BJR
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
British Journal of Radiology (2003) 76, 536-540
© 2003 British Institute of Radiology
doi: 10.1259/bjr/21813112
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Services
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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Chooi, W K
Right arrow Articles by Morcos, S K
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Chooi, W K
Right arrow Articles by Morcos, S K

Full Paper

Multislice helical CT: the value of multiplanar image reconstruction in assessment of the bronchi and small airways disease

W K Chooi, FRCS, S Matthews, FRCR, M J Bull, FRCR and S K Morcos, FRCR

Department of Diagnostic Imaging, Northern General Hospital, Sheffield S5 7AU, UK

Correspondence: Dr S K Morcos, X-ray Department, Northern General Hospital, Sheffield S5 7AU, UK


   Abstract
Top
 Abstract
Introduction
 Materials and methods
 Results
 Discussion
 References
 
We examined 23 consecutive patients (11 males and 12 females with mean age of 56 years) with possible airway diseases to assess the impact of multiplanar image reconstruction (MPR) on the degree of confidence and accuracy in diagnosing bronchial abnormalities and emphysema. The thorax was scanned contiguously at 1 mm slice thickness using Siemens Volume Zoom Multislice CT scanner. Images were reconstructed at 1 mm slice thickness (lung windows L-600HU W-1600HU utilizing high spatial frequency algorithm) in the axial (10 mm apart), sagittal (4 images per lung) and coronal (6 images) plane. Paddle wheel image reconstructions were also performed in the assessment of bronchiectasis. Axial images were assessed with and without the help of MPR by three chest radiologists at two separate occasions (at least 4 weeks apart). The presence of bronchiectasis, emphysema and bronchiolitis in each lobe was documented on a confidence scale of 0 to 3. The overall mean confidence for each observer with and without MPR was compared. Consensus diagnosis was used as the gold standard for the assessment of the diagnostic accuracy of each observer. A confidence score of 2 or more for any lobe was considered diagnostic of the particular airway disease. The diagnostic accuracy for each observer with and without MPR was compared. Consensus reporting diagnosed bronchiectasis in 7 patients (30.4%), bronchiolitis in 5 patients (21.7%) and emphysema in 12 patients (52%). MPR did not increase the confidence of assessing the different abnormalities for all observers but improvement in diagnosing bronchiectasis was noted in two observers. The improvement did not reach statistical significance. However, agreement between observers in the diagnosis of bronchiectasis and emphysema was improved when the MPR images were used in conjunction with standard axial imaging (Kappa statistic improved from 0.29 to 0.54 for bronchiectasis and from 0.7 to 0.81 for emphysema). Agreement on the diagnosis of bronchiolitis was not improved by MPR for all observers. Our results suggest that MPR seems to improve the confidence in diagnosing bronchiectasis and emphysema.


   Introduction
Top
 Abstract
 Introduction
Materials and methods
 Results
 Discussion
 References
 
The introduction of multislice CT (MSCT) in 1998 was a major step forward in CT technology. The sub-second rotation time of the new scanners in association with the ability to perform multiple slices in a single rotation has made it possible to scan large areas of the body in a single breath hold [1]. Multiplanar and three-dimensional (3D) images of excellent quality can be produced, which can be of great benefit in many clinical situations including vascular imaging, evaluation of facial, spinal and pelvic fractures [2].

The value of MSCT in thoracic imaging has not been widely investigated and there are only few reports in the literature [3–6]. In addition, there is no consensus on how to make the best use of this new technology in imaging parenchymal and airway diseases of the lung. Since MSCT is capable of producing a large number of axial images and extensive multiplanar reformatted images, there is a need for practical imaging protocols that maximize the diagnostic yield without the production of an excessive number of images and minimize the time spent at the workstation. The protocols should be suitable for implementation by the radiographic staff.

