Repeatability of quantitative CT indexes of emphysema in patients evaluated for lung volume reduction surgery

PURPOSE: To evaluate the repeatability of quantitative computed tomographic (CT) indexes of emphysema and the effect of spirometric gating of lung volume during CT in candidates for lung volume reduction surgery (LVRS). MATERIALS AND METHODS: Initial and same-day repeat routine inspiratory spiral chest CT studies were performed in 29 LVRS candidates (group 1, routine study vs repeat study). In a separate cohort of 29 LVRS candidates, spiral chest CT studies were performed both without and with spirometric gating by using a spirometer to trigger scanning at 90% of vital capacity (group 2, spirometric gating study). In each study, Pearson and intraclass correlation coefficients were calculated to determine the agreement between multiple pairs of whole-lung quantitative CT indexes of emphysema, and mean values were compared with two-tailed paired t tests. RESULTS: Pearson and intraclass correlation coefficients were high for all quantitative CT indexes (all > or = 0.92). No significant differences were found between mean values of quantitative CT indexes in group 1. Variation in quantitative CT results was small but more prominent in group 2 than in group 1. The variation in quantitative CT results was primarily related to differences in lung volume (r(2) as great as 0.83). CONCLUSION: Repeatability of quantitative CT test results in LVRS candidates is high and unlikely to improve by using spirometric gating.     

Imaging of patients with severe emphysema considered for lung volume reduction surgery.

Lung volume reduction surgery has recently been reintroduced as a palliative treatment for patients with severe emphysema. Selection criteria vary between centres and imaging is extensively used, but the exact role of individual techniques in the selection process is still emerging.     

Visual classification of emphysema heterogeneity compared with objective measurements: HRCT vs spiral CT in candidates for lung volume reduction surgery

The aim of this study was to investigate whether spiral CT is superior to high-resolution computed tomography (HRCT) in evaluating the radiological morphology of emphysema, and whether the combination of both CT techniques improves the evaluation in patients undergoing lung volume reduction surgery (LVRS). The material consisted of HRCT (with 2-mm slice thickness) and spiral CT (with 10-mm slice thickness) of 94 candidates for LVRS. Selected image pairs from these examinations were evaluated. Each image pair consisted of one image from the cranial part of the lung and one image from the caudal part. The degree of emphysema in the two images was calculated by computer. The difference between the images determined the degree of heterogeneity. Five classes of heterogeneity were defined. The study was performed by visual classification of 95 image pairs (spiral CT) and 95 image pairs (HRCT) into one of five different classes of emphysema heterogeneity. This visual classification was compared with the computer-based classification. Spiral CT was superior to HRCT with 47% correct classifications of emphysema heterogeneity compared with 40% for HRCT-based classification ( p<0.05). The combination of the techniques did not improve the evaluation (42%). Spiral CT is superior to HRCT in determining heterogeneity of emphysema visually, and should be included in the pre-operative CT evaluation of LVRS candidates.     

Lung volume reduction surgery for emphysema: correlation of CT and V/Q imaging with physiologic mechanisms of improvement in lung function

PURPOSE: To compare the relationship between computer-derived and visually assessed ventilation-perfusion (V/Q) scintigraphy and computed tomographic (CT) scores in evaluating disease severity and distribution in identifying optimal candidates for lung volume reduction surgery (LVRS) and to correlate these radiologic indices with physiologic measures of outcome. MATERIALS AND METHODS: In 39 patients, preoperative V/Q and CT scans were visually scored by two radiologists for disease severity and distribution. Results were compared with computer-derived scores for the same cohort. These indices were correlated with clinical improvement measured with forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), and ratio of FEV(1) to FVC. RESULTS: The disease distribution scores measured with the different methods correlated closely: computer-based and visually assessed CT scores (r = 0.89, P <.001), computer-based and visually assessed V/Q scores (r = 0.83, P <.001), visually assessed CT and V/Q scores (r = -0.50, P <.001), and computer-derived CT and V/Q scores (r = -0.57, P =.015). Similarly, a statistically significant correlation was noted between each of the radiologic methods and clinical outcome measurements (P <.001). CONCLUSION: CT and V/Q preoperative assessment, with either visual scoring or computer-based algorithms, are nearly equivalent in their utility in predicting improvement in FEV(1) measures.     

