The image quality of deep-learning image reconstruction of chest CT images on a mediastinal window setting.

AIM: To assess the image quality of deep-learning image reconstruction (DLIR) of chest computed tomography (CT) images on a mediastinal window setting in comparison to an adaptive statistical iterative reconstruction (ASiR-V). MATERIALS AND METHODS: Thirty-six patients were evaluated retrospectively. All patients underwent contrast-enhanced chest CT and thin-section images were reconstructed using filtered back projection (FBP); ASiR-V (60% and 100% blending setting); and DLIR (low, medium, and high settings). Image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were evaluated objectively. Two independent radiologists evaluated ASiR-V 60% and DLIR subjectively, in comparison with FBP, on a five-point scale in terms of noise, streak artefact, lymph nodes, small vessels, and overall image quality on a mediastinal window setting (width 400 HU, level 60 HU). In addition, image texture of ASiR-Vs (60% and 100%) and DLIR-high was analysed subjectively. RESULTS: Compared with ASiR-V 60%, DLIR-med and DLIR-high showed significantly less noise, higher SNR, and higher CNR (p<0.0001). DLIR-high and ASiR-V 100% were not significantly different regarding noise (p=0.2918) and CNR (p=0.0642). At a higher DLIR setting, noise was lower and SNR and CNR were higher (p<0.0001). DLIR-high showed the best subjective scores for noise, streak artefact, and overall image quality (p<0.0001). Compared with ASiR-V 60%, DLIR-med and DLIR-high scored worse in the assessment of small vessels (p<0.0001). The image texture of DLIR-high was significantly finer than that of ASIR-Vs (p<0.0001). CONCLUSIONS: DLIR-high improved the objective parameters and subjective image quality by reducing noise and streak artefacts and providing finer image texture.

Image quality of multiplanar reconstruction of pulmonary CT scans using adaptive statistical iterative reconstruction.

OBJECTIVE: We investigated the image quality of multiplanar reconstruction (MPR) using adaptive statistical iterative reconstruction (ASIR). METHODS: Inflated and fixed lungs were scanned with a garnet detector CT in high-resolution mode (HR mode) or non-high-resolution (HR) mode, and MPR images were then reconstructed. Observers compared 15 MPR images of ASIR (40%) and ASIR (80%) with those of ASIR (0%), and assessed image quality using a visual five-point scale (1, definitely inferior; 5, definitely superior), with particular emphasis on normal pulmonary structures, artefacts, noise and overall image quality. RESULTS: The mean overall image quality scores in HR mode were 3.67 with ASIR (40%) and 4.97 with ASIR (80%). Those in non-HR mode were 3.27 with ASIR (40%) and 3.90 with ASIR (80%). The mean artefact scores in HR mode were 3.13 with ASIR (40%) and 3.63 with ASIR (80%), but those in non-HR mode were 2.87 with ASIR (40%) and 2.53 with ASIR (80%). The mean scores of the other parameters were greater than 3, whereas those in HR mode were higher than those in non-HR mode. There were significant differences between ASIR (40%) and ASIR (80%) in overall image quality (p<0.01). Contrast medium in the injection syringe was scanned to analyse image quality; ASIR did not suppress the severe artefacts of contrast medium. CONCLUSION: In general, MPR image quality with ASIR (80%) was superior to that with ASIR (40%). However, there was an increased incidence of artefacts by ASIR when CT images were obtained in non-HR mode.

Relationship between folic acid intake and gingival health in non-smoking adults in Japan.

OBJECTIVE: To assess the relationship between dietary intake of folate and gingival bleeding in non-smoking adults in Japan. MATERIALS AND METHODS: Data were obtained from residents who participated in the regional nutrition survey and survey of dental diseases conducted by the administrative office of northernmost prefecture of Japan. Dietitians visited households to collect data on dietary intake. Clinical parameters, including Community Periodontal Index (CPI) and bleeding on probing (BOP), were examined in community centers. Information on smoking habit was obtained from the interview. Then the data from 497 non-smoking adults with 20 teeth or more, aged 18 years or older, were analyzed. The relationship between dietary intake of folic acid and gingival bleeding status was estimated using multivariate analysis. RESULTS: Pearson's correlation coefficient showed a significant negative correlation between dietary folate level and bleeding on probing. The negative association between folate level and bleeding on probing remained statistically significant in multiple regression analysis (standardized beta = -0.204, P < 0.001). However, no significant association was found between CPI scores and folate intake level. CONCLUSIONS: The results suggest that dietary intake of folic acid, an important indicator of gingival bleeding in adults, may provide an important clinical target for intervention to promote gingival health.

