Cliff K. Choong

Hyperpolarized 3He diffusion MRI and histology in pulmonary emphysema.

Diffusion MRI of hyperpolarized 3He shows that the apparent diffusion coefficient (ADC) of 3He gas is highly restricted in the normal lung and becomes nearly unrestricted in severe emphysema. The nature of this restricted diffusion provides information about lung structure; however, no direct comparison with histology in human lungs has been reported. The purpose of this study is to provide information about 3He gas diffusivity in explanted human lungs, and describe the relationship between 3He diffusivity and the surface area to lung volume ratio (SA/V) and mean linear intercept (Lm) measurements—the gold standard for diagnosis of emphysema. Explanted lungs from patients who were undergoing lung transplantation for advanced COPD, and donor lungs that were not used for transplantation were imaged via 3He diffusion MRI. Histological measurements were made on the same specimens after they were frozen in the position of study. There is an inverse correlation between diffusivity and SA/V (and a positive correlation between diffusivity and Lm). An important result is that restricted 3He diffusivity separated normal from emphysematous lung tissue more clearly than the morphometric analyses. This effect may be due to the smaller histologic sampling size compared to the MRI voxel sizes. Magn Reson Med, 2006.

The EuroSCORE risk stratification system in the current era: how accurate is it and what should be done if it is inaccurate?

2009;35:59-61 Eur J Cardiothorac Surg Bridgewater Cliff K. Choong, Paul Sergeant, Samer A.M. Nashef, Julian A. Smith and Ben how accurate is it and what should be done if it is inaccurate? Editorial comment: The EuroSCORE risk stratification system in the current era: This information is current as of August 28, 2011 http://ejcts.ctsnetjournals.org/cgi/content/full/35/1/59 located on the World Wide Web at: The online version of this article, along with updated information and services, is

Effects of CT section thickness and reconstruction kernel on emphysema quantification relationship to the magnitude of the CT emphysema index.

RATIONALE AND OBJECTIVES Computed tomography (CT) section thickness and reconstruction kernel each influence CT measurements of emphysema. This study was performed to assess whether their effects are related to the magnitude of the measurement. MATERIALS AND METHODS Low-radiation-dose multidetector CT was performed in 21 subjects representing a wide range of emphysema severity. Images were reconstructed using 20 different combinations of section thickness and reconstruction kernel. Emphysema index values were determined as the percentage of lung pixels having attenuation lower than multiple thresholds ranging from -960 HU to -890 HU. The index values obtained from the different thickness-kernel combinations were compared by repeated measures analysis of variance and Bland-Altman plots of mean versus difference in all subjects, and correlated with quantitative histology (mean linear intercept, Lm) in a subset of resected lung specimens. RESULTS The effects of section thickness and reconstruction kernel on the emphysema index were significant (P < .001) and diminished as the index attenuation threshold was raised. The changes in index values from changing the thickness-kernel combination were largest for subjects with intermediate index values (10%-30%), and became progressively smaller for those with lower and higher index values. This pattern was consistent regardless of the thickness-kernel combinations compared and the HU threshold used. Correlations between the emphysema index values obtained with each thickness-kernel combination and Lm ranged from r = 0.55-0.68 (P = .007-.03). CONCLUSION The effects of CT section thickness and kernel on emphysema index values varied systematically with the magnitude of the emphysema index. All reconstruction techniques provided significant correlations with quantitative histology.

Benign Esophageal Tumors: Introduction, Incidence, Classification, and Clinical Features

Benign esophageal tumors comprise a diverse group of disorders that are rare in relation to malignant tumors or other benign conditions. The current article summarizes the literature with regard to the incidence and prevalence of benign tumors of the esophagus and discusses the various methods used to categorize these conditions. Summaries of important clinical features are provided for leiomyomas, esophageal cysts, fibrovascular polyps, papillomas, granular cell tumors and others.

Original investigationEffects of CT Section Thickness and Reconstruction Kernel on Emphysema Quantification: Relationship to the Magnitude of the CT Emphysema Index

RATIONALE AND OBJECTIVES Computed tomography (CT) section thickness and reconstruction kernel each influence CT measurements of emphysema. This study was performed to assess whether their effects are related to the magnitude of the measurement. MATERIALS AND METHODS Low-radiation-dose multidetector CT was performed in 21 subjects representing a wide range of emphysema severity. Images were reconstructed using 20 different combinations of section thickness and reconstruction kernel. Emphysema index values were determined as the percentage of lung pixels having attenuation lower than multiple thresholds ranging from -960 HU to -890 HU. The index values obtained from the different thickness-kernel combinations were compared by repeated measures analysis of variance and Bland-Altman plots of mean versus difference in all subjects, and correlated with quantitative histology (mean linear intercept, Lm) in a subset of resected lung specimens. RESULTS The effects of section thickness and reconstruction kernel on the emphysema index were significant (P < .001) and diminished as the index attenuation threshold was raised. The changes in index values from changing the thickness-kernel combination were largest for subjects with intermediate index values (10%-30%), and became progressively smaller for those with lower and higher index values. This pattern was consistent regardless of the thickness-kernel combinations compared and the HU threshold used. Correlations between the emphysema index values obtained with each thickness-kernel combination and Lm ranged from r = 0.55-0.68 (P = .007-.03). CONCLUSION The effects of CT section thickness and kernel on emphysema index values varied systematically with the magnitude of the emphysema index. All reconstruction techniques provided significant correlations with quantitative histology.

19F MR imaging of ventilation and diffusion in excised lungs.

