In this article, we present the design, validation, and imaging capabilities of a mechanically discretized ultrasound scanning apparatus (MEDUSA) that supports flexible development of ultrasound tomography (UST) algorithms for complex tissue structures. Ultrasound tomography in the recent decade has shown promising results in quantitative soft-tissue imaging for clinical breast cancer diagnostics. There is growing interest in applying tomographic techniques to image broader tissue structures that include bone, where imaging is significantly more challenging due to strong impedance mismatches and complex wave propagation within the region. Changes in data acquisition strategy, algorithms, and system design are necessary to enable quantitative imaging of soft-tissue with bone inclusions. The 36 degree-of-freedom (DOF) MEDUSA system allows free space positioning of acoustic transducers around an imaging target and enables investigation of imaging strategies not available in other UST systems. We present the mechanical design, parameter calibration, and tomographic imaging results using MEDUSA. Mono-/bistatic imaging and full-waveform inversion (FWI) results on real targets are presented and validates system performance capabilities for broader UST algorithm development for more complex tissue structures.