In our unit we have developed several practical protocols for the using MSCT in different clinical applications in a busy department with high demand on radiological time. In this report we will present our preliminary experience with the use of MSCT in imaging the bronchi. The diagnostic accuracy of the implemented protocol and the importance of multiplanar reformatted (MPR) images were investigated.


   Materials and methods
Top
 Abstract
 Introduction
 Materials and methods
Results
 Discussion
 References
 
Patients
23 patients (11 males and 12 females, mean age 56 years (range 20–74 years)) were referred for high resolution CT (HRCT) scanning of the lungs with symptoms suggestive of airway diseases, which included productive cough (11 cases), recurrent chest infection (5 cases), increasing shortness of breath (4 cases) and wheezing (4 cases).

CT protocol
All patients were examined on a Siemens Volume Zoom Multislice CT scanner (Forchheim, Germany). The whole thorax was scanned using a 1 mm collimation from the lung bases up to apices in end-inspiration. Images of 1 mm slice thickness were reconstructed at a window level of -600 Hounsfield Units (HU) and window width of 1600 HU utilizing a high spatial frequency algorithm in the following planes; axial (10 mm intervals from apices to bases), coronal (6 evenly spaced through the chest) and sagittal (4 images evenly spaced through each lung). The different technical parameters are presented in Table 1Go.


View this table:
[in this window]
[in a new window]
  		Table 1. Multislice CT, technical parameters

 
In cases with suspected bronchiectasis paddle wheel image reconstruction was performed to ensure imaging the bronchi along their long axis. The reconstruction was carried out at one-degree intervals in a 180-degree arc centred on the distal trachea. Two sets of paddle wheel reconstructions were performed: one set rotated from the axial to coronal and back to the axial plane and the other from sagittal to coronal to sagittal plane. This created 180 images (1 mm slice thickness) for each set that were reviewed at the workstation by the radiologist. Optimal images displaying the bronchi along their longitudinal axis were selected for hard copying.

The images were recorded on X-ray films (30 x 40 cm) with 20 frames per film.

Image interpretation
Images were divided into two separate sets of films for analysis. One set consisted of axial images only and the other consisted of axial images and MPR images. Three experienced chest radiologists reviewed the films. The two sets were analysed at least 4 weeks apart. The radiologists were blinded to the patients' specific clinical details. The images were assessed for the presence of bronchiectasis, bronchiolitis and emphysema. Bronchiectasis was considered to be present if the internal diameter of any given bronchus was greater than that of the accompanying artery (Figure 1Go), if the bronchus failed to taper peripherally (Figure 2Go), abutted the mediastinal pleura or was visualized within 1 cm of the pleura [7]. Bronchiolitis was defined as the presence of small, well-defined, centrilobular nodular, linear or branching structures (tree-in-bud appearance) [8]. Emphysema was defined as focal areas of low attenuation with associated vascular deficiency [8–10].



View larger version (79K):
[in this window]
[in a new window]
  		Figure 1. Axial image through the lung bases demonstrating bronchiectasis (arrows) in the basal segments of the left lower lobe. The bronchi are thick walled and have a diameter larger than that of the adjacent arteries.

 


View larger version (109K):
[in this window]
[in a new window]
  		Figure 2. Coronal image through the lungs demonstrating bronchiectasis of the left lower lobe. The dilated bronchi (arrows) are full of mucus and fail to taper peripherally.

 
Each lobe was assessed individually; the lingula was considered as a separate lobe. The radiologist assigned a score to indicate the degree of confidence that an abnormality was present or absent using a scale of 0–3 (0 indicated no abnormality, 1 possible, 2 probable and 3 definite abnormality). A score of 0 was assigned a value of 3 to reflect a high level of confidence in excluding abnormality.

All the films were reviewed several weeks after the initial assessment by two experienced chest radiologists to establish a consensus diagnosis on the presence or absence of a particular airways disease. The consensus report was used as the gold standard for comparison with the assessments of each individual radiologist. A score of 2 or more for any lobe was considered diagnostic for a particular airway disease. In total, each case was assessed 7 times.