Chest radiographic findings following video-assisted thoracoscopic lung volume reduction surgery for emphysema

Surgical reduction of lung volume is being investigated as a promising alternative in the treatment of selected patients with severe debilitating emphysema. Following bilateral video-assisted thoracoscopic surgical resection (VATS) of emphysematous lung tissue, patients show improvements in exercise tolerance, dyspnoea, increases in oxygenation, decreased airway obstruction and enhanced quality of life. The postoperative findings in the first 24 patients who underwent bilateral VATS volume reduction are described. Pneumothoraces developed in all patients, often with unusual shapes related to the surgical sutures. Perihilar, pulmonary and paramediastinal pulmonary parenchymal opacities were seen in approximately half of the patients, representing areas of pulmonary contusion, atelectasis and/or haemorrhage associated with the staple lines. The purpose of the present study is to describe the immediate postoperative chest radiographic appearances and to familiarize radiologists with the surgical procedure.     

多层螺旋CT三维重组对肺减容术前的形态学评估

目的探讨多层螺旋CT（MSCT）容积再现技术（VRT）显示肺气肿组织最佳的重组阈值区间，及其作为肺减容术（LVRS）靶区（拟行切除的肺气肿组织）显示手段的价值。方法对56例拟行LVRS的肺气肿患者行呼气相肺部扫描，按照CT检查时间的先后将患者分为A组和B组。以-1024～-960HU、-1024～-910HU分别作为LVRS手术靶区的重组阈值区间，对A组的原始薄层图像行VRT重组，并将2种重组阈值的VRT图像分别与轴面图像、多平面重组（MPR）图像对比，确定显示LVRS靶区的最佳重组阈值区间。B组根据A组选定的重组阈值区间进行VRT重组，计数并对比VRT与二维图像中直径≥3cm的肺大泡在各肺叶的分布，应用配对t检验验证2种计数结果。结果A组中以-1024 — -960HU作为肺气肿重组阈值区间的VRT图像对LVRS手术靶区显示较佳，与相对正常肺组织对比较鲜明，病变的程度、范围与二维图像符合程度高。B组中VRT图像与原始图像分析结果一致，对肺大泡的定位及计数结果与原始图像基本一致，肺右上、右中、右下、左上、左下叶计数对比，二维图像分别显示：（4．22±2．09）、（4、44±2．59）、（2．18±0．92）、（3．54±2．03）和（4．40±2．42）个；VRT分别显示：（4．12±2．12）、（4．44±2．59）、（2．18±0．87）、（3．50±1．99）和（4．28±2．28）个（t值分别为1．98、0．00、1．77、1．76、1．81，P值均〉0．05）。结论以-1024～-960HU作为肺气肿组织的重组阈值，VRT成像可以准确显示肺气肿的分布类型，立体直观的显示LVRS手术靶区，为术前形态评估和术后效果预测提供了新方法。     

Clinical evaluation of 99mTc-Technegas SPECT in thoracoscopic lung volume reduction surgery in patients with pulmonary emphysema

99mTc-Technegas (Tcgas) SPECT is useful for evaluating the patency of the airway and highly sensitive in detecting regional pulmonary function in pulmonary emphysema. The aim of this study is to evaluate regional ventilation impairment by this method pre and post thoracoscopic lung volume reduction surgery (LVRS) in patients with pulmonary emphysema. METHODS: There were 11 patients with pulmonary emphysema. The mean age of patients was 64.1 years. All patients were males. LVRS was performed bilaterally in 8 patients and unilaterally in 3 patients. Post inhalation of Tcgas in the sitting position, the subjects were placed in the supine position and SPECT was performed. Distribution of Tcgas on axial images was classified into 4 types, A: homogeneous, B: inhomogeneous, C: hot spot, D: defect. Three slices of axial SPECT images, the upper, middle and lower fields were selected, and changes in deposition patterns post LVRS were scored (Tcgas score). RESULTS: Post LVRS, dyspnea on exertion and pulmonary function tests were improved. Pre LVRS, inhomogeneous distribution, hot spots and defects were observed in all patients. Post LVRS, improvement in distribution was obtained not only in the surgical field and other fields, but also in the contralateral lung of unilaterally operated patients. In 5 patients some fields showed deterioration. The Tcgas score correlated with improvements in FEV1.0, FEV1.0% and %FEV1.0. CONCLUSION: Tcgas SPECT is useful for evaluating changes in regional pulmonary function post LVRS.     

