TECHNICAL NOTES Enhancement of Xeroradlograph Image Contrast Using Red Filtration 1 Lester Kallsher, M.D. Viewing xeroradiographs through red filters and/or fluoroscopy goggles increases the contrast markedly, thus allowing the image to be more easily perceived. INDEX TERMS:
Radiology and radiologists. Xerography
Radiology 119:477, May 1976
Considerable advances have been made in xeroradiography in the past several years, and it is now an accepted radiographic procedure. Characteristics such as edge enhancement and a wide image latitude have been helpful in delineating small lesions and microcalcifications. Nonetheless, the light blue shade (inherent in the toner) is poorly perceived by the eye, since the retina does not respond maximally to it. A common photographic technique for enhancing cloud patterns against a blue sky is to use a red filter; a filter transmits its own color but absorbs the other primary colors. A red filter absorbs blue light and thus increases the contrast between clouds and sky.
Fig. 1. Fig. 2.
I have discovered that xerographic images can be markedly enhanced by viewing them through deep red filters, such as those found in old fluoroscopy goggles. Subtle density changes and microcalcifications are made more visible. Since there is some light absorption through the filter, the intensity of the light used to view the xerograms should be increased. Figure 1 demonstrates a xerographic image viewed by normal white light; when compared to Figure 2, a xerogram viewed through a red filter, it is apparent that the contrast and detail are increased. Two other methods are suggested which alleviate the inconvenience of using red goggles: (a) The image can be viewed through a hand-held frame in which the red filter is mounted, or (b) the image can be viewed with a bright red photographic safe-light. We suggest a filter similar in color to a Kodak 25A red for maximum contrast. A yellow or amber filter can also be used and has the advantage of transmitting more reflected light, but gives less contrast than a red filter.
1 From the Departments of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Mass. 02114. Accepted for publication in November 1975. elk
Small fibroadenoma viewed without red filtration (left). The same lesion viewed witli red filtration. Note the increase in contrast (right).
477
Radiology and radiologists. Xerography
Radiology 119:477, May 1976
Considerable advances have been made in xeroradiography in the past several years, and it is now an accepted radiographic procedure. Characteristics such as edge enhancement and a wide image latitude have been helpful in delineating small lesions and microcalcifications. Nonetheless, the light blue shade (inherent in the toner) is poorly perceived by the eye, since the retina does not respond maximally to it. A common photographic technique for enhancing cloud patterns against a blue sky is to use a red filter; a filter transmits its own color but absorbs the other primary colors. A red filter absorbs blue light and thus increases the contrast between clouds and sky.
Fig. 1. Fig. 2.
I have discovered that xerographic images can be markedly enhanced by viewing them through deep red filters, such as those found in old fluoroscopy goggles. Subtle density changes and microcalcifications are made more visible. Since there is some light absorption through the filter, the intensity of the light used to view the xerograms should be increased. Figure 1 demonstrates a xerographic image viewed by normal white light; when compared to Figure 2, a xerogram viewed through a red filter, it is apparent that the contrast and detail are increased. Two other methods are suggested which alleviate the inconvenience of using red goggles: (a) The image can be viewed through a hand-held frame in which the red filter is mounted, or (b) the image can be viewed with a bright red photographic safe-light. We suggest a filter similar in color to a Kodak 25A red for maximum contrast. A yellow or amber filter can also be used and has the advantage of transmitting more reflected light, but gives less contrast than a red filter.
1 From the Departments of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Mass. 02114. Accepted for publication in November 1975. elk
Small fibroadenoma viewed without red filtration (left). The same lesion viewed witli red filtration. Note the increase in contrast (right).
477