Statistical analysis
The results from assessing axial alone and axial with MPR images were compared with the consensus diagnosis (gold standard) to determine the reporting accuracy of each group. Accuracy was determined by the sum of true positives and true negatives divided by the total number of cases. McNemar's paired test was used to assess differences between groups. The Wilcoxon sign rank test was used to assess the differences in observer confidence in axial versus axial with MPR reporting. A p-value of 0.05 or less was considered significant. Kappa (K) statistic was performed to assess correlation between radiologists. K values have been defined as the following: <=0.20 poor; 0.21–0.40 fair; 0.41–0.60 moderate; 0.61–0.80 good; and >=0.81 very good.


   Results
Top
 Abstract
 Introduction
 Materials and methods
 Results
Discussion
 References
 
Based on the consensus report bronchiectasis was diagnosed in 7 patients (30.4%), bronchiolitis in 5 patients (21.7%) and emphysema in 12 patients (52%).

There was no significant difference in the confidence or accuracy of reporting airways diseases with the addition of the MPR images (Figure 3Go) for any of the 3 radiologists (Tables 2, 3GoGo). However, some improvement was noted in diagnosing bronchiectasis for observers A and C but did not reach statistical significance using the McNemar's test.



View larger version (75K):
[in this window]
[in a new window]
  		Figure 3. Collapsed bronchiectatic right middle lobe (arrows) clearly depicted in the (a) coronal oblique view produced by paddle wheel image reconstruction in comparison with (b) axial imaging.

 

View this table:
[in this window]
[in a new window]
  		Table 2. Diagnostic confidence for each radiologist for reporting with axial images alone and axial with multiplanar reformatted (MPR) images

 

View this table:
[in this window]
[in a new window]
  		Table 3. Diagnostic accuracy using axial images alone and with multiplanar reformatted image (MPR)

 
Improvement in the agreement in diagnosing bronchiectasis was observed with MPR in comparison with axial imaging alone (from fair to moderate between observers A and B and from good to very good between observers A and C). MPR improved agreement in diagnosing emphysema from good to very good with observers B and C and from poor to fair with observers A and B. Agreement on the diagnosis of bronchiolitis was not improved by MPR for all observers and a better agreement was observed with axial images alone (Table 4Go).


View this table:
[in this window]
[in a new window]
  		Table 4. Agreement between observers using axial images alone and with multiplanar reformatted images (MPR) Kappa valuesa

 

   Discussion
Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
References
 
There have been few studies published in the literature assessing the diagnostic value of MPR in imaging the thorax [3–6]. Schoepf et al reported the efficiency of MSCT in imaging focal and diffuse lung disease using 1 mm slice thickness for scanning the whole thorax to produce contiguous axial images (5 mm slice thickness) and 1.25 mm axial images of the lungs at 10 mm intervals using high resolution algorithm [3]. Arakawa et al compared coronal MPR images with axial HRCT in the assessment of diffuse lung disease and concluded that coronal reformats were comparable with axial HRCT and revealed additional information regarding lesion conspicuity in 22% of cases [4]. In another study on the use of MSCT the authors recommended scanning the whole thorax with 4 x 2.5 mm collimation and 3 mm axial images at 10 mm intervals in the screening of bronchiectasis [5]. No MPR was used in this study. A further study concluded that coronal imaging alone could be used to accurately assess infiltrative lung disease without loss of diagnostic precision in comparison with standard axial imaging [6]. The use of only coronal images reduced the number of images required for review [6].

