Hence, a laboratory prototype, which allowed real-time signal capture and online signal analysis and data storage, was designed. Author(s):Dr. Jayaraj Joseph — Healthcare Technology Innovation Centre, IIT Madras Healthcare Technology Innovation Centre (HTIC) of IIT Madras is an R&D centre established through a joint initiative of IIT Madras and Department of Biotechnology (DBT), Government of India. The carotid artery is chosen as the site of measurement. The pulsers are designed to provide broadband excitation for maximum broadband transducer performance. This device has so far completed more than 640 measurements in field. Hence, a touch screen-based version of ARTSENS was developed. A rugged version was also developed to be used for field studies. Significant time was spent on porting the algorithms and developing a user interface. As this was a traditional embedded design, it was not possible to leverage the extensive set of algorithms that were already developed with LabVIEW for deployment in the embedded product.
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Strong correlations were observed between ARTSENS measurements and those made by the Aloka imaging system in this study. Validation Results ARTSENS technology was validated both a laboratory environment and clinical settings. The 5627RPP-1 permits use of an optimum short cable from the pulser to the transducer to avoid degradation due to attenuation and cable reflections that can occur at long cable lengths. Hence, HTIC developed a portable version of ARTSENS using a traditional embedded development platform. An OMAP L138 processor-based design was developed and the entire ARTSENS algorithm was ported to the processor.
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Figure 13. ARTSENS Desktop Prototype Multiple units of this design were made and deployed in various clinical centres for validation studies. Arterial wall stiffness has proven utility in early detection of vascular diseases and risk stratification. Local control and instrument memory is ideal for ensuring repeatable results in manual test set ups. This required the creation of a database of signals which could only be attained by extensive experimentation. The instrument was thus a fully functional unit and could be used for performing measurements on volunteers. Hence, the next step was creating dedicated laboratory equipment to capture and analyse signals in real time that would also allow the creation of a database of echo signals for development of automated measurement algorithms. Ultrasonic Pulser-Receivers Pulser architecture ensures fast rise times that when coupled with instrument selectable energy and damping options optimize the excitation pulse for the frequency of inspection.
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The VI illustrates the echo signal received from the artery, and the diameter waveforms measured after manual identification of vessel walls. The amplified echo signals were digitised using a NI USB-5133 digitiser at 100 MS/s and sent to the laptop. The project serves as a strong illustration to the amenability of NI hardware and software for rapid development of product concepts. ARTSENS was conceived as a vascular screening tool, and the next step in its evolution was to develop a portable product design. This meant development of an alternative sensing and measurement modality that did not need an image.
Laboratory Prototype for Image-Free Evaluation of Artery Stiffness Following the proof-of-concept experiment, it was very evident that the success of this R&D hinged on the creation of a robust and reliable signal processing and automated measurement algorithm. Pulse stability is achieved through the use of a fixed, regulated high voltage source. The small, lightweight package can be hand-held or mounted to a structure and drive up to 500 feet of cable back to the 5900PR host receiver for remote applications. The arterial wall motions can be tracked to obtain a distension waveform and also measure the end-diastolic diameter. Clinical studies generated enormous amounts of data that led to the evolution of advanced techniques for wall identification, rejection of incorrect anatomy, online evaluation of signal quality, segregation of high-quality measurements for improved reliability, and more. The linear regression correlation coefficient (r), for arterial stiffness index, β was 0.9, for arterial compliance, AC was 0.7 and for elastic modulus, Ep was 0.9. Increase in arterial stiffness with age was apparent in this study also.
All attenuators use relay switched resistors for accuracy and stability. In addition, high and low pass filters improve main bang recovery and noise response. This was inspired by the use of nonimaging ultrasound transducers for inspection of defects in metals. This experiment demonstrated that the artery walls could be visualised on the echo signals captured using a single element transducer and established that an image-free modality was indeed feasible. With computer control of individual settings through GPIB or RS-232, test parameters may be derived and then programmed for production volume analysis. These organisations collaborate with HTIC to develop affordable healthcare technologies for unmet clinical needs. HTIC delivers innovations and technologies that reach the field, enabling business and benefitting society. Since the measurement had to be performed noninvasively, it was decided to adopt an ultrasound-based sensing technique. Experiments with simulation platforms and artery phantoms demonstrated that ARTSENS could measure artery diameter and distension with error less than 10 percent and track wall motion with precision of 6 µm. The requirement of expensive technology and extensive technical expertise to use that technology limits wide-spread use of image-based arterial stiffness measurement in clinical practice. These can then be used along with blood pressure to calculate arterial stiffness estimates. The computer-controlled pulser-receiver family (5800PR, 5900PR, 5672RPP-1) incorporates design features to ensure optimal signal response.
Moreover, in the absence of an image, the operator had no means to know whether the probe was positioned correctly, and whether the echo signals received by the probe were actually coming from the carotid artery itself. To overcome this limitation, an automated algorithm needed to be developed. Since its inception in 2011, HTIC has evolved into a unique and leading medical technology innovation ecosystem in the country and brings together more than 20 medical institutions, industry, and government agencies. Clinical Need There is an unmet need for an affordable, easy-to-use technology to noninvasively measure arterial stiffness in an automated manner, which could be used by general medical practitioners and health workers. However, the identification of the artery anatomy from the echo signal was extremely difficult and had to be performed manually. The availability of SOM has now enabled us to take the project concept from prototype development to product design and deployment.