Method for High Accuracy Differential Pressure Measurements Using Fluid-Filled Catheters
The advantage of measuring differential pressure using fluid-filled catheters is that the system is relatively inexpensive, but the readings are not accurate and affected by the common mode pressure (CMP) distortion. High accuracy differential pressure measurements are required in various biomedical applications, such as in fluid-dynamic test rigs, or in the cath-lab, from cardiac valves efficacy to functional assessment of arterial stenoses. We have designed and built a unique system in which the pressure difference was measured along the fluid flow inside a rigid circular tube using a fluid-filled double-lumen catheter. The differential pressure measurements were taken across two side-holes near the catheter distal tip, spaced apart by 3 cm. The goal was to overcome the CMP error, which significantly distorted the output differential pressure signal and to formulate a restoration factor. A restoration formula was developed based on simultaneous gauge pressure measurements, and was tested in several different cases. Several representative cases are presented and show that the common mode artifact was reduced by factors of 12–27. The restored pressure gradient signal was validated using direct pressure drop measurements, and showed very good agreement.
Coronary Pressure Drop and Arterial Distensibility—Two Dependent Parameters
Blood pressure drop and arterial distensibility are important, allegedly independent, parameters that are indicative of the coronary arteries patency and atherosclerosis severity. In the present study we show that these two parameters are dependent, allowing to obtain both parameters from a single measurement, and to do so a high-resolution differential pressure measurement system is required. The objective of the study was to unveil the relationship between local fluid pressure drops and tube distensibility, through various scenarios of stenosis severity, tube diameter, and flow rate (for coronary hemodynamic conditions). The investigation was performed using validated Fluid–Structure Interaction (FSI) analysis on silicone mock arteries with intermediate size stenosis (0–65%). Highly accurate pressure drop measurements (±0.05 mmHg) were performed with our in-house fluid-filled double-lumen catheter measurement. The results indicated that our accurate pressure drop measurement method facilitated the differentiation among several levels of the mock arteries’ stiffness, with distensibilities ranging from 1 to 7%. Local pressure drops were markedly affected by the mock arteries’ stiffness and could be best described using a second-order polynomial function. These changes in pressure drop could be detected even when there was no stenosis present, and FFR values remained insensitive at 1.00. The results indicated the clinical potential of a high accuracy pressure drop-based parameter to be superior to FFR. Such a parameter would provide cardiovascular interventionalists with lesion-specific bio-mechanical and functional data, for improved real-time decision-making in the cath-lab.
Design of a low power viterbi decoder for wireless communication applications
In this paper, a novel low-power Viterbi decoder with soft decision is proposed. For the branch metric of the Viterbi decoder, our design employs a soft-decision method to improve its correction capability. In order to find the survivor path efficiently, we modify the classical Viterbi decoding algorithm into a new one. This new algorithm is similar to the register-exchange method with lower latency, but using RAM instead of register banks for recording the output bit-stream of the survivor path. Hence, our design can provide a low-power design. Finally, the chip of this design consumes about 28.6K gates using TSMC 0.18 μm CMOS technology. The power consumption of our chip is about 19.5mW at 100MHz.