Clinical evaluation of99mTc-Technegas SPECT in thoracoscopic lung volume reduction surgery in patients with pulmonary emphysema

^99mTc-Technegas (Tcgas) SPECT is useful for evaluating the patency of the airway and highly sensitive in detecting regional pulmonary function in pulmonary emphysema. The aim of this study is to evaluate regional ventilation impairment by this method pre and post thoracoscopic lung volume reduction surgery (LVRS) in patients with pulmonary emphysema.Methods: There were 11 patients with pulmonary emphysema. The mean age of patients was 64.1 years. All patients were males. LVRS was performed bilaterally in 8 patients and unilaterally in 3 patients. Post inhalation of Tcgas in the sitting position, the subjects were placed in the supine position and SPECT was performed. Distribution of Tcgas on axial images was classified into 4 types, A: homogeneous, B: inhomogeneous, C: hot spot, D: defect. Three slices of axial SPECT images, the upper, middle and lower fields were selected, and changes in deposition patterns post LVRS were scored (Tcgas score).Results: Post LVRS, dyspnea on exertion and pulmonary function tests were improved. Pre LVRS, inhomogeneous distribution, hot spots and defects were observed in all patients. Post LVRS, improvement in distribution was obtained not only in the surgical field and other fields, but also in the contralateral lung of unilaterally operated patients. In 5 patients some fields showed deterioration. The Tcgas score correlated with improvements in FEV_1.0, FEV_1.0% and %FEV_1.0.Conclusion: Tcgas SPECT is useful for evaluating changes in regional pulmonary function post LVRS.     

单侧肺减容术肺切除量对兔阻塞性肺气肿疗效的影响

目的　评价单侧肺减容术 (LVRS)肺切除量对兔阻塞性肺气肿疗效的影响。方法　建立新西兰大白兔阻塞性肺气肿模型 ,将 5 0只肺气肿兔随机分为肺气肿组 (A组 )、小量LVRS组 (B组 )、中量LVRS组 (C组)、大量LVRS组(D组 )和假手术组(E组 ) 5组 ,每组各 10只 ,8周后进行肺功能和肺组织学检查。结果　与A组比较 ,C组的潮气量、0 3s用力呼气容积 (FEV0 3 )、FEV0 3 /FVC(用力肺活量)、PaO2 、平均肺泡数和肺泡隔面密度增加 ,功能残气量、PaCO2 、肺总容积和肺泡直径降低 (P <0 0 5 ) ,而B、D、E组无明显变化 (P >0 0 5 )。组织学检查C组气道炎症减轻 ,肺气肿明显改善。结论　单侧适量LVRS可有效改善兔阻塞性肺气肿。     

微创封堵法肺减容术的实验研究

目的评价钢圈加生物胶封堵法治疗兔肺气肿的有效性和可行性。方法制备兔肺气肿模型16只，分为封堵组10只，对照组6只。封堵组兔行钢圈加生物胶法封堵两前叶支气管，分别测量兔气肿前、气肿后、术后1周及4周4个时间点2组的静态气道压（Pmax）、最大呼气流量（PEF）、呼气末肺容积（EEV）及血氧分压（PO2），并观察封堵组钢圈咳出（或移位）和肺萎陷情况。结果封堵组的Pmax在气肿前、后分别为（20．0±1．3）和（17．1±1．4）cm H2O（1cm H2O=0．098kPa）。术后1周时封堵组Pmax为（19．2±1．4）cm H2O，对照组为（17．1±1．5）cm H2O（F=6．68，P〈0．05）。术后4周时封堵组Pmax为（19．2±1．4）cm H2O，对照组为（16．6±1．2）cm H2O（F=12．10，P〈0．01）；封堵组EEV为（86±8）ml，对照组为（96±4）ml（F=5．72，P〈0．05）。封堵组封堵术后1周及4周Pmax均比气肿后高（P值均〈0．01）；气肿后EEV比气肿前增加（P〈0．01），术后1周比气肿后减少（P〈0．05）。结论应用钢圈加生物胶封堵法进行兔肺减容术，能改善肺功能，且这种作用能较长期存在。     

