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The value of digital tomosynthesis of the chest as a problem-solving tool for suspected pulmonary nodules and hilar lesions detected on chest radiography
European Journal of Radiology 84 (2015) 1012–1018
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European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
The value of digital tomosynthesis of the chest as a problem-solving tool for suspected pulmonary nodules and hilar lesions detected on chest radiography Angela Galea a,∗ , Paul Dubbins b,1 , Richard Riordan b,1 , Tarig Adlan b,1 , Carl Roobottom b,1 , David Gay b,1 a b
Peninsula Radiology Academy, William Prance Road, Plymouth PL65WR, UK Plymouth Hospital NHS Trust, Plymouth PL68DH, UK
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Article history: Received 2 June 2014 Received in revised form 28 November 2014 Accepted 9 February 2015 Keywords: Digital tomosynthesis Chest radiology Lung nodules Hilar lesions
a b s t r a c t Objectives: To assess the capability of digital tomosynthesis (DTS) of the chest compared to a posteroanterior (PA) and lateral chest radiograph (CXR) in the diagnosis of suspected but unconfirmed pulmonary nodules and hilar lesions detected on a CXR. Computed tomography (CT) was used as the reference standard. Materials and method: 78 patients with suspected non-calcified pulmonary nodules or hilar lesions on their CXR were included in the study. Two radiologists, blinded to the history and CT, prospectively analysed the CXR (PA and lateral) and the DTS images using a picture archiving and communication workstation and were asked to designate one of two outcomes: true intrapulmonary lesion or false intrapulmonary lesion. A CT of the chest performed within 4 weeks of the CXR was used as the reference standard. Inter-observer agreement and time to report the modalities were calculated for CXR and DTS. Results: There were 34 true lesions confirmed on CT, 12 were hilar lesions and 22 were peripheral nodules. Of the 44 false lesions, 37 lesions were artefactual or due to composite shadow and 7 lesions were real but extrapulmonary simulating non-calcified intrapulmonary lesions. The PA and lateral CXR correctly classified 39/78 (50%) of the lesions, this improved to 75/78 (96%) with DTS. The sensitivity and specificity was 0.65 and 0.39 for CXR and 0.91 and 1 for DTS. Based on the DTS images, readers correctly classified all the false lesions but missed 3/34 true lesions. Two of the missed lesions were hilar in location and one was a peripheral nodule. All three missed lesions were incorrectly classified on DTS as composite shadow. Conclusions: DTS improves diagnostic confidence when compared to a repeat PA and lateral CXR in the diagnosis of both suspected hilar lesions and pulmonary nodules detected on CXR. DTS is able to exclude most peripheral pulmonary nodules but caution and further studies are needed to assess its ability to exclude hilar lesions. © 2015 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Despite the inferior performance of chest radiography (CXR) to computed tomography (CT) scanning it remains the initial examination for the majority of pulmonary disease due to its low cost, easy access and low radiation dose. Obvious pulmonary lesions
∗ Corresponding author. Tel.: +44 7800511681. E-mail addresses: [email protected] (A. Galea), [email protected] (P. Dubbins), [email protected] (R. Riordan), [email protected] (T. Adlan), [email protected] (C. Roobottom), [email protected] (D. Gay). 1 Tel.: +44 1752437437. http://dx.doi.org/10.1016/j.ejrad.2015.02.007 0720-048X/© 2015 Elsevier Ireland Ltd. All rights reserved.
detected on CXR clearly need further investigation and CT scanning is recommended. Chest radiography however has a low sensitivity and specificity for the detection of early lung cancer [1]. Lung cancer is the leading cause of cancer globally and is associated with poor outcome [2–4]. However the 2011 US National Lung Screening Trial demonstrated that early detection reduces mortality and emphasizes the need to detect early cancer [5]. Small pulmonary nodules carry a low risk of lung cancer but may require further investigation and often patients with lung nodules undergo CT scanning for evaluation. Alternative investigations, without the high cost or radiation dose of CT scanning that offer increased accuracy in pulmonary and hilar lesions suspicious for cancer would be useful in the investigation of pulmonary disease.
A. Galea et al. / European Journal of Radiology 84 (2015) 1012–1018 Table 1 The various indications for referral for a chest radiograph. Some patients were referred for more than one symptom. Indication
In-patient N = number of patients
Out-patient N = number of patients
Cough Shortness of breath Chest pain Infection Arrythmia Other (e.g. weight loss, arthritis)
3 3 4 1 2 4
29 21 8 3 2 10
A radiologist will frequently identify a small group of CXRs that are equivocal either because of an inability to correctly characterise a visualised abnormality as soft tissue or calcified and therefore likely benign or an inability to determine the location of the lesion as intra- or extrapulmonary. The radiologist may be unsure whether a lesion is real or composite especially if it lies in a region of heavy anatomical noise such as the lung hila or apices. Patients with equivocal CXRs due to one of the above findings were included in the study to assess the role of digital tomosynthesis (DTS) in confirming or excluding a potentially significant abnormality. DTS is a type of limited angle tomography whereby about sixty low dose images are acquired over a limited range of X-ray tube movement in the cranio-caudal axis. The raw images are used to reconstruct contiguous coronal images in the antero-posterior axis through the area of interest. Tomosynthesis evolved from the technique of tomography, which was used to evaluate, inter alia the lung hila, the kidneys and the petrous temporal bones. Increasing concern about the patient dose from CT has resulted in a resurgence of interest in tomographic techniques such as tomosynthesis because of the associated low radiation dose. Digital tomosynthesis reduces composite artefact due to anatomical noise by providing better depth resolution thus separating the structures in the antero-posterior dimension. DTS can correctly differentiate between lesions of the rib cage, pleurally based lesions and intrapulmonary lesions [6–13]. Improved contrast resolution of DTS when compared to CXR results in better calcium detection [13]. Advantages when compared to CT relate to cost and dose reduction. The role of DTS in the evaluation of pulmonary nodules has been explored in previous studies [14–16]. In this study we chose a more pragmatic approach by assessing both non-calcified intrapulmonary nodules and hilar masses using CT as the gold standard. The purpose of this study is to assess whether DTS can be used instead of a repeat PA and lateral chest radiograph in the evaluation of an equivocal chest radiograph. 2. Method 2.1. Patients The study was approved by the regional ethics committee. This was a single centre, prospective observational study. All inpatients and outpatients with an equivocal finding on chest radiograph were included. The indications for the initial chest radiograph were varied so as to simulate clinical practice and are shown in Table 1. All patients included in the study consented to have a repeat PA and lateral CXR, a DTS and a CT chest within 4 weeks of their initial CXR. 2.2. Digital tomosynthesis A General Electric (GE, Buc, France) VolumeRAD system with a high-quality digital detector with rapid read-out was used, which relies on the GE Definium 8000 digital X-ray system to acquire the
