Transcranial sonography (TCS) is a well-established neuroimaging technique that allows for visualizing several
brainstem structures, including the substantia nigra, and helps for the diagnosis and differential diagnosis of
various movement disorders, especially in Parkinsonian syndromes. However, proximate brainstem anatomy can
hardly be recognized due to the limited image quality of B-scans. In this paper, a visualization system for the
diagnosis of the substantia nigra is presented, which utilizes neuronavigated TCS to reconstruct tomographical
slices from registered MRI datasets and visualizes them simultaneously with corresponding TCS planes in realtime.
To generate MRI tomographical slices, the tracking data of the calibrated ultrasound probe are passed to
an optimized slicing algorithm, which computes cross sections at arbitrary positions and orientations from the
registered MRI dataset. The extracted MRI cross sections are finally fused with the region of interest from the
ultrasound image. The system allows for the computation and visualization of slices at a near real-time rate.
Primary tests of the system show an added value to the pure sonographic imaging. The system also allows for
reconstructing volumetric (3D) ultrasonic data of the region of interest, and thus contributes to enhancing the
diagnostic yield of midbrain sonography.