Mammography Goes Digital

New Delhi

Appropriate diagnosis of an ailment is mandatory for it to be dealt with using precise curative measures. For the various sensitive parts of our body, we have different techniques for disease diagnosis. Digital Mammography is an advanced technique used for the detection of breast diseases in women.

Digital Mammography, also called full-field digital mammography (FFDM), is a system in which the x-ray film is replaced by solid-state detectors that convert x-rays into electrical signals. These detectors are similar to those found in digital cameras. The electrical signals are used to produce images of the breast that can be seen on a computer screen or printed on special film similar to conventional mammograms. Digital mammography is essentially the same as the screen-film system.

Digital mammography is used to evaluate a patient with abnormal clinical findings—such as a breast lump or lumps—that have been found by the woman. Diagnostic mammography may also be done after an abnormal screening mammography in order to determine the cause of the area of concern on the screening exam.

Digital mammography has a number of attributes that may help a small breast tumor stand out from surrounding normal tissue: the efficient absorption of incident x-ray photons, a linear response over a broad range of radiation intensity, and comparatively little system noise.

Computer-aided detection (CAD) systems use a digitized mammographic image that can be obtained from either a conventional film mammogram or a digitally acquired mammogram. The computer software then searches for abnormal areas of density, mass, or calcification that may indicate the presence of cancer. The CAD system highlights these areas on the images, alerting the radiologist to the need for further analysis.

How Digital Works?

Like standard film mammography, digital mammography uses x-rays to produce images of breast tissue. The difference is that with digital mammography, an electronic x-ray detector—a phosphor screen—replaces the film cassette and converts the x-ray photons to light, which in turn passes through a fiber-optic cable to a device that converts the light to a digitized signal for display on a computer monitor. The radiologist can alter the orientation, magnification, brightness and contrast of the images as desired.

As with film mammography, optimal positioning and compression are critical in identifying a suspicious lesion. Unlike film mammography, which requires the technologist to develop films in a darkroom where the wait time ranges from two to five minutes, here the technologist will know within 30 seconds whether the images are satisfactory.

The question of image display is a key practical aspect of these methods. An efficient means of reading screening mammograms is vital for reasons of both cost containment and reader fatigue. Film has proved to be a convenient and time-efficient mode of display.

How Well Does Digital Mammography Perform?

A large-scale, multi-center clinical trial was designed to measure differences in diagnostic accuracy between digital mammography and film mammography, an x-ray examination used to screen for breast cancer. Results showed that, for the entire population of women studied, digital and film mammography had very similar screening accuracy. However, the study revealed that digital mammography was significantly better in screening women in three subgroups, such as those:

• under age 50 (no matter what level of breast tissue density they had).
• of any age with very dense dense breasts.
• of any age who are pre- or peri-menopausal (defined as women who had a final menstrual period within 12 months of their mammograms).

Advantages of Digital Mammography

• Compared with the 10-15 minutes needed for conventional film mammography, digital mammography images are acquired in less than a minute. A faster exam may induce more women to comply with screening at recommended intervals, and it makes the facilities more efficient.
• Spot-view digital systems now are available to help guide breast biopsy by recording a snapshot of the area of interest. This permits more rapid and accurate needle placement, speeding the biopsy procedure and minimizing discomfort.
• The superior contrast resolution (especially in dense breast tissues) and its ability to manipulate images might in time make for more accurate detection of breast cancers.
• Digital mammography lends itself well to another innovation, computer-aided detection (CAD), which obtains a second, computerized reading in the hope of finding more cancers or more accurately gauging signs of malignancy.
• Computerized mammograms may be archived in various ways, easily retrieved, and copied exactly. Digital mammograms also can be transmitted from one location to another, permitting off-line interpretation and expert consultation (telemammography).
• Digital mammography offers the possibility of three-dimensional breast tomography using relatively low radiation doses.

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