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Chin Med J (Engl)
Chin Med J (Engl)
CM9
Chinese Medical Journal
0366-6999
2542-5641
Lippincott Williams & Wilkins Hagerstown, MD

CMJ-2024-582
10.1097/CM9.0000000000003297
00012
3
Correspondence
Initial clinical evaluation of chest digital tomosynthesis in adult patients with COVID-19 pneumonia
Li Zhanxia 1
Wu Xiuhua 1
Zhang Guobin 2
Wu Dianliang 3
Zhang Yunjiao 1
Wang Chengji 4
Zou Lumin 5
Gu Xiaohua 1
Ren Tao 1
Wei Peifang
1 Department of Pulmonary and Critical Care Medicine, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200233, China
2 Department of Radiology, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200233, China
3 School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
4 Shanghai Laboratory Animal Research Center, Shanghai 201808, China
5 E-COM Technology Limited, Beijing 100176, China
Correspondence to: Tao Ren, Department of Pulmonary and Critical Care Medicine, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, No. 600 Yishan Road, Xuhui District, Shanghai 200233, China E-Mail: liuyuanrentao@sjtu.edu.cn
14 8 2024
20 9 2024
137 18 22392241
24 2 2024
Copyright © 2024 The Chinese Medical Association, produced by Wolters Kluwer, Inc. under the CC-BY-NC-ND license.
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0

OPEN-ACCESSTRUE
SDCT
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pmcTo the Editor: The coronavirus disease 2019 (COVID-19) pandemic has caused a significant global health crisis, led to staggering mortality rates, and imposed a substantial economic burden.[1] Pneumonia is the leading cause of mortality in patients with COVID-19. During outbreak peaks, the surge in patients severely strained healthcare systems, highlighting the need for rapid and cost-effective screening methods. Although chest X-ray (CXR) is affordable and convenient, its low sensitivity limits its effectiveness for detecting lung abnormalities. Computed tomography (CT) is considered the gold standard for diagnosing pneumonia, including COVID-19 pneumonia, but it exposes patients to high doses of radiation (3–7 mSv) far exceeding the annual threshold of 1 mSv recommended by the World Health Organization. Even low-dose CT delivers an average effective dose of 1.6 mSv, adding to the patient’s radiation burden.[2]

Digital tomosynthesis (DTS) has emerged as a promising imaging technique that combines the tomographic capabilities of CT with the benefits of lower radiation exposure and greater cost-effectiveness. Studies have demonstrated the efficacy of DTS for providing detailed images of lung lesions by reducing overlapping structures,[3,4] making DTS a viable alternative for the assessment of pneumonia, including COVID-19 pneumonia. We developed a three-dimensional digital radiography (3D-DR) system, which is a novel, multimodal three-dimensional tomographic and soft tissue medical imaging system based on DTS technology that delivers lower radiation doses than conventional DTS. Published studies on DTS systems report an effective dose of approximately 0.13 mSv.[4] In this study, we attempted low-dose DTS using the 3D-DR system and obtained a total effective dose of 0.08 mSv, which is close to the radiation dose of standard dual-view X-ray (0.06–0.25 mSv) and approximately one-fiftieth of CT. The primary objective of this study was to evaluate and compare the diagnostic performance of CXR and 3D-DR for the detection of COVID-19 pneumonia. Additionally, this study was performed to educate radiologists and physicians about common DTS imaging features, facilitating the rapid identification and treatment of patients with pneumonia.

This study was approved by the Ethics Committee of Shanghai Sixth People’s Hospital (No. 2022-KY-048(K)), with written informed consent obtained from all participants. We included patients who were hospitalized between December 1, 2022, and February 1, 2023 and confirmed to have severe acute respiratory syndrome coronavirus 2 infections by nasopharyngeal swab polymerase chain reaction and pneumonia by chest CT. They had high-risk factors for severe illness, including unvaccinated status, age ≥60 years, residency in long-term care facilities, chronic diseases (e.g., cardiovascular diseases, chronic kidney disease, chronic respiratory diseases, diabetes, neurocognitive disorders, obesity), and immunocompromised conditions (e.g., undergoing chemotherapy/radiotherapy for cancer, using steroids/immunosuppressants/biologics). These patients exhibited at least one of the warning signs of severe illness, including: (1) worsening hypoxemia or increased oxygen requirements (saturation of peripheral oxygen ≤93% on room air), (2) respiratory rate ≥30 breaths/min, (3) persistent high fever with elevated inflammatory markers (C-reactive protein, ferritin, erythrocyte sedimentation rate), significantly elevated lactate levels, or progressive lymphopenia. Imaging assessments were needed to evaluate lung lesions. The exclusion criteria included pregnancy, age <18 years, body mass index >33 kg/m2, and inability to cooperate with the examinations. The final study population comprised 40 patients (22 males, 18 females; mean age, 65 ± 16 years). They underwent DTS within 72 hours after undergoing a CT scan [Supplementary Figure 1, http://links.lww.com/CM9/C145].

