Parametric imaging of ultrasonic backscatter of fixed sheep brain

Ultrasound backscatter properties of aggregate brain tissue are available in the literature, however, reporting on the spatial variation of backscatter over tissue volumes is limited. The spatial variation of the apparent integrated backscatter (AIB) and the logarithmic backscatter amplitude decay constant (BADCL) was characterized for 1-cm thick samples from the coronal, sagittal and transverse anatomic planes of fixed sheep brain. Submerged samples were exposed to ultrasound using broadband transducers with center frequencies of 3.5, 5.0, 7.5, and 10 MHz by scanning over the samples in half-beamwidth step sizes to measure the backscattered signal. Parametric images of the AIB and BADCL showed a clear correlation between morphological features in the tissue samples and the images with the AIB giving the better representation of the overall tissue structure. Over all samples and frequencies, the range of the spatial mean of the AIB was −77.7 to −59.8 dB with the standard deviation ranging from 3.14 to 6.99 dB. The spatial mean of the BADCL ranged from 0.0350 to 0.152 μs⁻¹ with standard deviations ranging from 0.0820 to 0.111 μs⁻¹. For both parameters, morphological features of the tissue become more distinctive with increasing frequency.