12th IFToMM World Congress, Besanc ¸on, June 18-21, 2007 CK-xxx Kinematic design of a gravity compensated robot for device for ultrasound examination and assessment of endothelial dysfunction. M. Solazzi * A. Frisoli † M. Bergamasco ‡ E. Sotgiu § PERCRO, Scuola Superiore Sant’Anna Pisa, Italy Abstract—This paper presents a novel robotic device for the execution of a medical examination for the assessment of cardiovascular risk. The device is a 5 DOFs robot for the accurate positioning of an ultrasound probe for the evalu- ation of the endothelial function. The robot is completely backdrivable, and allows the clinician either to handle the probe directly, like in the traditional medical procedures, or moving it through two rate-control joysticks. The system guarantees a more precise, stable and quick positioning of the probe, improving the reliability of the results and the objectivity of the examination. Keywords:Kinematic design, medical robotics, gravity compensa- tion I. Introduction The advantages of robotic systems in the medical field are related to their capabilities of carrying out movements and/or complex tasks, with high accuracy, precision and stability, guaranteeing the repetitive execution of such op- erations without problems about tiredness. In the area of robotic systems for tele-echography, we can distinguish three main categories: telemedicine systems, mainly sup- porting image transmission and manipulation for remote di- agnosis [1], systems for robotic-automated ultrasound ex- amination [2], [3], and systems for remote execution of echography with or without force feedback [4], [5], [6], [7]. Robots for ultrasound examination have been also built at the University of British Columbia ([8]), with a kinematics based on a double parallelogram and with 6 DOFs. An- other example is constituted by the “WAB” system realized at the Takanishi Laboratory of the Waseda University, used for evaluating the dilation of the carotid artery. Both sys- tems are not used as backdrivable robots, and are normally operated through a force sensor mounted on the ultrasound probe. The dysfunction of the endothelium is a systemic process associated with the pathogenesis, progressions and clinical manifestation of atherosclerosis. The high resolution ul- trasonography is now largely used as an accepted and reli- able medical procedure for the evaluation of the endothe- * E-mail: solazzi@sssup.it † E-mail: a.frisoli@sssup.it ‡ E-mail: m.bergamasco@sssup.it § E-mail: sotgiu@sssup.it Fig. 1. Ultrasound image of the brachial artery lial function, measuring brachial artery dilation following reactive hyperemia, induced by 5 minutes of forearm is- chemy (flow mediated dilation, FMD) [9]. Figure 1 shows a typical ultrasound image, where a cross section of the vessel is visible. Using this technique, the presence of al- tered endothelium-dependent vasodilation has been demon- strated in the brachial artery of patients with several car- diovascular risk factors [10]. The ultrasound evaluation of the endothelial function quickly caught on in clinical field because of his advantages of non invasivity, easiness and feasibility, against to the venous plethysmography (for long considered the standard). The manual procedure, commonly daily performed, presents still several limitations, since the analysis requires a long period of observation, lasting about 10-15 minutes, during which the ultrasound probe should keep a fixed po- sition, but should be also at the same time compliant with the involuntary displacements of the patient’s arm. This normally poses several issues in terms of repeatability of the examination, introducing a considerable variability in- tra and inter-observer, and a lack of objectivity in the diag- nosis. This has clearly a direct impact on the cost and qual- ity of the sanitary services. In order to overcome all these limitations, in this paper we present the design and the con- trol of a novel robotic system, called EchoDev, expressly designed to carry out robotic-assisted ultrasound examina- tion for the evaluation of the endothelial function. Figure 2 shows a scheme of the intended modality of execution of the ultrasound examination using the EchoDev system to handle the probe. With respect to conventional manipulators, the devised robot is fully backdrivable and gravity-compensated. The 1