Electrical and Computer Engineering

The blood pressure monitoring market is currently dominated by cuff-based blood pressure monitors which have numerous shortcomings. The current products are not only bulky and restrictive but they also inflate the cuffs to an uncomfortable degree while in use. This leads to the second major drawback, which is the inability to provide the user with continuous readings of their blood pressure.  Our product aims to cover those shortcomings and provide users with a more seamless blood pressure measurement experience that does not hinder their daily lives while providing accurate and continuous measurements of their blood pressure to give them better insight into their health condition. The device will be wearable and will be composed of two main subsystems: The first part is a wearable hardware subsystem which will contain the required sensors, a microcontroller, and a bluetooth module to communicate with the second subsystem. And the second main part is a software subsystem in the...

Localization of a needle's tip in ultrasound images is often a challenge during percutaneous procedures due to the inherent limitations of ultrasound imaging. A new method is proposed for tip localization with curvilinear arrays using local image statistics over a region extended from the partially visible needle shaft. First, local phase-based image projections are extracted using orientation-tuned Log-Gabor filters to coarsely estimate the needle trajectory. The trajectory estimation is then improved using a best fit iterative method. To account for the typically discontinuous needle shaft appearance, a geometric optimization is then performed that connects the extracted inliers of the point cloud. In the final stage, the enhanced needle trajectory points are passed to a feature extraction method that uses a combination of spatially distributed image statistics to enhance the needle tip. The needle tip is localized using the enhanced images and calculated trajectory. Validation results obtained from 150 ex vivo ultrasound scans show an accuracy of 0.43 ± 0.31 mm for needle tip localization.

Purpose This paper presents a new approach to detect a standard handheld needle in ultrasound-guided interventions. Methods Our proposal is to use natural hand tremor, which causes minute displacement of the needle, to detect the needle in ultrasound B-mode images. Subtle displacements arising from tremor motion have a periodic pattern which is usually imperceptible to the naked eye in the B-mode image. We use these displacement measurements in a spatiotemporal framework to detect linear structures with periodic pattern among a sequence of frames. The needle trajectory is estimated as a linear path in the image having maximum spectral correlation with the time trace of displacement due to tremor. A coarse estimation process is followed by a fine estimation step, where the motion pattern is analyzed along spatiotemporal linear paths with various angles originating from the estimated puncture site, within the trajectory channel. Spectral coherency is derived for each sample path versus the reference path, and the needle trajectory is identified as the mean of the sample paths with the maximum coherence within the tremor frequency range. Results To evaluate the detection accuracy, we tested the method in vivo on porcine tissue, where the needle was inserted into the biceps femoris muscle. To understand whether tremor itself affects needle position, the maximum angular change due to tremor was calculated: mean, standard deviation (SD) and root-mean-square (RMS) measurement B Parmida Beigi

We propose a novel learning-based approach to detect an imperceptible hand-held needle in ultrasound images using the natural tremor motion. The minute tremor induced on the needle however is also transferred to the tissue in contact with the needle, making the accurate needle detection a challenging task. The proposed learning-based framework is based on temporal analysis of the phase variations of pixels to classify them according to the motion characteristics. In addition to the classification, we also obtain a probability map of the segmented pixels by cross-validation. A Hough transform is then used on the probability map to localize the needle using the segmented needle and posterior probability estimate. The two-step probability-weighted localization on the segmented needle in a learning framework is the key innovation which results in localization improvement and adaptability to specific clinical applications. The method was tested in vivo for a standard 17 gauge needle inserted at 50-80°insertion angles and 40-60 mm depths. The results showed an average accuracy of (2.12°, 1.69 mm) and 81% AE 4% for localization and classification, respectively.

Current 2-D ultrasound technology is unable to perform a midline neuraxial needle insertion under real-time ultrasound guidance using a standard needle and without an assistant. The aim of the work described here was to determine the feasibility of a new technology providing such capability, starting with a study evaluating the selected puncture site. A novel 3-D ultrasound imaging technique was designed using thick-slice rendering in conjunction with a custom needle guide (3DUS 1 Epiguide). A clinical feasibility study evaluated the ability of 3DUS 1 Epiguide to identify the epidural needle puncture site for a midline insertion in the lumbar spine. We hypothesized that (i) the puncture site identified by 3DUS 1 Epiguide was within a 5-mm radius from the site chosen by standard palpation, and (ii) the difference between the two puncture sites was not correlated to the patient characteristics age, weight, height, body mass index and gestational age. The mean (±standard deviation) distances between puncture sites determined by 3DUS 1 Epiguide and palpation were 3.1 (±1.7) mm and 2.8 (±1.3) mm, for the L2-3 and L3-4 interspaces of 20 patients, respectively. Distances were comparable to intra-observer variability, indicating the potential for a thick-slice rendering of 3-D ultrasound along the Epiguide trajectory to select the puncture site of a midline neuraxial needle insertion. The long-term potential benefits of this system include increased efficiency and use of anesthesia, and a reduction in the frequency and severity of the complications from incorrect needle insertions. Epidural success in the most difficult cases (e.g., the obese) will be the focus of future work.

Background: We developed a real-time 3D ultrasound thick slice rendering technique and innovative Epiguide needle-guide as an adjunct to single-operator midline epidural needle insertions. Study goals were to determine feasibility of the technique in a porcine model and compare the visibility of standard and echogenic needles. Methods: Thirty-four lumbar needle insertions were performed on six intact porcine spines ex vivo. Ultrasound scanning identified the insertion site and, using an Epiguide, the needle was guided into the epidural space through the ligamentum flavum in the midline plane, watched in real-time on the 3D ultrasound. Entry into the epidural space was judged by a loss-of-resistance technique. Needle visibility was rated by the anesthesiologist performing the technique using a 4-point scale; (0=cannot see, 1=poor, 2=satisfactory, 3=excellent), and later by an independent assessor viewing screenshots. The procedure was repeated at all lumbar levels using either the standard or echogenic needle. Results: Successful loss-of-resistance to fluid was achieved in 76% of needle insertions; needle visibility with echogenic needles (94.2% rated satisfactory/excellent) was significantly better than with standard needles (29.4% satisfactory/excellent, P <0.0001). Successful loss-of-resistance was 93% when mean needle visibility was rated as 'excellent'. Inter-observer agreement between assessors was 'near-perfect' (weighted kappa=0.83). Conclusion: It is feasible to perform 3D ultrasound-guided real-time single-operator midline epidural insertions, in a porcine model. Echogenic needles were found to consistently improve needle visibility; and improved needle visibility tended to increase successful entry into epidural space.