Reproducibility of temporal volume change in CT of lung cancer: comparison of computer software and manual assessment.

The purpose of this study was to investigate the reproducibility of volumetric software evaluation and manual evaluation of tumour growth. Three observers manually evaluated whether tumour volume was increasing, if it was unchanged, or if it had decreased in size in 2 serial CT examinations of 45 solid lung cancers. The tumour volumes were calculated 3 times using volumetric software and were evaluated using the same classifications as for manual evaluation. Both data sets were divided into three groups: growth or reduction with consistency among all three evaluations (group A), growth or reduction with consistency between only two evaluations (group B), and others (group C). The volume variation and relative volume variation were calculated from the median volumes measured by volumetric software. Although all 45 tumours were categorised in group A by volumetric software, only 21 tumours were categorised in group A by manual assessment. The relative volume variation of the manual assessment was 88.5 +/- 76.5%, 20.8 +/- 28.3% and 12.9 +/- 12.8% in group A, B and C, respectively. Significant differences were found between groups A and B (p<0.01) and between groups A and C (p<0.001). Inconsistency is often seen in manual assessment; in contrast, evaluation using volumetric software has good reproducibility, even when the relative change in tumour volume is small.

One-dimensional quantitative evaluation of peripheral lung adenocarcinoma with or without ground-glass opacity on thin-section CT images using profile curves.

The purpose of our investigation was to compare the usefulness of the subjective visual assessment of ground-glass opacity (GGO) with a quantitative method that used a profile curve to determine prognosis. 96 adenocarcinomas were studied. Three diameters ([D1]-[D3]) were defined for estimating the diameter of tumours on the monitor: the distance between two points was measured using software that displays a CT density profile across the tumour. One experienced and one less experienced radiologist independently evaluated the following six parameters: the three diameters [D1]-[D3]; the solid portion of total tumour in the two different ratios ([D2]/[D1], [D3]/[D1]); and the area ratio of GGO for total opacity to subjective visual evaluation. Interobserver agreement between the two radiologists of the diameters (mean bias+/- 1.96 standard deviations) was as follows: [D1], -0.7 +/- 6 mm; [D2], 0.4 +/- 4.4 mm; and [D3], -0.1 +/- 4.2 mm (Bland and Altman's method). Interobserver agreement was fair in evaluating the area ratio of GGO (kappa test, kappa = 0.309). Univariate logistic regression analysis revealed that two ratios ([D2]/[D1], [D3]/[D1]) might be significantly useful in estimating lymph node metastasis (p < 0.026), lymph duct invasion (p < 0.001) and recurrence (p < 0.015). Observation of the area ratio of GGO by an experienced radiologist would be necessary for estimating lymph node metastasis (p = 0.04) and lymph duct invasion (p < 0.001). We concluded that the ratio of solid component to total tumour, which is obtainable in a more objective and simple way using profile curves obtained by software, is a more useful method of estimating prognosis than is visual assessment.

Association of dietary habits with symptoms of temporomandibular disorders in Bangladeshi adolescents.

The prevalences of signs and symptoms of temporomandibular disorder (TMD) in Bangladeshi adolescents and their associations with intake of various hard food items were investigated. A group of 1200 randomly selected high school students aged 12-17 years from three communities (rural, semi-urban and urban) completed a questionnaire on dietary habits and presence of TMD symptoms and were examined clinically. In bivariate analysis, no significant relationship was observed between TMD symptoms and eating of hard foods. However, in logistic regression analysis, clicking showed a significant correlation with consumption of hard vegetable and fruits more than three times per week (P < 0.05). A statistically significant correlation was also observed between consumption of all hard food items (at least one item in each of the four categories of hard food) more than 12 times per week and pain in the temporomandibular joint (TMJ) (P < 0.05). A positive association was found between pain in the TMJ and older age (15-17 years) (P < 0.001). The prevalence of pain in the TMJ was significantly higher in males (P < 0.01). Prevalences of clicking and pain in the TMJ were significantly higher in subjects living in a rural area than in subjects living in an urban area (P < 0.01 and P < 0.01, respectively). Subjects having one or more decayed, missing and filled teeth (DMFT) showed significantly higher prevalences of clicking (P < 0.01) and restricted mouth opening (P < 0.01). The results suggest that prevalence of TMD symptoms are related to prolonged consumption of hard food items.

