Biomedical subjects

C N Riviere

Publications and source records attributed to C N Riviere.

6 recordsLinked to original sources

PubMed2005

Preliminary evaluation of a mobile robotic device for navigation and intervention on the beating heart.

This article describes the development and preliminary testing of a mobile robotic device to facilitate minimally invasive beating-heart intrapericardial intervention. The HeartLander robot will be introduced beneath the pericardium via subxiphoid incision, adhere to the epicardium, navigate to any location, and administer therapy under the control of the physician. As compared to current robotic cardiac surgical techniques, this novel paradigm obviates immobilization of the heart and eliminates access limitations. Furthermore, it does not require lung deflation and differential ventilation and thus could enable outpatient cardiac surgery. The current HeartLander prototypes use suction to maintain prehension of the epicardium and wire actuation to perform locomotion. A fiber optic videoscope displays visual feedback to the physician, who controls the device through a joystick interface. The initial prototype demonstrated successful prehension, turning, and locomotion on open-chest, beating-heart porcine models where the pericardium was removed (N = 3). A smaller second-generation prototype with an injection system demonstrated locomotion and myocardial injection of dye, both performed with the pericardium intact (N = 3). These trials illustrate the feasibility of using a miniature mobile robot to navigate upon the beating heart and perform intrapericardial therapy.

Animals↗

PubMed2000

Intraoperative tremor monitoring for vitreoretinal microsurgery.

An instrument for intraoperative sensing of surgeons' hand tremor during vitreoretinal microsurgery has been developed. The instrument uses inertial sensing to detect tremor in six degrees of freedom. Instrument tip velocity is computed using the sensor data. The displacement amplitude of the tremor is then approximated analytically by modeling the velocity as sinusoidal. The instrument presently estimates oscillations at physiological tremor frequencies with error of less than 7%.

Humans↗

PubMed1999

3-D position measurement for microsurgical evaluation.

A compact system for high-resolution three-dimensional measurement of microsurgical instrument tip position in the laboratory is under development. The system is useful for quantification of tremor, wander, and drift, as well as for other studies characterizing surgeons' motion in microsurgery, and for evaluation of engineered devices for enhancement of microsurgical positioning accuracy. Preliminary results are presented.

Equipment Design↗

PubMed1998

Adaptive canceling of physiological tremor for improved precision in microsurgery.

Physiological hand tremor impedes microsurgery. We present both a novel adaptive algorithm for tremor estimation and a new technique for active real-time canceling of physiological tremor. Tremor is modeled online using the weighted-frequency Fourier linear combiner (WFLC). This adaptive algorithm models tremor as a modulating sinusoid, and tracks its frequency, amplitude, and phase. Piezoelectric actuators move the surgical instrument tip in opposition to the motion of tremor, effectively subtracting the tremor from the total motion. We demonstrate the technique in one dimension using a cantilever apparatus as a benchtop simulation of the surgical instrument. Actual hand motion, prerecorded during simulated surgery, is used as input. In 25 tests, WFLC tremor compensation reduces the rms tip motion in the 6-16 Hz tremor band by 67%, and reduces the rms error with respect to an a posteriori estimate of voluntary motion by 30%. The technique can be implemented in a hand-held microsurgical instrument.

Algorithms↗

PubMed1997

Adaptive Fourier modeling for quantification of tremor.

A new computational method for quantification of tremor, the weighted frequency Fourier linear combiner (WFLC), is presented. This technique rapidly determines the frequency and amplitude of tremor by adjusting its filter weights according to a gradient search method. It provides continual tracking of frequency and amplitude modulations over the course of a test. By quantifying time-varying characteristics, the WFLC assists in correctly interpreting the results of spectral analysis, particularly for recordings exhibiting multiple spectral peaks. It therefore supplements spectral analysis, providing a more accurate picture of tremor than spectral analysis alone. The method has been incorporated into a desktop tremor measurement system to provide clinically useful analysis of tremor recorded during handwriting and drawing using a digitizing tablet. Simulated data clearly demonstrate tracking of variations in frequency and amplitude. Clinical recordings then show specific examples of quantification of time-varying aspects of tremor.

Algorithms↗

PubMed1996

Effects of age and disability on tracking tasks with a computer mouse: accuracy and linearity.

Many individuals with movement disorders are unable to make efficient use of graphical computer interfaces commonly employed in personal computers. In this study, performance limitations in target tracking with a computer mouse were studied for eight young subjects aged 19 to 29 (M = 23, SD = 3), four old subjects aged 70 to 73 (M = 72, SD = 1), and five motor-disabled subjects aged 37 to 74 (M = 65, SD = 16). Subjects tracked simple one- and two-dimensional motions at various frequencies. Performance was measured using an accuracy index derived from root-mean-square error, and a linearity index based on coherence estimation. A maximum bandwidth of 2 Hz for accuracy of mouse use was found, which often decreased due to advanced age or motor disability. Tracking linearity of all groups decreased as frequency increased. A significant degree of nonlinearity existed in all results (p < 0.05), with disabled subjects nearing complete nonlinearity in two-dimensional tracking. The data show that with advanced age and disability, mouse use becomes increasingly inaccurate and nonlinear. Assistive computer interfacing techniques, such as signal filtering, may improve mouse use.

Adult↗