Chest Imaging Original Research

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1 Chest Imaging Original Research Song et al. CT of Mycobacterium avium-intracellulare Complex Pulmonary Disease Chest Imaging Original Research Jong Woon Song 1 Won-Jung Koh 2 Kyung Soo Lee 1 Ji Young Lee 1 Myung Jin Chung 1 Tae Sung Kim 1 O Jung Kwon 2 Song JW, Koh W-J, Lee KS, et al. Keywords: bronchiectasis, bronchiolitis, CT, highresolution CT, lung infections, Mycobacterium aviumintracellulare complex, pulmonary function tests DOI: /JR Received December 5, 2007; accepted after revision May 1, This study was supported by the SRC/ERC Program of MOST/KOSEF (R ). 1 Department of Radiology and Center for Imaging Science, Sungkyunkwan University School of Medicine, Samsung Medical Center, 50, Ilwon-Dong, Kangnam-Ku, Seoul , Korea. ddress correspondence to K. S. Lee (kyungs.lee@samsung.com). 2 Division of Pulmonary and Critical Care Medicine, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. WE This is a Web exclusive article. JR 2008; 191:W160 W X/08/1914 W160 merican Roentgen Ray Society High-Resolution CT Findings of Mycobacterium avium-intracellulare Complex Pulmonary Disease: Correlation with Pulmonary Function Test Results OJECTIVE. The purpose of our study was to analyze the high-resolution CT findings of the nodular bronchiectatic form of Mycobacterium avium-intracellulare complex (MC) pulmonary disease and to correlate the extent of high-resolution CT findings with pulmonary function test (PFT) results. MTERILS ND METHODS. From January 2005 through December 2005, we identified 47 patients (mean age, 58 ± 13 years; age range, years; male female ratio, 11:36) with the nodular bronchiectatic form of MC pulmonary disease who underwent both high-resolution CT and PFTs. High-resolution CT findings were reviewed retrospectively in terms of the presence and extent of bronchiectasis, cellular or inflammatory bronchiolitis (centrilobular small nodules and tree-in-bud signs), cavity, nodule, and other findings. The extent of the abnormalities seen on high-resolution CT was scored by modifying the cystic fibrosis scoring system proposed by Helbich and coworkers. The scores were correlated with PFT results using Spearman s correlation coefficient. RESULTS. On high-resolution CT, the three most frequently observed patterns of parenchymal abnormalities were, in decreasing order of frequency, cellular bronchiolitis (n = 47, 100%), bronchiectasis (n = 46, 98%), and consolidation (n = 27, 57%). The total CT score showed a significant correlation with the residual volume total lung capacity (RV/TLC) ratio (r = 0.572, p < 0.001), forced expiratory volume in 1 second (FEV 1 ) value (r = 0.426, p = 0.003), forced vital capacity (FVC) value (r = 0.360, p = 0.013), peak expiratory flow value (r = 0.352, p = 0.015), and peak expiratory flow between 25% and 75% of the forced vital capacity (FEF 25 75% ) (r = 0.289, p = 0.049). CONCLUSION. CT scoring of pulmonary abnormalities correlates with measures of functional impairment in patients with MC pulmonary disease. M ycobacterium avium-intracellulare complex (MC) pulmonary infection, which has been reported to be increasing in incidence [1], is a highly complex disease in terms of its clinical presentation and management. MC organisms are ubiquitous, and an MC pulmonary infection may simulate clinically pulmonary tuberculosis [1]; therefore, an awareness of the initial and follow-up highresolution CT findings and of clinical correlation is mandatory for the diagnosis and management of this disease. The MC pulmonary infection has been differentiated into two distinct subtypes upper lobe cavitary disease and nodular bronchiectatic disease [1]. The results of several studies using chest CT have shown that the presence of bilateral multifocal cellular or inflammatory bronchiolitis (i.e., the presence of centrilobular small nodules and branching nodular structures, the so-called tree-in-bud sign) and of bronchiectasis distributed mainly in the right middle lobe