Lung ultrasound volume sweep imaging for respiratory illness: a new horizon in expanding imaging access

Abstract

BackgroundRespiratory illness is a leading cause of morbidity in adults and the number one cause of mortality in children, yet billions of people lack access to medical imaging to assist in its diagnosis. Although ultrasound is highly sensitive and specific for respiratory illness such as pneumonia, its deployment is limited by a lack of sonographers. As a solution, we tested a standardised lung ultrasound volume sweep imaging (VSI) protocol based solely on external body landmarks performed by individuals without prior ultrasound experience after brief training. Each step in the VSI protocol is saved as a video clip for later interpretation by a specialist.MethodsDyspneic hospitalised patients were scanned by ultrasound naive operators after 2 hours of training using the lung ultrasound VSI protocol. Separate blinded readers interpreted both lung ultrasound VSI examinations and standard of care chest radiographs to ascertain the diagnostic value of lung VSI considering chest X-ray as the reference standard. Comparison to clinical diagnosis as documented in the medical record and CT (when available) were also performed. Readers offered a final interpretation of normal, abnormal, or indeterminate/borderline for each VSI examination, chest X-ray, and CT.ResultsOperators scanned 102 subjects (0–89 years old) for analysis. Lung VSI showed a sensitivity of 93% and a specificity of 91% for an abnormal chest X-ray and a sensitivity of 100% and a specificity of 93% for a clinical diagnosis of pneumonia. When any cases with an indeterminate rating on chest X-ray or ultrasound were excluded (n=38), VSI lung ultrasound showed 92% agreement with chest X-ray (Cohen’s κ 0.83 (0.68 to 0.97, p<0.0001)). Among cases with CT (n=21), when any ultrasound with an indeterminate rating was excluded (n=3), there was 100% agreement with VSI.ConclusionLung VSI performed by previously inexperienced ultrasound operators after brief training showed excellent agreement with chest X-ray and high sensitivity and specificity for a clinical diagnosis of pneumonia. Blinded readers were able to identify other respiratory diseases including pulmonary oedema and pleural effusion. Deployment of lung VSI could benefit the health of the global community.

Volume sweep imaging lung teleultrasound for detection of COVID-19 in Peru: a multicentre pilot study

“…Previously, we demonstrated high lung ultrasound VSI agreement to standard-of-care chest X-ray in a USA-based hospital setting. 12 It is expected these results would apply in rural areas, but independent verification will still be important if possible. Also, as this was a time-sensitive pilot study based on convenience sampling, formal sample size calculations were not performed prior to opening the study.…”

“…In a previous study, the images obtained by the standardised VSI protocol were sufficient to allow diagnosis in all cases even without tailoring the examination to an abnormal finding. 12 Additionally, even suboptimal imaging still can provide useful clinical information. Furthermore, VSI examinations can be repeated at minimal cost as many times as necessary in cases of suboptimal imaging.…”

“…Clinical study of lung VSI has shown excellent visualisation of pneumonia, pleural effusion, and pulmonary oedema. 12 This imaging technique is shown in figure 2 and involves sweeps of the ultrasound probe based on external body landmarks over the anterior, lateral, and posterior lungs. Acquisitions of each lung field are obtained in the transverse and sagittal orientations for redundancy and improved diagnostic accuracy.…”

“…Open access lung ultrasound VSI has been previously tested and shown to be highly effective for pulmonary disease detection including pneumonia. 12 Incorporation of lung ultrasound VSI with telemedicine therefore offers a new way to bring imaging to underserved populations for the evaluation of respiratory diseases. We hypothesised that lung VSI could be integrated into an asynchronous teleultrasound system to increase access to medical imaging (figure 1).…”

“…Teleultrasound shows great promise in expanding imaging access, but the fundamental problem relating to a lack of specialists persists 7 8. Volume sweep imaging (VSI) circumvents the problem of a lack of trained sonographers by shifting image acquisition to individuals with minimal medical and ultrasound background through utilisation of standardised sweeps of the ultrasound probe based on external body landmarks which are recorded as video clips for expert remote interpretation 5 8–11. VSI can be used for a variety of indications including breast, obstetrics, right upper quadrant, and thyroid scanning.…”