CT of emphysema

This article focuses on three main topics: (1) the importance of emphysema as a serious respiratory disease, (2) qualitative assessment of emphysema using CT, and (3) the emerging importance of quantitative CT in the evaluation of patients with emphysema for surgery and drug therapy. CT also can identify the major anatomic subtypes of emphysema. CT is critical in the assessment of patients with the potential for lung volume reduction surgery. CT may well be superior to pulmonary function tests in the longitudinal assessment of current and proposed drug therapies for the treatment of emphysema.     

Automated lobar quantification of emphysema in patients with severe COPD

Automated lobar quantification of emphysema has not yet been evaluated. Unenhanced 64-slice MDCT was performed in 47 patients evaluated before bronchoscopic lung-volume reduction. CT images reconstructed with a standard (B20) and high-frequency (B50) kernel were analyzed using a dedicated prototype software (MevisPULMO) allowing lobar quantification of emphysema extent. Lobar quantification was obtained following (a) a fully automatic delineation of the lobar limits by the software and (b) a semiautomatic delineation with manual correction of the lobar limits when necessary and was compared with the visual scoring of emphysema severity per lobe. No statistically significant difference existed between automated and semiautomated lobar quantification (p > 0.05 in the five lobes), with differences ranging from 0.4 to 3.9%. The agreement between the two methods (intraclass correlation coefficient, ICC) was excellent for left upper lobe (ICC = 0.94), left lower lobe (ICC = 0.98), and right lower lobe (ICC = 0.80). The agreement was good for right upper lobe (ICC = 0.68) and moderate for middle lobe (IC = 0.53). The Bland and Altman plots confirmed these results. A good agreement was observed between the software and visually assessed lobar predominance of emphysema (kappa 0.78; 95% CI 0.64–0.92). Automated and semiautomated lobar quantifications of emphysema are concordant and show good agreement with visual scoring. No financial support to disclose. A potential conflict of interest is noted in that one author is an employee of Siemens.     

用于评估慢性阻塞性肺疾病（COPD）病人气管壁厚度的多层螺旋CT新方法与肺功能检查的相关性研究

CT对气管壁厚度的定量评估被证明是慢性阻塞性肺疾病（COPD）病人气道壁重塑的标志。本研究目的是采用多层CT（MDCT）3D支气管树成像,使用新的定量方法判断COPD病人大小支气管壁厚度与通气障碍功能性参数之间的相关性。对31例病人（吸烟者／COPD病人,非吸烟者／对照组）与气管轴线垂直的MDCT邻近截面进行了定量评估,     

Pulmonary emphysema: subjective visual grading versus objective quantification with macroscopic morphometry and thin-section CT densitometry.

PURPOSE: To compare subjective visual grading of pulmonary emphysema with macroscopic morphometry and computed tomographic (CT) densitometry. MATERIALS AND METHODS: In 62 consecutive patients who underwent thinsection CT before surgical lung resection, emphysema was objectively quantified with computer-assisted macroscopic morphometry and CT densitometry. The percentage of lung macroscopically occupied by emphysema was compared with the percentage occupied on CT scans by pixels with attenuation values lower than a predefined threshold (CT densitometry). Three readers with varying degrees of expertise subjectively graded emphysema with visual assessment at two reading sessions. Data from objective quantification and subjective grading were analyzed with correlation coefficients, and interobserver and intraobserver agreement were calculated. RESULTS: Subjective grading of emphysema showed less agreement with the macroscopic reference standard results (r = 0.439-0.505; P < .05) than with objective CT densitometric results (r = 0.555-0.623; P < .001). The 95% CIs for the intercepts of the linear regression lines were suggestive of systematic subjective overestimation of emphysema by all three readers. Interobserver agreement was moderate (kappa = 0.431-0.589). Intraobserver agreement was good to excellent (kappa = 0.738-0.936). The expertise of individual readers did not substantially influence results. CONCLUSION: Systematic overestimation and moderate interobserver agreement may compromise subjective visual grading of emphysema, which suggests that subjective visual grading should be supplemented with objective methods to achieve precise, reader-independent quantification of emphysema.     

CT diagnosis of congenital lobar emphysema

Congenital lobar emphysema can be diagnosed by conventional chest films, but it may be difficult to determine which is the affected lobe or the etiology. This report presents the computed tomographic (CT) appearance of this entity and also emphasizes the significant role CT may have in its diagnosis.     