and lingular division of the left upper lobe is indicative of the nodular bronchiectatic form of MC pulmonary infection [2 6]. ccording to a prospective study [7], approximately one third of patients with high-resolution CT findings of bilateral bronchiectasis plus cellular bronchiolitis have a nontuberculous mycobacterial pulmonary infection, and in these cases, MC is the most common cause. The high-resolution CT findings of bilateral bronchiectasis and cellular bronchiolitis in an MC pulmonary infection may simulate those in cystic fibrosis in which the predominant CT abnormalities are bilateral bronchiectasis, peribronchial wall thickening, mosaic perfusion, and mucous plugging [8 14]. W160 JR:191, October 2008

2 CT of Mycobacterium avium-intracellulare Complex Pulmonary Disease In cystic fibrosis, a number of scoring systems have been proposed and are used for both clinical treatment and research purposes. High-resolution CT scoring systems are also a potentially useful surrogate for predicting prognosis in patients with this disease [8 14]. lthough bronchiectasis and cellular bronchiolitis are the major high-resolution CT findings in the nodular bronchiectatic form of MC pulmonary infection, to the best of our knowledge, the scoring system used for the evaluation of the extent of disease has not been the topic of a published study. Furthermore, the relationship between high-resolution CT findings and pulmonary function test (PFT) results has not been reported. Thus, the purpose of our study was to analyze the highresolution CT findings of the nodular bronchiectatic form of MC pulmonary disease and to correlate the extent of high-resolution CT findings with PFT results. Materials and Methods The institutional review board approved this retrospective study with a waiver of informed consent. Patients and Diagnoses For a 1-year period from January 2005 through December 2005, we identified 89 untreated new patients with MC pulmonary infection who fulfilled the merican Thoracic Society criteria for the diagnosis of nontuberculous mycobacterial disease [1]. Most patients had been referred to the outpatient-based bronchiectasis-specific clinic of our hospital. For a diagnosis of MC pulmonary disease, sputum acid-fast bacillus (Ziehl-Neelsen method) staining and culture examinations for Mycobacteria organisms were performed at least three times in each of the 89 patients. ronchoscopy also was performed for bronchial washing or transbronchial lung biopsy was performed in 70 of the 89 patients. In all cases, sputum examinations were performed within 0 34 days (mean, 9 days) of CT, and bronchoscopic samples were obtained within 0 24 days (mean, 7 days) of CT. Expectorated sputum and samples obtained with bronchoscopy were examined using acid-fast bacil lus staining and then were cultured for Mycobacteria organisms using 3% Ogawa egg medium (Shinyang Chemical Co. Ltd.). Colony numbers were counted after incubation for as long as 8 weeks, and identification of nontuberculous Mycobacteria species was con firmed using a polymerase chain reaction restriction fragment length polymorphism method based on the rpo gene [15]. ecause non tuberculous mycobacterial disease is a subacute or chronic pulmonary infection, the absence of con current bacterial infection was ensured by clinical history that is, the absence of symptoms and signs of acute respiratory infection including purulent sputum, high fever, or sepsis. Of the 89 patients, 70 patients were thought to have the nodular bronchiectatic form of MC pulmonary disease on the basis of high-resolution CT findings of bilateral patchy areas of bronchiectasis and cellular or inflammatory bronchiolitis (centrilobular small nodules and tree-in-bud signs) irrespective of the presence of cavities in the upper lobes. Of these 70 patients, 47 patients (mean age, 58 ± 13 years; range, years), in whom both high-resolution CT and pulmonary function test (PFT) results were available, were included in the study. The 47 patients included 11 men (mean age ± SD, 66 ± 14 years; age range, years) and 36 women (mean age, 56 ± 12 years; age range, years) (p = 0.06, Mann-Whitney U test). In these patients, PFTs were performed within 3 weeks (mean, 8 days; range, 0 21 days) of the high-resolution CT examination. Patients complained of cough (n = 41), sputum (n = 41), fever (n = 1), and weight loss (n = 1). Of these 47 patients, two had a history of smoking (ex-smokers, with 20-pack years and 100-pack years, respectively). CT cquisition CT scans were obtained using a helical technique; a 4-MDCT scanner (LightSpeed QX/i, GE Healthcare; 18 patients) and an 8-MDCT unit (LightSpeed Ultra, GE Healthcare; 29 patients) were used. IV contrast medium was not given to any of the patients. helical CT technique (collimation of 2.5 mm, 120 kvp, 70 m, beam width of 10 mm, and beam pitch of ) was used, and all CT data were reconstructed using a high-spatial-frequency algorithm. Expiratory CT scans were not obtained. The image data were reconstructed with a 2.5-mm section thickness for transverse images and a 2.0-mm section thickness for coronal images. Scans were obtained from the lung apices to the lung bases. The scan data were displayed directly on monitors of a PCS (Path Speed or Centricity 2.0, GE Healthcare Integrated Imaging Solutions). The monitors displayed both mediastinal (window width, 400 H; window level, 20 H) and lung (window width, 1,500 H; window level, 700 H) window images. CT Scoring System We developed a CT scoring system of nontuberculous mycobacterial disease (Table 1) in which the extent of lung involvement was recorded and calculated. Various kinds of scoring systems have been reported [8 14]; our scoring system was created by modifying the previously used scoring system proposed by Helbich and coworkers [9, 10]. total maximum score of 42 was allocated for evaluating the overall extent of a lung lesion. Scores were given by considering the lobar volume decrease and the presence, severity, and extent of bronchiectasis, cellular or inflammatory bronchiolitis, cavity, nodules, consolidation, bullae, emphysema, and mosaic perfusion in both lungs. Two independent chest radiologists with 2 and 18 years experience interpreting chest CT, respectively, evaluated retrospectively the chest CT scans and completed scoring sheets. When there were discrepancies in their readings, final decisions were reached by consensus. The observers were unaware of the PFT results. Six lung lobes in each patient, with the lingual division of the left upper lobe being considered a separate lobe, were assessed for the presence of lung parenchymal abnormalities. Each lung lobe was evaluated for the presence and extent of the lung abnormalities mentioned earlier. The laterality (i.e., unilateral or bilateral) and the locations of the lung lesions were also analyzed. total of 282 lung lobes in 47 patients (six lobes per patient) with MC infection was evaluated for the presence of lung lesions. ronchiectasis was defined to be present when the diameter of the bronchial lumen was greater than that of the adjacent pulmonary artery without tapering of bronchial lumen diameter (Fig. 1). ecause bronchial wall thickening and mucus plugging are frequently accompanied by bronchiectasis, those findings were considered under the subcategory of bronchiectasis. ronchial wall thickness was estimated by measuring the ratio of the thickness of the airway wall to the outer diameter of the corresponding bronchus. Mucus plugging was regarded as present when a broad linear or branching attenuation lesion was observed in a proximal airway (lobar, segmental, or subsegmental bronchus) and was associated with airway dilatation. ronchiolitis, the cellular or inflammatory type, was defined as the presence of centrilob ular small nodules (< 10 mm in diameter) and branching nodular structures (i.e., tree-in-bud signs) on high-resolution CT scans (Fig. 2). Dif ferent from Helbich and colleagues [9, 10], we did not consider tree-in-bud signs (most of which indicated cellular or inflammatory bronchiolitis) as mucus plug ging; thus, these signs were not included in scoring mucus plugging. The presence of other abnormalities was also recorded including the following: cavities; nodules, mm in diameter; lobular con solidation of mm in diameter with a polygonal shape, peribronchial consolidation, or segmental consoli- JR:191, October 2008 W161

