# Review of Advanced Medical Telerobots
## 2 Medical Telerobotic Topologies
### Single-Leader Single-Follower Telerobotic Rehabilitation  
During the last decade, the topic of robotic rehabilitation has attracted a great deal of interest as adjunct (or ultimately replacement) interventions, which can significantly reduce the load on healthcare systems (please see [219]).This is since stroke is the leading cause of significant motor disabilities and results in excessive economic pressure on healthcare systems. Telerobotic rehabilitation [64; 85; 91] is a natural extension of robotic rehabilitation, which can provide equal opportunity, regarding access to rehabilitation services, to the people, regardless of geographical and accessibility limitations. Telerobotic rehabilitation architectures allow for remote multimodal and tele-physical sensorimotor interaction between an in-hospital clinician and an in-home patient. The technology has been recently proposed, and several research centers are focusing on the realization of such a technology. Telerobotic rehabilitation can provide patients with an immersive experience of real-time telertherapy and interpersonal interaction. The teleoperated system realizes a new paradigm for delivering intensive active-assist therapy for patients regardless of accessibility issues. This technology has not been utilized on a large scale yet. However, due to the COVID-19 crisis, the need for such technology is pronounced. The pandemic has affected the accessibility of those in need of rehabilitation centers, and this is a major concern for patients in isolation and those with co-morbidity resulting in a significant pause for delivery of rehabilitation services. The pause, unfortunately, can have a permanent impact on the lost sensorimotor capabilities of those patients since the chances of post-stroke recovery are at a maximum during the three months following a stroke when the brain has maximum plasticity, after which plasticity is rapidly lost. Telerobotic rehabilitation will address this need by enabling clinicians to have wide-range access to patients across the country (including in rural areas) to conduct various objective sensorimotor assessments and rehabilitation interventions. This is to promote high and equal access to healthcare services and is a major need globally. Beyond accessibility at the time of crisis or for remote areas in the country, the technology can significantly increase the number of hours in which a remote patient can receive rehabilitation and sensorimotor assessment services. More information about the COVID-19 and medical robotics is available in [220; 221; 222]. The realization of telerobotic rehabilitation was not possible in the past for reasons such as the requirement of critical sensitivity of active-assist technologies and multimodal sensorimotor rendering systems to the quality of service (QoS) of communication networks, concerns about reliability and resiliency of the network, and security of data transfers(see, for instance [223; 224]). It is shown that latency, jitter, and packet loss not only can deteriorate the fidelity of information rendering, but it can also result in a phenomenon called \"non-passive network coupling.\" This results in an exponential energy accumulation at ports of the telerobotic communication and can potentially result in asynchronous out-of-control behavior of the coupled robotic systems. When the two multimodal robotic modules (e.g., one at the patient's side and the other at the therapist's side) are coupled through a network, degraded QoS can even result in \"instability\" which can be a significant safety concern and has been a bottleneck for the realization of telerobotic rehabilitation. This calls for the design and implementation of novel control architectures to provide safe remote sensorimotor rehabilitation as a line of development for modern healthcare systems addressing the critical challenges of the current robotic and digital rehabilitation systems.