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Tactile imaging, also called "mechanical imaging", "stress imaging" or "computerized palpation", is a medical imaging modality that translates the sense of touch into a digital image. The tactile image is a function of ''P(x,y,z)'', where ''P'' is the pressure on soft tissue surface under applied deformation and ''x,y,z'' are coordinates where pressure ''P'' was measured. The tactile image is a pressure map on which the direction of tissue deformation must be specified. Tactile imaging closely mimics manual palpation, since the probe of the device with a pressure sensor array mounted on its face acts similar to human fingers during clinical examination, deforming soft tissue by the probe and detecting resulting changes in the pressure pattern. Interpretation: Inverse problem solution for ''P(x,y,z)'' would allow reconstruction of the tissue elasticity distribution ''(E)'' as function of the same coordinates ''E(x,y,z).'' The tissue elasticity image brings valuable information about the tissue or organ because the tissue elasticity modulus is highly sensitive to tissue structural changes accompanying various physiological and pathological processes. Unfortunately, the inverse problem solution is hardly possible for most real objects because it is non-linear and ill posed problem. However, it appeared that the tactile image ''per se'', ''P(x,y,z),'' closely reflects the information content of the elasticity image and reveals tissue or organ anatomy and elasticity structure. The tissue elasticity at specified location can be estimated on the basis of spatial gradients within ''P(x,y,z)''. Figure 1 presents an experiment on a composite tissue phantom examined by a tactile imaging probe illustrating the ability to visualize the structure of the object. == History == Historically, the human sense of touch has been the most prevalent and successful medical diagnostic technique. A great variety of diseases were diagnosed through tactile sensing. We find in Kahun Gynecological Papyrus 〔(The Kahun Gynaecological Papyrus. 1825 B.C. )〕 dated 1825 B.C.: "''Discernere eam quae concepit'' ... like that finger upon her menaa." Hippocrates in 400 B.C. wrote: “Such swellings as are soft, free from pain, and yield to the finger, ... and are less dangerous than the others. ... then, as are painful, hard, and large, indicate danger of speedy death; but such as are soft, free of pain, and yield when pressed with the finger, are more chronic than these...”.〔(Hippocrates. The Book of Prognostics. 400 B.C. )〕 During the last century, traditional physical examination techniques were becoming outmoded and were often considered of little clinical value in comparison with many other modern diagnostic technologies. Palpation is only briefly addressed in medical school, and few physicians have the tactile ability to detect subtle variations of tissue elasticity. Few physicians are willing to devote the necessary time to master the technique, despite the fact that the American Cancer Society guidelines suggest for women that clinical breast examination (CBE) be part of a periodic health examination 〔American Cancer Society. 2010. Breast Cancer Facts & Figures 2009–2010. Atlanta, GA: American Cancer Society, Inc. pp.1-40〕 and the American Urological Association in their 2009 Best Practices Statement recommended that men who wish to be screened for prostate cancer should have both a prostate-specific antigen (PSA) test and a digital rectal examination (DRE). The first description of a technical implementation related to Tactile Imaging was given in the late 1970s by Frei et al.〔Frei EH, Sollish BD, Yerushalmi S. inventors; Yeda Research and Development Co. Ltd., assignee. Instrument for viscoelastic measurement. U.S. Patent 4,144,877; 1979.〕 who proposed an instrument for breast palpation that used a plurality of spaced piezoelectric force sensors. The sensors were pressed against the breast tissue by a pressure member which applied a given periodic or steady stress to the tissue. A different principle for evaluating the pattern of pressure distribution over a compressed breast was proposed by Gentle in 1980s. The pressure distribution was monitored optically by using the principle of frustrated total internal reflection to generate a brightness distribution. Then, Sabatini et al. built a robotic system for discriminating mechanical inhomogeneities in a soft tissue using a finger-like palpation device equipped with a fingertip piezoelectric polymer film tactile sensor. The first review about the tactile sensor development for robots is dated by 1986.〔 Yardley AMM, Baker KD. ( Tactile Sensors for Robots: A Review ). In: The world Yearbook of Robotics Research and development. Eds. Scott PB. 1986: 47-83.〕 Mechanical imaging, as a modality of medical diagnostics using mechanical sensors, was introduced in the 1990s by Sarvazyan〔Sarvazyan AP, Skovoroda AR. June 1996. Method and apparatus for elasticity imaging. U.S. Patent 5,524,636; 1996.〕 and later by Wellman ''et al.'' at Harvard University. Many physical principles have been explored for the realization of tactile sensors: resistive, inductive, capacitive, optoelectric, magnetic, piezoelectric and electroacoustic principles, in a variety of configurations. Since mid-nineties, Tactile Imaging became the main area of research activities of (Artann Laboratories, Inc. ) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「tactile imaging」の詳細全文を読む スポンサード リンク
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