Ultrahigh-field diffusion weighted MR imaging of the chicken eye in vivo throughout the in ovo period

Abstract

Purpose : Ultrahigh-field MRI (UHF-MRI) with an in-plane resolution of less than 100 μm is known as MR microscopy (MRM). This technique provides highly resolved anatomical images and allows quantitative assessment of different tissue types using diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI). The aim of the present study was to evaluate the feasibility of combined anatomical MRM as well as quantitative DWI and DTI to assess the developing chicken eye in vivo and in ovo.

Methods : Thirty-eight fertilized chicken eggs were examined at 7 Tesla (ClinScan, Bruker BioSpin, Germany) acquiring a dataset comprising T2-weighted anatomical images (T2w Turbo Spin Echo Sequence), DWI (SE-EPI, b-value: 0., 400, 800, 1000 s/mm²) and DTI (EPI-Sequence (MDDW) with 20 directions and b-values: 0, 1000 s/mm²). To reduce motion artifacts, the eggs were moderately cooled before and during MRI. Two eggs were imaged daily for the entire developmental period, and 36 eggs were examined pairwise at only one time point of the embryonic period to show the cooling and MRI influence. The ocular development was anatomically and quantitatively assessed.

Results : Starting from the D5 embryonic stage (116-124 hours), MRM allowed differentiation between lens and vitreous body. The lens core and periphery were first identified at D9. DWI and DTI allowed quantification of lens maturation based on a decrease in apparent diffusion coefficient (ADC) values and an increase of fractional anisotropy (FA) (see Fig. 1). Repeated moderate cooling and repeated MRI had no influence on the development of the chicken embryo eyes.

Conclusions : MRM allows in vivo assessment of embryonic development of the chicken eye in ovo without affecting normal development. The method provides anatomical information supplemented by quantitative evaluation of lens development using DWI/DTI derived ADC and FA values. With increasing availability of ultrahigh-field MR systems, this technique may provide a noninvasive complementary tool in the field of experimental ophthalmology.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Fig. 1: Course of ADC and FA values of the developing lens. Maturation of the lens leads to a decrease in ADC values and an increase in FA values as the ultrastructural complexity of the lens increases.