3 Song et al. TLE 1: CT Scoring System Used to ssess the Extent of Mycobacterium avium-intracellulare Complex Pulmonary Disease CT Finding (Maximum No. of Points) dation; bulla; emphysema; mosaic perfusion; and lobar volume reduction. ecause cavities were frequently accompanied by bronchiectasis and bronchiolitis in MC pulmonary disease [7], the severity and extent of bronchiectasis and bronchiolitis were also counted. ullae and emphysema were defined according to the Fleischner Society s glossary of terms [16]. Mosaic perfusion was defined as one or more areas of decreased lung attenuation with oligemic pulmonary vessels. ecause we did not have expiratory CT data, mosaic perfusion was regarded as present and was differentiated from emphysema when the areas in question showed lower attenuation than the surrounding normal lung parenchyma but their attenuation was > 950 H [17]. Pulmonary Function Tests Forced spirometry and plethysmography were performed with pulmonary function units. In all patients, pulmonary function was evaluated within 3 weeks of the time of the CT examinations. The functional indexes measured were forced Score Subtotal ronchiectasis (12 points) Severity bsent Mild (bronchus diameter > adjacent vessel diameter) Moderate (bronchus diameter = 2 3 vessel diameter) Severe (bronchus diameter > 3 vessel diameter) Extent bsent 1 5 segments 6 9 segments > 9 segments ronchial wall thickening bsent Mild (wall thickness = adjacent vessel diameter) Moderate (vessel diameter < wall thickness < 2 vessel diameter) Severe (wall thickness 2 vessel diameter) Mucus plugging bsent 1 5 segments 6 9 segments > 9 segments ronchiolitis (6 points) Severity bsent Mild (identifiable; peripheral lung < 2 cm from pleura) Moderate (definite; involvement > 2 cm from pleura) Severe (extensive; extending to central lung) Extent bsent 1 5 segments 6 9 segments > 9 segments Cavity (6 points) Severity bsent Mild (diameter < 3 cm) Moderate (3 cm < diameter Severe (diameter 5 cm) < 5 cm) Extent bsent 1 3 in number 4 5 in number > 5 in number Nodules (10 30 mm in diameter) (3 points) bsent 1 5 segments 6 9 segments > 9 segments Consolidation, lobular, segmental, or bsent < 3 segments 3 5 segments > 5 segments peribronchial (3 points) ullae (3 points) bsent Unilateral (< 4 in number) ilateral (< 4 in number) ilateral ( 4 in number) Emphysema (3 points) bsent 1 5 segments > 5 segments N Mosaic perfusion (3 points) bsent 1 5 segments > 5 segments N Lobar volume decrease (3 points) bsent 1 lobe 2 lobes 3 lobes Total CT score (add subtotals) a Note Scoring system is a modified version of the scoring system used to evaluate cystic fibrosis [9, 10]. N = not applicable. a Maximum possible score = 42 points. Fig. 1 Representative figures show how extent of bronchiectasis was estimated on high-resolution CT scans in patients with Mycobacterium avium-intracellulare complex pulmonary disease., ronchiectasis, scored as 1 in terms of severity, in superior segment of right lower lobe of 72-year-old man. lso note tree-in-bud sign (arrows)., ronchiectasis, scored as 3 in terms of severity and as 2 in terms of bronchial wall thickening (arrows), in anteromedial and posterior basal segments of left lower lobe of 63-year-old woman. W162 JR:191, October 2008

