measured in 40 seropositive patients, were at least 200 cells per microliter in 10 patients and were less that 200 cells per microliter in 30. RESULTS: Seropositive patients had a higher prevalence of lymphadenopathy at chest radiography (P< .05). The seropositive patients had a lower prevalence of consolidation (P< .05), cavitation (P< .01), and postprimary pattern (P< .05) at CT. HIV-seropositive patients had a higher frequency of miliary (P< .01) and extrapulmonary disease (P< .001). Similar features of pulmonary TB were observed in seropositive patients with mild and severe immunosuppression. CONCLUSION: HIV-seropositive patients had a lower prevalence of localized parenchymal disease and a higher prevalence of disseminated disease at CT.

AIDS-Related Opportunistic Infections↗
PubMed1996

Optimization of thoracic spiral CT: effects of iodinated contrast medium concentration.

PURPOSE: To determine the effect of varying iodine concentration on arterial enhancement and perivenous artifact during thoracic spiral computed tomographic (CT) scanning. MATERIALS AND METHODS: One hundred thirty-eight outpatients received 15.0 g (n = 76) or 22.5 g (n = 62) of iodine (300 mg/mL iodine) while undergoing thoracic spiral CT. Patients received either undiluted contrast medium, 1:1 normal saline dilution, or 3:1 normal saline dilution. Contrast medium was injected at a flow rate determined to deliver the entire iodine dose within 40 seconds. Attenuation was measured within arteries and veins. Three blinded thoracic radiologists independently graded perivenous artifact and arterial enhancement. RESULTS: Perivenous artifacts were statistically significantly reduced with successive iodine dilution (P < .002). Arterial enhancement was statistically significantly better with 15.0 g of iodine diluted 1:1 when compared with the same iodine dose undiluted or diluted 3:1 (P < .01). Arterial enhancement achieved with 15.0 g of iodine diluted 1:1 was not statistically significantly lower than that achieved with 22.5 g of iodine diluted 1:1 (P > .31); however, venous artifact was greater with 22.5 g of iodine (P < .004). CONCLUSION: Reduced iodine concentration appears to diminish perivenous artifact and to result in improved arterial enhancement during thoracic spiral CT.

Adult↗
PubMed1996

Radiographic appearance of central venous catheters.

Central venous catheters (CVCs) are defined as venous access devices whose tips terminate in the superior or inferior vena cava, regardless of insertion site. CVCs allo reliable, painless, and repeated entry into the venous system and are commonly used for the administration of IV therapy, parenteral nutrition, and blood products as well as for the periodic blood sampling, hemodynamic monitoring, and hemodialysis. Catheter composition and design vary and depend on the duration of intended use and specific functions required. The purpose of this essay is to illustrate commonly used catheters, discuss factors governing catheter selection, and review important catheter-related complications.

Adult↗
PubMed1993

Parenchymal opacification in chronic infiltrative lung diseases: CT-pathologic correlation.

To correlate areas of parenchymal opacification on thin-section computed tomographic (CT) scans with histologic findings in patients with chronic infiltrative lung disease, the CT and histologic findings were evaluated in 29 patients with 11 such diseases. Open-lung biopsy was performed after CT. The area of predominant involvement was classified as air space, interstitium, or a mixture of both. A pathologic score of disease activity was assigned, and the extent of fibrosis was assessed whenever fibrosis was present. Parenchymal opacification on CT scans corresponded to abnormalities that affected mainly the air spaces in three patients (10%), the interstitium in 13 patients (45%), or both to a similar degree in 13 patients (45%). In 25 of 29 patients (86%), parenchymal opacification was associated with potentially treatable or reversible disease. Abnormalities considered irreversible were seen in three patients with end-stage fibrosis and one patient with talcosis. Parenchymal opacification on thin-section CT scans is a nonspecific finding in diseases that affect the air spaces, interstitium, or both but usually indicates potentially treatable or reversible disease.

Adult↗
PubMed1992

Primary tuberculosis in childhood: radiographic manifestations.

The aim of the study was to review the radiologic features of primary tuberculosis in childhood and to determine whether differences in patterns of disease occur among age and ethnic groups. Chest radiographs of 191 children with pediatric primary tuberculosis were reviewed by two observers. Lymphadenopathy, present in 92% of cases, was the most common abnormality identified on the initial chest radiograph and typically involved the hilar and paratracheal regions. Parenchymal abnormalities, identified in 70% of cases, occurred more commonly in the right lung (P less than .001). Children 0-3 years of age had a higher prevalence of lymphadenopathy (P less than .01) and a lower prevalence of parenchymal abnormalities (P less than .001) than older children. A lower prevalence of lymphadenopathy was found in whites than in nonwhites (P less than .02). The radiologic abnormalities often progressed in the initial follow-up. Lymphadenopathy, with or without concomitant parenchymal abnormality, is the radiologic hallmark of primary tuberculosis in childhood. However, distinct age-related and racial differences in presenting patterns of disease exist and should be recognized.