Quantitation of emphysema with three-dimensional CT densitometry: comparison with two-dimensional analysis, visual emphysema scores, and pulmonary function test results

PURPOSE: To compare lung densitometric measurements that use a three-dimensional (3D) reconstruction of the lungs with those obtained from analysis of two-dimensional (2D) computed tomographic (CT) images, visual emphysema scores, and data from pulmonary function tests. MATERIALS AND METHODS: Thoracic helical CT scans were obtained in 60 adult patients (35 with no visual evidence of emphysema and 25 with emphysema). The lungs were reconstructed as a 3D model on a commercial workstation, with a threshold of -600 HU. By analysis of histograms, the proportions of lung volumes with attenuation values below -950, -910, and -900 HU were measured, in addition to mean lung attenuation. These values were compared with lung densitometric results obtained from 2D CT images, visual emphysema scores, and data from pulmonary function tests. RESULTS: Quantitation of emphysema with 3D reconstruction was efficient and accurate. Correlation was good among densitometric quantitation with 3D analysis, that obtained with 2D analysis (r = 0.98-0.99), and visual scoring (r = 0.74-0.82). Correlation was reasonable between 3D densitometric quantitation and the diffusing capacity of the lungs for carbon monoxide (DLCO) (r = -0.57 to -0.64), total lung capacity (r = 0.62-0.71), forced expiratory volume in 1 second (FEV1) (r = -0.57 to -0.60), and the ratio of FEV1 to forced vital capacity (FVC) (r = -0.75 to -0.82). The visual CT quantitation of emphysema correlated best with DLCO (r = -0.82) and FEV1/FVC (r = -0.89). CONCLUSION: Lung densitometry with 3D reconstruction of helical CT data is a fast and accurate method for quantifying emphysema.     

Advanced emphysema: preoperative chest radiographic findings as predictors of outcome following lung volume reduction surgery.

PURPOSE: To determine whether preoperative chest radiographic findings alone can reliably predict which patients will achieve the best functional outcome of lung volume reduction surgery. MATERIALS AND METHODS: The preoperative chest radiographs obtained in 57 patients who had undergone lung volume reduction surgery were retrospectively scored by five blinded readers for severity and distribution of emphysema, evidence of lung compression, disease heterogeneity, and other features. Comparisons were made with the 3-6-month postoperative functional outcome for each patient. RESULTS: High disease heterogeneity (score > 2) and unequivocal lung compression (score 1) both were 100% predictive of a favorable outcome (FEV1 increase, > or = 30%). Low heterogeneity (score < 1) was 94% predictive of an unfavorable outcome (FEV1 increase < 30%), as was a lack of lung compression, which was 92% predictive of an unfavorable outcome. These two features also correlated with an improved 6-minute walk test result, although this correlation was weaker. CONCLUSION: Chest radiography alone may be sufficient for initial screening. High disease heterogeneity and lung compression on chest radiographs are highly predictive of a favorable functional outcome.     

Sources of error in lung densitometry with CT

RATIONALE AND OBJECTIVES: To determine and analyze the most important error sources in lung CT densitometry in vivo. METHODS: The authors examined the influences of CT acquisition errors, physiologic changes, and image segmentation errors on lung densitometry. Among others, spatial dependency and long-term reproducibility of the density measurements of blood and air were examined over a period of 4 years in a group of 28 patients with pulmonary emphysema. These results were related to the measured lung densities in this group. RESULTS: The density measurement of blood and air is strongly dependent on the position in the thorax. Despite full-scanner calibrations, x-ray tube replacement can induce a significant increase in measured blood density. CONCLUSIONS: A change in a lung density parameter over time can actually be the result of tube replacement or changing blood density. A simple postprocessing technique can correct for these changes.     