The role of helical CT in imaging diseases of the airways was recently reviewed by Grenier et al [11]. Thin section CT is accepted as a reliable method for imaging bronchiectasis but has some limitations. The gaps between image slices could result in focal areas of bronchiectasis being overlooked within the "skip" regions. In addition, depiction of the bronchi along the long axis is limited in axial imaging [11]. These problems can be resolved by volume imaging with helical CT. This permits the formation of contiguous thin slice images that can be viewed as a "stack" using the cine mode on the workstation, thus enabling the radiologist to follow bronchi throughout their divergent pathway from the hilum [11]. Furthermore, the acquired data can be used to produce 3D virtual bronchogram that can display the bronchial tree up to the 7th order division [11, 12]. Virtual bronchography may improve detection of subtle cylindrical bronchiectasis and aid differentiation of lung cysts from cystic bronchiectasis and has been shown to add diagnostic and morphological information in 31% of patients [11, 12].

The accuracy of MSCT with its capability of producing MPR images of almost isotropic resolution in assessing airways diseases has not yet been documented. However, Grenier et al indicated that this new technology has the potential of improving the evaluation of airway diseases in comparison with single slice CT [11].

In this study we attempted to determine if coronal, sagittal and paddle wheel MPR, in addition to axial imaging improved the accuracy and confidence in diagnosing bronchiectasis, bronchiolitis and emphysema. We found that MPR imaging did not alter the confidence, but some improvement in the accuracy of assessing bronchiectasis was observed, although it did not reach statistical significance. The number of patients in this study was rather small and a larger study may confirm the observed trend. In addition, the absence of an increase in the diagnostic confidence between axial and MPR images may reflect the fact that all the radiologists involved in this study are experienced in cross-sectional assessment of airways disease. Perhaps MPR images could be of greater help to general radiologists and trainees who may find that depiction of the bronchi along their long axis is easier to assess. According to our results using Kappa statistical analysis better agreement was observed in assessment of bronchiectasis with MPR indicating the interpretation of these additional images is easier as more consistent reporting between observers was observed. MPR did not have a major impact on the diagnosis of bronchiolitis and emphysema. However, we found that coronal and sagittal images were useful in assessing the distribution of emphysema, particularly for patients undergoing assessment for volume reduction surgery.

Although MSCT increases patient throughput and allows high quality MPR images, consideration needs to be given to the radiation dose received with volume in comparison with sequential HRCT imaging. For the protocol used in this study the stated CT dose index (CTDIw) is 10.3 mGy; the same as sequential HRCT acquisition (1 mm slice thickness, 15 mm gap) [13]. However, the effective radiation dose for both techniques is 4 mSV and 1 mSV, respectively, indicating an increase of the radiation dose by a factor of 4 with volume imaging. Since a gap interval of 10 mm, not 15 mm, is the most commonly applied interval in standard axial HRCT imaging, the difference in the effective radiation dose would be less.

Our experience so far suggests that axial, coronal and sagittal images are sufficient in most cases. The images are produced independently by the radiographic staff and provided as hard copies for reporting. Paddle wheel imaging is used only when further information is required. In our practice 3D imaging of the bronchi is not used routinely in assessment of the airways as it is time consuming and not practical in a busy department. However, 3D imaging offers useful information in cases with abnormalities of the trachea and major bronchi.

The hard copying of axial, coronal and sagittal images does result in an increased film cost. This is offset by an increase in the number of patients scanned per session and the reduced costs incurred for the more efficient use of the radiologist's time since the protocol can be run without direct radiologist supervision. Reporting of images at the workstation is not practical if adequate facilities are not available.

Our protocol is modified for the breathless patients who are unable to hold their breath for 20–30 s (the time required for high resolution volume imaging). In these patients only sequential imaging is preferred to limit breathing artefacts associated with volume imaging. These patients are scanned at 8–10 evenly spaced levels through their chest during quiet respiration employing 2 x 0.5 mm collimation. Axial images of 1 mm slice thickness are produced with minimal motion artefact.

In summary our preliminary experience suggests that MPR has the potential to increase the confidence in diagnosing bronchiectasis and emphysema, but no major impact on the assessment of bronchiolitis.

Received for publication September 25, 2002. Revision received February 7, 2003. Accepted for publication May 12, 2003.


