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Subtraction Technic: Video and Color Methods

Subtraction Technic: Video and Color Methods Subtraction Technic: Video and Color Methods 1 Robert E. Wise , M.D. and Jorge Ganson , M.D. 2 Department of Diagnostic Radiology Lahey Clinic Foundation 605 Commonwealth Avenue Boston, Mass. 02215 ↵ 2 Resident in Radiology. Excerpt The current high level of interest in angiographic procedures had led to a search for methods which yield more information from angiography than can be obtained with conventional viewing. Since conventional roentgen procedures cannot produce a higher level of information than that already attainable without increasing the dosage of contrast medium beyond a safe level, it appears logical to seek additional methods of improving informational yield. Photographic Subtraction The theoretical basis of subtraction of radiographs is not new, the original description having been published by Ziedses des Plantes in 1935 (1) with elaborations in 1938 and 1963 (2, 3). The technic cancels or subtracts, in theory at least, all the picture elements common to a pair of radiographs after one of them has been converted to a negative image or diapositive. The two radiographs are then superimposed in perfect registration and a third composite image is made photographically. if a density, usually in the form of an injected contrast medium, has been added to one of the radiographs, the added density will then stand out with increased contrast. In practice, all the picture elements cannot be canceled because of imperfect registration and difficulty in making a perfect densitometric diapositive. Although seemingly inexpensive, the method is time-consuming and in the final analysis costly. The time element also prevents interpretation during the course of a study and thus limits its usefulness in deciding further conduct of the examination. for these reasons, although the method is sound, it has been little used and few articles have appeared in the literature (4–13). Videp Subtraction Holman, while working with closed-circuit television, conceived the idea of utilizing television cameras to produce a subtracted image. He designed such a device and published a description of it in 1963 (14). The photographic and video technics have the same theoretical basis. Radiographs must be made before and after injection of a contrast medium for both. In the video method two television cameras are required with the polarity of one reversed to create a diapositive image. Each camera is equipped with a lens system with both focus and aperture variable. Each has electronic controls for fine focus, gain, contrast, brightness, and linearity. The images from each camera are superimposed on a single monitor, resulting in a subtracted image. The apparatus we are currently using is commercially available and is essentially that originally described by Holman. The cameras are of the Vidicon type with industrial synchronization, random interlace, and a 525 line-scan rate. We have had limited experience with a fiying-spot scanner subtraction device. In this, a fiying-spot cathode tube simultaneously scans two radiographs by optically dividing the light through a system of mirrors and lenses. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Radiology Radiological Society of North America, Inc.

Subtraction Technic: Video and Color Methods

Wise, Robert E.; Ganson, Jorge
Radiology , Volume 86 (5): 814 – May 1, 1966
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References (6)

Publisher
Radiological Society of North America, Inc.
Copyright
Copyright © 1966 by Radiological Society of North America
ISSN
1527-1315
eISSN
0033-8419
DOI
10.1148/86.5.814
pmid
5327628
Publisher site
See Article on Publisher Site

Abstract

Subtraction Technic: Video and Color Methods 1 Robert E. Wise , M.D. and Jorge Ganson , M.D. 2 Department of Diagnostic Radiology Lahey Clinic Foundation 605 Commonwealth Avenue Boston, Mass. 02215 ↵ 2 Resident in Radiology. Excerpt The current high level of interest in angiographic procedures had led to a search for methods which yield more information from angiography than can be obtained with conventional viewing. Since conventional roentgen procedures cannot produce a higher level of information than that already attainable without increasing the dosage of contrast medium beyond a safe level, it appears logical to seek additional methods of improving informational yield. Photographic Subtraction The theoretical basis of subtraction of radiographs is not new, the original description having been published by Ziedses des Plantes in 1935 (1) with elaborations in 1938 and 1963 (2, 3). The technic cancels or subtracts, in theory at least, all the picture elements common to a pair of radiographs after one of them has been converted to a negative image or diapositive. The two radiographs are then superimposed in perfect registration and a third composite image is made photographically. if a density, usually in the form of an injected contrast medium, has been added to one of the radiographs, the added density will then stand out with increased contrast. In practice, all the picture elements cannot be canceled because of imperfect registration and difficulty in making a perfect densitometric diapositive. Although seemingly inexpensive, the method is time-consuming and in the final analysis costly. The time element also prevents interpretation during the course of a study and thus limits its usefulness in deciding further conduct of the examination. for these reasons, although the method is sound, it has been little used and few articles have appeared in the literature (4–13). Videp Subtraction Holman, while working with closed-circuit television, conceived the idea of utilizing television cameras to produce a subtracted image. He designed such a device and published a description of it in 1963 (14). The photographic and video technics have the same theoretical basis. Radiographs must be made before and after injection of a contrast medium for both. In the video method two television cameras are required with the polarity of one reversed to create a diapositive image. Each camera is equipped with a lens system with both focus and aperture variable. Each has electronic controls for fine focus, gain, contrast, brightness, and linearity. The images from each camera are superimposed on a single monitor, resulting in a subtracted image. The apparatus we are currently using is commercially available and is essentially that originally described by Holman. The cameras are of the Vidicon type with industrial synchronization, random interlace, and a 525 line-scan rate. We have had limited experience with a fiying-spot scanner subtraction device. In this, a fiying-spot cathode tube simultaneously scans two radiographs by optically dividing the light through a system of mirrors and lenses.

Journal

Radiology – Radiological Society of North America, Inc.

Published: May 1, 1966

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