In vivo label-free observation of tumor-related blood vessels in small animals using a newly designed photoacoustic 3D imaging system

Introduction: Photoacoustic technology can be used for non-invasive imaging of blood vessels. In this paper, we report on our prototype photoacoustic imaging system with a newly designed ultrasound sensor and its visualization performance of microvascular in animal. Methods: We fabricated an experimental system for animals using a high-frequency sensor. The system has two modes: still image mode by wide scanning and moving image mode by small rotation of sensor array. Optical test target, euthanized mice and rats, and live mice were used as objects. Results: The results of optical test target showed that the spatial resolution was about 2 times higher than that of our conventional prototype. The image performance in vivo was evaluated in euthanized healthy mice and rats, allowing visualization of detailed blood vessels in the liver and kidneys. In tumor-bearing mice, different results of vascular induction were shown depending on the type of tumor and the method of transplantation. By utilizing the video imaging function, we were able to observe the movement of blood vessels around the tumor. Conclusion: We have demonstrated the feasibility of the system as a less invasive animal experimental device, as it can acquire vascular images in animals in a non-contrast and non-invasive manner.

Design of a Characterisation Environment for a MEMS Ultrasound Sensor under Guided Ultrasonic Wave Excitation

Microelectromechanical Systems (MEMS) are a current subject of research in the field of structural health monitoring (SHM) for the detection of guided ultrasonic waves (GUW). The dispersive behaviour of GUW, reflections and other kinds of wave interactions might result in a complex wave field that requires a specific analysis and interpretation of the recorded signals. This makes it difficult or impossible to interpret the sensor signal regarding the distinguishability between the sensor transfer behaviour and the specific behaviour of the test structure. Therefore, a proper application-suited design of the tested structure is crucial for reliable sensor characterisation. The aim of this contribution is the design and evaluation of a setup that allows a representative situation for a GUW application and provides a defined vibration energy for a MEMS sensor characterisation. Parameters such as the specimen’s geometry, material properties and the sensor specifications are taken into account as well as the experimental settings of the GUW excitation. Furthermore, the requirements for the test application case are discussed.

Endoscopic ultrasonography in the diagnosis of pathology of the gastrointestinal tract

Endoscopic ultrasonography is a relatively new endoscopic method of examination to determine the invasion of tumors of the gastrointestinal tract, detection and sizing of pancreatic tumors, diagnosis of chronic pancreatitis, pathology of the biliary tract. The method combines the possibilities of two studies: endoscopic and ultrasound. The study is performed using a video endoscope, at the end of which is a scanning ultrasound sensor. The advantages of endoscopic ultrasound over traditional ultrasound examination through the anterior abdominal wall are that the ultrasound sensor under visual control through the lumen of the digestive tract can be carried out directly to the investigated object. The use of very high frequencies of ultrasound provides high image quality with a resolution of less than 1 mm, inaccessible to other research methods (ultrasound, computer tomography and magnetic resonance imaging, endoscopic cholangiopancreatography).

Periodic Tubular Structures and Phononic Crystals towards High-Q Liquid Ultrasonic Inline Sensors for Pipes

The article focuses on a high-resolution ultrasound sensor for real-time monitoring of liquid analytes in cylindrical pipes, tubes, or capillaries. The development of such a sensor faces the challenges of acoustic energy losses, including dissipation at liquid/solid interface and acoustic wave radiation along the pipe. Furthermore, we consider acoustic resonant mode coupling and mode conversion. We show how the concept of phononic crystals can be applied to solve these problems and achieve the maximum theoretically possible Q-factor for resonant ultrasonic sensors. We propose an approach for excitation and measurement of an isolated radial resonant mode with minimal internal losses. The acoustic energy is effectively localized in a narrow probing area due to the introduction of periodically arranged sectioned rings around the tube. We present a sensor design concept, which optimizes the coupling between the tubular resonator and external piezoelectric transducers. We introduce a 2D-phononic crystal in the probing region for this purpose. The Q-factor of the proposed structures show the high prospects for phononic crystal pipe sensors.

Arterial Flow and Diameter-based Blood Pressure Models-an In-silico Comparison

<div>This paper investigates the best method for obtaining highly accurate blood pressure values in non-invasive measurements when using an ultrasound sensor. Deviations of the model should be less than 5 mmHg from the actual values. Different blood pressure models were analyzed and qualitatively compared. Relevant arterial parameters such as luminal area, flow velocity and pulse wave velocity, of 729 subjects were extracted from a computer simulated database and served as input parameters. Due to pulse wave variations through the arterial tree, such as viscoelasticity and arterial stiffness, the applied algorithms need to be specifically adapted to each arterial site. In-silico model comparison at different arterial sites were used to identify the parameters for individual equations that deduce the blood pressure at different arteries (carotid, brachial and radial). A linear model calibrated luminal area pulse wave to blood pressure and revealed to be most accurate model. The model was validated with a commercial pressure sensor in an ex-vivo experimental setup. The results showed an in-silico pulse pressure correlation of 0:978 and mean difference of (-2.134 ±2.477) mmHg at the radial artery and ex-vivo pressure correlation of 0:994 and mean difference of (0.554 ±2.315) mmHg.</div>

Arterial Flow and Diameter-based Blood Pressure Models-an In-silico Comparison

<div>This paper investigates the best method for obtaining highly accurate blood pressure values in non-invasive measurements when using an ultrasound sensor. Deviations of the model should be less than 5 mmHg from the actual values. Different blood pressure models were analyzed and qualitatively compared. Relevant arterial parameters such as luminal area, flow velocity and pulse wave velocity, of 729 subjects were extracted from a computer simulated database and served as input parameters. Due to pulse wave variations through the arterial tree, such as viscoelasticity and arterial stiffness, the applied algorithms need to be specifically adapted to each arterial site. In-silico model comparison at different arterial sites were used to identify the parameters for individual equations that deduce the blood pressure at different arteries (carotid, brachial and radial). A linear model calibrated luminal area pulse wave to blood pressure and revealed to be most accurate model. The model was validated with a commercial pressure sensor in an ex-vivo experimental setup. The results showed an in-silico pulse pressure correlation of 0:978 and mean difference of (-2.134 ±2.477) mmHg at the radial artery and ex-vivo pressure correlation of 0:994 and mean difference of (0.554 ±2.315) mmHg.</div>