History
A 53-year-old male patient, suffering from progressive worsening of dyspnea with mild productive cough within the context of tobacco consumption (45 pack-years) over the last decade, was diagnosed with chronic obstructive pulmonary disease (COPD), grade GOLD 3, with severe emphysema and hyperinflation. The predominance of emphysematous lesions in the right upper lobe (RUL) led to the consideration of an endobronchial treatment of emphysema by endobronchial valve (EBV) deposition – an interventional procedure aiming to reduce the lung volume in order to improve ipsilateral diaphragmatic motion and subsequently, the patient’s respiratory condition. The EBV treatment was targeted at the RUL. An ultra-high resolution (UHR) chest CT was indicated for post-procedural evaluation.
Diagnosis
The chest CT prior to the EBV deposition revealed the completeness of the right major and minor fissures,
providing key information to ensure the absence of collateral ventilation. CT images, obtained 3 months after
EBV deposition, showed three valves deposited in the right apical, posterior and anterior segmental bronchi
enabling obstructions of the corresponding bronchi. An upward and anterior displacement of the right major fissure with complete atelectasis of the RUL was visualized. Numerous low-attenuation areas were seen
bilaterally in both lungs, indicating a heterogeneous emphysema distribution.
EBV treatment had favorable effects on the patient’s outcome including a reduction of his dyspnea and
improved results at the six-minute walk test.
Courtesy of Department of Thoracic Imaging, University Centre of Lille, France
Fig. 1: A coronal MPR image of pre-EBV deposition (Fig. 1a) shows low attenuation areas in both lungs, with a predominant distribution in the RUL, indicating severe emphysema. The RUL is seen completely collapsed in the post EBV deposition image (Fig. 1b). A VRT image (Fig. 1c) shows the interrupted bronchus of the RUL (arrow).
Courtesy of Department of Thoracic Imaging, University Centre of Lille, France
Fig. 2: A sagittal MPR image of the pre-EBV deposition (Fig. 2a) shows the completeness of the right major and minor fissures. The same view of the post EBV deposition (Fig. 2b) shows the upward and anterior displacement of the right major fissure with complete atelectasis of the RUL (arrowheads).
Courtesy of Department of Thoracic Imaging, University Centre of Lille, France
Fig. 3: cVRT images (Figs. 3a–3c) and oblique MPR images (Figs. 3d–3f) show three valves deposited in the right apical, posterior and anterior segmental bronchi and a completely collapsed RUL. Both cVRT and MPR views are reconstructed using 0.2 mm low-dose UHR images.
Comments
Emphysema is a major subtype of COPD, a progressive lung disease characterized by long-term breathing problems and poor airflow. It cannot be cured; however, different treatments are available to help manage the symptoms, e.g., EBV deposition. This treatment has shown favorable effects on patients' outcomes, including effective improvements in lung function, exercise tolerance and quality of life. [1] [2] [3] The eligibility of EBV treatment requires a thorough analysis of the emphysema distribution as well as the absence of collateral ventilation that could hamper atelectasis of the treated lobe. [4] All these pieces of information are provided by the chest CT examination prior to the procedure. The post-procedural chest CT validates the correct position of the deposited valves and provides analysis of the lobar atelectasis induced by the valves.
This case was performed with NAEOTOM Alpha, a newly developed CT scanner with photon-counting detectors QuantaMax™, providing energy-resolved CT data at improved spatial resolution, with inherent spectral information and improved tissue contrasts, without electronic noise. [5] A low-dose UHR scan mode was applied, using a special tin filter optimizing the X-ray spectrum. The UHR mode features a slice collimation of 120 x 0.2 mm, in which the subpixels of the detector with a size of 0.15 x 0.18 mm2 (at the isocenter) are read out individually. There are no physical septa between the pixels, each group of 4 x 6 sub-pixels is confined by collimator grids. This increases the spatial resolution without degrading the geometric dose efficiency of the detector, resulting in an improved anatomic conspicuity in CT imaging at low radiation dose. Furthermore, electronic noise is eliminated by setting up a predefined digital threshold for counting X-ray photons far above the electronic noise floor, which leads to less image noise and potentially a reduction of the radiation dose. As the electronic noise is particularly dominant at low X-ray flux, its absence has a particular impact on the low-dose chest CT scanning with improved image quality. Another important improvement in chest CT is the higher contrast-to-noise ratio (CNR) due to the missing down-weighting of lower energy X-ray photons. In the image reconstruction process, a model based iterative reconstruction approach – Quantum Iterative Reconstruction (QIR) – is applied for further image noise reduction. Owing to the reduced image noise, even low-dose UHR images (0.2 mm) can be used for three-dimensional reconstructions, such as cinematic volume rendering technique (cVRT), demonstrating a photo-realistic visualization of anatomical details.
As shown in this case, chest CT imaging plays an important role in patient selection prior to an EBV treatment and follow-up evaluation after the treatment. High-resolution (HR) images are traditionally associated with higher dose necessary for image noise reduction in thinner slices, but now, UHR images can be acquired with low dose providing the level of image details needed.
Examination Protocol