Association of caries and treatment experiences with subjective symptoms of temporomandibular disorders in female adolescents.

A 2-year cohort study of subjective symptoms of temporomandibular disorders (TMD) was performed. A total of 229 female adolescents, all 15 years of age, completed questionnaires and underwent dental examinations at baseline, 1- and 2-year follow-up surveys. The questionnaire included questions on typical TMD symptoms; i.e. temporomandibular joint (TMJ) noise, tiredness in jaws, pain on jaw movements, and difficulty in mouth opening. The relative risk was computed to determine the relationships of the baseline number of filled teeth (FT) and decayed, missing and filled teeth (DMFT) increment with the incidence of TMD. The percentage of subjects with one or more subjective symptoms at 17 years of age was 30.6%, significantly higher than the percentages at 15 (17.0%) and 16 (19.7%) years of age (P < 0.01). The symptom-emerging rate of TMJ noise during the 2-year period was 13.5%, which was the highest among the rates of possible subjective symptoms. Individuals with a 2-year increment in DMFT of > or =2 had a 2.14-times increased risk of experiencing mild symptoms, and individuals with baseline FT of > or =3 had 2.41-times increased risk of experiencing mild or severe subjective symptoms. The results of this study showed that TMD symptoms occurred in a relatively high percentage of female adolescents during the 2-year period and suggested that DMFT is one factor affecting the incidence of TMD.

Comparison of remnant-like lipoprotein particles in postmenopausal women with and without coronary artery disease and in men with coronary artery disease.

It is known that hypertriglyceridemia is a risk factor of coronary artery disease (CAD) in postmenopausal women. This study prospectively examined whether remnant lipoprotein, an atherogenic triglyceride-rich lipoprotein, may have a significant risk and prognostic values in postmenopausal women with angiographically verified CAD. Remnant-like lipoprotein particles cholesterol (RLP cholesterol) levels in fasting serum were measured in 134 consecutive postmenopausal women with (n = 56) or without (n = 78) CAD by an immunoseparation method. The women with CAD were followed for < or =24 months until occurrence of the following clinical coronary events: readmission or coronary revascularization due to recurrent or refractory angina pectoris, nonfatal myocardial infarction, and cardiac death. Multivariate logistic regression analysis showed that high RLP cholesterol levels (>5.7 mg/dl cholesterol; 90th percentile of the distribution of RLP cholesterol levels in controls) were a significant risk factor for the presence of CAD independent of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and other traditional risk factors. Kaplan-Meier analysis demonstrated that women with CAD and higher RLP cholesterol levels had a significantly higher probability of developing coronary events (p <0.001). In multivariate Cox hazard analysis, high RLP cholesterol levels as well as diabetes and hypercholesterolemia were a significant predictor of future coronary events independent of other risk factors in women with CAD (odds ratio 9.7, 95% confidence intervals 1.3 to 20.3, p = 0.02). In conclusion, increased levels of RLP cholesterol are a significant and independent risk factor of CAD and predict future coronary events in postmenopausal women with CAD.

[Cardiac conduction abnormalities after neoadjuvant chemotherapy with doxorubicin and docetaxel for primary breast carcinoma: a case report].

A 65-year-old woman with primary breast carcinoma (T 3 N 0 M 0) received neoadjuvant chemotherapy consisting of 4 cycles of 50 mg.m-2 doxorubicin (ADM) and 60 mg.m-2 docetaxel (TXT). The patient received 50 mg.m-2 ADM and 60 mg.m-2 TXT intravenously on day 1 of each cycle every three weeks. The patient underwent transthoracic echocardiography and electrocardiography (ECG) before surgery and these results were normal. ECG showed bigeminy, trigeminy after intubation and incomplete AV block (Mobitz type II) during and after surgery. The patient recovered from these arrhythmias on the first postoperative day. Our data indicate one possibility that the management of anesthetic condition might easily induce the cardiac conduction abnormalities of this patient using ADM as neoadjuvant chemotherapy.