   References
Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 

  1. Dawson P, Lees WR. Multi-slice technology in computed tomography. Clin Rad 2001;56:302–9.[CrossRef][Medline]
  2. Sablayrolles JL. Present and future trends in MDCT applications. Eur Radiol 2002;12 (Suppl 2):s1–s31.
  3. Schoepf UJ, Bruening RD, Hong C, Eibel R, Aydemir S, Crispin A, et al. Multislice helical CT of focal and diffuse lung disease: comprehensive diagnosis with reconstruction of contiguous and high-resolution CT sections from a single thin-collimation scan. AJR Am J Roentgenol 2001;177:179–84.[Abstract/Free Full Text]
  4. Arakawa H, Sasaka K, Lu WM, Nakajima Y, Fujioka M. Multiplanar reformation images produced by multi-detector row CT: comparison with high resolution CT. Radiology 2001;221 (P):204.
  5. Remy-Jardin MJ, Campistron P, Mastora I, Delannoy V, Remy J. Diagnosis of bronchiectasis with multidetector spiral CT: optimization of the acquisition protocol. Radiology 2001;221 (P):356.
  6. Remy-Jardin MJ, Campistron P, Amara A, Mastora I, Delannoy V, Duhamel A, et al. Workflow issue with multislice CT of the thorax: Usefulness of multiplanar reformations in the diagnostic approach of infiltrative lung disease. Eur Radiol 2002;12(Suppl. 1):134.[CrossRef][Medline]
  7. Kim JS, Muller NL, Park CS, Grenier PA, Herold CJ. Cylindrical bronchiectasis: diagnostic findings on thin section CT. AJR Am J Roentgenol 1997;168:751–4.[Abstract/Free Full Text]
  8. Webb WR, Muller NL, Naidich DP. High resolution CT of the Lung, 2nd Edn. Philadelphia, New York: Lippincott-Raven, 2001:41–108.
  9. Bergin CJ, Muller NL, Miller RR. CT in the qualitative assessment of emphysema. J Thorac Imaging 1986;1:94–103.[Medline]
  10. Thurbeck WM, Muller NL. Emphysema: definition, imaging and quantification. AJR Am J Roentgenol 1994;163:1017–25.[Abstract/Free Full Text]
  11. Grenier PA, Beigelman-Aubry C, Fetita C, Preteux F, Brauner MW, Lenoir S. New frontiers in CT imaging of airways disease. Eur Radiol 2002;12:1022–44.[CrossRef][Medline]
  12. Remy-Jardin M, Remy J, Artaud D, Fribourg M, Duhamel A. Volume rendering of the tracheobronchial tree: clinical evaluation of bronchographic images. Radiology 1998;208:761–70.[Abstract/Free Full Text]
  13. Siemens Somatom Volume Zoom Application Guide. Software version A40. 2002.



This article has been cited by other articles:


Home page
 Am. J. Roentgenol.Home page
K. Takahashi, B. Thompson, W. Stanford, Y. Sato, K. Nagasawa, H. Sato, M. Kubota, A. Kashiba, and H. Sugimori
Visualization of normal pulmonary fissures on sagittal multiplanar reconstruction MDCT.
Am. J. Roentgenol., August 1, 2006; 187(2): 389 - 397.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Roentgenol.Home page
J. D. Dodd, C. A. Souza, and N. L. Muller
Conventional high-resolution CT versus helical high-resolution MDCT in the detection of bronchiectasis.
Am. J. Roentgenol., August 1, 2006; 187(2): 414 - 420.
[Abstract] [Full Text] [PDF]

Home page
 Br. J. Radiol.Home page
W K Chooi and S K Morcos
High resolution volume imaging of airways and lung parenchyma with multislice CT
Br. J. Radiol., December 1, 2004; 77(suppl_1): S98 - S105.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Services
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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Chooi, W K
Right arrow Articles by Morcos, S K
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Chooi, W K
Right arrow Articles by Morcos, S K

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
BJR DMFR IMAGING  ALL BIR JOURNALS