Rationale and Objectives
To investigate potential benefits and drawbacks of the clinical use of chest tomosynthesis (CTS), to what extent CTS obviates the need for chest computed tomography (CT), and what reduction in radiation dose thereby can be achieved.
Materials and Methods
The Regional Ethical Review Board approved the follow-up study of patients examined with CTS as part of clinical routine. For each case, two radiologists in consensus determined whether CT would have been performed, had CTS not been an option, and whether CTS was an adequate examination. Thereafter, it was determined whether the use of CTS instead of CT in retrospect was beneficial, neutral, or detrimental for the radiological work-up. The radiation dose to the patient population was determined both for the actual clinical situation and for the alternative scenario that would result, had CTS not been available.
Results
During 1 month 3.5 years before the survey, 149 patients (74 women, age 18–91 years) had undergone CTS for clinical purposes. It was judged that CT would have been performed in 100 cases, had CTS not been available, and that CTS obviated the need for CT in 80 cases. CTS was judged as beneficial, neutral, and detrimental for the radiological work-up in 85, 13, and two cases, respectively. For the entire study population, the use of CTS decreased the average effective dose from 2.7 to 0.7 mSv.
Conclusions
The present study indicates that CTS may have benefits for the radiological work-up as it has the potential to both optimize the use of CT resources and reduce the effective dose to the patient population. A drawback is that CTS examinations may fail to reveal pathology visible with CT and in clinically doubtful cases further investigations including other imaging procedures should be considered.
Chest tomosynthesis (CTS) refers to the technique of acquiring multiple low-dose projection radiographs of the chest over a limited angular range and using these radiographs to reconstruct section images. In this way, a volumetric representation can be obtained at radiation doses lower than reported for computed tomography (CT) . Although the volumetric representation is not as isotropic as in CT, the section images contain much less of the overlaying anatomy than conventional chest radiographs (CXR). As the disturbance because of this anatomy may be the main limiting factor for detection of pathology in CXR , it can be anticipated that its reduction will lead to improved diagnostic accuracy with CTS in comparison to CXR.
A significant improvement for CTS in comparison to CXR in detection of pathology has been reported. The main focus of recent research has been detection and/or visibility of parenchymal nodules. Dobbins et al. found that 70% of CT-proven nodules were visible with CTS in contrast to 22% with CXR. Vikgren et al. obtained similar results, where 92% of CT-proven nodules were visible with CTS and 28% with CXR. This increased visibility of pulmonary lesions achieved with CTS has been reported to increase the diagnostic accuracy and confidence . Additionally, Vikgren et al. performed a detectability study and showed that only 16% of the CT-proven nodules were detected using CXR, whereas 56% were detected with CTS. The threefold increase in sensitivity thus reported by Vikgren et al. has later been confirmed in studies by Yamada et al. , Jung et al. , Zachrisson et al. , and Asplund et al. .
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Materials and methods
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Imaging Procedure
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Analysis of the use of CTS on the Radiological Outcome
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Analysis of the use of CTS on the Radiation Dose
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Results
Study Population and Patient Characteristics
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Table 1
Description of the Study Population: Sex, Age, and Follow-Up Time Presented as the Number of Cases, Mean, Median (bold values), and Range ( n = numbers, yr = years, mo = months)
Sex Clinical Referrals ( n = 76) Radiological Referrals ( n = 73) Cases ( n ) Age (yr) Follow-Up (mo) Cases ( n ) Age (yr) Follow-Up (mo) Men ( n = 75) 39 61, 65 (18–85) 36, 44 (1–44) 36 59, 62 (21–91) 38, 44 (3–44) Women ( n = 74) 37 68, 71 (35–86) 41, 44 (3–44) 37 59, 61 (25–88) 37, 44 (2–44)
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Radiological Outcome
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Table 2
The Availability of CT Data for Confirming or Ruling out Pathology on the CTS Examinations and the Results of the CTS in Terms of Radiological Outcome
Criterion Clinical Referrals ( n = 76) Radiological Referrals ( n = 73) CT-proven pathology before CTS 57 (75%) 7 (10%) CT during follow-up 40 (53%) 33 (45%) CT if CTS not available 69 (91%) 31 (42%) CTS beneficial 58 (84%) 27 (87%) CTS neutral 10 (15%) 3 (10%) CTS detrimental 1 (1%) 1 (3%)
CT, computed tomography; CTS, chest tomosynthesis.
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Radiation Dose
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Table 3
The Radiation Dose to the Patient Population for the Two Scenarios (the Actual Clinical Scenario and the Hypothetical Alternative Scenario)
Referral Type Clinical Scenario Alternative Scenario Examination Cases ( n ) Effective Dose (mSv) Examination Cases ( n ) Effective Dose (mSv) Clinical referrals ( n = 76) CTS ∗ 61 0.18 CXR 7 0.06 CT 54 4.0 CTS + CT 15 4.18 CT 15 4.0 Radiological referrals ( n = 73) CTS 68 0.14 None 42 0 CT 26 4.0 CTS + CT 5 4.14 CT 5 4.0
CT, computed tomography; CTS, chest tomosynthesis; CXR, chest radiograph.
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Discussion
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Conclusions
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