Effects of quality assurance regulatory enforcement on performance of mammography systems: evidence from large-scale surveys in Taiwan.

OBJECTIVE

The Standards for Medical Exposure Quality Assurance in mammography systems were enacted on July 1, 2008, in Taiwan. This study aimed to evaluate the trends in performance of mammography units before and after the regulation started on the basis of annual on-site surveys from 2008 to 2010.

MATERIALS AND METHODS

On-site measurements were conducted on 215, 205, and 209 mammography units in 2008, 2009, and 2010, respectively, which accounted for more than 95% of all units in Taiwan. Phantom image quality, average glandular dose (AGD), and half-value layer were evaluated on all systems. Processor conditions, compression conditions, radiation output, and computed radiography exposure indicators were assessed on units participating in mammography screening in 2008 and on all units in the later years. Evaluations of maximum compression force and automatic exposure control reproducibility were added into the protocol from 2009 onward.

RESULTS

Mean phantom scores were improved significantly from 2008 to 2009 (11.63 ± 1.30 vs 12.31 ± 0.94, p < 0.05) and remained stable for 2010 (12.35 ± 0.87). Mean AGDs were 1.48 ± 0.47, 1.38 ± 0.41, and 1.37 ± 0.42 mGy over the 3 years, with a significant reduction from 2008 to 2009 (p < 0.05). For film-screen mammography systems, variations of sensitometric curves were greatly reduced in 2009 and 2010 when compared with 2008. Passing rates were increased after the regulation took effect in almost all aspects.

CONCLUSION

Results from large-scale on-site surveys showed an overall improvement in performance after quality assurance in mammography was enforced in Taiwan.