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projection images necessary for tomosynthesis reconstruction. A scout image of the chest is first obtained to confirm a correct position. The patient is then instructed to hold his/her breath for 10 s whilst 60 discrete images are acquired over an angular range of 35◦ to produce 50–60 coronal reconstructions of the chest. The tube voltage was set at 120 kVp. Each raw image delivers an average effective dose of 2 Sv resulting in a cumulative effective dose of 0.15 mSv for the average 70 kg male patient (this effective dose includes both the scout and raw images). 2.3. Computed tomography The CT examinations were performed using a 64 slice multidetector (HD750, GE Healthcare) scanner. The scan parameters used were: a set noise index of 39.68; 120 kV and a range of 100–750 mA. The CT slice thickness was 0.625 mm for all patients. The effective dose (based on an unenhanced scan) was calculated using a conversion factor from dose–length product (DLP) to E (EDLP ) of 0.017 mSv/(mGy cm) and was 4 mSv[17]. Thirty-two patients with suspected hilar lesions were scanned following an additional 100 mL intravenous bolus injection of iodinated contrast at a rate of 3.5 mL/s. All other patients had an unenhanced scan of the chest. 2.4. Image interpretation A nodule was defined according to the Fleischner Society Glossary of Terms as a rounded opacity, well or poorly defined measuring up to 3 cm in diameter [18]. A hilar lesion for the purpose of this study was defined as a lesion of any size but within 3 cm of the hilar point measured in the coronal/antero-posterior (AP) direction. Hilar lesions included hilar carcinomas, lung nodules within 3 cm of the hilar point and hilar adenopathy. The hilar point is formed as the descending superior pulmonary vein crosses anterior to the interlobar pulmonary artery [19,20]. 2.5. Data analysis Three radiologists with 30, 15 and 10 years experience participated in the study. Two radiologists with 30 and 10 years experience (reviewers 1 and 2) blinded to the patient history evaluated two series for each patient; one series contained a PA and lateral CXR whereas the second series contained a DTS of the chest. The series were randomly allocated with 4 weeks between each series to minimise recall bias. The time to report both series was recorded. For those patients with more than one lesion detected on their CXR and DTS only the most obvious abnormality that was initially raised as equivocal on their index CXR was analysed. All other incidental abnormalities were not included in the analysis. The readers were instructed to classify all intrapulmonary non-calcified peripheral nodules and hilar lesions as true lesions. Artefactual, calcified, pleural or extrapulmonary lesions were classified as false lesions as shown in Table 2. Readers were allowed to use processing tools such as windowing and zooming as they would in clinical practice. When there was a discrepancy amongst the readers, a third reader with 15 years experience was asked to arbitrate the findings. The CT images were analysed by a 4th radiologist with 6 years experience. 0.625 mm CT axial slices, 5 mm maximum intensity projection (MIP) axial, coronal and sagittal CT reformats were used to maximise lesion detection. The axial images were used to measure the largest diameter of the detected lesion for analysis. Coronal CT images were reconstructed for all lesions detected on CT and these were compared subjectively to the CXR and DTS findings. Any lesions detected on CXR and DTS were correlated with the reference standard CT into true positive and negative and false positive and
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Table 2 The classification of true and false lesions detected on CXR and DTS. The number of patients is shown in the parenthesis. CT was used as the reference method to determine the final diagnoses. n, number of lesions.
Intrapulmonary
True lesion (n)
False lesion (n)
Non-calcified peripheral nodule (22) Hilar nodule (7) Hilar mass (3) Hilar lymphadenopathy (1) Anterior mediastinal mass (1)
Granuloma (1) Pseudolesions hilar (19) Pseudolesions peripheral (18)
Extrapulmonary
Pleural plaque (3) Rib lesions (2) Nipple shadows (1)
negative lesions. A thoracic radiologist with 15 years experience arbitrated all equivocal lesions. 2.6. Statistical analysis Differences in the sensitivity and specificity were compared using McNemar’s tests, with a p-value of less than 0.05 considered to be a statistically significant. Subgroup analysis for non-calcified pulmonary nodules and hilar masses was performed. Inter-rater agreement for the two reviewers was assessed using kappa statistics. A kappa statistic of <0.4 was considered to be a fair agreement; 0.4–0.6 moderate; 0.6–0.8 good and >0.8 a very good agreement. All statistical analysis was conducted using the statistical programming language R [21]. 3. Results Seventy-eight patients were included in the study. There were 34 true lesions confirmed on CT, 12 were hilar lesions and 22 were peripheral nodules. Of the 44 false lesions, 37 lesions were artefactual or due to composite shadow and 7 lesions were real but extrapulmonary simulating non-calcified intrapulmonary lesions. Table 2 summarises the final diagnoses confirmed with CT. The repeat PA and lateral CXR correctly resolved 39/78 lesions (50%) whereas DTS resolved 75/78 lesions (96%). Graph 1 shows the percentage number of peripheral nodules, hilar masses and overall lesions resolved by CXR and DTS. The sensitivity for CXR and DTS was 0.65 and 0.91 respectively. This was statistically significant with a p-value of 0.0265. An example of a nodule that was detected on both modalities is shown in Fig. 1. The specificity of CXR and DTS was 0.39 and 1 respectively,
Table 3 Sensitivity and specificity for CXR and DTS. Confidence intervals are shown in brackets. CXR, chest radiograph including a PA and lateral; DTS, digital tomosynthesis. Variable (n = 78) Apparent prevalence True prevalence Sensitivity Specificity Positive predictive value Negative predictive value
CXR (95% CI) 0.63 (0.51, 0.74) 0.44 (0.32, 0.55) 0.65 (0.46, 0.8) 0.39 (0.24, 0.55) 0.45 (0.31, 0.6) 0.59 (0.39, 0.76)
DTS (95% CI) 0.4 (0.29, 0.51) 0.44 (0.32, 0.55) 0.91 (0.76, 0.98) 1 (0.88, 1) 1 (0.84, 1) 0.94 (0.82, 0.99)
this showed a clear statistical difference (p-value = <0.5). The sensitivity and specificity results for CXR and DTS are summarised in Table 3. Of the 39 lesions incorrectly classified on the PA and lateral CXR, 27 were classified as false positive lesions and 12 were false negative lesions. Examples of false positive and negative lesions on CXR are shown in Figs. 2 and 3. There were no false positive lesions with DTS but three true lesions where incorrectly classified as composite vascular pseudolesions. The incorrectly classified lesions on DTS include two hilar lung cancers and one peripheral carcinoid tumour (Fig. 4). Pseudolesions included composite shadows due to overlying ribs, vascular structures, cardiac fat pads and pulmonary scarring simulating a nodule. Of the 34 true lesions confirmed on CT, 15 were subsequently biopsy-proven lung cancers. Fourteen lesions remain indeterminate and are still being followed up with interval scans as per Fleischner Guidelines at the time of writing [22]. Five lesions were proven benign following biopsy and further imaging such as PET (Fig. 5). Eleven of the 15 cancers were detected on CXR and 12 with DTS. The missed cancers were located in the hila, the apices and the right mid-zone obscured by composite artefact afforded by the ribs and vascular structures. Fig. 4 is an example of a peripheral carcinoid cancer that was detected on CXR but although visible on DTS, was thought to represent composite vascular shadow. There were 32 suspected hilar lesions out of the 78 total lesions. Of these, 12 were true lesions confirmed on CT. Nineteen out of 32 (60%) and 30/32 (94%) were correctly classified on CXR and DTS respectively as shown in Graph 1. Eleven hilar lesions were overcalled on CXR and one lesion was missed. There were no false positives with DTS however 2 lesions were missed. Fig. 5 shows a left peri-hilar lesion that was missed on both CXR and DTS. The lesion can be seen on both modalities but is in a region of high anatomical noise. Analysis of inter-observer agreement for CXR resulted in kappa statistics of 0.41 for reviewers 1 and 2, suggesting moderate agreement between the reviewers, this improved to 0.83 for DTS for reviewers 1 and 2 suggesting very good agreement between the reviewers. The average time taken to report 78 PA and lateral CXR examinations was 64 and 67 s for reviewers 1 and 2 (range 30–150 s). The average time taken to report a DTS examination was 92 and 172 s for reviewers 1 and 2 respectively (range 45–400 s).
