Stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) are forms of radiation therapy that are highly conformal with steep dose gradients and a higher dose per fraction than conventional radiation therapy treatments. Frameless SRS/SRT requires image guided radiotherapy (IGRT) systems to ensure that the highly conformal dose is delivered to the correct location. Agreement between IGRT systems can change when using patient versus phantom data. Insight into how surface imaging tracks with internal imaging in the patient population cannot be obtained through phantom studies alone. The purpose of this study is to summarize the distribution of readings for each system, and to see how well the systems track with each other. Additionally, patient anatomy and other variables were investigated to see if there was a correlation between them and system agreement.