Rasika Rajapakshe PhD, Presenter: Nothing to Disclose

Analyze the quality control data collected since 1992 within the SMPBC.

SMPBC has been providing population breast screening to women in the province of British Columbia since 1988. All mammography machines within the program have been tested annualy by physicists. Available test data since 1992 was analaysed to estimate trends in radiation dose and image quality.

Mean Glandular Dose (MGD) measured with a 4.2 cm phantom was found to have increased from 0.91 to 2.03 mGy. However the highest average MGD of 2.13 mGy was recorded in 2003. Most of the increase occured during 1994-2001 period. The average phantom optical density has increased from 1.15 to 1.87 during the same period. The resulting mammography step wedge contrast (step 7 - step 5) change over the period is 0.63 to 0.93. Interestingly, no significant change in the ACR phantom score of masses was observed. There was a slight increase in the fibre score (4.25 to 4.81). However, the speck group score increased from 2.92 to 3.74.

Due to the introduction of newer high contrast screen film combinations in the mid to late 90's, the radiation exposure to the population screened in British Columbia has increased by a factor of 2.2 as estimated by the dose to 4.2 cm phantom. The improvemnt in image quality due to the higher dose is only seen with the increase in ACR phantom specks group score.

The increase in dose delivered within the SMPBC over past 12 years has lead to an improvement in the detectability of calcifications in mammograms as evaluated by the ACR phantom score.

Rajapakshe, R, Prospective Analysis of Quality Control Data from the Screening Mammography Program of British Columbia (SMPBC).  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5007247.html