title: Compression force and radiation dose in the Norwegian Breast Cancer Screening Program.
abstract: OBJECTIVE
  Compression force is used in mammography to reduce breast thickness and by that decrease radiation dose and improve image quality. There are no evidence-based recommendations regarding the optimal compression force. We analyzed compression force and radiation dose between screening centers in the Norwegian Breast Cancer Screening Program (NBCSP), as a first step towards establishing evidence-based recommendations for compression force.
  
  
  METHODS
  The study included information from 17 951 randomly selected screening examinations among women screened with equipment from four different venors at fourteen breast centers in the NBCSP, January-March 2014. We analyzed the applied compression force and radiation dose used on craniocaudal (CC) and mediolateral-oblique (MLO) view on left breast, by breast centers and vendors.
  
  
  RESULTS
  Mean compression force used in the screening program was 116N (CC: 108N, MLO: 125N). The maximum difference in mean compression force between the centers was 63N for CC and 57N for MLO. Mean radiation dose for each image was 1.09mGy (CC: 1.04mGy, MLO: 1.14mGy), varying from 0.55mGy to 1.31mGy between the centers. Compression force alone had a negligible impact on radiation dose (r2=0.8%, p=<0.001).
  
  
  CONCLUSIONS
  We observed substantial variations in mean compression forces between the breast centers. Breast characteristics and differences in automated exposure control between vendors might explain the low association between compression force and radiation dose. Further knowledge about different automated exposure controls and the impact of compression force on dose and image quality is needed to establish individualised and evidence-based recommendations for compression force.
authors.affiliation: Department of Life Sciences and Health, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, P.O. 4 St. Olavs Plass, 0130 Oslo, Norway.
authors.forename: Gunvor G
authors.initials: GG
authors.lastname: Waade
authors.affiliation: Department of Life Sciences and Health, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, P.O. 4 St. Olavs Plass, 0130 Oslo, Norway.
authors.forename: Audun
authors.initials: A
authors.lastname: Sanderud
authors.affiliation: Department of Life Sciences and Health, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, P.O. 4 St. Olavs Plass, 0130 Oslo, Norway; The Cancer Registry of Norway, P.O. 5313 Majorstuen, 0304 Oslo, Norway. Electronic address: solveig.hofvind@kreftregisteret.no.
authors.forename: Solveig
authors.initials: S
authors.lastname: Hofvind
mesh_terms: D000368:Aged; D001940:Breast / Q000000981:diagnostic imaging; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008327:Mammography / Q000379:methods* / Q000706:statistics & numerical data*; D008875:Middle Aged; D009664:Norway; D011312:Pressure; D011829:Radiation Dosage
keywords: Compression force; Mammographic screening; Mammography; Medical imaging; Radiation dose; Radiography