4 CT of Mycobacterium avium-intracellulare Complex Pulmonary Disease vital capacity (FVC), forced expiratory volume in 1 second (FEV 1 ), FEV 1 /FVC, peak expiratory flow (PEF), peak expira tory flow between 25% and 75% of the FVC (FEF 25 75% ), residual volume (RV), total lung capacity (TLC), and RV/TLC. These values were expressed as a percentage of the predicted value for patient age, sex, and height [18, 19]. CT Pulmonary Function Test Comparisons The scores of the high-resolution CT extent of disease were compared with the PFT results. The mean score of the two observers for each pattern Fig. 2 Representative figures show how extent of bronchiolitis was estimated on high-resolution CT scans in patients with Mycobacterium avium-intracellulare complex pulmonary disease., ronchiolitis in 48-year-old woman. This case was scored as 1 (mild) in terms of severity, with identifiable centrilobular small nodules and tree-in-bud sign within 2 cm from pleura, in lateral basal segment of left lower lobe., ronchiolitis in 56-year-old woman. This case was scored as 2 (moderate) in terms of severity, with centrilobular small nodules and tree-in-bud signs extending more than 2 cm from pleura, in superior segment of right lower lobe. ronchiolitis in right middle lobe was scored as 1 (mild). C, ronchiolitis in 24-year-old woman. This case was scored as 3 (severe) in terms of severity, with centrilobular small nodules and tree-in-bud sign extending to central lung, in right lower lobe. and the total extent of each lung abnormality were recorded and compared with each component of the PFT results. Statistical nalyses For statistical analyses, the commercially available statistics package program (SPSS version 11.0, SPSS) was used. Values are expressed as mean ± SDs in the text. Interobserver agreement for the extent of each pattern and total amount of lung abnormalities was calculated using Spearman s correlation coefficient. The analysis of the correlation between the scores of high-resolution CT for disease extent and the PFT results were also determined using Spearman s correlation coefficient. p value of less than 0.05 was considered statistically significant. Results CT Findings The most common of the high-resolution CT findings for MC pulmonary disease was bronchiolitis (n = 47, 100%) (Fig. 2), followed by bronchiectasis (n = 46, 98%) (Fig. 1), consolidation (n = 27, 57%), nodule (n = 19, 40%), cavity (n = 17, 36%), lobar TLE 2: Prevalence of the Patterns of Parenchymal bnormalities on High-Resolution CT in 47 Patients CT Pattern No. (%) of Patients Laterality of MC Involvement (No. of Patients) Right Lobe Location of MC Infection (No. of Lobes) Unilateral ilateral Upper Middle Lower Upper Left Lobe Lingular Segment ronchiolitis 47 (100) ronchiectasis 46 (98) Consolidation 27 (57) Nodules 19 (40) Cavity 17 (36) Lobar volume decrease 17 (36) Emphysema 15 (32) Mosaic perfusion 6 (13) ullae 5 (11) Note MC = Mycobacterium avium-intracellulare complex. Lower Total (n = 282) C JR:191, October 2008 W163

5 Song et al. TLE 3: Correlation etween High-Resolution CT Scores and Pulmonary Function Test Results CT Patterns FVC FEV 1 FEF 25 75% PEF RV/TLC r p r p r p r p r p ronchiolitis ronchiectasis < Consolidation Nodules Cavity Emphysema < Total CT score < Note Data presented in boldface show positive correlation between CT score and pulmonary function test results. FVC = forced vital capacity, FEV 1 = forced expiratory volume in 1 second, FEF 25 75% = peak expiratory flow between 25% and 75% of forced vital capacity, PEF = peak expiratory flow, RV = residual volume, TLC = total lung capacity. volume decrease (n = 17, 36%), emphysema (n = 15, 32%), mosaic perfusion (n = 6, 13%), and bullae (n = 5, 11%). The patterns of the parenchymal findings, frequency, and laterality and the locations of the lung lesions are summarized in Table 2. Of the various patterns of lung abnormalities, bronchiolitis and bronchiectasis were the two most extensive patterns of abnormality. ronchiolitis was bilateral in 42 (89%) of the 47 patients with the abnormality and involved 207 lobes (73%) among a total of 282 lobes. ronchiectasis was bilateral in 41 (89%) of 46 patients with the abnormality and involved 173 lobes (61%) among a total of 282 lobes. Interobserver agreement for the extent of each pattern of abnormalities was good and statistically significant. The r values for the agreement on the extent of