Biomedical subjects

P Dario

Publications and source records attributed to P Dario.

At least 19 recordsLinked to original sources

PubMed2005

A novel microstructural approach in tendon viscoelastic modelling at the fibrillar level.

Novel applications in rehabilitation, surgery and tissue engineering require the knowledge of the mechanical behaviour of the tissues at microstructural level. The aim of this work is to investigate the viscoelastic properties of the tendon from the interaction of its biological constituents in the fibrillar network. Traction, relaxation and creep in-vitro tests have been performed on porcine flexor digital tendons. A viscoelastic constitutive equation at finite deformation is presented. The fibrillar deformation modes are described through a network of adaptive links between collagen type I and decorin. The theoretical predictions fit accurately the experimental data. The results of the model demonstrate the mechanical importance of glycosaminoglycan chains of decorin for the differential recruitment and the activation of fibrillar collagen.

Biomechanical Phenomena↗

PubMed2005

Characterization of upper arm synergies during reaching tasks in able-bodied and hemiparetic subjects.

BACKGROUND: In the past, several studies showed the existence of a synergistic behavior between elbow and shoulder joints during reaching movements in able-bodied subjects. The aim of this paper was to characterize the modifications of upper arm synergies during reaching induced by stroke. METHODS: Ten able-bodied right-handed subjects, eight right-handed subjects with hemiparesis affecting the right (dominant) upper limb participated in the experiments. The kinematics of shoulder and elbow joints have been recorded in all the participants during selected reaching movements. From the eight-like plots characterizing the relationship between shoulder and elbow angular velocities, a topological parameter (named as C approximately ) representing the linear approximation of the synergy between the two angular velocities has been extracted. FINDINGS: The results of these experiments showed that C approximately could be used as a figure of merit for the comparison of performance in able-bodied and hemiparetic persons. The hemiparetic subjects showed a significantly higher spreading of the values of C approximately for the different reaching movements when compared with the performance of able-bodied subjects. INTERPRETATION: This work showed that hemiparesis modified upper arm synergies and could provide a protocol for the assessment of upper limb function. Moreover, important applications of this method could be found in the development of biomimetic algorithms for the control of upper extremities during reaching in humanoid robots, and in the design of customized "games" in neurorehabilitation procedures implemented by using robotic and mechatronic platforms.

Adult↗

PubMed2005

Intracorporeal Videoprobe (IVP).

The objective of the work in the EC project IVP is the development and evaluation of two prototypes of video systems:- a small wired videoprobe with a CMOS image sensorand- an autonomous video-capsule with a telemetric link for image data transfer to an external PC-based system.

Journal Article↗

PubMed2004

Kinematic strategies for lowering of upper limbs during suggestions of heaviness: a real-simulator design.

The aim of the experiment was to study possible differences between the kinematic strategies for the "involuntary" arm lowering of hypnotized highly susceptible subjects (H-Highs) and for the voluntary movement of non-hypnotizable simulators (Sims) during suggestions of arm heaviness (Part I). In addition, a comparison between awake susceptible subjects (W-Highs) and H-Highs was carried out to clarify the specific role of the hypnotic state and hypnotizability (Part II). Subjects' absorption and attentional/imagery capabilities were evaluated through neuropsychological tests. Their arm movements were monitored three-dimensionally at hand, wrist and elbow level through a Polhemus Fastrack system. A final interview collected self-reports concerning the perception of movement involuntariness. Neuropsychological tests showed better "absorption" and imagery capabilities in Highs. In the interview, H-Highs perceived a higher involvement in the task and greater involuntariness and difficulties in contrasting the arm lowering than the Sims. Kinematic analysis showed significant differences between H-Highs and Sims for arm displacements along the vertical axis and on the horizontal plane. In fact, the former lowered the left arm earlier and to a greater degree than the right arm; on the horizontal plane, a forearm flexion was observed for H-Highs on the right side. On comparing W-Highs and H-Highs, hypnosis appeared to magnify the waking motor strategies, but also to induce specific changes, mainly concerning the horizontal plane. These results cannot be interpreted on the basis of "role playing" and socio-cognitive factors. They are believed to be due to a balance between the effectiveness of the frontal executive control towards the selection of behaviors and movement automaticity, which is in line with the neo-dissociation theory of hypnosis.

Adult↗

PubMed2004

A protocol for the assessment of 3D movements of the head in persons with cervical dystonia.

