Ultrasonography and elastography of the brain and cerebellum of English Bulldog fetuses

The aim of this study was to evaluate B-mode ultrasonography and ARFI elastography of the central nervous system of canine fetuses as complementary methods to predict gestational age, monitor fetal development and establish standards. Ultrasound examinations were performed on 26 English Bulldog bitches at 34, 49 and 60 days of gestation. The circumference (C), area (A) and diameters of the short (D1) and long (D2) axis of the two cerebral hemispheres of the fetuses in cross-section were measured. Fetal cerebellum shape, echotexture, echogenicity, and transverse diameter (TCD) were evaluated in cross-section. Elastography was performed obtaining color elastograms and mean shear wave velocity (SWV m/s) of the fetal brain and cerebellar tissues. Ultrasound variables were correlated with gestational day (GD). Brain masses had a circular to oval shape, hyperechoic echogenicity, and homogeneous echotexture. C and D1 were the more accurate variables to predict gestational day, with the formulas: GD = 19.38 + 2,06∗C (R2 = 81%) and GD = 18.93 + 7.45∗D1 (R2 = 82%). Cerebellum had a “banana” shape, with hyperechogenic edges, hypoechoic echogenicity, and homogeneous echotexture. The TCD (P = 0.0001) and cerebellar stiffness (P = 0.0006) were greater at 60 days than at 49 days of gestation. The brain mass SWV was correlated positively with GD (P = 0.0001) and showed a gradual increase (P = 0.0001) in the three gestational timepoints evaluated. According to qualitative elastography, both brain mass and cerebellum became more rigid over the course of gestational days. It was possible to verify the development of the brain and cerebellum of canine fetuses during pregnancy by ultrasonographic characteristics and B-mode dimensions, as well as by evaluating the elasticity of these tissues through elastography. These unpublished findings allow a better follow-up of the central nervous system development in the prenatal period and may help in future studies with canine fetuses that present cerebral and cerebellar abnormalities.