Ultrasonic Parametric Imaging of the Brain

Advances in transcranial ultrasound are generating increased interest in understanding the ultrasonic properties of brain in a more detailed way. The goal of this study was to create two-dimensional maps of the brain for three ultrasonic parameters: speed of sound (SOS), frequency slope of attenuation (FSA) and the integrated backscatter coefficient (IBC). Ultrasonic measurements were performed on 1-cm thick slices of fresh bovine brain in a tank of physiologic saline at room temperature. 14 slices were prepared from the coronal anatomic plane of 5 brains and 14 slices were prepared from the sagittal plane of 4 brains. A mechanical scanning system was used to move a 5 MHz transducer in a rectangular grid pattern to perform measurements in steps equal to a half beam diameter (0.97 mm). Averaged over all 28 slices, the measured values (reported as mean ± standard deviation) were: SOS = (1522 ± 3) m/s, FSA = (0.43 ± 4.75) × 10-2dB/cm/MHz, IBC = (2.400 ± 3.688) × 10-3cm-1str-1. Measurements at individual sites were used to create parametric images of SOS, FSA and IBC for each tissue slice.