bronchiectasis, bronchiolitis, consolidation, and total lung abnormality were 0.665, 0.440, 0.369, and 0.786, respectively (p < 0.001, p = 0.002, p = 0.011, and p < 0.001, respectively; Spearman s correlation). High-Resolution CT Pulmonary Function Test Correlations The relationship of CT scores and PFT results is shown in Table 3. The total CT score showed a significant correlation with RV/TLC (r = 0.572, p < 0.001), FEV 1 (r = 0.426, p = 0.003), FVC (r = 0.360, p = 0.013), PEF (r = 0.352, p = 0.015), and FEF 25 75% (r = 0.289, p = 0.049). The extent of bronchiolitis showed a positive correlation with RV/TLC (r = 0.508, p = 0.001) and a negative correlation with PEF (%) (r = 0.369, p = 0.011) and FVC (r = 0.295, p = 0.044). The extent of bronchiectasis showed a positive correlation with RV/TLC (r = 0.600, p < 0.001) and a negative correlation with FEV 1 (r = 0.373, p = 0.010), FVC (r = 0.372, p = 0.011), and PEF (r = 0.316, p = 0.031) (Figs. 3 and 4). The extent of consolidation showed a positive correlation with RV/TLC (r = 0.364, p = 0.025) and a negative correlation with PEF (r = 0.324, p = 0.026). The extent of bullae, mosaic perfusion, and lobar volume decrease did not show any significant correlation with any individual index of pulmonary function (Table 3). Discussion To the best of our knowledge, using CT to score the extent of lung involvement in MC pulmonary disease has not been attempted in a previous study. In this study, we modified Fig. 3 Mycobacterium avium-intracellulare complex pulmonary disease in 64-year-old woman. and, High-resolution CT scans obtained at levels of bronchus intermedius () and right middle lobar bronchus () show bronchiolitis of tree-in-bud signs mainly in right middle lobe and lingular division of left upper lobe and also in both lower lobes. ronchiectasis is associated in lingular division. Total CT score was 18 with scores of bronchiectasis, bronchiolitis, consolidation, cavity, nodules, and lobar volume loss of 6, 6, 2, 2, 1, and 1, respectively. Pulmonary function test results were as follows: forced vital capacity (FVC), 111%; forced expiratory volume in 1 second (FEV 1 ), 104%; FEV 1 /FVC, 67%; peak expiratory flow between 25% and 75% of the forced vital capacity (FEF 25 75% ), 48%; total lung capacity (TLC), 111%; and residual volume (RV)/TLC, 41% of predicted value. W164 JR:191, October 2008

6 CT of Mycobacterium avium-intracellulare Complex Pulmonary Disease the cystic fibrosis scoring system [9, 10] to estimate the extent of lung involvement of MC pulmonary disease because the high-resolution CT scoring system in cystic fibrosis is reproducible and shows a good correlation with PFT results [8 14]. Furthermore, the nodular bronchiectatic form of MC pulmonary disease manifests similar high-resolution CT findings, with cellular or inflammatory bronchiolitis and bronchiectasis being the predominant findings in MC pulmonary disease just as in cystic fibrosis [2 7, 20]. In our study, the total extent of lung involvement in MC pulmonary disease showed significant correlation with RV/TLC, FEV 1, FVC, PEF, and FEF 25 75%. These results suggest that the extent of lung involvement in MC disease is significantly correlated with both restrictive and obstructive functional indexes. The extent of bronchiectasis was associated with derangement of FVC, FEV 1, and PEF and an increased amount of RV, whereas the extent of cellular bronchiolitis was associated with derangement of FVC and PEF and an increased amount of RV. The severity of pulmonary function abnormalities in airway obstruction is mainly based on FEV 1. The degree of hyperinflation, which can be measured by RV/TLC, also parallels the severity of airway obstruction [21 23]. In our study, indexes of bronchiectasis, nodules, cavity, emphysema, and the total CT score showed a significant correlation with FEV 1 derangement, and indexes Fig. 4 Mycobacterium avium-intracellulare complex pulmonary disease in 69-year-old woman. and, High-resolution CT scans obtained at levels of right middle lobar bronchus () and