Quantification of ground-glass opacity on high-resolution CT of small peripheral adenocarcinoma of the lung: pathologic and prognostic implications.

OBJECTIVE: The purpose of our study was to correlate the high-resolution CT findings of small peripheral adenocarcinoma of the lung with underlying histopathology and to evaluate the prognostic implications of the CT findings. MATERIALS AND METHODS: The high-resolution CT findings of small peripheral adenocarcinoma of the lung in 224 patients were analyzed by two independent observers for location, size, marginal characteristics, and extent of ground-glass opacity and necrosis. The pathologic specimens were reviewed by an experienced lung pathologist. RESULTS: One hundred and thirty-two patients had bronchioloalveolar carcinoma and 92 had adenocarcinoma. The extent of ground-glass opacity was greater in bronchioloalveolar carcinomas (mean +/- SD, 29% +/- 31.6%) than in other adenocarcinomas (8% +/- 13.3%) (p < 0.001). The extent of ground-glass opacity was significantly greater in patients without recurrence (p = 0.020) and those without nodal (p = 0.017) or distant (p = 0.007) metastases than in patients with nodal or distant metastases or in whom the carcinoma had recurred. CONCLUSION: The extent of ground-glass opacity in a nodule is greater in bronchioloalveolar carcinomas than in other adenocarcinomas. Greater extent of ground-glass opacity also correlates with improved prognosis.

Pulmonary involvement in primary Sjögren's syndrome: spectrum of pulmonary abnormalities and computed tomography findings in 60 patients.

The purpose of this study was to describe the high-resolution computed tomography (HRCT) findings of pulmonary involvement in primary Sjögren's syndrome. The study included 60 patients who met the diagnostic criteria for primary Sjögren's syndrome. The authors retrospectively reviewed the presence, extent, and distribution of various HRCT findings. Results showed that the most common HRCT findings were areas with ground-glass attenuation (92%), followed by subpleural small nodules (78%), non-septal linear opacity (75%), interlobular septal thickening (55%), bronchiectasis (38%), and cysts (30%).

Pitfalls in the interpretation of multidetector-row helical CT images at window width and level setting for lung parenchyma.

This article describes pitfalls in the interpretation of multidetector-row helical CT (MDCT) images at the window width and level settings for lung parenchyma. On MDCT, linear artifacts, which look like black and white linear densities and are called "hurricane artifacts," radiate out from objects that have very different densities from their neighbors. For the evaluation of fine parenchymal details, a low table speed/slice collimation should be used. In fact, axial (step and shoot) scanning may be more effective for the evaluation of fine details. Since artifacts from vessels highly enhanced by contrast medium cause data blackout in the surrounding areas at high table speed/slice collimation, pulmonary parenchyma in such situations should be evaluated with unenhanced CT. Although multidetector-row helical CT is a promising tool for the evaluation of lung parenchyma, it is important to identify its shortcomings due to artifacts when interpreting images at the window width and level settings for lung parenchyma and to apply the appropriate methods for eliminating such artifacts.

Demonstration of the exact anatomic tachycardia circuit in the fast-slow form of atrioventricular nodal reentrant tachycardia.

BACKGROUND: The tachycardia circuit in the fast-slow form of atrioventricular nodal reentrant tachycardia (FS-AVNRT) has not been convincingly defined. METHODS AND RESULTS: To define the tachycardia circuit, single extrastimuli were delivered during FS-AVNRT to 9 intra-atrial sites in 12 patients: the His bundle (HB) site; the superior portion of the HB site (S-HB); 3 arbitrarily divided sites on the AV junction extending from the HB site to the coronary sinus ostium (CSOS) (sites S, M, and I); the superior, posterior, and posteroinferior portions of the CSOS (S-CSOS, P-CSOS, and PI-CSOS, respectively); and the CSOS. The inferior portion of coronary sinus ostium (I-CSOS), at which the earliest retrograde activation was observed, was excluded. At each site, the longest coupling interval of the single extrastimulus that reset the tachycardia and the subsequent return cycle was measured. The mean tachycardia cycle length was 370+/-55 ms. The longest coupling intervals at sites S-HB, HB, S, M, I, CSOS, S-CSOS, P-CSOS, and PI-CSOS were 328+/-53, 360+/-55, 358+/-55, 358+/-54, 360+/-55, 338+/-56, 323+/-54, 331+/-56, and 321+/-58 ms, respectively, and the subsequent return cycles were 408+/-58, 371+/-55, 370+/-55, 372+/-56, 370+/-55, 396+/-56, 411+/-60, 405+/-58, and 412+/-59 ms, respectively. The longest coupling intervals at sites HB, S, M, and I were longer than those at S-HB, CSOS, S-CSOS, P-CSOS, and PI-CSOS (P<0.0001). The return cycles at sites HB, S, M, and I did not differ from the tachycardia cycle length, whereas those at CSOS, S-CSOS, P-CSOS, and PI-CSOS were longer than the tachycardia cycle length (P<0.0001). CONCLUSIONS: The perinodal atrium extending from the HB site to the I-CSOS is an integral limb of the reentry circuit in FS-AVNRT.

