An imaging system includes a plurality of elongated rails, a scanhead assembly, and a small animal mount assembly. The scanhead assembly is mounted to be moveable in a linear bidirectional manner along a longitudinal axis of the first rail. The small-animal mount assembly is mounted to be moveable in a linear bidirectional manner along a longitudinal axis of the second rail. The second rail is mounted relative to the first rail so the longitudinal axis of the second rail is at an angle to the longitudinal axis of the first rail. The imaging system may also comprise a needle injection assembly that is mounted to be moveable in a linear bi-directional manner along the longitudinal axis of the third rail. The third rail is mounted such that a longitudinal axis of the third rail is substantially coaxial to the longitudinal axis of the first rail.