inferior pulmonary vein () show extensive bronchiectasis, large areas of mosaic perfusion (arrows), and several small centrilobular nodules and cavitating nodules (arrowheads) in both lungs. Total CT score was 23 with scores of bronchiectasis, bronchiolitis, cavity, nodules, volume loss, emphysema, and bullae 6, 7, 4, 1, 1, 2, and 2, respectively. Pulmonary function test results were as follows: forced vital capacity (FVC), 61%; forced expiratory volume in 1 second (FEV 1 ), 70%; FEV 1 /FVC, 81%; peak expiratory flow between 25% and 75% of the forced vital capacity (FEF 25 75% ), 56%; total lung capacity (TLC), 91%; and residual volume (RV)/TLC, 60% of predicted value. of bronchiolitis, bronchiectasis, consolidation, nodules, cavity, and the total CT score showed a significant correlation with an increased amount of RV. ecause the findings of our study suggest that the high-resolution CT scoring of lung lesions has a significant correlation with the functional derangement in MC pulmonary disease, high-resolution CT scoring will be useful for predicting functional deterioration in patients with MC pulmonary disease. In addition, using this scoring system, one can objectively measure treatment response and assess the progression of the disease with or without treatment. Moreover, because the main CT findings of MC pulmonary disease are irreversible changes of bronchiectasis, scoring lung involvement in patients with MC pulmonary disease may enable one to predict the amount of irreversible lung damage, just as in patients with cystic fibrosis [8 14]. One may argue that PFTs rather than CT should be used as a follow-up study device once a significant correlation between CT scores and PFT results has been established. However, according to a study dealing with patients with cystic fibrosis [10], CT seems to have advantages over PFT results and clinical scoring systems in depicting pulmonary changes over time. Therefore, high-resolution CT, especially using a low-dose technique, may be more appropriate than PFTs for follow-up evaluation of patients with MC pulmonary disease. Our study has several limitations. First, in our study, the mean age of the 47 patients was 58 years, with the mean age of the 36 women being 56 years and that of the 11 men, 66 years. Thus, a mean age of 58 for our series seems to be rather young compared with those of other studies [3, 5, 6]. This may suggest a selection bias. Second, in our study, we characterized mild disease (score of 1) as occurring in up to five segments in many of the categories, which may be a rather generous use of the term mild. 4-point scoring system (e.g., score of 1 as involvement of 1 3 segments; score of 2, 4 6 segments; score of 3, 7 9 segments; and score of 4, 10 segments) might be more powerful in scoring lung involvement of MC pulmonary disease. Third, we did not obtain an expiratory CT study for the evaluation of mosaic perfusion areas. With expiratory CT, we could have assessed exactly the extent of airflow obstruction and air trapping (obstructive indexes of PFT) [24]. Last, two patients who were ex-smokers were included in our study population; in these patients, smoking might have caused morphologic abnormalities of the lungs independent of the parenchymal changes caused by MC infection and made an additional alteration to the functional abnormalities. In conclusion, we attempted to score the extent of lung involvement in MC pulmonary disease by modifying the cystic fibrosis scoring system [9, 10]. Using this modified scoring system, we identified that the total CT score shows a significant correlation with FVC, FEV 1, JR:191, October 2008 W165

7 Song et al. FEF 25 75%, PEF, and RV/TLC. Therefore, CT scoring of pulmonary abnormalities using a modified cystic fibrosis scoring system shows a correlation with measures of functional deterioration and thus allows one to estimate the functional impairment in patients with MC pulmonary disease. However, this is a preliminary study to show that our scoring system correlates with PFT results. Further studies, such as studies of the relationship between changes in serial high-resolution CT findings using our proposed scoring system and PFT changes, life-quality measurement, or mortality, need to be performed. References 1. [No authors listed]. Diagnosis and treatment of disease caused by nontuberculous mycobacteria. This official statement of the merican Thoracic Society was approved by the oard of Directors, March Medical Section of the merican Lung ssociation. m J Respir Crit Care Med 1997; 156(2 Pt 2):S1 S25 2. Moore EH. typical mycobacterial infection in the lung: CT appearance. Radiology 1993; 187: Hartman TE, Swensen SJ, Williams DE. Mycobacterium avium-intracellulare complex: evaluation with CT. Radiology 1993; 187: Swensen SJ, Hartman TE, Williams DE. Computed tomographic diagnosis of Mycobacterium avium-intracellulare complex in patients with bronchiectasis. Chest 1994; 105: Primack SL, Logan PM, Hartman TE, Lee KS, Müller NL. Pulmonary tuberculosis and Mycobacterium avium-intracellulare: a comparison of CT findings. Radiology 1995; 194: Lynch D, Simone PM, Fox M, ucher L, Heinig MJ. CT features of pulmonary Mycobacterium avium complex infection. J Comput ssist Tomogr 1995; 19: Koh WJ, Lee KS, Kwon OJ, Jeong YJ, Kwak S-H, Kim TS. ilateral bronchiectasis and bronchiolitis at thin-section CT: diagnostic implications in nontuberculous mycobacterial pulmonary infection. Radiology 2005; 235: halla M, Turcios N, ponte V, et al. Cystic fibrosis: scoring system with thin-section CT. Radiology 1991; 179: Helbich TH, Heinz-Peer G, Eichler I, et al. Cystic fibrosis: CT assessment of lung involvement in children and adults. Radiology 1999; 213: Helbich TH, Heinz-Peer G, Fleischmann D, et al. Evolution of CT findings in patients with cystic fibrosis. JR 1999; 173: de Jong P, Ottink MD, Robben SG, et al. Pulmonary disease assessment in cystic fibrosis: comparison of CT scoring systems and value of bronchial and arterial dimension measurements. Radiology 2004; 231: Castile R, Long F, Flucke R, et al. High resolution computed tomography of the chest in infants with cystic fibrosis. Pediatr Pulmonol 1999; 28: rody, Molina P, Klein JS, Rothman S, Ramagopal M, Swartz DR. High-resolution computed tomography of the chest in children with cystic fibrosis: support for use as an outcome surrogate. Pediatr Radiol 1999; 29: Santamaria F, Grillo G, Guidi G, et al. Cystic fibrosis: when should high-resolution computed tomography of the chest be obtained? Pediatrics 1998; 101: Lee H, Park HJ, Cho SN, ai GH, Kim SJ. Species identification of mycobacteria by PCR-restriction fragment length polymorphism of the rpo gene. J Clin Microbiol 2000; 38: ustin JH, Müller NL, Friedman PJ, et al. Glossary of terms for CT of the lungs: recommendations of the Nomenclature Committee of the Fleischner Society. Radiology 1996; 200: ankier, Maertelaer VD, Keyzer C, Gevenois P. Pulmonary emphysema: subjective visual grading versus objective quantification with macroscopic morphometry and thin-section CT densitometry. Radiology 1999; 211: Wanger J, Clausen JL, Coates, et al. Standardisation of the measurement of lung volumes. Eur Respir J 2005; 26: Miller MR, Hankinson J, rusasco V, et al.; TS/ ERS Task Force. Standardisation of spirometry. Eur Respir J 2005; 26: Jeong YJ, Lee KS, Koh WJ, Han J, Kim TS, Kwon OJ. Nontuberculous mycobacterial pulmonary infection in immunocompetent patients: comparison of thin-section CT and histopathologic findings. Radiology 2004; 231: Pellegrino R, rusasco V. On the cause of hyperinflation during bronchoconstriction. Eur Respir J 1997; 10: Pellegrino R, Viegi G, rusasco V. Interpretative strategies for lung function tests. Eur Respir J 2005; 26: Dykstra J, Scanlon PD, Kester MM, et al. Lung volumes in 4,774 patients with obstructive lung disease. Chest 1999; 115: Roberts HR, Wells U, Milne DG, et al. irflow obstruction in bronchiectasis: correlation between computed tomography features and pulmonary function tests. Thorax 2000; 55: W166 JR:191, October 2008