The imaging system can comprise a plurality of elongated rails, a scanhead assembly, and a small animal mount assembly. The scanhead assembly is selectively mounted onto a first rail and is constructed and arranged for movement in a linear bi-directional manner along the longitudinal axis of the first rail. The small-animal mount assembly is selectively mounted onto a second rail and is constructed and arranged for movement in a linear bi-directional manner along the longitudinal axis of the second rail. The second rail being mounted relative to the first rail such that the longitudinal axis of the second rail is at an angle to the longitudinal axis of the first rail. The imaging system can also comprise a needle injection assembly that is selectively mounted onto the third rail and is constructed and arranged for movement in a linear bi-directional manner along the longitudinal axis of the third rail. The third rail being mounted relative to the second rail and the first rail such that the longitudinal axis of the third rail is substantially coaxial to the longitudinal axis of the first rail. Alternatively, the needle injection assembly is mounted onto the first rail, such that the second rail is positioned therebetween the needle injection assembly and the scanhead assembly.