A bed for a medical treatment system. The system has a medical treatment device, such as a CT scanner or radiation therapy system, oriented in a spatial relationship with the bed. The bed has an elevation member, a support member for a patient subject, one section of the support member being mounted on the elevation member and the remaining section of the support member being cantilevered from the elevation member, a mount arranged to the support member, an attachment member arranged at the remaining section of the support member, a deflection member connecting the mount and the attachment member, and a sensor arranged on the deflection member. The sensor is in communication with a deflection calculation apparatus that correlates deflection measured by the sensor with the spatial relationship between the bed and the medical treatment device.