Perfluorinated gases, particularly C2F6, are potentially suitable alternatives to hyperpolarized noble gases for pulmonary airspace spin density and diffusion MRI. This work focuses mainly on 19F imaging of C2F6 gas in healthy and emphysematous explanted lungs, avoiding regulatory issues of human in vivo measurements. Three‐dimensional gradient echo and spin echo spin density images of human lungs can be made in 10 s with adequate signal‐to‐noise, demonstrating the feasibility for breathing dynamics to be captured during a succession of short breath holds. As expected, the spin echo images have much smaller susceptibility artifacts than the gradient echo images. 19F and 3He images of the same lungs are compared. The apparent diffusion coefficient (ADC) of C2F6 is sensitive to restrictions imposed by the lung microstructure: the average ADC is measured to be 0.018 cm2/s in healthy lungs versus 0.031 cm2/s in emphysematous lungs at a diffusion time Δ = 2.2 ms. The low free diffusivity of pure C2F6 (D0 = 0.033 cm2/s) places it in a regime where the ADC measurement allows the surface‐to‐volume ratio to be determined in each voxel, a potentially valuable quantitative characterization of regional lung tissue destruction in emphysema. Magn Reson Med, 2005.

Effects of diffusion time on short‐range hyperpolarized 3He diffusivity measurements in emphysema

To characterize the effect of diffusion time on short‐range hyperpolarized 3He magnetic resonance imaging (MRI) diffusion measurements across a wide range of emphysema severity.

Quality of life after lung transplantation

Despite the potential differences in patient characteristics, study designs, and types of instruments used, this review of the literature showed several common findings. Important improvements in QOL are reported after lung transplantation. These improvements were observed when cross-sectional comparisons were made across the cohort of candidates and recipients and during longitudinal follow-up of patients at pretransplant and posttransplant time points. The improvements in QOL after transplantation seem to be sustained for at least 1 to 3 years after transplant. Lung transplant recipients generally were satisfied with their decision to have undergone transplantation. Many issues require further clarification. Variables that may influence QOL before and after lung transplantation, such as age, sex, pretransplant diagnosis, and type of procedure performed, should be considered carefully as study variables. Carefully designed, prospective longitudinal studies with many patients would result in stronger conclusions regarding the importance of QOL assessment in lung transplantation. It would be useful for a few QOL measurement tools to emerge as standard instruments so that many centers and investigators could adopt them to use independently. Standard instruments would allow comparison of outcomes between centers and would allow meta-analyses of multiple studies using the same methodology. Interpretation of the studies would be improved because there would be improved familiarity with a few tools, rather than vague recognition of a large variety of tools.

Prospective European multicenter randomized trial of PleuraSeal for control of air leaks after elective pulmonary resection

OBJECTIVES We sought to evaluate the efficacy and safety of a synthetic bioresorbable pleural sealant (PleuraSeal; Covidien, Bedford, Mass) to treat air leaks after pulmonary resection. METHODS Patients with air leaks after lung resection were randomized to treatment with pleural sealant on air leak sites after standard methods of lung closure or standard lung closure only. The primary outcome variable was the percentage of patients remaining air leak free until discharge. The secondary outcome variables were the proportion of patients with successful intraoperative air leak sealing, time to last air leak, and durations of chest tube drainage and hospitalization. RESULTS The sealant group comprised 62 subjects, and the control group comprised 59 subjects. Most patients (98.3%) underwent open lobectomy for bronchogenic carcinoma. The overall success rates for intraoperative air leak sealing were as follows: sealant group, 71.0%; control group, 23.7% (P < .001). For grade 2 and 3 air leaks (n = 77), the intraoperative sealing rates were as follows: sealant group, 71.7%; control group, 9.1% (P < .001). More patients with grade 2 and 3 air leaks had their leaks remain sealed in the sealant group (43.5% vs 15.2%, P = .013). The median time from skin closure to last observable air leak was 6 hours (sealant group) versus 42 hours (control group, P = .718). No treatment-related complications were reported. No differences in drainage or hospitalization were observed. CONCLUSIONS In this multicenter study the pleural sealant was safe and effective treatment for intraoperative air leaks after lung resection. Significantly fewer patients with surgically relevant intraoperative air leaks had postoperative air leaks when the pleural sealant was applied.

Prolonged Stay in Intensive Care Unit Is a Powerful Predictor of Adverse Outcomes After Cardiac Operations

BACKGROUND The aim of this study was to examine the impact of prolonged intensive care unit (ICU) stay on in-hospital mortality and long-term survival. METHODS Prospectively collected data from 6,101 consecutive patients who underwent surgery between 2003 and 2007 were analyzed. Prolonged ICU stay was defined as a total duration of ICU stay of 3 days or more postoperatively, including readmissions; patients with an ICU stay less than 3 days were identified as controls. Univariate and multiple variable analyses were performed to identify risk factors associated with prolonged ICU stay. RESULTS Of 6,101 patients, 1,139 (18.7%) patients had a prolonged ICU stay. These patients had a higher ICU mortality (10%) compared with controls (0.6%; p < 0.001). On discharge from the ICU, their hospital mortality was still 6-fold higher (1.2%) compared with controls (0.2%; p < 0.001). Finally, the patients who had prolonged ICU stays had lower survival after discharge from the ICU-89.2% and 81.2% at 1 year and 3 years, respectively, compared with 97.8% and 93.6%, respectively, for controls (p < 0.001). Multiple variable analysis revealed prolonged ICU stay to be an independent predictor of prolonged hospital stay, higher hospital mortality, and poorer long-term survival (all p < 0.001). CONCLUSIONS Prolonged ICU stay is an important predictor of adverse immediate, short-term, and long-term outcomes after cardiac operations.