4. Discussion
Graph 1. This graph expressed as a percentage shows the number of lesions resolved by repeat PA and lateral CXR and DTS. There were 32 suspected hilar masses, 46 peripheral nodules and 78 lesions overall.
The aim of this study was to assess the clinical usefulness of DTS as an adjunct to CXR and instead of a repeat PA and lateral CXR for the detection of suspected but unconfirmed intrapulmonary and hilar lesions. Previous studies have demonstrated that DTS is superior to CXR for the detectability of pulmonary nodules [14,15,23] however these studies did not include hilar lesions. In this study DTS resolved the majority of suspected pulmonary nodules and hilar lesions with a clear improvement in specificity and inter-reader agreement when compared to a PA and lateral CXR. CT has a significantly better sensitivity than either CXR or
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Fig. 1. A 44-year-old gentleman was referred for a CXR due to a persistent cough. (a) The PA CXR shows an ill-defined opacity in the right lower zone. (b) The lateral CXR demonstrates a nodule below the hilum. (c) The DTS image confirms that the nodule is intrapulmonary. The nodule was FDG negative and did not change over a period of 18 months and is most likely in keeping with a benign hamartoma.
Fig. 2. A 58-year-old gentleman presented with a 4-week history of a cough. (a) The CXR shows 2 ill-defined nodules. The lesion marked 1 was detected on the initial CXR, lesion 2 was an incidental finding. (b) The DTS image shows lesion 1 is not intrapulmonary and is in keeping with a sclerotic focus within the 4th anterior rib. (c) DTS image with the anterior pleura in focus demonstrates lesion 2 is in keeping with a subpleural nodule.
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Fig. 3. A 65-year-old gentleman was referred for a CXR due to shortness of breath. (a) The CXR shows a prominent right hilum. (b) The DTS image was acquired on the same day as the CXR and demonstrates right hilar and tracheobronchial nodularity in keeping with sarcoidosis.
DTS and its role in the evaluation of an unequivocally abnormal radiograph is well established and not challenged by DTS. The specificities for CXR and DTS were 39% and 100% respectively in our study. Quaia et al. have reported similar specificities of 13–36% and 90–95% for CXR and DTS respectively in patients with suspected pulmonary lesions [24–26]. These results demonstrate that the specificity of DTS is similar to CT in this pre-selected group of patients. This suggests that the true value of DTS lies in its negative predictive value, or rather in its ability to exclude a suspected lesion. DTS classified 47 out of the 78 suspected
lesions as false. Before DTS was introduced, these 47 patients would have been referred for a CT chest in our institution in view of the equivocal CXR findings. Only 3/47 lesions were positive, therefore we could infer that by including DTS in the patient pathway we can avoid 47 CT scans (60%) in this cohort of patients with many advantages not least a reduction in patient ionisation dose. However, a further 27 incidental lesions were detected in the 47 patients on DTS and therefore some of these patients may require a CT for further evaluation of these incidental lesions.
Fig. 4. A 55-year-old lady was referred for a CXR due to right pleuritic chest pain. The nodule in the right cardiophrenic angle was detected on CXR but missed on DTS. (a, b) CXR and DTS images demonstrate the right cardiophrenic angle nodule. (c) The axial CT with fused PET image demonstrates mild tracer uptake in the nodule. The patient had a lobectomy and the histology was in keeping with carcinoid tumour.
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Fig. 5. A 66-year-old lady was a heavy smoker. She was referred by her GP for a CXR in view of a hoarse voice. (a) The CXR shows an ill-defined left perihilar lesion that was missed on CXR. (b) The DTS image again demonstrates the mass abutting the descending thoracic aorta. This was detected by one reviewer but was thought to represent composite vascular shadow by a third radiologist who arbitrated the finding. (c) The axial CT with fused PET demonstrates an active metabolic tumour in this region. This was biopsy-proven non-small cell lung cancer.
The evaluation of the lung hila is a challenging task for thoracic radiologists. In a UK audit assessing the retrospective diagnosis of missed lung cancer on 4452 chest radiographs, hilar lesions accounted for most of the misses with 42% of missed lung cancers located in the lung hila [27]. Ten of the 12 hilar lesions were detected with DTS and there were no false positives with DTS when compared to 11 with CXR. To our knowledge, this is the first study to assess the accuracy of DTS for suspected hilar lesions. These results suggest that detection of hilar lesions is not improved with DTS however DTS is more specific. Our numbers are small, however, we can infer that the role of DTS lies with problem-solving rather than detecting an abnormal lung hilum on CXR. DTS is unlikely to be adopted as an alternative to CXR for all but a few pre-selected patient populations. DTS has been evaluated in several pre-selected patient groups: in patients with known lung nodules the detection rate of CXR and DTS respectively has been shown to lie between 16–22% and 56–70% [14,23]; in the followup of patients with colorectal cancer the detection rate of lung nodules with DTS was higher at 87% however calcified granulomas were included as positive lesions in this study and this may have increased the detection rate [10]; Terzi et al. are evaluating the role of DTS as a screening tool for lung cancer in smokers [28]. The sensitivity for DTS in our study was 91% and this compares well with 85–95% [24,25] quoted in the literature in a similar patient group. These results infer that DTS has the best value in patients with suspected but unconfirmed pulmonary lesions. DTS is not without disadvantages, the hardware is more expensive [29] and while reporting time, though short, is twice that of CXR (average reporting times of 134 vs. 64 s respectively). The ionisation dose of DTS (0.15 mSv) is a fraction of the dose of a CT chest (4 mSv). Furthermore, DTS is a relatively new technique and there is potential for further dose optimisation. Hwang et al. [30] described a low dose setting for tomosynthesis resulting in a dose reduction of 67%. This reduction in dose produces an effective dose similar to that of a two-view CXR (PA and lateral). Further reduction in dose for DTS using techniques such as adaptive statistical reconstruction (ASIR) is possible in the future.
