Electric-Field-Based Guidance for Percutaneous Catheter Vessel Crossing.

Percutaneous procedures to divert blood flow from one blood vessel to another can be performed with intravascular catheters but demand a method to align a crossing needle from one vessel to another. Fluoroscopic imaging alone is not adequate, and it is preferable to have a sensor on one catheter that detects the correct alignment of an incoming needle. This can be implemented by generating dipole electric fields from the crossing catheter which are detected by a receiving catheter in the target vessel and, thus, can calculate and display the degree of alignment, permitting the operator to rotate the crossing catheter to guarantee alignment when deploying a crossing needle. Catheters were built using this concept and evaluated in vitro. The results show that accurate alignment is achieved, and a successful crossing can be made. The concept is being further developed for further clinical evaluation.

An Implantable Versatile Electrode-Driving ASIC for Chronic Epidural Stimulation in Rats.

This paper presents the design and testing of an electrode driving application specific integrated circuit (ASIC) intended for epidural spinal cord electrical stimulation in rats. The ASIC can deliver up to 1 mA fully programmable monophasic or biphasic stimulus current pulses, to 13 electrodes selected in any possible configuration. It also supports interleaved stimulation. Communication is achieved via only 3 wires. The current source and the control of the stimulation timing were kept off-chip to reduce the heat dissipation close to the spinal cord. The ASIC was designed in a 0.18- µm high voltage CMOS process. Its output voltage compliance can be up to 25 V. It features a small core area (<;0.36 mm(2)) and consumes a maximum of 114 µW during a full stimulation cycle. The layout of the ASIC was developed to be suitable for integration on the epidural electrode array, and two different versions were fabricated and electrically tested. Results from both versions were almost indistinguishable. The performance of the system was verified for different loads and stimulation parameters. Its suitability to drive a passive epidural 12-electrode array in saline has also been demonstrated.

A CMOS smart temperature and humidity sensor with combined readout.

A fully-integrated complementary metal-oxide semiconductor (CMOS) sensor for combined temperature and humidity measurements is presented. The main purpose of the device is to monitor the hermeticity of micro-packages for implanted integrated circuits and to ensure their safe operation by monitoring the operating temperature and humidity on-chip. The smart sensor has two modes of operation, in which either the temperature or humidity is converted into a digital code representing a frequency ratio between two oscillators. This ratio is determined by the ratios of the timing capacitances and bias currents in both oscillators. The reference oscillator is biased by a current whose temperature dependency is complementary to the proportional to absolute temperature (PTAT) current. For the temperature measurement, this results in an exceptional normalized sensitivity of about 0.77%/°C at the accepted expense of reduced linearity. The humidity sensor is a capacitor, whose value varies linearly with relative humidity (RH) with a normalized sensitivity of 0.055%/% RH. For comparison, two versions of the humidity sensor with an area of either 0.2 mm2 or 1.2 mm2 were fabricated in a commercial 0.18 µm CMOS process. The on-chip readout electronics operate from a 5 V power supply and consume a current of approximately 85 µA.

Chronic cuff electrode recordings from walking Göttingen mini-pigs.

We present data from cuff electrode recordings from a mixed sensory-/motor nerve as expressed during walking in chronically implanted Göttingen mini-pigs. Our results show that it is possible to filter out residual electromyographic interference and that the energy content of the resulting electroneurographic (ENG) signals modulate clearly with gait. The approach may be used to detect heel strike from cuff electrode measurements to control the timing of stimulation in implantable foot drop correction systems.

Novel haptic tool and input device for real time bilateral biomanipulation addressing endoscopic surgery.

In this paper a sensorised polymer microgripper is presented which can be used as a suitable end effector on an endoscopic microinstrument for robot-assisted and possibly teleoperated surgery to enable the operator to receive haptic feedback information on the forces generated during the procedure. A novel tweezers- like haptic input device is also described, which gives the operator the ability to remotely feel these forces generated by grasping operations with the microgripper. This feedback is used to control the amount of force applied in manipulation of tissues during the procedure. The mechanical and electronic design of the microgripper, microinstrument and haptic tweezers is also presented and preliminary results detailed.

The drawing test: assessment of coordination abilities and correlation with clinical measurement of spasticity.

OBJECTIVE: To assess the correlation between kinematic measures of movement (Drawing Test) and a clinical measure of spasticity (Ashworth Scale). DESIGN: Correlation study of Drawing Test and the Ashworth Scale scores. SETTING: Inpatient rehabilitation center. PARTICIPANTS: Forty-five poststroke hemiplegic subjects with various levels of spasticity (up to Ashworth Scale score of 3) and 8 able-bodied subjects with no sensorimotor deficits in their upper extremities. INTERVENTIONS: Subjects made self-paced, radial point-to-point movements between the left, and the right corners of a square (200 x 200 mm) on the surface of a drawing tablet. Hand coordinates were recorded from the mouse, which was attached to the hand. MAIN OUTCOME MEASURES: Correlation between (1) Drawing Test scores (time to perform the movement, radial [ y ] and tangential [ x ] distances between the end point of the movement and the target endpoint, standard error of the mean calculated as distances between the recorded path and its radial linear fit), and (2) Ashworth Scale scores. RESULTS: Drawing Test scores correlated highly with Ashworth Scale scores in 49 of 53 subjects, based on the multiple linear regression analysis. CONCLUSIONS: The Drawing Test, a quantitative metric of movement ability, correlated highly to the Ashworth Scale, a clinical measure of spasticity.