OBJECTIVE: To design and test a protocol for the assessment of neck movements in patients affected by cervical dystonia by using an electromagnetic system. This approach could overcome the limits of the current assessment scales in this specific field. BACKGROUND: Initial assessment and function recovery during treatments are diagnosed by the clinician using outcome scales which present many drawbacks in terms of easiness of use, sensitivity, and reliability. DESIGN: A three-dimensional motion analysis system was used to record six different head movements. METHODS: Six able-bodied subjects and 10 subjects affected by cervical dystonia participated in this study. For the different head movements three kinematic parameters (a symmetry index and two indexes related to the reduction of the range of motion) have been extracted in order to compare the performance of able-bodied and disabled persons. RESULTS: The features selected allowed highlighting of the differences between able-bodied and disabled subjects for the degrees of freedom of the neck. CONCLUSIONS: Using a motion analysis system, three kinematic features were extracted from head movements. They seem to allow a more objective assessment of the disability and a more appropriated strategy for the management of patients affected by cervical dystonia.

Adult↗

PubMed2004

Does hypnotizability affect human upright stance?

Subjects highly (Highs) and low susceptible to hypnosis (Lows) show different imagery and attentional capabilities and also peculiar somatomotor, vegetative and electroencephalographic differences in basal and task conditions. Since attention is one of the main component of hypnotic susceptibility and also a relevant factor for postural control, the aim of the experiment was to study actual differences between Highs and Lows at the eyes closure during upright stance. Visual and motor imagery as well as attentional/disattentional capabilities were evaluated through psychological tests. Posture was monitored though Elite systems during upright stance with open and closed eyes. At the eyes closure, Highs and Lows exhibited a different body sway modulation. Possible different compensation mechanisms are suggested for the two groups and interactions between attentional/arousal systems responsible of hypnotic phenomenology and postural control are underlined.

Adolescent↗

PubMed2003

Artificial neural network model of the mapping between electromyographic activation and trajectory patterns in free-arm movements.

Artificial neural networks (ANNs) have been used to identify the relationship between electromyographic (EMG) activity and arm kinematics during the execution of motor tasks. Although considerable work has been devoted to showing that ANNs perform this mapping, there has been little work to explore any relationship with physiological properties of the neuromuscular systems. A back-propagation through time (BPTT) ANN was used to map the EMG of five selected muscles (pectoralis major (PM), anterior deltoid (AD), posterior deltoid (PD), biceps brachii (BB) and triceps brachii (TB)) on arm kinematics in seven normal subjects performing three-dimensional unrestrained grasping movements. To investigate the physiological validity of the BPTT-ANN, inputs were artificially altered, and the predicted outputs were analysed. Results show that the BPTT-ANN performed the mapping correctly (root mean square (RMS) error between target and predicted outputs averaged across subject test sets was 0.092 +/- 0.015). Moreover, it provided insights into the roles of muscles in performing the movement (average indexes measuring the output alteration with respect to the target were 0.070 +/- 0.027, 0.356 +/- 0.172, 0.568 +/- 0.413, 0.510 +/- 0.268, 0.681 +/- 0.430 for PM, AD, PD, BB, TB, respectively, in the movement forward phase, and 0.077 +/- 0.015, 0.179 +/- 0.147, 0.291 +/- 0.247, 0.671 +/- 0.054, 0.232 +/- 0.097 in the return phase).

Adult↗

PubMed2002

Grasping and dissecting instrument for hand-assisted laparoscopic surgery: development and early clinical experience.

BACKGROUND: The operative potential of hand-assisted laparoscopic surgery (HALS) could be enhanced by the introduction of a new generation of assisting instruments. These tools will have to meet specific requirements of shape, function, and safety of use. METHODS: Problems related to the working environment of HALS and deriving projectual restrictions of HALS instruments were analyzed in order to develop and manufacture a working prototype with grasping and dissecting properties to assist during HALS procedures. The resulting instrument was mechanically and clinically tested in 22 HALS procedures. RESULTS: The additional benefit of the new device was particularly appreciated during dissection and isolation of vascular pedicles (nephrectomies and splenectomies). It was shown to be safe and effective in providing the additional assistance it was designed for. CONCLUSION: The described grasping and dissecting instrument for HALS is of great value in assisting the surgeon during fine dissection, as required in selected procedures. New generation of HALS instruments should comply with the functional and safety issues analyzed in this report.

Equipment Design↗

PubMed2002

Control of multifunctional prosthetic hands by processing the electromyographic signal.

The human hand is a complex system, with a large number of degrees of freedom (DoFs), sensors embedded in its structure, actuators and tendons, and a complex hierarchical control. Despite this complexity, the efforts required to the user to carry out the different movements is quite small (albeit after an appropriate and lengthy training). On the contray, prosthetic hands are just a pale replication of the natural hand, with significantly reduced grasping capabilities and no sensory information delivered back to the user. Several attempts have been carried out to develop multifunctional prosthetic devices controlled by electromyographic (EMG) signals (myoelectric hands), harness (kinematic hands), dimensional changes in residual muscles, and so forth, but none ofthese methods permits the "natural" control of more than two DoFs. This article presents a review of the traditional methods used to control artificial hands by means of EMG signal, in both the clinical and research contexts, and introduces what could be the future developments in the control strategy of these devices.