5. Conclusion In this study we have evaluated the role of DTS as a problem-solving tool for patients with suspected but unconfirmed pulmonary nodules or hilar lesions on their CXR. The low radiation dose for digital tomosynthesis and the relatively short time taken to report a DTS make it an attractive alternative to a repeat PA and lateral chest radiograph. DTS demonstrates clear improvements in sensitivity, inter-reader agreement and specificity when compared to PA and lateral CXR for the evaluation of the equivocal CXR. We propose that DTS can be used instead of a repeat PA and lateral CXR to problem-solve an equivocal CXR in patients with a low index of suspicion of a lung nodule or hilar lesion. Whilst DTS can exclude most peripheral lesions it is less accurate for hilar lesions and further studies are needed. Conflicts of interest The authors have no conflicts of interest and no disclosures. References [1] Kaneko M, Eguchi K, Ohmatsu H, Kakinuma R, Naruke T, Suemasu K, et al. Peripheral lung cancer: screening and detection with low-dose spiral CT versus radiography. Radiology 1996;201(3):798–802. [2] Alberg AJ, Ford JG, Samet JM. Epidemiology of lung cancer: ACCP evidencebased clinical practice guidelines, 2nd ed. Chest 2007;132(Suppl. 3):29S–55S. [3] WHO. WHO fact sheet. World Heal. Organ. Website. [4] Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D. Global cancer statistics: 2011. CA Cancer J Clin 2011;61(2):69–90. Available from http://www.ncbi.nlm.nih.gov/pubmed/21296855 [5] Aberle DR, Adams AM, Berg CD, Black WC, Clapp JD, Fagerstrom RM, et al. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med 2011;365(5):395–409. [6] Yamada Y, Jinzaki M, Hashimoto M, Shiomi E, Abe T, Kuribayashi S, et al. Tomosynthesis for the early detection of pulmonary emphysema: diagnostic performance compared with chest radiography, using multidetector computed tomography as reference. Eur Radiol 2013;23(8):2118–26. Available from http://www.ncbi.nlm.nih.gov/pubmed/23515916 [7] Dobbins JT, Mcadams HP, Godfrey DJ, Li CM. Digital tomosynthesis of the chest. Imaging 2008;23(2):86–92.
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[8] Chen S, Zhao Z, Li J, Zhu W, Peng R. Assessment on the detectability of noncalcified pulmonary nodules with chest digital tomosynthesis. Chin J Med Imaging Technol 2011;27/11:1003–3289. [9] Kim EY, Chung MJ, Lee HY, Koh W-J, Jung HN, Lee KS. Pulmonary mycobacterial disease: diagnostic performance of low-dose digital tomosynthesis as compared with chest radiography. Radiology 2010;257(1):269–77. Available from http://www.ncbi.nlm.nih.gov/pubmed/20851944 [10] Jung HN, Chung MJ, Koo JH, Kim HC, Lee KS. Digital tomosynthesis of the chest: utility for detection of lung metastasis in patients with colorectal cancer. Clin Radiol 2011:1–7, http://dx.doi.org/10.1016/j.crad.2011.08.017. [11] Vikgren J, Zachrisson S, Svalkvist A, Johnsson AA, Boijsen M, Flinck A, et al. Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases. Radiology 2008;249(3):1034–41. Available from http://www.ncbi.nlm.nih.gov/ pubmed/18849504 [12] Galea A, Durran A, Adlan T, Gay D, Riordan R, Dubbins P, et al. Practical applications of digital tomosynthesis of the chest. Clin Radiol 2013;(December):1–7. Available from http://www.ncbi.nlm.nih.gov/pubmed/24333001 [accessed 18.01.14]. [13] Lee G, Jeong YJ, Kim KI, Song JW, Kang DM, Kim YD, et al. Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease. Clin Radiol 2012;68(4):376–82. [14] Dobbins JT, McAdams HP, Song J-W, Li CM, Godfrey DJ, DeLong DM, et al. Digital tomosynthesis of the chest for lung nodule detection: interim sensitivity results from an ongoing NIH-sponsored trial. Med Phys 2008;35(6):2554. Available from http://link.aip.org/link/MPHYA6/v35/i6/p2554/s1&Agg=doi [accessed 04.01.11]. [15] Jung HN, Chung MJ, Koo JH, Kim HC, Lee KS. Digital tomosynthesis of the chest: utility for detection of lung metastasis in patients with colorectal cancer. Clin Radiol 2012;67(March (3)):232–8. Available from http://www.ncbi.nlm.nih.gov/pubmed/21939964 [accessed 21.02.14]. [16] Vikgren J, Zachrisson S, Svalkvist A, Johnsson AA, Boijsen M, Flinck A, Kheddache S, Båth M. Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases. Radiology 2008;249(3):1034–41. [17] European Commission. European guidelines on quality criteria for computed tomography. Rep Eur 1999. Available from http://scholar.google.com/ scholar?hl=en&btnG=Search&q=intitle:European+guidelines+on+quiality+ criteria+for+computed+tomography#0 [accessed 02.02.14]. [18] Hansell DM, Bankier AA, MacMahon H, McLoud TC, Müller NL, Remy J. Fleischner Society: glossary of terms for thoracic imaging. Radiology 2008;246(3):697–722.
[19] Lavender JP, Doppman J. The hilum in pulmonary venous hypertension. Br J Radiol 1962;35(May):303–13. Available from http://www.ncbi.nlm.nih. gov/pubmed/14462916 [20] Felson B. Chest roentgenology. Saunders; 1973. p. 183 [chapter 5]. [21] R Core Team. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2013. Available from http://www.r-project.org/ [22] MacMahon H, Austin JHM, Gamsu G, Herold CJ, Jett JR, Naidich DP, et al. Guidelines for management of small pulmonary nodules detected on CT scans: a statement from the Fleischner Society. Radiology 2005: 395–400. [23] Vikgren J. Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases. Radiology 2008;249(3). [24] Quaia E, Baratella E, Poillucci G, Kus S, Cioffi V, Cova MA. Digital tomosynthesis as a problem-solving imaging technique to confirm or exclude potential thoracic lesions based on chest X-ray radiography. Acad Radiol 2013;20(May (5)):546–53. Available from: http://www.ncbi.nlm.nih.gov/pubmed/23473723 [accessed 0.02.14]. [25] Quaia E, Baratella E, Cioffi V, Bregant P, Cernic S, Cuttin R, et al. The value of digital tomosynthesis in the diagnosis of suspected pulmonary lesions on chest radiography: analysis of diagnostic accuracy and confidence. Acad Radiol 2010;17(10):1267–74. Available from http://www.ncbi. nlm.nih.gov/pubmed/20591695 [26] Quaia E, Baratella E, Cernic S, Lorusso A, Casagrande F, Cioffi V, et al. Analysis of the impact of digital tomosynthesis on the radiological investigation of patients with suspected pulmonary lesions on chest radiography. Eur Radiol 2012:1912–22. [27] Anbu Nedumaran P, Duncan K, Warwick R. National audit of diagnosis of lung cancer on chest radiography; 2005. Available from http://www.rcr. ac.uk/audittemplate.aspx?PageID=1020&AuditTemplateID=108 [28] Terzi A, Bertolaccini L, Viti A, Comello L, Ghirardo D, Priotto R, Grosso M. Lung cancer detection with digital chest tomosynthesis: baseline results from the observational study SOS. J Thorac Oncol 2013;8(6):685–92. [29] Vlahos I. Commentary on: comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease. Clin Radiol 2013;68(4):336–7, http://dx.doi.org/10.1016/j.crad.2012.09.006. [30] Hwang HS, Chung MJ, Lee KS. Digital tomosynthesis of the chest: comparison of patient exposure dose and image quality between standard default setting and low dose setting. Korean J Radiol 2013;14(May (3)):525–31. Available from http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3655311&tool= pmcentrez&rendertype=abstract
Contents lists available at ScienceDirect
European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad
The value of digital tomosynthesis of the chest as a problem-solving tool for suspected pulmonary nodules and hilar lesions detected on chest radiography Angela Galea a,∗ , Paul Dubbins b,1 , Richard Riordan b,1 , Tarig Adlan b,1 , Carl Roobottom b,1 , David Gay b,1 a b
Peninsula Radiology Academy, William Prance Road, Plymouth PL65WR, UK Plymouth Hospital NHS Trust, Plymouth PL68DH, UK
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Article history: Received 2 June 2014 Received in revised form 28 November 2014 Accepted 9 February 2015 Keywords: Digital tomosynthesis Chest radiology Lung nodules Hilar lesions