多层螺旋CT评价肺气肿患者肺功能的可行性

目的探索建立肺气肿通气功能障碍的CT分级标准及可行性。方法147例受试者自愿接受多层螺旋CT（MSCT）及常规肺功能（PFT）检查，间隔不超过1周。以数字表法将患者随机分成2组：A组120例，比较MSCT肺功能与PFT之间的相关性，并以PFT为金标准将其分为正常、轻、中、重度肺功能损害4组，用来建立肺气肿通气功能障碍的MSCT分级标准。B组27例，评估上述分级标准的准确性。测定CT肺功能的定量指标：容积比（Vex／in）、吸气相平均肺密度（MLDin）、呼气相平均肺密度（MLDex）、平均肺密度比（MLDex／in）、吸气相-910HU的像素指数（Piin-910）、呼气相-910HU的像素指数（Piex-910）、-910HU的像素指数比（Piex／in-910）。结果MSCT肺定量指标与PFT之间存在相关性，其中以Piex／in-910与FEV1％的相关性最佳（r=-0．905，P＜0．01）。正常肺功能者60例，轻度下降者22例，中度下降者21，重度下降者17例，所建立的分级标准能较好地反映肺气肿通气功能障碍，其中以Piex／in-910诊断效能最高（x^2=0．267，P=0．966，准确性81．5％），其初步标准为：正常0～9．9，轻度10．0～34．9，中度35．0～74．9，重度≥75．0。结论MSCT肺定量指标评价肺气肿通气功能障碍是可行的，其中以Piex／in-910诊断效能最高。     

Improved correlation between CT emphysema quantification and pulmonary function test by density correction of volumetric CT data based on air and aortic density

Objectives

To determine the improvement of emphysema quantification with density correction and to determine the optimal site to use for air density correction on volumetric computed tomography (CT).

Methods

Seventy-eight CT scans of COPD patients (GOLD II–IV, smoking history 39.2 ± 25.3 pack-years) were obtained from several single-vendor 16-MDCT scanners. After density measurement of aorta, tracheal- and external air, volumetric CT density correction was conducted (two reference values: air, −1000 HU/blood, +50 HU). Using in-house software, emphysema index (EI) and mean lung density (MLD) were calculated. Differences in air densities, MLD and EI prior to and after density correction were evaluated (paired t-test). Correlation between those parameters and FEV₁ and FEV₁/FVC were compared (age- and sex adjusted partial correlation analysis).

Results

Measured densities (HU) of tracheal- and external air differed significantly (−990 ± 14, −1016 ± 9, P < 0.001). MLD and EI on original CT data, after density correction using tracheal- and external air also differed significantly (MLD: −874.9 ± 27.6 vs. −882.3 ± 24.9 vs. −860.5 ± 26.6; EI: 16.8 ± 13.4 vs. 21.1 ± 14.5 vs. 9.7 ± 10.5, respectively, P < 0.001). The correlation coefficients between CT quantification indices and FEV₁, and FEV₁/FVC increased after density correction. The tracheal air correction showed better results than the external air correction.

Conclusion

Density correction of volumetric CT data can improve correlations of emphysema quantification and PFT.     

CT scores of emphysema and oxygen desaturation during low-grade exercise in patients with emphysema

Purpose: We evaluated the usefulness of CT for assessing oxygen desaturation during walking in patients with emphysema.Material and Methods: The study comprised 32 patients with emphysema (mean age 67±6 years). Serial CT images of 5 mm were obtained from the apex to the basal regions of the lung during deep inspiration. The severity of emphysema was scored by four physicians according to a visual method. A six-minute walking test and oxygen desaturation (pSO₂) measurements were performed.Results and Conclusion: The mean CT score of the four observers was signfiicantly correlated with the nadir pSO₂ and ΔpSO₂, but did not correlate with the total distance walked. These results suggest that CT may be used for the assessment of oxygen desaturation during low-grade exercise in patients with emphysema.     

肺气肿的CT表现和临床应用研究

目的研究不同类型肺气肿的CT表现及临床应用。方法将33例尸检标本从气管灌注10％福尔马林，使肺膨胀至正常状态，1周后经气管注入氧气，直至液体全部从胸膜表面逸出，制成固定的充气标本，类似正常状态下肺组织，再将标本行冠状面及横轴面扫描。选取标本内有肺气肿的23例，分析其内肺气肿的表现及分布，然后将标本切成10mm厚层，进行CT、病理对照。对15例经病理或临床综合诊断证实的病例行螺旋CT扫描，包括肺气肿合并感染11例，合并孤立性结节4例，分析肺气肿合并症的CT特征。结果（1）23例肺气肿的标本中，小叶中心型肺气肿21例，全小叶型肺气肿5例，均与小叶中心型并发，间隔旁型肺气肿19例，瘢痕旁型肺气肿3例。（2）肺气肿均累及双侧肺野，呈大致对称或相近分布，17例（17／23）表现为2种或2种以上类型肺气肿并发。（3）肺气肿合并感染的14例（临床病例11例，标本3例）中，均见“假空洞”或“假蜂窝”影（实变肺野内未被充填的气肿腔）；肺气肿合并结节者4例，见“假胸膜凹陷征”（间隔旁气肿或肺大泡的壁与结节相连）。结论肺气肿的CT表现、分布及多种类型合并存在等特点对空腔性病变的鉴别有帮助。提出肺气肿合并症的CT特征，“假空洞”影、“假蜂窝”影、“假胸膜凹陷征”及其对临床诊断与鉴别诊断的作用。     