Age Factors↗
PubMed1991

Chronic diffuse infiltrative lung disease: comparison of diagnostic accuracy of high-resolution and conventional CT.

We compared the accuracies of high-resolution CT (HRCT) and conventional CT in determining the specific diagnoses in 75 consecutive patients with chronic diffuse infiltrative lung disease. Without knowledge of clinical or pathologic data, two reviewers independently assessed three separate sets of CT scans in random order: three HRCT scans, three 10-mm collimation CT scans obtained at the same levels as the HRCT scans, and a complete conventional CT scan. The HRCT scans were obtained at the level of the aortic arch, tracheal carina, and 1 cm above the right hemidiaphragm by using 1.5-mm collimation and a high spatial resolution algorithm. Observers gave the most likely diagnosis along with their degree of diagnostic confidence. The correct diagnosis, irrespective of confidence level, was reached with 71% of the HRCT scans and with 72% of both the corresponding 10-mm and complete conventional CT scans. Confidence level 1 (definite) was reached with 49% of HRCT scans, 31% of corresponding 10-mm scans, and 43% of complete conventional CT examinations; the correct diagnosis was made in 92%, 96%, and 94% of those examinations, respectively. In none of the patients were findings on the limited HRCT scan normal when findings on the conventional CT scan were abnormal. We conclude that in most patients with chronic infiltrative lung disease a specific diagnosis can be made by obtaining a limited number of HRCT scans.

Adult↗
PubMed1990

CT in differential diagnosis of diffuse pleural disease.

The CT features of benign and malignant pleural diseases have been described. However, the accuracy of these features in the differential diagnosis of diffuse pleural disease has not been assessed before. Without knowledge of clinical or pathologic data, we reviewed the CT findings in 74 consecutive patients with proved diffuse pleural disease (39 malignant and 35 benign). The patients included 53 men and 21 women 23-78 years old. Features that were helpful in distinguishing malignant from benign pleural disease were (1) circumferential pleural thickening, (2) nodular pleural thickening, (3) parietal pleural thickening greater than 1 cm, and (4) mediastinal pleural involvement. The specificities of these findings were 100%, 94%, 94%, and 88%, respectively. The sensitivities were 41%, 51%, 36%, and 56%, respectively. Twenty-eight of 39 malignant cases (sensitivity, 72%; specificity, 83%) were identified correctly by the presence of one or more of these criteria. Malignant mesothelioma (n = 11) could not be reliably differentiated from pleural metastases (n = 24). We conclude that CT is helpful in the differential diagnosis of diffuse pleural disease, particularly in differentiation of malignant from benign conditions.

Actinomycosis↗
PubMedDate not supplied

Primary malignant pulmonary hemangiopericytoma.

A primary malignant pulmonary hemangiopericytoma was diagnosed in a 45-year-old woman who complained of 10 months of cough and exertional dyspnea. One year after resection of the mass, a metastatic lesion was removed from the contralateral lung. The literature on this unusual pulmonary lesion is reviewed.

Biopsy↗
PubMedDate not supplied

Sarcoidosis activity: correlation of HRCT findings with those of 67Ga scanning, bronchoalveolar lavage, and serum angiotensin-converting enzyme assay.

PURPOSE: The objective of this study was to correlate the findings of sarcoidosis on high resolution CT (HRCT) with indexes of disease activity as measured with 67Ga scan, bronchoalveolar lavage (BAL), and serum angiotensin-converting enzyme (SACE) assay. METHOD: Twenty-nine patients with proven sarcoidosis underwent HRCT scan, 67Ga scan, BAL, and SACE assay within a 1 month period. The extent of parenchymal involvement by nodules, consolidation, ground-glass attenuation, and linear opacities was quantified to the nearest 10% of surface area affected on the CT examination. Whole-lung gallium uptake was quantified and the percentage of BAL-recovered lymphocytes (BAL-%LC) and SACE levels obtained by chart review. CT scores of disease extent were correlated with measured indexes of activity using the Spearman rank correlation coefficient. RESULTS: The mean extent of nodules, consolidation, ground-glass attenuation, and linear opacities on HRCT images was 15.1 +/- 16.6, 1.6 +/- 4.0, 17.5 +/- 25.4, and 7.6 +/- 9.6%, respectively. The extent of nodules and consolidation correlated with the intensity of lung gallium uptake (r = 0.46, p < 0.02), BAL-%LC (r = 0.50, p < 0.01), and SACE levels (r = 0.38, p < 0.05). No significant correlation was found between extent of ground-glass attenuation or linear opacities with any indexes of disease activity. CONCLUSION: On HRCT scan, nodules and consolidation in sarcoidosis reflect disease activity as measured by 67Ga scan, BAL, and SACE assay.

Adult↗