a b s t r a c t Objectives: To assess the capability of digital tomosynthesis (DTS) of the chest compared to a posteroanterior (PA) and lateral chest radiograph (CXR) in the diagnosis of suspected but unconfirmed pulmonary nodules and hilar lesions detected on a CXR. Computed tomography (CT) was used as the reference standard. Materials and method: 78 patients with suspected non-calcified pulmonary nodules or hilar lesions on their CXR were included in the study. Two radiologists, blinded to the history and CT, prospectively analysed the CXR (PA and lateral) and the DTS images using a picture archiving and communication workstation and were asked to designate one of two outcomes: true intrapulmonary lesion or false intrapulmonary lesion. A CT of the chest performed within 4 weeks of the CXR was used as the reference standard. Inter-observer agreement and time to report the modalities were calculated for CXR and DTS. Results: There were 34 true lesions confirmed on CT, 12 were hilar lesions and 22 were peripheral nodules. Of the 44 false lesions, 37 lesions were artefactual or due to composite shadow and 7 lesions were real but extrapulmonary simulating non-calcified intrapulmonary lesions. The PA and lateral CXR correctly classified 39/78 (50%) of the lesions, this improved to 75/78 (96%) with DTS. The sensitivity and specificity was 0.65 and 0.39 for CXR and 0.91 and 1 for DTS. Based on the DTS images, readers correctly classified all the false lesions but missed 3/34 true lesions. Two of the missed lesions were hilar in location and one was a peripheral nodule. All three missed lesions were incorrectly classified on DTS as composite shadow. Conclusions: DTS improves diagnostic confidence when compared to a repeat PA and lateral CXR in the diagnosis of both suspected hilar lesions and pulmonary nodules detected on CXR. DTS is able to exclude most peripheral pulmonary nodules but caution and further studies are needed to assess its ability to exclude hilar lesions. © 2015 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Despite the inferior performance of chest radiography (CXR) to computed tomography (CT) scanning it remains the initial examination for the majority of pulmonary disease due to its low cost, easy access and low radiation dose. Obvious pulmonary lesions
∗ Corresponding author. Tel.: +44 7800511681. E-mail addresses: [email protected] (A. Galea), [email protected] (P. Dubbins), [email protected] (R. Riordan), [email protected] (T. Adlan), [email protected] (C. Roobottom), [email protected] (D. Gay). 1 Tel.: +44 1752437437. http://dx.doi.org/10.1016/j.ejrad.2015.02.007 0720-048X/© 2015 Elsevier Ireland Ltd. All rights reserved.
detected on CXR clearly need further investigation and CT scanning is recommended. Chest radiography however has a low sensitivity and specificity for the detection of early lung cancer [1]. Lung cancer is the leading cause of cancer globally and is associated with poor outcome [2–4]. However the 2011 US National Lung Screening Trial demonstrated that early detection reduces mortality and emphasizes the need to detect early cancer [5]. Small pulmonary nodules carry a low risk of lung cancer but may require further investigation and often patients with lung nodules undergo CT scanning for evaluation. Alternative investigations, without the high cost or radiation dose of CT scanning that offer increased accuracy in pulmonary and hilar lesions suspicious for cancer would be useful in the investigation of pulmonary disease.
A. Galea et al. / European Journal of Radiology 84 (2015) 1012–1018 Table 1 The various indications for referral for a chest radiograph. Some patients were referred for more than one symptom. Indication
In-patient N = number of patients
Out-patient N = number of patients
Cough Shortness of breath Chest pain Infection Arrythmia Other (e.g. weight loss, arthritis)
3 3 4 1 2 4
29 21 8 3 2 10
A radiologist will frequently identify a small group of CXRs that are equivocal either because of an inability to correctly characterise a visualised abnormality as soft tissue or calcified and therefore likely benign or an inability to determine the location of the lesion as intra- or extrapulmonary. The radiologist may be unsure whether a lesion is real or composite especially if it lies in a region of heavy anatomical noise such as the lung hila or apices. Patients with equivocal CXRs due to one of the above findings were included in the study to assess the role of digital tomosynthesis (DTS) in confirming or excluding a potentially significant abnormality. DTS is a type of limited angle tomography whereby about sixty low dose images are acquired over a limited range of X-ray tube movement in the cranio-caudal axis. The raw images are used to reconstruct contiguous coronal images in the antero-posterior axis through the area of interest. Tomosynthesis evolved from the technique of tomography, which was used to evaluate, inter alia the lung hila, the kidneys and the petrous temporal bones. Increasing concern about the patient dose from CT has resulted in a resurgence of interest in tomographic techniques such as tomosynthesis because of the associated low radiation dose. Digital tomosynthesis reduces composite artefact due to anatomical noise by providing better depth resolution thus separating the structures in the antero-posterior dimension. DTS can correctly differentiate between lesions of the rib cage, pleurally based lesions and intrapulmonary lesions [6–13]. Improved contrast resolution of DTS when compared to CXR results in better calcium detection [13]. Advantages when compared to CT relate to cost and dose reduction. The role of DTS in the evaluation of pulmonary nodules has been explored in previous studies [14–16]. In this study we chose a more pragmatic approach by assessing both non-calcified intrapulmonary nodules and hilar masses using CT as the gold standard. The purpose of this study is to assess whether DTS can be used instead of a repeat PA and lateral chest radiograph in the evaluation of an equivocal chest radiograph. 2. Method 2.1. Patients The study was approved by the regional ethics committee. This was a single centre, prospective observational study. All inpatients and outpatients with an equivocal finding on chest radiograph were included. The indications for the initial chest radiograph were varied so as to simulate clinical practice and are shown in Table 1. All patients included in the study consented to have a repeat PA and lateral CXR, a DTS and a CT chest within 4 weeks of their initial CXR. 2.2. Digital tomosynthesis A General Electric (GE, Buc, France) VolumeRAD system with a high-quality digital detector with rapid read-out was used, which relies on the GE Definium 8000 digital X-ray system to acquire the