The 3D-DR imaging system was developed by upgrading MultiX Impact system (Siemens Healthineers, Malvern, PA, USA) and the Digital Instrument Operating System software (E-COM Technologies, Inc., Beijing, China), which integrated an X-ray generator, mechanical motion components, control system, and X-ray detector (Thales, La Défense, France). Dual-energy exposure technology allows clinicians to achieve a more accurate diagnosis. A dedicated imaging workstation and analysis system were established.

DTS examinations began with a scout image to check patient positioning. Posteroanterior views were acquired at 75 kVp. The scout image was used as the CXR image for subsequent analyses. If the positioning was satisfactory, the system calculated the appropriate low-dose exposure (mAs) for the tomosynthesis scan, involving linear sweeps of the X-ray tube over a 30° angle at 75 kVp. The detector entrance dose was 0.5 μGy, with additional copper filtration and a nominal focal spot of 0.6 mm. The breath-hold acquisition time was 5–10 seconds. Sixty low-dose projections were obtained at regular intervals, with a slice interval of 4 mm. Images were reconstructed with a 1-mm slice interval. The total effective dose for a standard patient was 0.08 mSv [Supplementary Figure 2, http://links.lww.com/CM9/C145]. CT imaging was performed with a dual-source CT scanner (Somatom Force, Siemens Healthineers, Malvern, PA, USA). Scans were reconstructed with a slice thickness of 1–5 mm and a 400-mm field of view, with an estimated effective dose of 7 mSv.

Two board-certified pulmonary radiologists with 23 and 8 years of experience in thoracic image interpretation reviewed the CXR and DTS images. Images were presented in a randomized order on the basis of modality and viewed independently. The following imaging findings were evaluated: ground-glass opacities (GGOs), consolidations with or without air bronchogram, reticulations, and linear consolidations. The diagnostic performance of CXR and DTS was compared to that of CT, which was utilized as the reference standard for both observers. Interobserver agreement was assessed via Cohen’s kappa statistic. McNemar’s test was used to compare the diagnostic performance of CXR and DTS. Statistical significance was set at P <0.05, and the data were analyzed with SPSS Statistics software, version 26 (IBM, Armonk, NY, USA).

Among the 40 patients with pneumonia, 34 had GGOs, 27 had consolidations, seven had reticular opacities, and 18 had linear consolidations. Some patients showed multiple patterns simultaneously [Supplementary Figures 3–7, http://links.lww.com/CM9/C145]. DTS detected GGOs, localized bronchiectasis, and reticular patterns of interlacing fibrotic bands, which were challenging to identify on CXR because of overlapping structures. DTS provided comprehensive information on lesion location, distribution, and extent, which is crucial for evaluating lung fibrosis and other structural changes associated with COVID-19 pneumonia. Compared with CXR images, DTS images effectively distinguished GGOs from consolidations, providing superior diagnostic capability [Supplementary Figures 4–6, http://links.lww.com/CM9/C145]. DTS also offered clearer visualization of exudation and consolidation, aiding in disease progression assessment [Figure 1]. Additionally, DTS avoided surface interference, such as the oxygen tubing artifacts observed on X-rays, and provided excellent visualization of the pulmonary vasculature and airways [Supplementary Figures 3 and 7, http://links.lww.com/CM9/C145].