Algorithms↗

PubMed2002

A two DoF finger for a biomechatronic artificial hand.

Current prosthetic hands are basically simple grippers with one or two degrees of freedom, which barely restore the capability of the thumb-index pinch. Although most amputees consider this performance as acceptable for usual tasks, there is ample room for improvement by exploiting recent progresses in mechatronics design and technology. We are developing a novel prosthetic hand featured by multiple degrees of freedom, tactile sensing capabilities, and distributed control. Our main goal is to pursue an integrated design approach in order to fulfill critical requirements such as cosmetics, controllability, low weight, low energy consumption and noiselessness. This approach can be synthesized by the definition "biomechatronic design", which means developing mechatronic systems inspired by living beings and able to work harmoniously with them. This paper describes the first implementation of one single finger of a future biomechatronic hand. The finger has a modular design, which allows to obtain hands with different degrees of freedom and grasping capabilities. Current developments include the implementation of a hand comprising three fingers (opposing thumb, index and middle) and an embedded controller.

Artificial Limbs↗

PubMed2000

On automatic identification of upper-limb movements using small-sized training sets of EMG signals.

We evaluate the performance of a variety of neural and fuzzy networks for discrimination among three planar arm-pointing movements by means of electromyographic (EMG) signals, when learning is based on small-sized training sets. The aim of this work is to underline the importance that the sparse data problem has in designing pattern classifiers with good generalisation properties. The results indicate that one of the proposed fuzzy networks is more robust than the other classifiers when working with small training sets.

Arm↗

PubMed2000

A novel mechatronic tool for computer-assisted arthroscopy.

This paper describes a novel mechatronic tool for arthroscopy, which is at the same time a smart tool for traditional arthroscopy and the main component of a system for computer-assisted arthroscopy. The mechatronic arthroscope has a cable-actuated servomotor-driven multi-joint mechanical structure, is equipped with a position sensor measuring the orientation of the tip and with a force sensor detecting possible contact with delicate tissues in the knee, and incorporates an embedded microcontroller for sensor signal processing, motor driving and interfacing with the surgeon and/or the system control unit. When used manually, the mechatronic arthroscope enhances the surgeon's capabilities by enabling him/her to easily control tip motion and to prevent undesired contacts. When the tool is integrated in a complete system for computer-assisted arthroscopy, the trajectory of the arthroscope is reconstructed in real time by an optical tracking system using infrared emitters located in the handle, providing advantages in terms of improved intervention accuracy. The computer-assisted arthroscopy system comprises an image processing module for segmentation and three-dimensional reconstruction of preoperative computer tomography or magnetic resonance images, a registration module for measuring the position of the knee joint, tracking the trajectory of the operating tools, and matching preoperative and intra-operative images, and a human-machine interface that displays the enhanced reality scenario and data from the mechatronic arthroscope in a friendly and intuitive manner. By integrating preoperative and intra-operative images and information provided by the mechatronic arthroscope, the system allows virtual navigation in the knee joint during the planning phase and computer guidance by augmented reality during the intervention. This paper describes in detail the characteristics of the mechatronic arthroscope and of the system for computer-assisted arthroscopy and discusses experimental results obtained with a preliminary version of the tool and of the system.

Arthroscopes↗

PubMed2000

Effects of infusion of glucose-insulin-potassium on myocardial function after a recent myocardial infarction.

UNLABELLED: We studied the effects of glucose, insulin, and KCl infusion (GIK), on regional myocardial perfusion and function by 99m-Tc-tetrofosmin-gated SPECT. METHODS: We studied 21 male patients with their first uncomplicated acute myocardial infarction (AMI). All patients underwent a rest and submaximal stress before and after 24-hour infusion of GIK-solution (group A) or saline solution (group B). RESULTS: Group A showed better stress tolerance and ischaemic threshold improvement after GIK infusion whilst no statistical differences were found between basal and post-infusion test in group B. At first the stress test in group A, of the 192 segments analysed, 52 (27%) showed reversible perfusion defect. In group B, of 144 segments analysed, 31 (21%) showed reversible perfusion defect. A post-infusion analysis in group A showed a post-GIK end-diastolic significant count improvement in 21 segments, and a post-GIK end-systolic count improvement in 22 segments. In group B, perfusion increase was observed only in 4 segments, whilst systolic thickening increase was observed only in 1 segment. CONCLUSION: These data demonstrate the efficacy of GIK infusion to improve regional myocardial perfusion and function mainly in segments adjacent to the recently infarcted area.

Adult↗

PubMed1999

Development and in vitro testing of a miniature robotic system for computer-assisted colonoscopy.

