A comparison of calibration data from full field digital mammography units for breast density measurementsReport as inadecuate

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BioMedical Engineering OnLine

, 12:114

First Online: 09 November 2013Received: 30 August 2013Accepted: 23 October 2013


BackgroundBreast density is a significant breast cancer risk factor measured from mammograms. The most appropriate method for measuring breast density for risk applications is still under investigation. Calibration standardizes mammograms to account for acquisition technique differences prior to making breast density measurements. We evaluated whether a calibration methodology developed for an indirect x-ray conversion full field digital mammography FFDM technology applies to direct x-ray conversion FFDM systems.

MethodsBreast tissue equivalent BTE phantom images were used to establish calibration datasets for three similar direct x-ray conversion FFDM systems. The calibration dataset for each unit is a function of the target-filter combination, x-ray tube voltage, current × time mAs, phantom height, and two detector fields of view FOVs. Methods were investigated to reduce the amount of calibration data by restricting the height, mAs, and FOV sampling. Calibration accuracy was evaluated with mixture phantoms. We also compared both intra- and inter-system calibration characteristics and accuracy.

ResultsCalibration methods developed previously apply to direct x-ray conversion systems with modification. Calibration accuracy was largely within the acceptable range of ± 4 standardized units from the ideal value over the entire acquisition parameter space for the direct conversion units. Acceptable calibration accuracy was maintained with a cubic-spline height interpolation, representing a modification to previous work. Calibration data is unit specific, can be acquired with the large FOV, and requires a minimum of one reference mAs sample. The mAs sampling, calibration accuracy, and the necessity for machine specific calibration data are common characteristics and in agreement with our previous work.

ConclusionThe generality of our calibration approach was established under ideal conditions. Evaluation with patient data using breast cancer status as the endpoint is required to demonstrate that the approach produces a breast density measure associated with breast cancer.

KeywordsBreast density Calibration Phantom imaging Direct x-ray conversion Full field digital mammography AbbreviationsaIndex reserved for adipose breast tissue equivalent material


bIntercept of the open detector exposure relationships

BCalibration application additive parameter


BTEBreast tissue equivalent

ElrsMean exposure at given sub-region rs and baseline phantom height in cm

FFDMfull field digital mammography

FOVfield of view

gIndex reserved for fibroglandular breast tissue equivalent material

GEGeneral Electric Senographe 2000D FFDM unit


H1Hologic Selenia unit 1

H2Hologic Selenia unit 2

H3Hologic Selenia unit 3

kIndex designating a sampled height

lSubscript index reserved for breast tissue equivalent material

LCCLeft cranial caudal

LIlLogarithmic intercept

LRENatural logarithm of the relative exposure

LREl rsNatural logarithm of the relative exposure at rs as a function of increasing baseline phantom height in cm

mSlope of the open detector exposure relationships

MCalibration application multiplier factor

mAsMilliampere × second


PGPercent glandular

PGcalA calibrated quantity

pvaAdipose pixel value in the LRE domain

pvgGlandular pixel value in the LRE domain

pvrawRaw image pixel value


R2Coefficient of determination

RElrsRelative mean exposure at a given sub-region rs and baseline phantom height in cm


ROIRegion of interest

SEStandard error

SDStandard deviation

tkBaseline phantom sample height in cm

μlEffective x-ray attenuation coefficient in cm


xArbitrary mAs quantity

xrThe reference, 160 mAs.

Electronic supplementary materialThe online version of this article doi:10.1186-1475-925X-12-114 contains supplementary material, which is available to authorized users.

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Author: Erin EE Fowler - Beibei Lu - John J Heine

Source: https://link.springer.com/

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