Figure 1 Images of a 42-year-old male with COVID-19 pneumonia and chronic kidney disease, showing persistent high fever and elevated inflammatory markers. (A) CXR revealed linear consolidation in the right lower lung field (orange arrow). (B, C) represented different layers of DTS images. (B) showed clearer and more extensive linear consolidation in both the right (orange arrow) and left lung (yellow arrow). (C) highlighted a consolidation area in the right lower lung (encircled in orange), consistent with the CT image but not visible on CXR. The blue arrow indicated clearly visible airways. (D, E) CT images confirmed the linear consolidations (orange arrows) observed in the DTS images. (F) DTS image showed the consolidation in the right lower lung (orange encircled area), consistent with (C). New exudates in both lower lungs (yellow arrows) suggested progression of the patient’s condition, which are not as visible on the CT images (D, E). DTS displayed airway details (blue arrow). COVID-19: Coronavirus disease 2019; CT: Computed tomography; CXR: Chest X-ray; DTS: Digital tomosynthesis; WL: Window level; WW: Window width.

The sensitivity and accuracy of DTS for detecting lung lesions were significantly greater than those of CXR (P <0.01, Supplementary Table1, http://links.lww.com/CM9/C145). Interobserver agreement regarding DTS findings was good to very good (κ = 0.68–0.81) and superior to that regarding CXR findings (κ = 0.48–0.61). For DTS, agreement was very good for consolidations (κ = 0.81) and good for linear consolidations (κ = 0.76), GGOs (κ = 0.74) and reticulations (κ = 0.68). For CXR, the agreement was moderate to good, with κ values of 0.61 for consolidation, 0.56 for linear consolidation, 0.53 for GGO, and 0.48 for reticulations.

Our study presents the use of our 3D-DR system for the tomographic assessment of patients with COVID-19 pneumonia. With a radiation dose of only 0.08 mSv, this method provides detailed diagnostic information through multiple X-ray exposures at different energy levels, especially for detecting consolidations, linear consolidations, and GGOs.

The enhanced imaging capability of DTS makes it an ideal tool for tracking imaging changes in patients at high risk for pneumonia. Additionally, the system is easy to deploy and of relatively low cost (1.5 times the cost of CXR), similar to a mobile CXR unit, and convenient for bedside use. This provides a viable alternative for patients who are unable to undergo chest CT scans or who require short-term follow-up, reducing radiation exposure while ensuring high-quality imaging. The cost effectiveness, portability, and bedside usability of DTS make it invaluable in clinical settings, especially for critically ill patients.

Future research should further integrate artificial intelligence with DTS to potentially increase the sensitivity and accuracy of pneumonia detection.[5] Given the clear visualization of the pulmonary vasculature provided by 3D-DR, future studies could explore its application in pulmonary vascular research to enhance our understanding and management of vascular complications associated with pneumonia and other lung diseases.

This study has several limitations. First, the relatively small sample size may impose constraints. However, this investigation serves as a proof of concept for the application of DTS for the identification of COVID-19 pneumonia. Second, the lack of lateral chest radiographs in the imaging analysis could diminish the radiographic sensitivity for lesion detection. Considering that DTS imaging is primarily based on posterior–anterior views, comparisons at only this level are more meaningful. In clinical settings, bedside chest radiographs are typically performed only in the posterior–anterior view to reduce unnecessary radiation exposure. We plan to conduct a prospective multicenter study to validate the efficacy of 3D-DR for the detection and management of pneumonia, including but not limited to COVID-19 pneumonia. Future studies may also investigate the application of 3D-DR to pulmonary vascular imaging.

Our study demonstrates the feasibility and clinical value of using 3D-DR for DTS for the diagnosis and monitoring of COVID-19 pneumonia. DTS offers a promising alternative, providing superior image sensitivity, a lower radiation dose, and bedside usability, making it a valuable tool for managing severe respiratory diseases.

Funding

The work was supported by the National Natural Science Foundation of China (No. 82104771), Key Program of the National Natural Science Foundation of China (No. 81930001), Shanghai Jiao Tong University Medical-Industrial Intersection Research Fund Project (No. YG2021QN94), Open Fund of Xuzhou Medical University (No. XXKF202119), and Shanghai Sixth People’s Hospital Emergency Special Project for Combating COVID-19 (No. ynxg202208).

Conflicts of interest

None.

Supplementary Material

How to cite this article: Li ZX, Wu XH, Zhang GB, Wu DL, Zhang YJ, Wang CJ, Zou LM, Gu XH, Ren T. Initial clinical evaluation of chest digital tomosynthesis in adult patients with COVID-19 pneumonia. Chin Med J 2024;137:2239–2241. doi: 10.1097/CM9.0000000000003297
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