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projection images necessary for tomosynthesis reconstruction. A scout image of the chest is first obtained to confirm a correct position. The patient is then instructed to hold his/her breath for 10 s whilst 60 discrete images are acquired over an angular range of 35◦ to produce 50–60 coronal reconstructions of the chest. The tube voltage was set at 120 kVp. Each raw image delivers an average effective dose of 2 Sv resulting in a cumulative effective dose of 0.15 mSv for the average 70 kg male patient (this effective dose includes both the scout and raw images). 2.3. Computed tomography The CT examinations were performed using a 64 slice multidetector (HD750, GE Healthcare) scanner. The scan parameters used were: a set noise index of 39.68; 120 kV and a range of 100–750 mA. The CT slice thickness was 0.625 mm for all patients. The effective dose (based on an unenhanced scan) was calculated using a conversion factor from dose–length product (DLP) to E (EDLP ) of 0.017 mSv/(mGy cm) and was 4 mSv[17]. Thirty-two patients with suspected hilar lesions were scanned following an additional 100 mL intravenous bolus injection of iodinated contrast at a rate of 3.5 mL/s. All other patients had an unenhanced scan of the chest. 2.4. Image interpretation A nodule was defined according to the Fleischner Society Glossary of Terms as a rounded opacity, well or poorly defined measuring up to 3 cm in diameter [18]. A hilar lesion for the purpose of this study was defined as a lesion of any size but within 3 cm of the hilar point measured in the coronal/antero-posterior (AP) direction. Hilar lesions included hilar carcinomas, lung nodules within 3 cm of the hilar point and hilar adenopathy. The hilar point is formed as the descending superior pulmonary vein crosses anterior to the interlobar pulmonary artery [19,20]. 2.5. Data analysis Three radiologists with 30, 15 and 10 years experience participated in the study. Two radiologists with 30 and 10 years experience (reviewers 1 and 2) blinded to the patient history evaluated two series for each patient; one series contained a PA and lateral CXR whereas the second series contained a DTS of the chest. The series were randomly allocated with 4 weeks between each series to minimise recall bias. The time to report both series was recorded. For those patients with more than one lesion detected on their CXR and DTS only the most obvious abnormality that was initially raised as equivocal on their index CXR was analysed. All other incidental abnormalities were not included in the analysis. The readers were instructed to classify all intrapulmonary non-calcified peripheral nodules and hilar lesions as true lesions. Artefactual, calcified, pleural or extrapulmonary lesions were classified as false lesions as shown in Table 2. Readers were allowed to use processing tools such as windowing and zooming as they would in clinical practice. When there was a discrepancy amongst the readers, a third reader with 15 years experience was asked to arbitrate the findings. The CT images were analysed by a 4th radiologist with 6 years experience. 0.625 mm CT axial slices, 5 mm maximum intensity projection (MIP) axial, coronal and sagittal CT reformats were used to maximise lesion detection. The axial images were used to measure the largest diameter of the detected lesion for analysis. Coronal CT images were reconstructed for all lesions detected on CT and these were compared subjectively to the CXR and DTS findings. Any lesions detected on CXR and DTS were correlated with the reference standard CT into true positive and negative and false positive and
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Table 2 The classification of true and false lesions detected on CXR and DTS. The number of patients is shown in the parenthesis. CT was used as the reference method to determine the final diagnoses. n, number of lesions.
Intrapulmonary
True lesion (n)
False lesion (n)
Non-calcified peripheral nodule (22) Hilar nodule (7) Hilar mass (3) Hilar lymphadenopathy (1) Anterior mediastinal mass (1)
Granuloma (1) Pseudolesions hilar (19) Pseudolesions peripheral (18)
Extrapulmonary
Pleural plaque (3) Rib lesions (2) Nipple shadows (1)
negative lesions. A thoracic radiologist with 15 years experience arbitrated all equivocal lesions. 2.6. Statistical analysis Differences in the sensitivity and specificity were compared using McNemar’s tests, with a p-value of less than 0.05 considered to be a statistically significant. Subgroup analysis for non-calcified pulmonary nodules and hilar masses was performed. Inter-rater agreement for the two reviewers was assessed using kappa statistics. A kappa statistic of <0.4 was considered to be a fair agreement; 0.4–0.6 moderate; 0.6–0.8 good and >0.8 a very good agreement. All statistical analysis was conducted using the statistical programming language R [21]. 3. Results Seventy-eight patients were included in the study. There were 34 true lesions confirmed on CT, 12 were hilar lesions and 22 were peripheral nodules. Of the 44 false lesions, 37 lesions were artefactual or due to composite shadow and 7 lesions were real but extrapulmonary simulating non-calcified intrapulmonary lesions. Table 2 summarises the final diagnoses confirmed with CT. The repeat PA and lateral CXR correctly resolved 39/78 lesions (50%) whereas DTS resolved 75/78 lesions (96%). Graph 1 shows the percentage number of peripheral nodules, hilar masses and overall lesions resolved by CXR and DTS. The sensitivity for CXR and DTS was 0.65 and 0.91 respectively. This was statistically significant with a p-value of 0.0265. An example of a nodule that was detected on both modalities is shown in Fig. 1. The specificity of CXR and DTS was 0.39 and 1 respectively,
Table 3 Sensitivity and specificity for CXR and DTS. Confidence intervals are shown in brackets. CXR, chest radiograph including a PA and lateral; DTS, digital tomosynthesis. Variable (n = 78) Apparent prevalence True prevalence Sensitivity Specificity Positive predictive value Negative predictive value
CXR (95% CI) 0.63 (0.51, 0.74) 0.44 (0.32, 0.55) 0.65 (0.46, 0.8) 0.39 (0.24, 0.55) 0.45 (0.31, 0.6) 0.59 (0.39, 0.76)
DTS (95% CI) 0.4 (0.29, 0.51) 0.44 (0.32, 0.55) 0.91 (0.76, 0.98) 1 (0.88, 1) 1 (0.84, 1) 0.94 (0.82, 0.99)
this showed a clear statistical difference (p-value = <0.5). The sensitivity and specificity results for CXR and DTS are summarised in Table 3. Of the 39 lesions incorrectly classified on the PA and lateral CXR, 27 were classified as false positive lesions and 12 were false negative lesions. Examples of false positive and negative lesions on CXR are shown in Figs. 2 and 3. There were no false positive lesions with DTS but three true lesions where incorrectly classified as composite vascular pseudolesions. The incorrectly classified lesions on DTS include two hilar lung cancers and one peripheral carcinoid tumour (Fig. 4). Pseudolesions included composite shadows due to overlying ribs, vascular structures, cardiac fat pads and pulmonary scarring simulating a nodule. Of the 34 true lesions confirmed on CT, 15 were subsequently biopsy-proven lung cancers. Fourteen lesions remain indeterminate and are still being followed up with interval scans as per Fleischner Guidelines at the time of writing [22]. Five lesions were proven benign following biopsy and further imaging such as PET (Fig. 5). Eleven of the 15 cancers were detected on CXR and 12 with DTS. The missed cancers were located in the hila, the apices and the right mid-zone obscured by composite artefact afforded by the ribs and vascular structures. Fig. 4 is an example of a peripheral carcinoid cancer that was detected on CXR but although visible on DTS, was thought to represent composite vascular shadow. There were 32 suspected hilar lesions out of the 78 total lesions. Of these, 12 were true lesions confirmed on CT. Nineteen out of 32 (60%) and 30/32 (94%) were correctly classified on CXR and DTS respectively as shown in Graph 1. Eleven hilar lesions were overcalled on CXR and one lesion was missed. There were no false positives with DTS however 2 lesions were missed. Fig. 5 shows a left peri-hilar lesion that was missed on both CXR and DTS. The lesion can be seen on both modalities but is in a region of high anatomical noise. Analysis of inter-observer agreement for CXR resulted in kappa statistics of 0.41 for reviewers 1 and 2, suggesting moderate agreement between the reviewers, this improved to 0.83 for DTS for reviewers 1 and 2 suggesting very good agreement between the reviewers. The average time taken to report 78 PA and lateral CXR examinations was 64 and 67 s for reviewers 1 and 2 (range 30–150 s). The average time taken to report a DTS examination was 92 and 172 s for reviewers 1 and 2 respectively (range 45–400 s).