High-resolution CT using multidetector CT equipment: evaluation of image quality in 11 cadaveric lungs and a phantom.

OBJECTIVE: The aim of this study was to evaluate the image quality and diagnostic efficacy of multidetector high-resolution CT (HRCT) by comparing it with single-detector HRCT and by comparing the noise and artifact of multidetector HRCT images with a phantom. SUBJECTS AND METHODS: Multidetector HRCT with six parameters and single-detector HRCT were performed on cadaveric lungs. The image quality and diagnostic efficacy of multidetector HRCT were evaluated in comparison with those of single-detector HRCT. A phantom was scanned, and image artifact and noise were investigated. RESULTS: . The image quality of multidetector HRCT with axial 1.25 mm x 4i (four images per gantry rotation) mode was equal to that of single-detector HRCT. The image quality of multidetector HRCT with other modes was worse than that on single-detector HRCT. The diagnostic efficacy of multidetector HRCT with high-quality mode (pitch, 3:1) and axial mode was equal to that of single-detector HRCT. The diagnostic efficacy on multidetector HRCT with high-speed mode (pitch, 6:1) was worse than that on single-detector HRCT. In the phantom study, images made in high-speed mode had strong artifacts. Noise in the axial mode was milder than that in high-speed mode but more severe than that in high-quality mode. CONCLUSION: The image quality of axial HRCT with multidetector CT is equal to that on single-detector HRCT. Axial HRCT with multidetector CT is appropriate for evaluating subtle lung abnormalities, but high-speed mode is unsuitable. Using the high-quality mode degrades image quality but is still worthwhile.

Invasive and noninvasive thymoma: distinctive CT features.

PURPOSE: The purpose of this work was to evaluate the CT features of thymoma and to determine the most helpful findings in differentiating invasive from noninvasive thymoma. METHOD: The CT scans from 27 patients with invasive thymoma and 23 with noninvasive thymoma were independently assessed by two observers without knowledge of their invasiveness. The presence and distribution of various CT findings were independently analyzed. RESULTS: Invasive thymomas were more likely to have lobulated (16/27, 59%) or irregular (6/27, 22%) contours than noninvasive thymomas (8/23, 35% and 1.5/23, 6%, respectively) (p < 0.05). Invasive thymomas had a higher prevalence of low attenuation areas within the tumor (16/27, 60%) than noninvasive thymomas (5/23, 22%) (p < 0.001) as well as foci of calcification (14.5/27, 54% vs. 6/23, 26%; p < 0.01). CONCLUSION: The presence of lobulated or irregular contour, areas of low attenuation, and multifocal calcification is suggestive of invasive thymoma.

Pulmonary involvement in mixed connective tissue disease: high-resolution CT findings in 41 patients.

The objective of this study was to describe the pulmonary abnormalities on high-resolution computed tomography (CT) in patients with mixed connective tissue disease (MCTD). The study included 41 patients who met the diagnostic criteria for MCTD and showed abnormal findings on high-resolution CT. The presence, extent, and distribution of various high-resolution CT findings were evaluated. The predominant abnormalities included areas of ground-glass attenuation (n = 41), subpleural micronodules (n = 40), and nonseptal linear opacities (n = 32). Other common findings included peripheral predominance (n = 40), lower lobe predominance (n = 39), intralobular reticular opacities (n = 25), architectural distortion (n = 20), and traction bronchiectasis (n = 18). Less common findings included honeycombing, ill-defined centrilobular nodules, airspace consolidation, interlobular septal thickening, thickening of bronchovascular bundles, bronchial wall thickening, bronchiectasis, and emphysema. Pulmonary involvement of MCTD is characterized by the presence of ground-glass attenuation, nonseptal linear opacities, and peripheral and lower lobe predominance. Ill-defined centrilobular opacities were uncommonly seen.

