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Assessment of Interstitial Lung Disease Using Lung Ultrasound Surface Wave Elastography

A Novel Technique With Clinicoradiologic Correlates

Clay, Ryan MD*; Bartholmai, Brian J. MD; Zhou, Boran PhD; Karwoski, Ronald BA; Peikert, Tobias MD*; Osborn, Thomas MD§; Rajagopalan, Srinivasan PhD; Kalra, Sanjay MD*; Zhang, Xiaoming PhD

doi: 10.1097/RTI.0000000000000334
Original Articles
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Purpose: Optimal strategies to detect early interstitial lung disease (ILD) are unknown. ILD is frequently subpleural in distribution and affects lung elasticity. Lung ultrasound surface wave elastography (LUSWE) is a noninvasive method of quantifying superficial lung tissue elastic properties. In LUWSE a handheld device applied at the intercostal space vibrates the chest at a set frequency, and the lung surface wave velocity is measured by an ultrasound probe 5 mm away in the same intercostal space. We explored LUWSE’s ability to detect ILD and correlated LUSWE velocity with physiological, quantitative, and visual radiologic features of subjects with known ILD and of healthy controls.

Materials and Methods: Seventy-seven subjects with ILD, mostly caused by connective tissue disease, and 19 healthy controls were recruited. LUSWE was performed on all subjects in 3 intercostal lung regions bilaterally. Comparison of LUSWE velocities pulmonary function testing, visual assessment, and quantitative analysis of recent computed tomographic imaging with Computer-Aided Lung Informatics for Pathology Evaluation and Rating (CALIPER) software.

Results: Sonographic velocities were higher in all lung regions for cases, with the greatest difference in the lateral lower lung. Median velocity in m/s was 5.84 versus 4.11 and 5.96 versus 4.27 (P<0.00001) for cases versus controls, left and right lateral lower lung zones, respectively. LUSWE velocity correlated negatively with vital capacity and positively with radiologist and CALIPER-detected interstitial abnormalities.

Conclusions: LUSWE is a safe and noninvasive technique that shows high sensitivity to detect ILD and correlated with clinical, physiological, radiologic, and quantitative assessments of ILD. Prospective study in detecting ILD is indicated.

Departments of *Pulmonary and Critical Care Medicine

Radiology

§Rheumatology

Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN

Supported by NIH R01HL125234 from the National Heart, Lung, and Blood Institute. Statistical consultation for this project was supported by Grant Number UL1 TR000135 from the National Center for Advancing Translational Sciences (NCATS). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH. A portion of Brian Bartholmai’s effort for development and validation of the lung ultrasound surface wave elastography technique is funded by NIH grant R01HL124234. Brian Bartholmai and Mayo Clinic are entitled to royalties from CALIPER software, licensed to Imbio, LLC. Some of the CALIPER technology is patent pending.

The authors declare no conflicts of interest.

Correspondence to: Ryan Clay, MD, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 (e-mail: rclayMD@gmail.com).

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