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Image Processing Algorithms for Digital Mammography: A Pictorial Essay¹

¹ From the Department of Radiology (E.D.P., B.M.H., S.R.A., R.E.J., M.E.B.), Lineberger Comprehensive Cancer Center (E.B.C.), and Department of Computer Science (S.M.P.), University of North Carolina, 101 Manning Dr, Chapel Hill, NC 27514-4226; the Department of Medical Imaging, University of Toronto, Ontario, Canada (M.J.Y.); the Department of Radiology, Thomas Jefferson University, Philadelphia, Pa (A.D.A.M.); the Department of Radiology, University of Virginia, Charlottesville (M.B.W.); the Department of Radiology, University of Pennsylvania, Philadelphia (E.F.C.); the Department of Radiology, Johns Hopkins University, Baltimore, Md (L.L.F.); and the Department of Radiology, Massachusetts General Hospital, Boston (D.B.K.). Recipient of a Certificate of Merit award for a scientific exhibit at the 1998 RSNA scientific assembly. Received October 5, 1999; revision requested November 12; final revision received February 7, 2000; accepted February 16. Supported in part by grant RO1-CA60193-05 from the National Cancer Institute; grant 282-97-0078 from the Office of Women's Health, Department of Health and Human Services; grant DAMD 17-94-J-4345 from the U.S. Army Medical Research and Material Command; grant 7289 from the Canadian Breast Cancer Research Initiative; and grants RO1-CA6019, RO1-CA75145-01A1, and RO1-CA60183 from the National Cancer Institute. Address correspondence to E.D.P. (e-mail: etpisano@med.unc.edu).

View larger version (66K): [in a new window]   Figure 1a.   (a) Photographic magnification of a craniocaudal screen-film mammogram shows a cyst. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the same lesion.

View larger version (68K): [in a new window]   Figure 1b.   (a) Photographic magnification of a craniocaudal screen-film mammogram shows a cyst. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the same lesion.

View larger version (68K): [in a new window]   Figure 1c.   (a) Photographic magnification of a craniocaudal screen-film mammogram shows a cyst. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the same lesion.

View larger version (64K): [in a new window]   Figure 1d.   (a) Photographic magnification of a craniocaudal screen-film mammogram shows a cyst. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the same lesion.

View larger version (65K): [in a new window]   Figure 1e.   (a) Photographic magnification of a craniocaudal screen-film mammogram shows a cyst. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the same lesion.

View larger version (68K): [in a new window]   Figure 1f.   (a) Photographic magnification of a craniocaudal screen-film mammogram shows a cyst. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the same lesion.

View larger version (76K): [in a new window]   Figure 1g.   (a) Photographic magnification of a craniocaudal screen-film mammogram shows a cyst. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the same lesion.

View larger version (74K): [in a new window]   Figure 2a.   (a) Mediolateral oblique screen-film mammogram shows two masses (arrows), which both proved to be infiltrating ductal carcinomas with associated ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the larger, inferior carcinoma. (c) Photographic magnification of a digital mammogram processed with MIW shows the larger lesion. (d) Digital mammogram processed with MMIW shows both cancers very well. (e) Photographic magnification of d shows the larger lesion. (f) Photographic magnification of a digital mammogram processed with unsharp masking shows the larger lesion. (Courtesy of D.B.K.)

View larger version (107K): [in a new window]   Figure 2b.   (a) Mediolateral oblique screen-film mammogram shows two masses (arrows), which both proved to be infiltrating ductal carcinomas with associated ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the larger, inferior carcinoma. (c) Photographic magnification of a digital mammogram processed with MIW shows the larger lesion. (d) Digital mammogram processed with MMIW shows both cancers very well. (e) Photographic magnification of d shows the larger lesion. (f) Photographic magnification of a digital mammogram processed with unsharp masking shows the larger lesion. (Courtesy of D.B.K.)

View larger version (120K): [in a new window]   Figure 2c.   (a) Mediolateral oblique screen-film mammogram shows two masses (arrows), which both proved to be infiltrating ductal carcinomas with associated ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the larger, inferior carcinoma. (c) Photographic magnification of a digital mammogram processed with MIW shows the larger lesion. (d) Digital mammogram processed with MMIW shows both cancers very well. (e) Photographic magnification of d shows the larger lesion. (f) Photographic magnification of a digital mammogram processed with unsharp masking shows the larger lesion. (Courtesy of D.B.K.)