4. Discussion
Graph 1. This graph expressed as a percentage shows the number of lesions resolved by repeat PA and lateral CXR and DTS. There were 32 suspected hilar masses, 46 peripheral nodules and 78 lesions overall.
The aim of this study was to assess the clinical usefulness of DTS as an adjunct to CXR and instead of a repeat PA and lateral CXR for the detection of suspected but unconfirmed intrapulmonary and hilar lesions. Previous studies have demonstrated that DTS is superior to CXR for the detectability of pulmonary nodules [14,15,23] however these studies did not include hilar lesions. In this study DTS resolved the majority of suspected pulmonary nodules and hilar lesions with a clear improvement in specificity and inter-reader agreement when compared to a PA and lateral CXR. CT has a significantly better sensitivity than either CXR or
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Fig. 1. A 44-year-old gentleman was referred for a CXR due to a persistent cough. (a) The PA CXR shows an ill-defined opacity in the right lower zone. (b) The lateral CXR demonstrates a nodule below the hilum. (c) The DTS image confirms that the nodule is intrapulmonary. The nodule was FDG negative and did not change over a period of 18 months and is most likely in keeping with a benign hamartoma.
Fig. 2. A 58-year-old gentleman presented with a 4-week history of a cough. (a) The CXR shows 2 ill-defined nodules. The lesion marked 1 was detected on the initial CXR, lesion 2 was an incidental finding. (b) The DTS image shows lesion 1 is not intrapulmonary and is in keeping with a sclerotic focus within the 4th anterior rib. (c) DTS image with the anterior pleura in focus demonstrates lesion 2 is in keeping with a subpleural nodule.
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Fig. 3. A 65-year-old gentleman was referred for a CXR due to shortness of breath. (a) The CXR shows a prominent right hilum. (b) The DTS image was acquired on the same day as the CXR and demonstrates right hilar and tracheobronchial nodularity in keeping with sarcoidosis.
DTS and its role in the evaluation of an unequivocally abnormal radiograph is well established and not challenged by DTS. The specificities for CXR and DTS were 39% and 100% respectively in our study. Quaia et al. have reported similar specificities of 13–36% and 90–95% for CXR and DTS respectively in patients with suspected pulmonary lesions [24–26]. These results demonstrate that the specificity of DTS is similar to CT in this pre-selected group of patients. This suggests that the true value of DTS lies in its negative predictive value, or rather in its ability to exclude a suspected lesion. DTS classified 47 out of the 78 suspected
lesions as false. Before DTS was introduced, these 47 patients would have been referred for a CT chest in our institution in view of the equivocal CXR findings. Only 3/47 lesions were positive, therefore we could infer that by including DTS in the patient pathway we can avoid 47 CT scans (60%) in this cohort of patients with many advantages not least a reduction in patient ionisation dose. However, a further 27 incidental lesions were detected in the 47 patients on DTS and therefore some of these patients may require a CT for further evaluation of these incidental lesions.
Fig. 4. A 55-year-old lady was referred for a CXR due to right pleuritic chest pain. The nodule in the right cardiophrenic angle was detected on CXR but missed on DTS. (a, b) CXR and DTS images demonstrate the right cardiophrenic angle nodule. (c) The axial CT with fused PET image demonstrates mild tracer uptake in the nodule. The patient had a lobectomy and the histology was in keeping with carcinoid tumour.
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Fig. 5. A 66-year-old lady was a heavy smoker. She was referred by her GP for a CXR in view of a hoarse voice. (a) The CXR shows an ill-defined left perihilar lesion that was missed on CXR. (b) The DTS image again demonstrates the mass abutting the descending thoracic aorta. This was detected by one reviewer but was thought to represent composite vascular shadow by a third radiologist who arbitrated the finding. (c) The axial CT with fused PET demonstrates an active metabolic tumour in this region. This was biopsy-proven non-small cell lung cancer.
The evaluation of the lung hila is a challenging task for thoracic radiologists. In a UK audit assessing the retrospective diagnosis of missed lung cancer on 4452 chest radiographs, hilar lesions accounted for most of the misses with 42% of missed lung cancers located in the lung hila [27]. Ten of the 12 hilar lesions were detected with DTS and there were no false positives with DTS when compared to 11 with CXR. To our knowledge, this is the first study to assess the accuracy of DTS for suspected hilar lesions. These results suggest that detection of hilar lesions is not improved with DTS however DTS is more specific. Our numbers are small, however, we can infer that the role of DTS lies with problem-solving rather than detecting an abnormal lung hilum on CXR. DTS is unlikely to be adopted as an alternative to CXR for all but a few pre-selected patient populations. DTS has been evaluated in several pre-selected patient groups: in patients with known lung nodules the detection rate of CXR and DTS respectively has been shown to lie between 16–22% and 56–70% [14,23]; in the followup of patients with colorectal cancer the detection rate of lung nodules with DTS was higher at 87% however calcified granulomas were included as positive lesions in this study and this may have increased the detection rate [10]; Terzi et al. are evaluating the role of DTS as a screening tool for lung cancer in smokers [28]. The sensitivity for DTS in our study was 91% and this compares well with 85–95% [24,25] quoted in the literature in a similar patient group. These results infer that DTS has the best value in patients with suspected but unconfirmed pulmonary lesions. DTS is not without disadvantages, the hardware is more expensive [29] and while reporting time, though short, is twice that of CXR (average reporting times of 134 vs. 64 s respectively). The ionisation dose of DTS (0.15 mSv) is a fraction of the dose of a CT chest (4 mSv). Furthermore, DTS is a relatively new technique and there is potential for further dose optimisation. Hwang et al. [30] described a low dose setting for tomosynthesis resulting in a dose reduction of 67%. This reduction in dose produces an effective dose similar to that of a two-view CXR (PA and lateral). Further reduction in dose for DTS using techniques such as adaptive statistical reconstruction (ASIR) is possible in the future.