Acute respiratory distress syndrome and acute interstitial pneumonia: comparison of thin-section CT findings.

PURPOSE: The purpose of this work was to compare the thin-section CT findings of acute respiratory distress syndrome (ARDS) with those of acute interstitial pneumonia (AIP). METHOD: The thin-section CT scans from 25 patients with ARDS and 25 with AIP were independently assessed by two observers without knowledge of clinical and pathologic data. The presence, extent, and distribution of various CT findings were independently analyzed. RESULTS: Honeycombing was seen more frequently in lobes of patients with AIP (26%) than in lobes with ARDS (8%) (p < 0.001). Compared with patients with ARDS, a greater number of patients with AIP had a predominantly lower lung zone distribution (p < 0.05) and a symmetric distribution (p < 0.05) of the parenchymal abnormalities. CONCLUSION: Patients with AIP have a greater prevalence of honeycombing and are more likely to have a symmetric bilateral distribution and a lower lung zone predominance than patients with ARDS. However, significant overlap exists among the CT findings.

The effect of calcium on Fas-mediated apoptosis and secondary necrosis of Jurkat cells.

Our previous study using a new microscopic system indicated that apoptotic cells undergo secondary necrosis during treatment with anti-Fas antibody and calcium. In this study, we compared the time-lapse appearance of apoptosis and secondary necrosis of Jurkat cells during treatment with anti-Fas antibody with and without calcium in individual cells. Apoptosis developed in 97% and 81% of cells during 36-hour-treatment with anti-Fas antibody with and without calcium, respectively. The apoptosis of Jurkat cells showed a characteristic pattern of time-lapse morphological change. Less than 1% of the apoptotic cells divided into apoptotic bodies. There was budding in all the other apoptotic cells, but no apoptotic bodies formed. We confirmed that secondary necrosis occurs in individual apoptotic cells during treatment with anti-Fas antibody. Neither the pattern of time-lapse morphological change nor the time interval between the beginning of apoptotic budding and secondary necrosis were related to the presence of calcium. This study clarified the characteristic pattern of time-lapse morphological change in Jurkat cells during treatment with anti-Fas antibody, and presented direct evidence that individual apoptotic cells undergo secondary necrosis. The presence of calcium did not affect the pattern of morphological change or the time interval between the beginning of apoptotic budding and secondary necrosis.

[A comparison of the effectiveness of transtracheal heating and humidification system in maintaining body temperature during general anesthesia with low flow gases].

We evaluated the effectiveness of transtracheal heating and humidification system in maintaining body temperature during general anesthesia with low flow gases in 12 gastric cancer patients. Patients were divided into two group; Control group A in which a hot-water circulating system was used and group B in which a transtracheal heating and humidification system by ANAMED HUMITUBE was used, during gastric cancer operation. Compared to the hot-water circulating system, the transtracheal heating and humidification system is more effective for maintaining body temperature and humidification after abdominal lavage by warm saline water. But there was no difference between the two groups about awakening from general anesthesia. We concluded that transtracheal heating and humidification system by ANAMED HUMITUBE is effective in maintaining body temperature under general anesthesia with low flow gases.

[Severe laryngeal edema after tracheal extubation--report of a case].

An 80-year old female underwent subtotal esophagectomy with neck lymphnode dissection for esophageal cancer. The tracheal intubation was done repeatedly. Anesthesia was maintained with O2-N2O-isoflurane. No complications were observed during the operation. About thirty minutes after tracheal extubation, she developed airway obstruction with tracheal tug and stridor. Severe laryngeal edema was found by bronchofiberscopy. Percutaneous minitracheostomy was performed under ventilation support by laryngeal mask airway. Seven days later, bronchoscopy examination revealed that the laryngeal edema had disappeared. It should be kept in mind that severe laryngeal edema could develop immediately after extubation.