In vivo assessment of the mechanical properties of crystalline lenses in a rabbit model using ultrasound elastography: Effects of ultrasound frequency and age

Qingmin Wang; Ying Zhu; Meng Shao; Haoming Lin; Siping Chen; Xin Chen; Azra Alizad; Mostafa Fatemi; Xinyu Zhang

doi:10.1016/j.exer.2019.05.002

In vivo assessment of the mechanical properties of crystalline lenses in a rabbit model using ultrasound elastography: Effects of ultrasound frequency and age

Exp Eye Res. 2019 Jul:184:258-265. doi: 10.1016/j.exer.2019.05.002. Epub 2019 May 8.

Authors

Qingmin Wang¹, Ying Zhu², Meng Shao², Haoming Lin², Siping Chen², Xin Chen², Azra Alizad³, Mostafa Fatemi³, Xinyu Zhang⁴

Affiliations

¹ School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, China; National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen, China; Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Shenzhen, China; School of Information Science and Technology, Fudan University, Shanghai, China.
² School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, China; National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen, China; Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Shenzhen, China.
³ Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States.
⁴ School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, China; National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen, China; Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Shenzhen, China; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States. Electronic address: xyzhang9@szu.edu.cn.

PMID: 31077713
DOI: 10.1016/j.exer.2019.05.002

Abstract

Purpose: The occurrence of presbyopia and cataract is closely related to changes in the mechanical properties of the crystalline lens. There are no established methods so far for in vivo assessment. By introducing ultrasound elastography, we proposed group velocity (V_g) of an induced shear wave as a new biomarker to characterize the mechanical properties of the lens in our previous study. Here, we investigated the effect of the ultrasound frequency on measurement accuracy and validated the results with a conventional ex vivo compression testing. We also demonstrated a change trend in V_g and its correlation with age in a rabbit model.

Methods: Eight New Zealand white rabbits were fed normally from the fourth to seventh month. An ultrasound elastography system was developed to measure V_gin vivo on every eye once per month. The performances when using a high-frequency (L22-11v) and low-frequency (L11-4v) probe were compared. Rabbits were sacrificed after in vivo measurements by the end of the seventh month and this was followed by ex vivo ultrasound measurements and conventional compression tests on the extracted lenses.

Results: The results demonstrated that there were no significance differences in V_g between measurements with high-frequency (USE-HF) and low-frequency (USE-LF) probes in the same month-age group. The mean V_g and the standard deviation of four rabbits that were 7 months old were 2.37 ± 0.24 m/s, 2.36 ± 0.25 m/s, 2.43 ± 0.26 m/s and 2.44 ± 0.38 m/s, with USE-HF for ex vivo and in vivo measurements and USE-LF for ex vivo and in vivo measurements, respectively. There were no significant differences (p > 0.05) and they were all in agreement with the results of compression tests, which was 16.16 ± 1.84 kPa in Young's modulus. The results also showed that V_g increased with age. In combination with the results of our previous study, V_g showed a relatively sharp increase from 2 to 5 months, while it had a slight increase from 5 to 7 months.

Conclusions: The USE-HF and USE-LF has comparable accuracy in V_g measurements while USE-HF had an advantage regarding better spatial resolution. The change trend of V_g was in accord with the growth phase of New Zealand white rabbits, which usually results in sexual maturity at 5 months old. This implies that V_g can be used as a biomarker parameter for evaluating the mechanical properties of the lens undergoing physiological changes.

Keywords: Acoustic radiation force; Age; Crystalline lens; Frequency; Mechanical properties; Shear wave; Ultrasound elastography.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aging / physiology*
Animals
Biomechanical Phenomena
Elastic Modulus
Elasticity / physiology*
Elasticity Imaging Techniques*
Lens, Crystalline / physiology*
Lens, Crystalline / ultrastructure
Rabbits
Ultrasonography