5. Conclusion In this study we have evaluated the role of DTS as a problem-solving tool for patients with suspected but unconfirmed pulmonary nodules or hilar lesions on their CXR. The low radiation dose for digital tomosynthesis and the relatively short time taken to report a DTS make it an attractive alternative to a repeat PA and lateral chest radiograph. DTS demonstrates clear improvements in sensitivity, inter-reader agreement and specificity when compared to PA and lateral CXR for the evaluation of the equivocal CXR. We propose that DTS can be used instead of a repeat PA and lateral CXR to problem-solve an equivocal CXR in patients with a low index of suspicion of a lung nodule or hilar lesion. Whilst DTS can exclude most peripheral lesions it is less accurate for hilar lesions and further studies are needed. Conflicts of interest The authors have no conflicts of interest and no disclosures. References [1] Kaneko M, Eguchi K, Ohmatsu H, Kakinuma R, Naruke T, Suemasu K, et al. Peripheral lung cancer: screening and detection with low-dose spiral CT versus radiography. Radiology 1996;201(3):798–802. [2] Alberg AJ, Ford JG, Samet JM. Epidemiology of lung cancer: ACCP evidencebased clinical practice guidelines, 2nd ed. Chest 2007;132(Suppl. 3):29S–55S. [3] WHO. WHO fact sheet. World Heal. Organ. Website. [4] Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D. Global cancer statistics: 2011. CA Cancer J Clin 2011;61(2):69–90. Available from http://www.ncbi.nlm.nih.gov/pubmed/21296855 [5] Aberle DR, Adams AM, Berg CD, Black WC, Clapp JD, Fagerstrom RM, et al. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med 2011;365(5):395–409. [6] Yamada Y, Jinzaki M, Hashimoto M, Shiomi E, Abe T, Kuribayashi S, et al. Tomosynthesis for the early detection of pulmonary emphysema: diagnostic performance compared with chest radiography, using multidetector computed tomography as reference. Eur Radiol 2013;23(8):2118–26. Available from http://www.ncbi.nlm.nih.gov/pubmed/23515916 [7] Dobbins JT, Mcadams HP, Godfrey DJ, Li CM. Digital tomosynthesis of the chest. Imaging 2008;23(2):86–92.
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[8] Chen S, Zhao Z, Li J, Zhu W, Peng R. Assessment on the detectability of noncalcified pulmonary nodules with chest digital tomosynthesis. Chin J Med Imaging Technol 2011;27/11:1003–3289. [9] Kim EY, Chung MJ, Lee HY, Koh W-J, Jung HN, Lee KS. Pulmonary mycobacterial disease: diagnostic performance of low-dose digital tomosynthesis as compared with chest radiography. Radiology 2010;257(1):269–77. Available from http://www.ncbi.nlm.nih.gov/pubmed/20851944 [10] Jung HN, Chung MJ, Koo JH, Kim HC, Lee KS. Digital tomosynthesis of the chest: utility for detection of lung metastasis in patients with colorectal cancer. Clin Radiol 2011:1–7, http://dx.doi.org/10.1016/j.crad.2011.08.017. [11] Vikgren J, Zachrisson S, Svalkvist A, Johnsson AA, Boijsen M, Flinck A, et al. Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases. Radiology 2008;249(3):1034–41. Available from http://www.ncbi.nlm.nih.gov/ pubmed/18849504 [12] Galea A, Durran A, Adlan T, Gay D, Riordan R, Dubbins P, et al. Practical applications of digital tomosynthesis of the chest. Clin Radiol 2013;(December):1–7. Available from http://www.ncbi.nlm.nih.gov/pubmed/24333001 [accessed 18.01.14]. [13] Lee G, Jeong YJ, Kim KI, Song JW, Kang DM, Kim YD, et al. Comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease. Clin Radiol 2012;68(4):376–82. [14] Dobbins JT, McAdams HP, Song J-W, Li CM, Godfrey DJ, DeLong DM, et al. Digital tomosynthesis of the chest for lung nodule detection: interim sensitivity results from an ongoing NIH-sponsored trial. Med Phys 2008;35(6):2554. Available from http://link.aip.org/link/MPHYA6/v35/i6/p2554/s1&Agg=doi [accessed 04.01.11]. [15] Jung HN, Chung MJ, Koo JH, Kim HC, Lee KS. Digital tomosynthesis of the chest: utility for detection of lung metastasis in patients with colorectal cancer. Clin Radiol 2012;67(March (3)):232–8. Available from http://www.ncbi.nlm.nih.gov/pubmed/21939964 [accessed 21.02.14]. [16] Vikgren J, Zachrisson S, Svalkvist A, Johnsson AA, Boijsen M, Flinck A, Kheddache S, Båth M. Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases. Radiology 2008;249(3):1034–41. [17] European Commission. European guidelines on quality criteria for computed tomography. Rep Eur 1999. Available from http://scholar.google.com/ scholar?hl=en&btnG=Search&q=intitle:European+guidelines+on+quiality+ criteria+for+computed+tomography#0 [accessed 02.02.14]. [18] Hansell DM, Bankier AA, MacMahon H, McLoud TC, Müller NL, Remy J. Fleischner Society: glossary of terms for thoracic imaging. Radiology 2008;246(3):697–722.
[19] Lavender JP, Doppman J. The hilum in pulmonary venous hypertension. Br J Radiol 1962;35(May):303–13. Available from http://www.ncbi.nlm.nih. gov/pubmed/14462916 [20] Felson B. Chest roentgenology. Saunders; 1973. p. 183 [chapter 5]. [21] R Core Team. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2013. Available from http://www.r-project.org/ [22] MacMahon H, Austin JHM, Gamsu G, Herold CJ, Jett JR, Naidich DP, et al. Guidelines for management of small pulmonary nodules detected on CT scans: a statement from the Fleischner Society. Radiology 2005: 395–400. [23] Vikgren J. Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases. Radiology 2008;249(3). [24] Quaia E, Baratella E, Poillucci G, Kus S, Cioffi V, Cova MA. Digital tomosynthesis as a problem-solving imaging technique to confirm or exclude potential thoracic lesions based on chest X-ray radiography. Acad Radiol 2013;20(May (5)):546–53. Available from: http://www.ncbi.nlm.nih.gov/pubmed/23473723 [accessed 0.02.14]. [25] Quaia E, Baratella E, Cioffi V, Bregant P, Cernic S, Cuttin R, et al. The value of digital tomosynthesis in the diagnosis of suspected pulmonary lesions on chest radiography: analysis of diagnostic accuracy and confidence. Acad Radiol 2010;17(10):1267–74. Available from http://www.ncbi. nlm.nih.gov/pubmed/20591695 [26] Quaia E, Baratella E, Cernic S, Lorusso A, Casagrande F, Cioffi V, et al. Analysis of the impact of digital tomosynthesis on the radiological investigation of patients with suspected pulmonary lesions on chest radiography. Eur Radiol 2012:1912–22. [27] Anbu Nedumaran P, Duncan K, Warwick R. National audit of diagnosis of lung cancer on chest radiography; 2005. Available from http://www.rcr. ac.uk/audittemplate.aspx?PageID=1020&AuditTemplateID=108 [28] Terzi A, Bertolaccini L, Viti A, Comello L, Ghirardo D, Priotto R, Grosso M. Lung cancer detection with digital chest tomosynthesis: baseline results from the observational study SOS. J Thorac Oncol 2013;8(6):685–92. [29] Vlahos I. Commentary on: comparison of chest digital tomosynthesis and chest radiography for detection of asbestos-related pleuropulmonary disease. Clin Radiol 2013;68(4):336–7, http://dx.doi.org/10.1016/j.crad.2012.09.006. [30] Hwang HS, Chung MJ, Lee KS. Digital tomosynthesis of the chest: comparison of patient exposure dose and image quality between standard default setting and low dose setting. Korean J Radiol 2013;14(May (3)):525–31. Available from http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3655311&tool= pmcentrez&rendertype=abstract