X-ray equipment used in mammography has "significantly improved" over the past five years in quality, according to surveys conducted by the Food and Drug Administration. The FDA, which monitors the equipment, found in its 1988 review that only 13 percent of equipment it examined was providing substandard imaging, compared to 36 percent in 1985.

In the early days of mammography, many women were screened with X-ray equipment designed for general use; quality of the images was erratic, officials said. According to the FDA report, published in the journal Radiology, more equipment is in use that was specifically designed for mammograms. In addition, the report said, systems have been developed that are "more sensitive to X-rays and thus create a clearer image."

There has been some increase in radiation, the report found, but current levels -- less than one rad per breast -- are still about two thirds lower than those found in a survey 11 years ago and are "well within FDA safety guidelines."

Officials at the FDA and the Department of Health and Human Services said they hope that the survey results will encourage more women to have regular mammograms. A report earlier this year showed that fewer than 33 percent of women over 40 underwent regular mammograms. About 44,000 women will die this year of breast cancer, second only to lung cancer as the leading cause of cancer deaths among women.