In this article we present a new concept for computer-assisted colonoscopy based on a miniature robot capable of propelling itself semiautonomously along the colon. The miniature robot is designed to perform the same functions as current colonoscopy systems-i.e., visualization and tissue sampling for biopsy-and exploits an innovative inchworm-like locomotion principle based on adhering to the colon wall by vacuum suction. The miniature robot is connected by a thin and flexible umbilical cable to an external control unit; this unit provides pneumatic actuation signals in the appropriate sequence to the miniature robot, and information on the robot's functioning to the endoscopist, who can either teleoperate or directly supervise its operation. A prototype colonoscopy system using this robot has been fabricated and tested in vitro, with promising results. The proposed concept has strong potential for further development, since miniaturization and functional integration of instrumentation and tools, together with computer assistance, not only make colonoscopy more acceptable, but can also open up a wide range of new applications in endoluminal diagnosis, therapy, and surgery.

Animals↗

PubMed1999

Adaptive fuzzy control of electrically stimulated muscles for arm movements.

A modified adaptive Takagi-Sugeno (TS) fuzzy logic controller (FLC) is proposed that allows a simulated elbow-like biomechanical system to accurately track sigmoidal and sinusoidal trajectories in the sagittal plane. The work is a first effort towards the implementation of a system to restore elbow movements in quadriplegics using functional neuromuscular stimulation. The single-joint musculo-skeletal system is composed of a co-contractable pair of electrically stimulated muscles; the muscle model accounts for the increase in fatigue during the tracking exercise. In the proposed controller structure, a reinforcement learning scheme is used to accomplish the parameter tuning, and the parameter projection algorithm guarantees the system stability during the adaptation process. The controller performance is evaluated using computer simulation experiments and compared with the performance achievable when a standard proportional-integrative-derivative (PID) controller is employed for the same application. The modified adaptive TSFLC outperforms the PID controller in all tested situations, with a clear-cut advantage in the case of high-frequency sinusoidal trajectories (angular frequencies spanning the interval 8-12 rad s-1). The standard controller suffers from a dramatic increase in root mean square (RMS) tracking error above the value at 8 rad s-1, e.g. ERMS > or = 0.013, whereas the correlation coefficient between the actual and desired trajectory falls almost to zero, starting from the value rho approximately equal to 0.97 at 8 rad s-1. On the other hand, the adaptive TSFLC yields ERMS < or = 0.015, with rho > or = 0.78, over the whole range of tested angular frequencies.

Arm↗

PubMed1999

A hybrid approach to EMG pattern analysis for classification of arm movements using statistical and fuzzy techniques.

In this paper, a hybrid approach is presented for discriminating a few upper limb movements by processing the electromyographic (EMG) signals from selected shoulder muscles. Statistical techniques, such as the Generalized Likelihood Ratio test, the Principal Component Analysis, autoregressive parametric modeling techniques and cepstral analysis techniques, combined with a fuzzy logic based classifier (the Abe-Lan network) are used to construct low-dimensional feature spaces with high classification rates. The experimental results show the ability of the algorithm to correctly classify all the EMG patterns related to the selected planar arm pointing movements. Moreover, the structure presented offers promise for real-time applications because of the low computation costs of the overall algorithm.

Adult↗

PubMed1998

Manufacturing and microscopical characterisation of polyurethane nerve guidance channel featuring a highly smooth internal surface.

The present study demonstrates the possibility of manufacturing polyurethane [ChronoFlex (CF)] nerve guidance channels (NGCs) featuring a highly smooth internal surface. Comparative SEM and AFM observations prove marked differences between the internal surface microgeometry of Silastic and CF channels. SEM of CF samples shows a surface with no detectable roughness, while Silastic channels show transversal rows along the entire surface. AFM digital image of Silastic samples show a surface with a rough microgeometry defined by a tridimensional pattern with peaks up to 1400 nm. AFM digital image of CF samples show, indeed, an essentially flat microgeometry with the highest level at 545 nm. These preliminary results suggest that the association of an innovative sequential deposition manufacturing technique with the new CF polyurethane may produce NGCs with a smoother surface microgeometry, in comparison to NGCs obtained from commercial Silastic tubes.

Biocompatible Materials↗

PubMed1998

An algorithm for detecting the onset of muscle contraction by EMG signal processing.

The Generalized Likelihood Ratio (GLR) test is proposed for estimating the time instant of muscle contraction onset via electromyographic (EMG) signal processing. In contrast to commonly used threshold-based estimation methods, the proposed algorithm proves to be reasonably accurate even for low levels of EMG activity; the improved behaviour of the GLR test comes with just a modest increase in the computational complexity. A set of computer simulation experiments are presented, where the proposed algorithm and two different threshold-based estimators are studied; also, we discuss the results of analysing the EMG recordings of selected proximal muscles of the upper limb in a hemiparetic subject.

Algorithms↗