Impact of errors in recorded compressed breast thickness measurements on volumetric density classification using volpara v1.5.0 software.
OBJECTIVE
Mammographic density has been demonstrated to predict breast cancer risk. It has been proposed that it could be used for stratifying screening pathways and recommending additional imaging. Volumetric density tools use the recorded compressed breast thickness (CBT) of the breast measured at the x-ray unit in their calculation; however, the accuracy of the recorded thickness can vary. The aim of this study was to investigate whether inaccuracies in recorded CBT impact upon volumetric density classification and to examine whether the current quality control (QC) standard is sufficient for assessing mammographic density.


METHODS
Raw data from 52 digital screening mammograms were included in the study. For each image, the clinically recorded CBT was artificially increased and decreased in increments of 1 mm to simulate measurement error, until ±15% from the recorded CBT was reached. New images were created for each 1 mm step in thickness resulting in a total of 974 images which then had volpara density grade (VDG) and volumetric density percentage assigned.


RESULTS
A change in VDG was observed in 38.5% (n = 20) of mammograms when applying ±15% error to the recorded CBT and 11.5% (n = 6) was within the QC standard prescribed error of ±5 mm.


CONCLUSIONS
The current QC standard of ±5 mm error in recorded CBT creates the potential for error in mammographic density measurement. This may lead to inaccurate classification of mammographic density. The current QC standard for assessing mammographic density should be reconsidered.
Department of Life Sciences and Health, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, Box 4, St. Olavs Plass, 0130, Oslo, Norway and School of Health Sciences, University of Salford, Salford M6 6PU, United Kingdom.
Gunvor Gipling
GG
Waade
Volpara Solutions Limited, P.O. Box 24404, Manners St Central, Wellington 6142, New Zealand.
Ralph
R
Highnam
The Intervention Centre, Oslo University Hospital, Rikshospitalet, 4950 Nydalen, Norway.
Ingrid H R
IHR
Hauge
Discipline of Medical Radiation Sciences, Faculty of Health Sciences, University of Sydney, M205, Cumberland Campus, 75 East Street, Lidcombe, Sydney, NSW, 2141, Australia.
Mark F
MF
McEntee
Department of Screening, Cancer Registry of Norway, N-0304, Oslo, Norway and Department of Life Sciences and Health, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, Box 4, St. Olavs Plass, 0130, Oslo, Norway.
Solveig
S
Hofvind
Department of Radiology, Norfolk & Norwich University Hospital, Norwich NR4 7UY, United Kingdom.
Erika
E
Denton
The Countess of Chester Hospitals NHS Foundation Trust, Chester, CH2 1UL, United Kingdom.
Judith
J
Kelly
School of Health Sciences, University of Salford, Salford M6 6PU, United Kingdom.
Jasmine J
JJ
Sarwar
School of Health Sciences, University of Salford, Salford M6 6PU, United Kingdom and Karolinska Institute, Stockholm, Sweden.
Peter
P
Hogg