Fig. 1. Bottom: The first 3D<unk>  images of biologic tissue (lamb kidney). Top: MRIs of the same kidney.Thermoacoustic imaging was originally proposed by Theodore Bowen in 1981 as a strategy for studying the absorption properties of human tissue using virtually any kind of electromagnetic radiation. But Alexander Graham Bell first reported the physical principle upon which<unk>  is based a century earlier. He observed that audible sound could be created by illuminating an intermittent beam of sunlight onto a rubber sheet. Shortly after Bowen's work was published, other researchers proposed methodology for<unk>  using microwaves. In 1994 researchers used an infrared laser to produce the first<unk>  images of near-infrared optical absorption in a tissue-mimicking phantom, albeit in two dimensions (2D). In 1995 other researchers formulated a general reconstruction algorithm by which 2D<unk>  images could be computed from their "projections," i.e.<unk>  computed tomography (TCT). By 1998 researchers at Indiana University Medical Center extended TCT to 3D and employed pulsed microwaves to produce the first fully three-dimensional (3D)<unk>  images of biologic tissue an excised lamb kidney (Fig. 1). The following year they created the first fully 3D<unk>  images of cancer in the human breast, again using pulsed microwaves (Fig. 2). Since that time,<unk>  has gained widespread popularity in research institutions worldwide. As of 2008, three companies were developing commercial<unk>  systems – Seno Medical, Endra, Inc. and OptoSonics, Inc. Fig. 2: First 3D<unk>  image of breast cancer. From left to right: axial, coronal and sagittal views of the cancer (arrows).
Thermoacoustic imaging
Photoacoustic imaging
Vibroacoustic stimulation
Real ear measurement
Multispectral optoacoustic tomography
Tympanometry
Ultrasound-modulated optical tomography
Vibroacoustic therapy