CT assessment of pulmonary emphysema using teleradiology

PURPOSE: The present study assessed the usefulness of CT for diagnosis of pulmonary emphysema (PE) using teleradiology. METHODS: We reviewed 95 cases (56 men and 39 women, ranging in age from 18 to 89 years) who had undergone CT examination between June 2002 and January 2003. CT images were transmitted via ISDN by DICOM to our hospital, and displayed in 4-image and 1-image format for reading on an image viewer. RESULTS: In 72 of the total 95 cases, both 1-image and 4-image displays were normal, and no PE was detected. Of the remaining 23 patients, PE was found in 22 on 4-image display and in all 23 on 1-image display. The same grade and subtype were observed on 4-image and 1-image displays in 19 cases. On the other hand, difference in diagnosis between the two types of display was obtained in four cases, in which mild low attenuation areas (LAAs) such as grade 1 or grade 2 centrilobular emphysema were found on the 1-image display but not seen on the 4-image display. CONCLUSIONS: The diagnosis of PE can be made by CT examination using teleradiology even in cases of mild lesions, when, for example, LAAs were found on the 1-image display but not seen on the other one. Therefore, teleradiology enables rapid diagnosis even in medical institutions where no expert chest radiologist is present.     

Radiographic and CT demonstration of mammary emphysema

The radiographic and CT appearance of air within the mammary parenchyma is described along with a discussion of the possible routes of dissection of gas from regions of subcutaneous emphysema into the breast tissue.     

Detection and quantification of the parenchymal abnormalities in emphysema using pulmo-CT.

We aimed to determine the degree and extent of parenchymal abnormalities on pulmo-CT in patients with emphysema. The study group consisted of 29 patients (18 male, 11 female; mean age 57.9+/-13). The diagnosis was based on clinical symptoms, pulmonary function tests (PFT) values, and chest CT findings. All of the patients CT scans were obtained during suspended deep inspiration from the apices to the costophrenic angles. The mean lung attenuation (MLD) and parenchymal abnormalities related to emphysema were quantitatively calculated with tables, histograms and graphics at the whole lung. The lung density measurements revealed a mean density of -898.48+/-51.37 HU in patients with emphysema and -825.1+/-25.5 HU in control group. In addition, mean percentage of subthreshold attenuation values was found as 12.03+/-15.75 and 1.07+/-0.83 in patients with emphysema and control group, respectively. Compared with control group, the patients with emphysema had a significantly lower inspiratory MLD (p<0.05). Additionally, statistically significant correlations were seen between the MLD and percentage of subthreshold values (r=0.44, p<0.05). In contrast, there was poor correlation between PFT measurements and the subthreshold values. In conclusion, pulmo-CT is a quick, simple method for quantitative confirmation of the presence of parenchymal abnormalities of lung as mosaic attenuation and should be used in combination with other radiological methods and PFT as it gives additional information to routine examinations in patients with emphysema.     

CT定量成像技术评估肺气肿的价值

肺气肿CT 定量评估的方法 主要有密度测定法、像素指数法及容积测定法,其与肺部病理结果 具有较好的相关性,与肺功能测定相比具有自身独特的优势,在肺气肿的诊断及评估中具有重要作用.定量评估受多种因素的影响,在临床应用中需合理控制影响因素,提高定量评估的准确性及可重复性.     

Contrast enhanced CT-scans are not comparable to non-enhanced scans in emphysema quantification

Systemic, interventional and surgical treatments have gone new ways in treatment of emphysema. For longitudinal therapy monitoring and as end-points for clinical trials, quantification of the disease is necessary. Sensitive, easy to measure, as well as stable and reproducible parameters have to be characterized. One parameter that might affect emphysema quantification is IV contrast enhancement, which might also be indicated. Whether or not the contrast enhanced scan is also suited for emphysema quantification or an additional scan is necessary, a retrospective analysis of 12 adult patients undergoing clinically indicated both, a non-enhanced and enhanced thin section MSCT within a week (median 0 days, range 0-4 days) was done. The in-house YACTA software was used for automatic quantification of lung and emphysema volume, emphysema index, mean lung density, and 5th, 10th, 15th percentile.After IV contrast administration, the median CT derived lung volume decreased mild by 1.1%, while median emphysema volume decreased by relevant 11%. This results in a decrease of median emphysema index by 9%. The median lung density (15th percentile) increased after contrast application by 18 HU (9 HU).CT quantification delivers emphysema values that are clearly affected by IV contrast application. The detected changes after contrast application show the results of higher density in the lung parenchyma. Therefore the amount of quantified emphysema is reduced and the lung density increased after contrast enhancement. In longitudinal analyses, non-enhanced scans should be the reference, while enhanced scans cannot be used.