Methods and apparatus for measuring and characterizing the localized electromagnetic wave absorption properties of biologic tissues (12) in vivo, using incident electromagnetic waves to produce resultant acoustic waves (26). Multiple acoustic transducers (33) are acoustically coupled to the surface of the tissue for measuring acoustic waves produced in the tissue when the tissue is exposed to a pulse of electromagnetic radiation. The multiple transducer signals are then combined to produce an image of the absorptivity of the tissue, which image may be used for medical diagnostic purposes. In specific embodiments, the transducers are moved to collect data from multiple locations, to facilitate imaging. Specific arrangements of transducers are illustrated. Also, specific mathematical reconstruction procedures are described for producing images from transducer signals.

Photoacoustic breast scanner

Presents a new imaging method based on the classical Hall effect (HE), which describes the origin of a detectable voltage from a conductive object moving in a magnetic field. HE images are formed using ultrasound imaging techniques in a magnetic field. These images reflect the electrical properties of the sample. To demonstrate the feasibility of this method, images of plastic and biological samples are collected. The contrast mechanism and signal-to-noise issues are discussed. Since electrical parameters vary widely among tissue types and pathological states, HE imaging may be a useful tool for biological research and medical diagnosis.

Hall effect imaging

The discovery of highly active piezoelectric polymer materials was first reported in 1969. Since then an enormous amount of research work has been conducted, mainly aimed at discovering the structure and properties of these fascinating materials with the further aim of improving their piezoelectric and pyroelectric behaviour. An equally vast amount of literature devoted to applications of these polymers has appeared and even a cursory glance at all this shows that they have been applied as the basis for a wide range of devices. The subject has now reached a degree of maturity and in the nondestructive testing field, there is perhaps a 'niche market' emerging for transducers based on polyvinylidene fluoride and its derivatives. In certain areas such as miniature under water hydrophones, piezoelectric polymers have become the material of choice. This being so, it is appropriate to review the subject.

https://iopscience.iop.org/article/10.1088/0957-0233/6/3/001/pdf

Industrial applications of piezoelectric polymer transducers

Methods and apparatus for measuring and characterizing the localized electromagnetic wave absorption properties of biologic tissues in vivo, using incident electromagnetic waves to produce resultant acoustic waves. Multiple acoustic transducers arranged on an rotatable imaging bowl are acoustically coupled to the surface of the tissue for measuring acoustic waves produced in the tissue when the tissue is exposed to a pulse of electromagnetic radiation. The multiple transducer signals are then combined to produce an image of the absorptivity of the tissue, which image may be used for medical diagnostic purposes. Specific mathematical reconstruction procedures are described for producing images from transducer signals. Specific arrangements of transducers are illustrated, and noise reduction techniques are described.

Thermoacoustic computed tomography scanner

Determination of blood glucose level is a frequently occurring procedure in diabetes care. As the most common method involves collecting blood drops for chemical analysis, it is invasive and liable to afflict a degree of pain and cause a skin injury. To eliminate these disadvantages, this thesis focuses on pulsed photoacoustic techniques, which have potential ability in non-invasive blood glucose

/pdf/pulsed-photoacoustic-techniques-and-glucose-determination-in-51acwfklpg.pdf

Pulsed Photoacoustic Techniques and Glucose Determination in Human Blood and Tissue

A new laser-ultrasound transducer for medical applications

Characterisation of laser-ultrasound signals from an optical absorption layer within a transparent fluid

Modelling of a photoacoustic probe designed for medical applications

Interest in medical diagnostic ultrasound has progressively increased over the last two decades. The advent of sophisticated technology has enhanced the reliability and the user-friendliness of ultrasound systems, together with significant improvement in the quality of data available to clinicians. Much of the development work has been based on external scanning techniques; however, more recently, systems have been developed for invasive ultrasound investigations inside the lumen of blood vessels. Cardiovascular disease, the morbidity and mortality of which have reached epidemic proportions in the western world, remains a major challenge for the health care professionals, scientists and economists alike.

Developments in a Photoacoustic Probe for Potential Use in Intra-Arterial Imaging and Therapy

We have previously reported our observations that, at laser wavelengths of 1,064 and 532 nm, following repeated exposure to short pulses at power density levels well below those reported to cause permanent damage to biological tissue, the photoacoustic signal detected using an ultrasound probe diminishes significantly. Examination by electron microscopy of such tissue at the site at which repeated laser pulse exposures have been made reveals little evidence of structural changes to the tissue. The effect that we have observed remains unexplained.

P.A. Payne

Papers

A new laser-ultrasound transducer for medical applications

Characterisation of laser-ultrasound signals from an optical absorption layer within a transparent fluid

Modelling of a photoacoustic probe designed for medical applications

Developments in a Photoacoustic Probe for Potential Use in Intra-Arterial Imaging and Therapy

Optical Wavelength Effects Observed in Photoacoustic Signals from Biological Tissue