https://orcid.org/0000-0001-6930-4246
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ABSTRACT
Introduction
Limited data exist regarding the long-term pulmonary sequelae of COVID-19. Identifying features utilizing multiple imaging modalities engenders a clearer picture of the illness’s long-term consequences.
Areas Covered
This review encompasses the common pulmonary findings associated with different imaging modalities during acute and late remission stages of COVID-19 pneumonia.
Expert Opinion
Chest x-ray, a common preliminary diagnostic imaging technique, is not optimal for extended care due to limited tissue contrast resolution providing suboptimal assessment of pulmonary pathology and subtle interval changes. Ultrasound may be utilized on a case-by-case basis in certain patient populations, or in countries with limited resources. Chest CT’s accessibility, high tissue contrast and spatial resolution make it the foremost modality for long-term COVID-19 follow-up. While MRI can viably monitor extrapulmonary disease due to its lack of radiation and high inherent soft-tissue contrast, it has limited pulmonary utility due to motion artifact and alveolar gas decreasing lung signal. Although 18F-FDG-PET/CT is costly and has limited specificity, it can provide molecular level data and inflammation quantification. Lung perfusion scintigraphy may also explain COVID-19 induced thromboembolic events and persistent dyspnea despite normal structural imaging and testing results. Correlating the long-term pulmonary findings of COVID-19 with each imaging modality is essential in elucidating the post-recovery course.
Article highlights
Many COVID-19 patients suffer from long-term sequelae months after initial disease recovery.
Imaging plays a pivotal role in the non-invasive assessment of the extent of pulmonary involvement during long-term follow-up.
Although the diagnostic utility is suboptimal due to limited field of view in lungs and operator expertise dependency, the feasibility, affordability, and lack of ionizing radiation associated with lung ultrasonography create a potential niche for this imaging modality in certain patient populations, such as pregnant women and those in low-income countries.
Although useful in initial presentation and readily available, CXR is not optimal for long-term follow-up of COVID-19 due to limited sensitivity in detecting the primary abnormality and evolving changes.
Chest CT can be very useful in long-term follow-up, due to its high contrast and spatial resolution in assessing lung tissue.
Chest CT findings in chronic settings primarily include residual ground-glass opacities, scar, and organizing pneumonia, along with fibrotic change as evidenced by interstitial septal thickening and honeycombing.
Abnormal findings have been reported on chest CT months after COVID-19 recovery.
While MRI is not utilized routinely for lung imaging, low field MRI not only shows relatively higher signal intensity of the lung parenchyma but also is comparable to CT with respect to sensitivity, and thus may be useful in investigating the long-term pathophysiological findings of COVID-19.
Although not practical for daily clinical practice of medicine (due to radiation burden, costs, and time-consuming imaging protocols), 18F-FDG-PET/CT can also be useful in the detection of the extra-pulmonary COVID-19 infection and may be beneficial in long-term follow-up of both pulmonary and systemic sequelae of this disease in certain cases.
V/Q SPECT-CT scans may have great utility in diagnosing small vessel obstruction, identifying parenchymal damage, and monitoring COVID-19 survivors struggling with persistent dyspnea.
Declaration of interest
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants, or patents received or pending, or royalties.