Inter- and intraobserver variability in the evaluation of dynamic breast cancer MRI.
OBJECTIVE
To quantify variations within and between observers ascribable to manual region of interest (ROI) placement in patients with breast cancer undergoing dynamic MRI.


METHODS
Expert and nonexpert observers independently outlined tumor ROIs on 30 dynamic T(1)-weighted (T(1)W) MRI scans on five occasions over two months. Lesion size (number of pixels) and kinetic parameter estimates, including the transfer constant (K(trans)), were calculated for each ROI placement. Inter- and intraobserver variability was assessed with respect to the interval between drawings, lesion morphology, and observer experience.


RESULTS
For the nonexpert, the variability reduced with decreasing time intervals between ROI drawings (the coefficient of variance (wCV) values at two months, two weeks, one day, and same-day time intervals were respectively 11.6%, 10.7%, 4.8%, and 2.6% for lesion size, and 8.9%, 9.7%, 6.7%, and 3.2% for K(trans)). For the expert observer, the variability was smaller overall and more constant, but improved for same-day ROI placements (region size wCV: 7.5%, 6.2%, 7.1%, and 3.7%; K(trans) wCV: 5.4%, 5.3%, 5.6%, and 4.5%).


CONCLUSIONS
Significant observer variability in manual ROI placement occurs in dynamic MRI of breast cancer. For serial patient studies, ROI placements should be outlined at the same sitting to minimize observer error.
Beresford
Mark J
MJ
Mount Vernon Cancer Centre, Northwood, United Kingdom. mjberesford@yahoo.co.uk
Padhani
Anwar R
AR
Taylor
N Jane
NJ
Ah-See
Mei-Lin
ML
Stirling
J James
JJ
Makris
Andreas
A
d'Arcy
James A
JA
Collins
David J
DJ
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008875:Middle Aged; D015588:Observer Variation; D011361:Professional Competence / Q000706:statistics & numerical data*; D011785:Quality Assurance, Health Care / Q000379:methods; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis