Radiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online before print March 28, 2008, 10.1148/radiol.2473071228
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2473071228v1
247/3/862    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bankier, A. A.
Right arrow Articles by Gevenois, P. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bankier, A. A.
Right arrow Articles by Gevenois, P. A.
(Radiology 2008;247:862-870.)
© RSNA, 2008

Thoracic Imaging

Regional Heterogeneity of Air Trapping at Expiratory Thin-Section CT of Patients with Bronchiolitis: Potential Implications for Dose Reduction and CT Protocol Planning1

Alexander A. Bankier, MD, Sheida Mehrain, MD, Daniela Kienzl, MD, Michael Weber, PhD, Marc Estenne, MD, PhD, and Pierre Alain Gevenois, MD, PhD

1 From the Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215 (A.A.B.); Department of Radiology, Medical University of Vienna, Austria (S.M., D.K., M.W.); and Lung Transplantation Unit (M.E.) and Department of Radiology (P.A.G.), Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. Received July 23, 2007; revision requested September 20; revision received October 10; accepted December 17; final version accepted January 7, 2008. Address correspondence to A.A.B. (e-mail: abankier{at}bidmc.harvard.edu).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Purpose: To prospectively determine whether the regional distribution of air trapping in patients with suspected or overt bronchiolitis is heterogeneous, and to determine the effect that a simulated reduction of computed tomographic (CT) sections and of scanned anatomic regions would have on the assessment of the extent of air trapping.

Materials and Methods: For this Ethical Committee–approved study, multi–detector row CT (collimation, 4 x 1 mm; rotation time, 0.5 second; 140 kVp; and 80 effective mAs) was performed in 47 lung transplant recipients (23 women, 24 men; mean age, 41 years ± 12 [standard deviation]; 18 without bronchiolitis, 18 with potential bronchiolitis, and 11 with bronchiolitis, as determined by lung function measurements). Images were reconstructed with a thickness of 1 mm at an increment of 10 mm. The extent of air trapping in the upper, middle, and lower lung regions was correlated. Differences between regions and the interaction between patients and regions were tested with an analysis of variance. The extent of air trapping was calculated for six simulated examination protocols.

Results: Correlations between the upper and middle (r = 0.930), the upper and lower (r = 0.756), and the middle and lower lung regions (r = 0.863) were significant (P < .001). The extent of air trapping increased from the upper to the lower lung region, with significant differences between regions (P < .001). There was a significant interaction between patients and lung regions (P < .001). Simulated examination protocols resulted in significantly different extents of air trapping (P < .001).

Conclusion: The regional distribution of the extent of air trapping in suspected or overt bronchiolitis is heterogeneous. Because the extent of air trapping can depend on the examination protocol, identical protocols are needed when air trapping is being compared within and between patients.

© RSNA, 2008


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Bronchiolitis occurs in common pulmonary diseases, such as infection, hypersensitivity pneumonitis, connective tissue disorders, inhalation injury, bronchiectasis, and sarcoidosis. It is also associated with inflammatory bowel disease, drug reactions, and bronchiolitis obliterans, either in its idiopathic form or as a manifestation of chronic rejection after bone marrow or lung transplantation (1,2). The clinical diagnosis of bronchiolitis is made primarily on the basis of patient history and pulmonary function tests. Expiratory thin-section computed tomography (CT), however, can help detect air trapping before functional tests indicate a disease, giving this technique a part to play in the diagnosis of bronchiolitis (2,3).

Expiratory thin-section CT complements inspiratory CT, thus exposing patients to additional radiation. The multi–detector row technology can further increase the delivered dose by up to 300% (4). Radiation exposure from expiratory CT can be decreased by reducing the tube current (5). A further decrease can be achieved by reducing the number of expiratory CT sections or by restricting volumetric acquisitions to predefined regions of the lungs. This would require that the predefined CT sections or lung regions are representative of the entire lung or that the distribution of air trapping is homogeneous. In patients without bronchiolitis, however, air trapping is heterogeneously distributed and is more extensive in the lower lung regions (6,7). If this heterogeneity was also present in patients with bronchiolitis, the potential for a reduction of radiation dose by means of a reduction of the number of CT sections or anatomic regions scanned could be limited. Thus, the aim of our study was to prospectively determine whether the regional distribution of air trapping in patients with suspected or overt bronchiolitis is heterogeneous and to determine the effect that a simulated reduction of the number of CT sections and of scanned anatomic regions would have on the assessment of the extent of air trapping.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Patients
The protocol of this study was approved by the Ethics Committee of our university. Written informed consent was obtained from all patients. Between May 2003 and April 2004, we prospectively included 49 consecutive patients after double-lung transplantation (n = 30) or combined heart-lung transplantation (n = 19) on the occasion of their annual routine follow-up CT examination. All patients were in clinically and functionally stable condition at the time of the study, and no patient had acute infection, acute allograft rejection, bronchial hyperreactivity, or asthma. Two patients who had combined heart-lung transplantation were later excluded because of severe breathing artifacts that precluded the assessment of air trapping on their CT images. Therefore, the final study group consisted of 47 patients (23 women, 24 men; mean age, 41 years ± 12 [standard deviation]; range, 22–59 years). The median time since transplantation was 49 months (range, 12–171 months). Indications for transplantation were cystic fibrosis in 23 patients, chronic pulmonary hypertension in seven patients, bronchiectasis in six patients, chronic obstructive pulmonary disease in four patients, Eisenmenger syndrome in four patients, idiopathic pulmonary fibrosis in two patients, and sarcoidosis in one patient.

Pulmonary Function Tests and Grading of Bronchiolitis Obliterans Syndrome
Pulmonary function testing was performed either the day before or the day after the CT examination. Measurements of forced vital capacity and forced expiratory volume in one second (FEV1) were obtained by using a spirometer (2400; Sensormedics, Anaheim, Calif), according to the guidelines of the American Thoracic Society (8). Predicted values for static and dynamic lung volumes were derived from the literature (8,9).

The severity of bronchiolitis obliterans syndrome (BOS) was graded according to the revised recommendations of the International Society for Heart and Lung Transplantation (10). Accordingly, a BOS score of 0 (clinically silent airway disease) indicated an FEV1 of more than 90% of the best postoperative baseline and a forced midexpiratory flow (FEF25%–75%) of more than 75% of the postoperative baseline (signifying that BOS was not present). A BOS score of 0p (potential airway disease) indicated a sustained decline of FEV1 to between 81%–90% of the best postoperative baseline and/or a decline of FEF25%–75% to 75% or less of the postoperative baseline. A BOS score of 1 (overt airway disease) indicated a sustained decline in FEV1 to 66%–80% of the best postoperative value. A BOS score of 2 (overt airway disease) indicated a sustained decline in FEV1 to 50%–65% of the best postoperative value. A BOS score of 3 (overt airway disease) indicated a sustained decline in FEV1 to less than 50% of the best postoperative value.

At the time our study was performed, 18 (38%) of 47 patients had a BOS score of 0; 18 (38%) had a score of 0p; five (12%) had a score of 1; three (6%) had a BOS score of 2; and three (6%) had a score of 3. Of the 18 patients with a BOS score of 0p, the diagnosis was made on the basis of a sustained decline of FEV1 between 81% and 90% of the best postoperative baseline in three patients, a decline of FEF25%–75% of 75% or less of the postoperative baseline in eight patients, and a combination of both in seven patients.

Image Acquisition
CT images were obtained with a commercially available four-channel scanner (Somatom Volume Zoom 4; Siemens Medical Solutions, Forchheim, Germany). The tube voltage was consistently set at 140 kVp and 80 effective mAs. Beam collimation was 4 x 1 mm, and tube rotation time was 0.5 second. Intravenous contrast material was not administered. All CT examinations were performed from the base to the apex of the lungs during a breath hold in the supine position at full suspended inspiration and full suspended expiration. Breath hold was rehearsed at both lung volumes with each patient prior to the CT examination. Images were reconstructed with a section thickness of 1 mm, a section increment of 10 mm, and image matrix of 512 x 512, and a high-resolution reconstruction algorithm (B60f) was used. At our institution, this CT examination protocol is routinely used in the clinical follow-up of lung transplant recipients.

Image Analysis
Images were analyzed on a computer workstation (GDM-F520; Sony Electronics, Park Ridge, NJ) equipped with a 21-inch viewing monitor that conformed to the Digital Imaging and Communication in Medicine standard (11). The display window was set at a center of –600 HU and a width of 1600 HU, which is the routine lung window setting used at our institution. Image analysis was performed independently by two board-certified radiologists (A.A.B. and P.A.G., with 14 and 22 years experience in thoracic CT interpretation). Each radiologist analyzed all 47 expiratory CT examinations one time in random order. The radiologists were unaware of any clinical or lung function information. All CT sections obtained above the level of the diaphragm were analyzed. Each CT section was assessed individually.

CT at full suspended inspiration.—Because our study was focused exclusively on air trapping, CT images obtained at full suspended inspiration were used only for comparison with the corresponding CT images obtained at full suspended expiration. Bronchial and vascular abnormalities were not recorded, but they were used to overcome the potentially confounding features of airway and vascular diseases (12).

CT at full suspended expiration.—Air trapping was considered as present on the expiratory CT images when lung regions failed to increase in attenuation and/or failed to decrease in volume, compared to the corresponding inspiratory images (1,13). The diagnosis of air trapping was made on the basis of visual assessment; quantitative measurements were not obtained. The scoring system used to assess the extent of air trapping was adapted from prior studies (7,13,14) and modified slightly, whereby the number of possible scores was increased from five to six to allow for a more subtle grading of air trapping. A score of 0 = no air trapping seen on the section, 1 = less than 20% of the parenchyma showed air trapping, 2 = 20%–39% of the parenchyma showed air trapping, 3 = 40%–59% of the parenchyma showed air trapping, 4 = 60%–79% of the parenchyma showed air trapping, and 5 = 80% or more of the parenchyma showed air trapping.

The score attributed to each CT section was entered in a computer spreadsheet (MedCalc; MedCalc, Mariakerke, Belgium). To ensure that the readers began at the same anatomic level, the starting image number was determined by reader consensus prior to the independent reading sessions.

To obtain the average air trapping score for a given CT examination, the scores for all sections were summed and then divided by the number of sections acquired in a patient. The average air trapping score for a given CT examination was expressed as a percentage of the maximum possible score—that is, the score that theoretically would have been obtained if all sections in a patient had been attributed a score of 5.

Statistical Analysis
All statistical analyses were performed with a personal computer with commercially available software packages (StatXact, version 5.0, Statistical Solutions, Saugus, Mass; SPSS, version 14.0, SPSS, Chicago, Ill). Normally distributed data were expressed as means ± standard deviation and skewed data were expressed as medians with their 25% and 75% quartiles. For all tests, a P value of less than .05 was considered to indicate a significant difference.

Regional distribution of air trapping.—The lung of each patient (Fig 1) was split into an upper, middle, and lower region by dividing the number of acquired CT sections by three. If the number of CT sections was not a multiple of three, either the first or the first two most apical sections were deleted, given that these sections contained the least surface of lung parenchyma and thus the least amount of potential air trapping.


Figure 1
View larger version (151K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1: Lung CT shows upper (dotted lines, UL), middle (dashed lines, ML), and lower (solid lines, LL) regions, as defined for this study. Each region contained equal number of sections.

 
To determine the extent of air trapping for each of the three lung regions and for each patient, the average air trapping scores were calculated. Potential differences between the extent of air trapping in the upper, middle, and lower lung regions were tested for significance with analysis of variance for repeated measurements. For this analysis of variance, an individual patient was considered as a random factor. This allowed operating with different numbers of CT sections in different patients, without the need to calculate individual averages to compare patients. Moreover, this allowed assessing the interaction between individual patients and the six protocols.

The same analysis of variance was used to test for potential differences in the extent of air trapping between individual patients and to test for a potential interaction between the extent of air trapping in individual patients and the three lung regions. Correlation coefficients were computed to quantify the relation between the extent of air trapping in the upper, middle, and lower lung regions. Other than for the analysis of variance, the correlations were computed on the basis of the average air trapping scores of each region in each patient. To assess the predictive power of the extent of air trapping in a given lung region, correlation coefficients were squared.

Effect of simulated CT protocols on extent of air trapping.—The original CT protocol used in this study was termed protocol 1. Given this protocol and the resulting air trapping scores documented in the computer spreadsheet, we created models of five additional simulated CT protocols, each with a reduced number of sections. These were termed protocols 2–6. The five additional simulated protocols were generated by using the image material and reading results available from protocol 1. As a result, no additional radiation was delivered to the patients, and no additional reading sessions were performed.

First, CT sections for each simulated protocol were predefined (Table 1, Fig 2). Second, the individual air trapping scores from protocol 1 that corresponded to the CT sections of simulated protocols 2–6 were identified on the spreadsheet. Third, the average air trapping score was calculated for each protocol and for each patient.


View this table:
[in this window]
[in a new window]

  		Table 1. Examination Protocols

 

Figure 2
View larger version (168K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2: Lung CT shows anatomic levels (dashed lines) for six protocols compared in this study.

 
The design of our simulated protocols was largely derived from the experience of previous investigations. Our clinical protocol (protocol 1) corresponded to one used by Miller et al (15), Gevenois et al (16), Copley et al (17), and Bankier et al (18,19). Protocol 2 corresponded to one used by Choi et al (20). Protocol 3 corresponded to one used by Leung et al (14), Mastora et al (21), and Worthy et al (22), whereby the five sections of the last study were not preset at fixed anatomic levels but were equally spaced between the aortic arch and the diaphragm. Protocol 4 corresponded to one used by Lee et al (23), Konen et al (24), Arakawa and Webb (13), Knollmann et al (25), de Jong et al (26), and Tanaka et al (27). Protocol 5 corresponded to one used by Berstad et al (28). Protocol 6 was designed to investigate the effect of a further reduction in CT sections, with an exclusive focus on the lower lung regions, where most air trapping is seen in asymptomatic patients (6,27).

To visualize individual changes in the extent of air trapping according to the six protocols, air trapping scores were plotted for each patient and each protocol. Then, average air trapping scores were calculated for each protocol, and potential overall differences between the scores were tested with a Friedman statistic. If such differences were detected, pairwise comparisons were performed by using a Wilcoxon test. Average air trapping scores were also calculated for the subgroups of patients with clinically silent (BOS 0), potential (BOS 0p), and overt (BOS 1–3) airway disease. Again, a Friedman statistic was performed to test potential differences of average air trapping scores between protocols for significance.

Finally, the agreement between readers for each of the six examination protocols was assessed with a weighted {kappa} statistic (29). The asymptotic standard errors of the mean and the 95% confidence intervals for {kappa} were calculated. All {kappa} were interpreted as recommended (29,30): {kappa} = 0–0.20 indicated poor agreement, {kappa} = 0.21–0.40 indicated fair agreement, {kappa} = 0.41–0.60 indicated moderate agreement, {kappa}= 0.61–0.80 indicated good agreement, and {kappa} = 0.81–1.00 indicated excellent agreement.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Regional Distribution of Air Trapping
The extent of air trapping (Fig 3) increased from the upper to the middle lung region and from the middle to the lower lung region, with all differences between the lung regions reported as significant (P < .001). Differences in the extent of air trapping were also significant between individual patients (P < .001). The significant interaction between individual patients and lung regions (P < .001) indicated that the magnitude of regional differences in the extent of air trapping differed between patients. The correlations between the upper and middle (r = 0.930), the upper and lower (r = 0.756), and the middle and lower lung regions (r = 0.863) were all significant (P < .001). The squared correlation coefficients between the upper and middle (r2 = 0.865), the upper and lower (r2 = 0.572), and the middle and lower lung regions (r2 = 0.744) corresponded to a predictive power of 86%, 57%, and 74%, respectively, for predicting the extent of air trapping.


Figure 3
View larger version (147K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3: Lung CT shows average extent of air trapping in upper, middle, and lower regions. Averages are percentages with 95% confidence intervals in square brackets. Differences between lung regions were significant.

 
Effect of Simulated CT Protocols on Extent of Air Trapping
There was variability of individual air trapping scores between protocols, with this variability being most pronounced with protocols 4, 5, and 6 (Figs 4, 5).Regarding the average air trapping scores for each protocol, the overall differences between the scores were significant (P < .001). The P value for the comparison between protocol 1 and 2 was significant (Table 2). The P values tended to become significant for the comparisons involving protocol 4 and are systematically significant for comparisons involving protocols 5 and 6. The air trapping scores (Table 3) for the subgroups of patients with clinically silent (BOS 0), potential (BOS 0p), and overt (BOS 1–3) bronchiolitis showed differences in scores between protocols were significant (P < .001).


Figure 4
View larger version (22K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4: Graph shows individual air trapping scores plotted for each patient and each protocol. Substantial variability of individual air trapping scores between protocols are seen with increased variability for protocols 4–6.

 

Figure 5
View larger version (8K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 5: Graph shows average air trapping score for each protocol. Differences between protocols were significant (P < .001).

 

View this table:
[in this window]
[in a new window]

  		Table 2. P Values for Pairwise Comparisons of Average Air Trapping Scores between Protocols

 

View this table:
[in this window]
[in a new window]

  		Table 3. Average Air Trapping Scores for the Six Protocols according to BOS Stage

 
The weighted {kappa} used to assess agreement between observers for each of the six protocols (Table 4) were interpreted as good throughout.


View this table:
[in this window]
[in a new window]

  		Table 4. Agreement between Readers

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 
Our study findings confirm that in patients with suspected or overt bronchiolitis the regional distribution of air trapping is heterogeneous. Significant differences were indeed found between the extent of air trapping in the upper, middle, and lower regions of the lung. Simultaneously, the extent of air trapping increased from the upper to the lower lung regions. Significant correlations between the extent of air trapping in the upper, middle, and lower lung regions indicate that this increase is consistent between patients. As shown by the squared coefficients, however, the predictive power of these correlations can be rather low. This suggests that the extent of air trapping in one given lung region is not necessarily representative of the remaining regions. On one hand, the significant differences in the extent of air trapping between patients were not unexpected because our patients had different severities of disease. On the other hand, the significant interaction between individual patients and lung regions showed that the magnitude of regional differences in the extent of air trapping can vary substantially from patient to patient. This confirms that the regional distribution of air trapping is not only heterogeneous within, but also between, patients.

The heterogeneity of the regional distribution of air trapping had an effect on the extent of air trapping assessed with our simulated CT examination protocols. For the overall study group, the six protocols resulted in significantly different extents of air trapping. The six protocols also provided significantly different extents of air trapping for the subgroups of patients with clinically silent, potential, and overt bronchiolitis. Finally, individual air trapping scores showed substantial variability between protocols. This suggests that, regardless of the clinical severity of disease, the extent of air trapping can vary with the examination protocol. Comparisons of the extent of air trapping, assessed with different protocols, both within and between patients, must, therefore, be interpreted with caution. As a consequence, predefined protocols with the same number of sections should be used for cross-sectional and longitudinal studies of patients with suspected bronchiolitis if comparability of the extent of air trapping is required.

From a practical perspective, our results suggest that such a protocol should consist of at least three expiratory CT sections. In the context of our study, this would correspond to protocol 1, 2, 3, or 4. The markedly increased individual variability of the extent of air trapping with protocols 5 and 6, and the significant differences in air trapping scores obtained with other protocols, could support such a proposal. The tendency toward significant differences for comparisons involving protocol 4 further suggest that even protocols with three expiratory sections yield the risk for potentially relevant variability in the extent of air trapping. Given the overall heterogeneity of air trapping, however, caution should probably weight any choice toward protocols with higher sampling rates and, consequently, higher numbers of expiratory CT sections. In light of our results, this would correspond to protocol 1, 2, or 3.

In the literature, the sensitivities and specificities vary for the CT diagnosis of bronchiolitis obliterans after lung transplantation. Within the spectrum of variability, several studies with a higher number of acquired CT sections, similar to our protocols 1, 2, and 3, reported higher sensitivities and specificities for the detection of bronchiolitis (14,18,22). On the other hand, several studies with a lower number of acquired CT sections, similar to our protocols 4 and 5, reported lower sensitivities and specificities (23–25,28). Although this tendency is not straightforwardly consistent, it suggests that the number of CT sections could be one of the contributors to the variability in sensitivities and specificities for the CT diagnosis of bronchiolitis obliterans found in the literature. This observation also shows that—at least in the context of lung transplantation—our examination protocols extend beyond mere simulation to potentially reflect a real clinical situation.

Our study was conducted in lung transplant recipients, and one could object that its implications are limited to this subset of patients. However, bronchiolitis obliterans shares morphologic features with other small airways diseases (2). The extent of air trapping is also reasonably well related to a decrease in FEV1 (1,3,14,18,24,26). More important, bronchiolitis obliterans after lung transplantation is progressive and irreversible, and up to 70% of lung transplant recipients will eventually have various stages of the disease (31,32). Cohorts of lung transplant recipients therefore provide the rare opportunity to investigate one predefined subtype of bronchiolitis within a representative array of stages and clinical severities. Whether this is sufficient to justify the consideration of air trapping in lung transplant recipients a more general model for the radiologic manifestations of small airways diseases still remains to be confirmed. However, in clinical practice one often does not know what type of air trapping a patient might have, and the chances of heterogeneous or unexpected distribution of disease seems, if anything, higher than in our homogeneous population of transplant recipients.

Our study had limitations. First, our simulated examination protocols were compiled from the same set of original data and were thus based on the single initial evaluation of the original image set, with no additional readings performed. Obviously, this does not reflect the clinical situation in which a reader scoring a CT examination will inevitably take into account all of the information available. Because the interpretation of any given CT section is influenced by the adjacent sections, sections are more likely to be scored positively if adjacent sections show extensive areas of air trapping and vice versa. To allow conclusions regarding the diagnostic accuracy of the simulated protocols to be drawn from our data, each protocol would have to be scored in an independent and blinded manner by at least two independent readers. However, our simulated protocols were not designed to determine the diagnostic accuracy of CT in helping assess bronchiolitis but rather to investigate the effect of changes in the number and anatomic location of CT sections on the quantification of air trapping.

Second, the six protocols had six different total numbers of CT sections. This could have affected interreader agreement, which was found to be good for all six protocols. Since relatively fewer CT sections provide less opportunity for reader disagreement, interreader agreement could have been overestimated for the protocols that used fewer sections, but there is no way to determine whether the protocols created by using more CT sections counterbalanced this effect.

In conclusion, the regional distribution of air trapping in patients with suspected or overt bronchiolitis is heterogeneous. This limits the potential for dose reduction by means of a reduction of CT sections or by means of a restriction of volumetric acquisitions in predefined lung regions. Because the extent of air trapping can vary with the chosen examination protocol, identical protocols should be used when air trapping is compared within and between patients.


   ADVANCES IN KNOWLEDGE
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
IMPLICATION FOR PATIENT CARE
 References
 


   IMPLICATION FOR PATIENT CARE
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
References
 


   FOOTNOTES
 

Abbreviations: BOS = bronchiolitis obliterans syndrome • FEF25%–75% = forced midexpiratory flow • FEV1 = forced expiratory volume in 1 second

Author contributions: Guarantors of integrity of entire study, A.A.B., P.A.G.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, A.A.B., S.M., D.K., P.A.G.; clinical studies, S.M., P.A.G.; experimental studies, A.A.B., P.A.G.; statistical analysis, A.A.B., M.W.; and manuscript editing, all authors

Authors stated no financial relationship to disclose.


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 IMPLICATION FOR PATIENT CARE
 References
 

  1. Hansell DM, Rubens MB, Padley SP, Wells AU. Obliterative bronchiolitis: individual CT signs of small airways disease and functional correlation. Radiology 1997;203:721–726.[Abstract/Free Full Text]
  2. Hansell DM. Small airways diseases: detection and insights with computed tomography. Eur Respir J 2001;17:1294–1313.[Abstract/Free Full Text]
  3. Pipavath SJ, Lynch DA, Cool C, Brown KK, Newell JD. Radiologic and pathologic features of bronchiolitis. AJR Am J Roentgenol 2005;185:354–363.[Abstract/Free Full Text]
  4. Studler U, Gluecker T, Bongartz G, Roth J, Steinbrich W. Image quality from high-resolution CT of the lung: comparison of axial scans and of sections reconstructed from volumetric data acquired using MDCT. AJR Am J Roentgenol 2005;185:602–607.[Abstract/Free Full Text]
  5. Bankier AA, Schaefer-Prokop C, De Maertelaer V, et al. Air trapping: comparison of standard-dose and simulated low-dose thin-section CT techniques. Radiology 2007;242:898–906.[Abstract/Free Full Text]
  6. Lee KW, Chung SY, Yang I, Lee Y, Ko EY, Park MJ. Correlation of aging and smoking with air trapping at thin-section CT of the lung in asymptomatic subjects. Radiology 2000;214:831–836.[Abstract/Free Full Text]
  7. Webb WR, Stern EJ, Kanth N, Gamsu G. Dynamic pulmonary CT: findings in healthy adult men. Radiology 1993;186:117–124.[Abstract/Free Full Text]
  8. Standardization of spirometry, 1994 update: American Thoracic Society. Am J Respir Crit Care Med 1995;152:1107–1136.[Medline]
  9. Quanjer PH, Tammeling GJ, Cotes JE, Pedersen OF, Peslin R, Yernault JC. Lung volumes and forced ventilatory flows: report working party standardization of lung function tests, European Community for Steel and Coal—official statement of the European Respiratory Society. Eur Respir J Suppl 1993;16:5–40.[Medline]
  10. Estenne M, Maurer JR, Boehler A, et al. Bronchiolitis obliterans syndrome 2001: an update of the diagnostic criteria. J Heart Lung Transplant 2002;21:297–310.[CrossRef][Medline]
  11. Hemminger BM. Calibration of CRT monitors according to the DICOM grayscale standard display function [abstr]. Radiology 1999;213(P):583.[Abstract/Free Full Text]
  12. Worthy SA, Muller NL, Hartman TE, Swensen SJ, Padley SP, Hansell DM. Mosaic attenuation pattern on thin-section CT scans of the lung: differentiation among infiltrative lung, airway, and vascular diseases as a cause. Radiology 1997;205:465–470.[Abstract/Free Full Text]
  13. Arakawa H, Webb WR. Air trapping on expiratory high-resolution CT scans in the absence of inspiratory scan abnormalities: correlation with pulmonary function tests and differential diagnosis. AJR Am J Roentgenol 1998;170:1349–1353.[Abstract/Free Full Text]
  14. Leung AN, Fisher K, Valentine V, et al. Bronchiolitis obliterans after lung transplantation: detection using expiratory HRCT. Chest 1998;113:365–370.[CrossRef][Medline]
  15. Miller WT Jr, Kotloff RM, Blumenthal NP, Aronchick JM, Gefter WB, Miller WT. Utility of high resolution computed tomography in predicting bronchiolitis obliterans syndrome following lung transplantation: preliminary findings. J Thorac Imaging 2001;16:76–80.[CrossRef][Medline]
  16. Gevenois PA, De Vuyst P, Sy M, et al. Pulmonary emphysema: quantitative CT during expiration. Radiology 1996;199:825–829.[Abstract/Free Full Text]
  17. Copley SJ, Wells AU, Muller NL, et al. Thin-section CT in obstructive pulmonary disease: discriminatory value. Radiology 2002;223:812–819.[Abstract/Free Full Text]
  18. Bankier AA, Van Muylem A, Knoop C, Estenne M, Gevenois PA. Bronchiolitis obliterans syndrome in heart-lung transplant recipients: diagnosis with expiratory CT. Radiology 2001;218:533–539.[Abstract/Free Full Text]
  19. Bankier AA, Van Muylem A, Scillia P, De Maertelaer V, Estenne M, Gevenois PA. Air trapping in heart-lung transplant recipients: variability of anatomic distribution and extent at sequential expiratory thin-section CT. Radiology 2003;229:737–742.[Abstract/Free Full Text]
  20. Choi YW, Rossi SE, Palmer SM, DeLong D, Erasmus JJ, McAdams HP. Bronchiolitis obliterans syndrome in lung transplant recipients: correlation of computed tomography findings with bronchiolitis obliterans syndrome stage. J Thorac Imaging 2003;18:72–79.[CrossRef][Medline]
  21. Mastora I, Remy-Jardin M, Sobaszek A, Boulenguez C, Remy J, Edme JL. Thin-section CT finding in 250 volunteers: assessment of the relationship of CT findings with smoking history and pulmonary function test results. Radiology 2001;218:695–702.[Abstract/Free Full Text]
  22. Worthy SA, Park CS, Kim JS, Muller NL. Bronchiolitis obliterans after lung transplantation: high-resolution CT findings in 15 patients. AJR Am J Roentgenol 1997;169:673–677.[Abstract/Free Full Text]
  23. Lee ES, Gotway MB, Reddy GP, Golden JA, Keith FM, Webb WR. Early bronchiolitis obliterans following lung transplantation: accuracy of expiratory thin-section CT for diagnosis. Radiology 2000;216:472–477.[Abstract/Free Full Text]
  24. Konen E, Gutierrez C, Chaparro C, et al. Bronchiolitis obliterans syndrome in lung transplant recipients: can thin-section CT findings predict disease before its clinical appearance? Radiology 2004;231:467–473.
  25. Knollmann FD, Ewert R, Wundrich T, Hetzer R, Felix R. Bronchiolitis obliterans syndrome in lung transplant recipients: use of spirometrically gated CT. Radiology 2002;225:655–662.[Abstract/Free Full Text]
  26. de Jong PA, Dodd JD, Coxson HO, et al. Bronchiolitis obliterans following lung transplantation: early detection using computed tomographic scanning. Thorax 2006;61:799–804.[Abstract/Free Full Text]
  27. Tanaka N, Matsumoto T, Miura G, et al. Air trapping at CT: high prevalence in asymptomatic subjects with normal pulmonary function. Radiology 2003;227:776–785.[Abstract/Free Full Text]
  28. Berstad AE, Aalokken TM, Kolbenstvedt A, Bjortuft O. Performance of long-term CT monitoring in diagnosing bronchiolitis obliterans after lung transplantation. Eur J Radiol 2006;58:124–131.[CrossRef][Medline]
  29. Cohen J. Weighted kappa: nominal scale agreement with provision for scaled disagreement or partial credit. Psychol Bull 1968;70:213–220.[CrossRef]
  30. Liebetrau AM. Measures of association. In: Sage University papers on quantitative applications in the social sciences, series 07-032. Newbury Park, Calif: Sage, 1983; 32–36.
  31. Arcasoy SM, Kotloff RM. Lung transplantation. N Engl J Med 1999;340:1081–1091.[Free Full Text]
  32. Estenne M, Hertz MI. Bronchiolitis obliterans after human lung transplantation. Am J Respir Crit Care Med 2002;166:440–444.[Free Full Text]




This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2473071228v1
247/3/862    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bankier, A. A.
Right arrow Articles by Gevenois, P. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bankier, A. A.
Right arrow Articles by Gevenois, P. A.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
RADIOLOGY RADIOGRAPHICS RSNA JOURNALS ONLINE