View larger version (77K): [in a new window]   Figure 2d.   (a) Mediolateral oblique screen-film mammogram shows two masses (arrows), which both proved to be infiltrating ductal carcinomas with associated ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the larger, inferior carcinoma. (c) Photographic magnification of a digital mammogram processed with MIW shows the larger lesion. (d) Digital mammogram processed with MMIW shows both cancers very well. (e) Photographic magnification of d shows the larger lesion. (f) Photographic magnification of a digital mammogram processed with unsharp masking shows the larger lesion. (Courtesy of D.B.K.)

View larger version (109K): [in a new window]   Figure 2e.   (a) Mediolateral oblique screen-film mammogram shows two masses (arrows), which both proved to be infiltrating ductal carcinomas with associated ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the larger, inferior carcinoma. (c) Photographic magnification of a digital mammogram processed with MIW shows the larger lesion. (d) Digital mammogram processed with MMIW shows both cancers very well. (e) Photographic magnification of d shows the larger lesion. (f) Photographic magnification of a digital mammogram processed with unsharp masking shows the larger lesion. (Courtesy of D.B.K.)

View larger version (125K): [in a new window]   Figure 2f.   (a) Mediolateral oblique screen-film mammogram shows two masses (arrows), which both proved to be infiltrating ductal carcinomas with associated ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the larger, inferior carcinoma. (c) Photographic magnification of a digital mammogram processed with MIW shows the larger lesion. (d) Digital mammogram processed with MMIW shows both cancers very well. (e) Photographic magnification of d shows the larger lesion. (f) Photographic magnification of a digital mammogram processed with unsharp masking shows the larger lesion. (Courtesy of D.B.K.)

View larger version (75K): [in a new window]   Figure 3a.   (a) Mediolateral oblique screen-film mammogram shows a spiculated mass in the axillary portion of the breast, which proved to be an infiltrating ductal carcinoma with associated cribriform and solid-type ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the lesion. (c, d) Digital mammogram processed with unsharp masking (c) and photographic magnification of c (d) show the lesion.

View larger version (113K): [in a new window]   Figure 3b.   (a) Mediolateral oblique screen-film mammogram shows a spiculated mass in the axillary portion of the breast, which proved to be an infiltrating ductal carcinoma with associated cribriform and solid-type ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the lesion. (c, d) Digital mammogram processed with unsharp masking (c) and photographic magnification of c (d) show the lesion.

View larger version (65K): [in a new window]   Figure 3c.   (a) Mediolateral oblique screen-film mammogram shows a spiculated mass in the axillary portion of the breast, which proved to be an infiltrating ductal carcinoma with associated cribriform and solid-type ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the lesion. (c, d) Digital mammogram processed with unsharp masking (c) and photographic magnification of c (d) show the lesion.

View larger version (126K): [in a new window]   Figure 3d.   (a) Mediolateral oblique screen-film mammogram shows a spiculated mass in the axillary portion of the breast, which proved to be an infiltrating ductal carcinoma with associated cribriform and solid-type ductal carcinoma in situ at open surgical biopsy. (b) Photographic magnification of a shows the lesion. (c, d) Digital mammogram processed with unsharp masking (c) and photographic magnification of c (d) show the lesion.

View larger version (148K): [in a new window]   Figure 4a.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (154K): [in a new window]   Figure 4b.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (137K): [in a new window]   Figure 4c.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (158K): [in a new window]   Figure 4d.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (136K): [in a new window]   Figure 4e.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (138K): [in a new window]   Figure 4f.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (132K): [in a new window]   Figure 4g.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (146K): [in a new window]   Figure 4h.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (128K): [in a new window]   Figure 4i.   (a) Photographic magnification of a mediolateral oblique screen-film mammogram shows a cluster of calcifications, which proved to be atrophic breast tissue at core biopsy. (b-g) Photographic magnifications of a digital mammogram processed with MIW (b), HIW (c), MMIW (d), CLAHE (e), unsharp masking (f), and peripheral equalization (g) show the clustered calcifications. (h, i) Digital mammogram processed with Trex processing (h) and photographic magnification of h (i) show the calcifications. (Courtesy of the University of Virginia and L.L.F.)

