Detecting regional lung properties using audio transfer functions of the respiratory system

Acoustic Methods for Pulmonary Diagnosis

Recent developments in sensor technology and computational analysis methods enable new strategies to measure and interpret lung acoustic signals that originate internally, such as breathing or vocal sounds, or are externally introduced, such as in chest percussion or airway insonification. A better understanding of these sounds has resulted in a new instrumentation that allows for highly accurate as well as portable options for measurement in the hospital, in the clinic, and even at home. This review outlines the instrumentation for acoustic stimulation and measurement of the lungs. We first review the fundamentals of acoustic lung signals and the pathophysiology of the diseases that these signals are used to detect. Then, we focus on different methods of measuring and creating signals that have been used in recent research for pulmonary disease diagnosis. These new methods, combined with signal processing and modeling techniques, lead to a reduction in noise and allow improved feature extraction and signal classification. We conclude by presenting the results of human subject studies taking advantage of both the instrumentation and signal processing tools to accurately diagnose common lung diseases. This paper emphasizes the active areas of research within modern lung acoustics and encourages the standardization of future work in this field.

Novel Microwave Torso Scanner for Thoracic Fluid Accumulation Diagnosis and Monitoring

Thoracic fluid accumulation is one of the significant and early-stage manifestations of fatal diseases, such as lung-cancer, liver-failure and congestive heart-failure. Currently, computational-tomography (CT)-Scan is the most widely used tool for the detection of thoracic fluid. Yet, it is unable to detect small amounts of fluid, has ionizing radiation and lacks mobility. On the other hand, microwave imaging systems have emerged as an accurate and portable complementary diagnostic tool. However, there is a lack of a complete clinical platform that can fulfill the requirements of accurate and reliable imaging. Therefore, a microwave torso scanner that is designed to meet those requirements is presented. In this system, two elliptical-arrays of microwave antennas (sensors) transmit signals towards the torso and collect the back-scattered signals. The captured signals are then processed by a frequency-based imaging algorithm to form microwave images that display a possible accumulated fluid. The system successfully detects and localized small volumes (3 mL) of fluid injected at different places inside a torso-phantom. As preparations for future clinical trials, the system is tested on healthy subjects to define the threshold range of healthy scenario images.

Evaluation of the use of frequency response in the diagnosis of pleural effusion on a phantom model of the human lungs

Pleural effusion is one of the most widespread respiratory diseases in the world. Current diagnostic techniques include a combination of medical history and x-ray or CT scan imaging of the chest. However, these techniques are expensive and impractical in resource limited settings. We propose a new method based on sound transmission into the respiratory system through the chest wall. To evaluate this technique, a sine sweep signal with a frequency range between 100 Hz and 1000 Hz was transmitted into a phantom model of the human lungs capable of simulating healthy and effused conditions. The frequency response of the model under both conditions was computed and compared to evaluate the diagnostic performance of the new method. The results indicate that there is a significant difference between the frequency response of healthy and effused lungs, which suggests that the new technique may be suitable for the clinical diagnosis of pleural effusion.

Lung water detection using acoustic techniques

The presence of an excessive amount of water in lung is a sign of pulmonary edema which can be caused by heart failure. The current solutions for lung water detection involve the use of X-ray, CT scan or serum biomarkers, which require bulky and expensive instruments as well as long measurement duration. This paper reports on a study conducted on the use of a different sensing modality to detect the presence of water in lung. The main contributions of the paper are twofold: 1) we propose to employ acoustic (or sound) based techniques for lung water detection. The design is simple and can be implemented on a portable or wearable system; 2) we establish the feasibility of sound-based techniques for lung water detection, by carrying out experimental studies using four feature extraction methods combined with two classification methods. The findings of this study will be beneficial to the design of portable devices for rapid and accurate lung water detection.