Auscultation has been the basis for diagnosis lung diseases, but supplementation by imaging is often required. Our goal is to describe the PALIScope (Passive Acoustic Lung Imaging), an array of acoustic sensors and an algorithm that assembles a dynamic image that is useful for diagnosis and monitoring lung diseases.
The PALIScope is composed of 42 microphones, attached to the back by gentle negative pressure that records sounds during tidal breathing. An algorithm filters interferences and selects, from lung sounds frequencies, a band that carries the information required to assemble a consistent lung image. The signals are converted to energy over every 0.17 seconds at each sensor. To smooth the transitions between sensors, the dissipation of the signals was fitted to a mathematical function, and a gray level frame is constructed (white = no signal, black = maximal signal). The final image is one breath sequence of these frames. Subjects: Healthy nonsmoker adults and patients with space occupying processes.
Normal image: As inspiration starts, the intensity and spatial distribution of the image increase, almost symmetrically, firstly at the upper zones. During expiration, which is of lower sound, the intensity fades towards the center. Image 1. Disease states: Changes in tissue composition or alteration of airflow may modify 1-3 characteristics of the image, intensity, distribution or dynamics/symmetry. Space occupying process affects the intensity and distribution. Image 2. Airway and parenchymal diseases affect the time sequence and symmetry. Image 3.
The PALIScope processes sounds and assembles a dynamic lung image that is consistent in healthy subjects and possesses distinct abnormalities in diseases. Therefore, it offers easily obtainable, quantifiable, functional and potentially structural information on the lung, some of which can otherwise be obtained only by combining multiple imaging modalities.
The PALIScope may facilitate bedside diagnosis and physiological studies of the lung.Images are shown at: http://www.sheba.co.il/lung-image.
I.B. Dov, Deep Breeze Ltd.