View larger version (17K): [in a new window]   Figure 5.   Histogram for a digital mammogram. The range of intensity values representing breast tissue is seen on the right. These are automatically recognized by HIW. HIW then chooses a display range based on this breast tissue range. In this example, a 30%-100% range is chosen. Then, the output range of the display device is mapped to the selected intensity window range (the 30% location maps to black, the 100% location maps to white).

View larger version (51K): [in a new window]   Figure 6a.   Application of MMIW to digital mammograms. (a) Mediolateral oblique digital mammogram shows dense tissue (D), fat (F), pectoral muscle (M), and uncompressed fat (UF). The black area is the background. (b) Same image as in a after segmentation and cropping shows the muscle, dense tissue, compressed fat, and uncompressed fat portions of the image as different portions of the gray scale of the image. (c) Graph shows how the recorded intensity of the different regions in the image is mapped to the different displayed intensities in d. (d) Same mammogram as in a after automatic application of MMIW.

View larger version (59K): [in a new window]   Figure 6b.   Application of MMIW to digital mammograms. (a) Mediolateral oblique digital mammogram shows dense tissue (D), fat (F), pectoral muscle (M), and uncompressed fat (UF). The black area is the background. (b) Same image as in a after segmentation and cropping shows the muscle, dense tissue, compressed fat, and uncompressed fat portions of the image as different portions of the gray scale of the image. (c) Graph shows how the recorded intensity of the different regions in the image is mapped to the different displayed intensities in d. (d) Same mammogram as in a after automatic application of MMIW.

View larger version (19K): [in a new window]   Figure 6c.   Application of MMIW to digital mammograms. (a) Mediolateral oblique digital mammogram shows dense tissue (D), fat (F), pectoral muscle (M), and uncompressed fat (UF). The black area is the background. (b) Same image as in a after segmentation and cropping shows the muscle, dense tissue, compressed fat, and uncompressed fat portions of the image as different portions of the gray scale of the image. (c) Graph shows how the recorded intensity of the different regions in the image is mapped to the different displayed intensities in d. (d) Same mammogram as in a after automatic application of MMIW.

View larger version (56K): [in a new window]   Figure 6d.   Application of MMIW to digital mammograms. (a) Mediolateral oblique digital mammogram shows dense tissue (D), fat (F), pectoral muscle (M), and uncompressed fat (UF). The black area is the background. (b) Same image as in a after segmentation and cropping shows the muscle, dense tissue, compressed fat, and uncompressed fat portions of the image as different portions of the gray scale of the image. (c) Graph shows how the recorded intensity of the different regions in the image is mapped to the different displayed intensities in d. (d) Same mammogram as in a after automatic application of MMIW.

View larger version (23K): [in a new window]   Figure 7.   Clipping with CLAHE. Graphs show how CLAHE redistributes the mapped intensities of the pixels in an image.

View larger version (19K): [in a new window]   Figure 8.   Application of unsharp masking. A weighted, low-pass (LP) filtered image is subtracted from the original image. For consistency in display, the data are then rescaled and an offset is added when necessary.

View larger version (16K): [in a new window]   Figure 9.   Effect of varied thickness of compressed breast tissue. Schematics of the compressed breast show that it consists of two regions: a central region of approximately uniform thickness and a margin where thickness varies. In the margin, variation in transmitted x-ray fluence occurs due to changes in both breast thickness and composition. CC = craniocaudal, R = radius, T = thickness.

View larger version (24K): [in a new window]   Figure 10a.   Peripheral equalization. (a) A smoothed representation of the image, s(x,y), is obtained with a low-pass filtering operation. The low-pass filter (shown schematically in one dimension) is a first-order Butterworth filter with a cutoff frequency of 0.05 cycles per millimeter. (b) Overview of the thickness equalization processing technique. For each point in the margin, the smoothed image is used to determine a correction factor.

View larger version (48K): [in a new window]   Figure 10b.   Peripheral equalization. (a) A smoothed representation of the image, s(x,y), is obtained with a low-pass filtering operation. The low-pass filter (shown schematically in one dimension) is a first-order Butterworth filter with a cutoff frequency of 0.05 cycles per millimeter. (b) Overview of the thickness equalization processing technique. For each point in the margin, the smoothed image is used to determine a correction factor.

View larger version (26K): [in a new window]   Figure 11.   Profile of brightness as a function of position across a line of the original and corrected images. The vertical lines identify the margin. Note the reduction in the range of levels in the corrected data as a result of the adjustment in the margin.