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David TOUBOUL, Thu Mai Nguyen, Jean François Aubry, Jean Luc Gennisson, Mickael Tanter, Jeremy Bercoff, Joseph Colin; In Vivo Corneal Elasticity Changes After Collagen Cross-linking Using Supersonic Shear Wave Imaging. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6800.
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© ARVO (1962-2015); The Authors (2016-present)
To address elasticity changes after UVA-Riboflavin induced corneal collagen cross-linking (CXL) procedure with an innovative transient elastography technology based on Supersonic Shear wave Imaging (SSI).
21 porcine eyes were treated with a conventional CXL technique and we proposed SSI as a method for the ex vivo (n=17) and in vivo (n=4) assessment of the cornea elastic anisotropy. The tissue shear modulus can be retrieved from the speed of a shear wave propagating in this tissue. The shear wave is induced using a linear ultrasonic array to apply a transient ultrasound radiation force into the tissue. The resulting shear wave propagates transversally to the ultrasound beam axis. The probe is then switched to an ultrafast imaging mode (30000 frames/sec) to image the shear wave propagation and thus evaluate its local speed. We implemented SSI with high-frequency rotating arrays (15 MHz, 128 elements), performing 3D scans on porcine eyes to obtain a full corneal mapping of the elastic anisotropy.
After CXL, for the four in vivo eyes, the shear wave speed difference between the treated area and the untreated area was 56% ± 15. This value was comparable to the ratio obtained in the ex vivo experiments. However, the significant variability between different corneas emphasizes the necessity to monitor the CXL quality. Furthermore, there was a perfect correlation between the area the corneal was stiffened and the area of epithelium was removed, confirming the shielding effect of the epithelium regarding the Riboflavine.
This study demonstrates the feasibility to use SSI technology for in vivo monitoring of CXL. 3D scans provide a corneal elasticity mapping of the corneal surface, enhancing the visualization of the treated area. This technique can be applied in real-time to follow the corneal stiffening and could help the management of Keratoconus or further corneoplastic surgery procedures.
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