David Shoudy

A full-duplex ultrasonic through-wall communication and power delivery system

This paper presents a method for two-way ultrasonic communication and power delivery through thick metallic enclosures without physical penetration. Acousticelectric channels are implemented using a pair of coaxially aligned piezoelectric transducers having 25.4 mm diameters and 1 MHz nominal resonant frequencies, mounted on steel walls having lengths in the range of 57.15 to 304.8 mm. A protocol is described which uses ultrasonic waves to achieve simultaneous bidirectional communication through the metallic enclosures. It is shown that such channels are very frequency selective, and a carrier frequency selection and tracking algorithm is presented to choose a frequency of operation at which both adequate power delivery and reliable full-duplex communication are achieved. Using this algorithm, sufficient power is harvested to allow for the continuous operation of internal electronics which require an aggregate of less than 100 mW. Reliable communication of sensor data is achieved at rates in excess of 30 kbps.

An Ultrasonic Through-Wall Communication (UTWC) System Model

Ultrasonic waves at 1 MHz are used to send information across solid walls without the needs for through wall penetrations. A communication channel is established by attaching a set of three ultrasonic transducers to the wall. The first transducer transmits a continuous ultrasonic wave into the wall. The second transducer is mounted on the opposite side of the wall (inside) and operates as a receiver and signal modulator. The third transducer, the outside receiving transducer, is installed on the same side as the first transducer where it is exposed to the signal reflected from the blended interface of the inside wall and inside transducer. Inside sensor data is digitized and the bit state is used to vary in time the electrical load connected to the inside transducer, changing its acoustic impedance in accordance with each data bit. These impedance changes modulate the amplitude of the reflected ultrasonic signal. The modulated signal is detected at the outside receiving transducer, where it is then demodulated to recover the data. Additionally, some of the ultrasonic power received at the inside transducer is harvested to provide energy for the communication and sensor system on the inside. The entire system (ultrasonic, solid wall, and electronic) is modeled in the electrical domain by means of electro-mechanical analogies. This approach enables the concurrent simulation of the ultrasonic and electronic components. A model of the communication system is implemented in an electronic circuit simulation package, which assisted in the analysis and optimization of the communication channel. Good agreement was found between the modeled and experimental results.

Real-time 3D electrical impedance imaging for ventilation monitoring of the lung: Pilot study.

We report an Electrical Impedance Tomography device capable of detecting gravity-induced regional ventilation changes in real-time without averaging or using a contrast medium. Changes in lung ventilation are demonstrated in right and left lateral decubitus position and compared to those seen in an upright and supine normal subject.

A magnetic resonance compatible E4D ultrasound probe for motion management of radiation therapy

There is recent interest in the use of ultrasound (US) and magnetic resonance (MR) imaging modalities for motion management during radiation therapy treatments. These imaging modalities aim to improve clinical outcomes by tracking tumor motion in order to increase the therapeutic ratio. The objective of this research is to develop an MR-compatible, real-time, three-dimensional ultrasound probe (E4D) for simultaneous MR and US imaging. The probe will be used in a system which leverages the real-time capabilities of ultrasound imaging and the soft-tissue image quality of MR for image guided radiation therapy (IgRT) of moving tumors.

Microfluidic Tissue Mesodissection in Molecular Cancer Diagnostics

We present a mesodissection platform that retains the advantages of laser-based dissection instrumentation with the speed and ease of manual dissection. Tissue dissection in clinical laboratories is often performed by manually scraping a physician-selected region from standard glass slide mounts. In this manner, costs associated with dissection remain low, but spatial resolution is compromised. In contrast, laser microdissection methods maintain spatial resolution that matches the requirements for analysis of important tissue heterogeneity but remains costly and labor intensive. We demonstrate a microfluidic tool for rapid extraction of histological regions of interest from formalin-fixed paraffin-embedded tissue, which uses a simple and automated method that is compatible with most downstream enzymatic reactions, including protocols used for next-generation DNA sequencing.

Comparison of impedance measurements near the skin of newborns and adults.

Electrical impedance tomography (EIT) is a non-invasive imaging technology that has been extensively studied for monitoring lung function of neonatal and adult subjects, especially in neonatal intensive care unit (NICU) and intensive care unit (ICU) environments. The sources of the total impedance in these applications include internal organs, near-boundary tissues, electrode-skin impedance, electrodes and conducting wires. This total impedance must be considered for system design and setting voltage gain since it will contribute to the measured voltage. To adapt a single instrument for use on infants and adults, we studied the difference between the impedance near the skin in both classes of patients. We used a simultaneous multi-source EIT (SMS-EIT) system to make impedance measurements. Characteristic resistance was calculated for two different current patterns: one that is more sensitive to boundary region impedance and another that is more sensitive to interior changes. We present ratios of these resistances to assess the relative contribution of near-skin effects to the overall impedance. Twenty adult ICU subjects (10 male, 10 female, age: 49.05  ±  16.32 years (mean  ±  standard deviation)) and 45 neonates (23 male, 22 female, gestational age: 37.67  ±  2.11 weeks, postnatal age, 2.56  ±  2.67 d) were studied at Columbia University Medical Center. Impedance measurements at 10 kHz were collected for approximately one hour from each subject. The characteristic resistance ratio for each subject was computed and analyzed. The result shows the impedance at or near the skin of newborns is significantly higher than in adult subjects.

Real-time 3D electrical impedance imaging for ventilation and perfusion of the lung in lateral decubitus position

We report a prototype Electrical Impedance Imaging System. It is able to detect the gravity-induced changes in the distributions of perfusion and ventilation in the lung between supine and lateral decubitus positions. Impedance data were collected on healthy volunteer subjects and 3D reconstructed images were produced in real-time, 20 frames per second on site, without using averaging or a contrast agent. Imaging data also can be reconstructed offline for further analysis.