Surgery – Truss – Pad
Patent
1990-02-27
1992-12-29
Howell, Kyle L.
Surgery
Truss
Pad
359 10, 359 30, A61B 600
Patent
active
051742985
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a system for imaging an object immersed in a scattering medium or an internal portion (for example a plane) of said scattering object. The system is described in its application to the field of medical imaging. It operates at visible or near-infrared wavelengths and therefore relates to a method of transillumination (or diaphanoscopy).
The essential difference between this system and those known in the technique lies in the fact that the scattered photons taken into account for the formation of the image have an associated frequency which is different from that of the other photons. This difference is obtained directly, within the organ, by Doppler effect. The system therefore permits a tomographic study of the organ.
The method described proposes an alternative to conventional medical imaging systems (x-radiation associated with a film, ultrasonic scanning, nuclear magnetic resonance). It permits the formation of three-dimensional images, which are immediately available, by transmission of visible or near-infrared light through a living organ. This method can also be applied to any scattering medium which is sufficiently transparent to light.
Transillumination as a means of diagnosis was employed for the first time in 1929 for the display of breast tumors. A description of a system of this type will be found in the article "Transillumination as an aid in the diagnosis of breast lesions" by M. Cutler, published in Surgery, Gynecology and Obstetrics, June, 1929. The device employed consisted solely of a lamp placed beneath the patient's breast whilst the medical practitioner directly observed the scattered light. All the devices employed since that time are improvements of this first system. The use of more powerful, cooled torches having sensitive surfaces in the near-infrared region by making use of infrared films or camera, the formation of images having two different wavelengths associated with a substantial treatment of the image, have not permitted a spectacular improvement. The main limitation arises from the very high value of the scattering coefficient within the biological tissues, even at wavelengths in which the absorption is lowest. Devices of this type are employed only for mammography and do not permit detection with any great degree of reliability either of tumors having small lower dimensions (1 cm) or of deep tumors even of larger size.
The method proposed by the INSERM Institute (U238) of Professor Jarry and described in the Doctorate thesis, Science speciality, upheld by S. Debray on June 12, 1987 before the University of Paris, Val de Marne and entitled "Device for laser transillumination of biological tissues, contributions of time resolution and of spectrophotometry" makes it possible to escape from the influence of scattering. The organ is illuminated by a laser beam. The detector placed opposite to the laser, behind the organ, is provided with a collimator. The selection of time of flight or time of traversal of the organ by the non-deviated photons or scattered photons makes it possible to avoid the need to take the scattered photons into account. In fact, in order to select the photons transmitted in a straight line, a pulsed laser is employed. This system also permits spectroscopic analysis of the organ (dye laser). Contrast and perception of details are improved.
The description of such a system will be found in the article "Study in simulation of the behavior of light in biological tissues" by Maarek and Jarry, published in Innovations Techniques Biologiques et Medicales, Volume 7, No. 3, 1985.
The use of a streak camera having a resolution of 5 picoseconds and a pulsed laser source has permitted the development of a tomographic imaging system as described in the article "Laser pulse tomography using a streak camera" by Y. Takguchi et al., published in Proceedings Image Detection and Quality, July, 1986. Tomography is made possible by recording of the back-scattered signal. Taking into account the weakness of the signal, this technique will be difficult
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IEEE Transactions on Computers, vol. C-24, No. 4, Apr. 1975, (New York, US), G. Wade et al.: "New Experiments and Analysis in Bragg-Diffraction Imaging", pp. 395-396.
Dolfi Daniel
Micheron Francois
General Electric CGR S.A.
Howell Kyle L.
Nasser Jr. Robert L.
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