Susquehanna Valley Imaging - Formerly Tristan Associates. Susquehanna Valley Imaging is a service of Geisinger Medical Center and is a multi-modality imaging center offering high-end imaging services using state-of-the-art equipment. With open appointments and the convenience of nearby parking, it provides the care you need close to home. Diagnostic imaging using more than one imaging modality, i.e. combining Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) to determine diagnosis. Office Hours: 8 am to 5 pm Monday-Friday Closed Saturday & Sunday.