Visual grading of emphysema severity in candidates for lung volume reduction surgery. Comparison between HRCT, spiral CT and "density-masked" images

Purpose: To investigate which of three types of CT imaging yielded the best results in estimating the degree of emphysema in patients undergoing evaluation for lung volume reduction surgery (LVRS), whether there was any difference in this regard between the cranial and caudal part of the lung, and whether the degree of emphysema had an impact on the estimation.Material and Methods: Four radiologists visually classified different degrees of emphysema on three different types of CT images into four groups. The degree of emphysema was calculated by a computer. The three types of images were as follows: HRCT images (2-mm slice thickness); spiral CT images (10-mm slice thickness); and density-masked images (spiral CT images printed with pixels below -960 HU, depicted in white).Results: The conventionally presented images from HRCT and spiral CT yielded the same results (60% respective 62% correct classifications) in assessing the degree of emphysema irrespective of localisation. Significantly improved results were obtained when the spiral CT images were presented as density-masked images (74%).Conclusion: There was no difference between HRCT and spiral CT in assessing the degree of emphysema in candidates for LVRS. Improvement can be achieved by the use of density-masked images.     

Size and morphology of the trachea before and after lung volume reduction surgery

OBJECTIVE: The purpose of this investigation was to determine the effect of lung volume reduction surgery on measured tracheal features. MATERIALS AND METHODS: Twenty-four male and 19 female patients with emphysema underwent lung volume reduction surgery, pulmonary function testing, and repeated CT. The tracheal air column was segmented from axial images. The sagittal and coronal dimensions of the intrathoracic trachea were determined. Tracheal morphology was quantified using the tracheal (coronal and sagittal dimensions) and circularity indexes. The results were compared with pulmonary function test results. RESULTS: Morphologic appearance of the intrathoracic trachea was consistent before and 3 months after surgery. The group means of the tracheal length, mean area, and volume were 78.60 mm (+/- 16.88 mm), 283.84 mm(2) (+/- 61.47 mm(2)), and 22.59 cm(3) (+/- 7.69 cm(3)), respectively, before surgery and 67.53 mm (+/- 15.78 mm), 309.12 mm(2) (+/- 79.83 mm(2)), and 20.99 cm(3) (+/- 7.27 cm(3)), respectively, after surgery (p < 0.05). Mean tracheal indexes were 0.85 (+/- 0.11) before surgery and 0.82 (+/- 0.04) after surgery (p < 0.01). Mean circularity indexes were 0.91 (+/- 0.03) before surgery and 0.90 (+/- 0.04) after surgery (p < 0.05). The size of the trachea was significantly correlated with lung volume before and after surgery (p < 0.05). The changes in tracheal features and changes in pulmonary function were not correlated (p > 0.05), except for tracheal area (p < 0.05). CONCLUSION: Our data suggest that tracheal dimensions reflect the severity of emphysema as reflected by increased lung volumes. Tracheal features were poor predictors of changes in postsurgical pulmonary function parameters evaluated in this preliminary study.     

Computerized estimation of the lung volume removed during lung volume reduction surgery

RATIONALE AND OBJECTIVES: This study was designed to develop an automated method for estimating lung volume removed during lung volume reduction surgery (LVRS) using computed tomography (CT). MATERIALS AND METHODS: The CT examinations of six patients who underwent bilateral LVRS were analyzed in this study. The resected lung tissue (right and left) was weighed during pathologic examination. An automated computer scheme was developed to estimate the lung volume removed using the CT voxel values and lung specimen weight. The computed fraction of lung volume removed was evaluated across a range of simulated surgical planes (ie, other than parallel to the CT image plane) and CT reconstruction kernels, and it was compared with the surgeons' postsurgical estimates. RESULTS: The computed fraction of the lung volume removed during LVRS was linearly correlated with the resected lung tissue weight (Pearson correlation = 0.697, P = .012). The computed fraction of lung volume removed ranged from 12.9% to 51.7% of the total lung volume. The surgeons' postsurgical estimates of lung volume removed ranged from 30% to 33%. The percent difference between the surgeons' estimates and the computed lung volume removed as a percentage of the surgeons' estimates ranged from -72.3% to 57.0% with mean absolute difference of 29.7% (+/-20.7). CONCLUSION: The preliminary findings of this study suggest that the proposed quantitative model should provide an objective measure of lung volume removed during LVRS that may be used to investigate the relationship between lung volume removed and outcome.