Effect of contrast dose on diagnostic performance in DCE-MR breast imaging

Abstract

Objective: To assess the diagnostic performance of breast magnetic resonance (MR) imaging as a function of gadolinium contrast dose using a retrospective reader study.

Material and methods: IRB approval was obtained prior to the start of this study and was HIPAA compliant. One-hundred and fifty MR breast examinations were included that were acquired between January 2001 and December 2006. Seventy-five patients received contrast doses (gadopentetate dimeglumine) by weight of 0.10 mmol/kg and 75 patients were imaged using fixed volumes of 20 ml. The images were assessed by two radiologists with performance calculated for each reader as well as a combined assessment. Dose response was measured by comparing performance between cases binned by dose: <=0.10; >0.10; and >0.13 mmol/kg. Statistical significance was calculated using a one-sided Z-test for differences in proportions with interobserver agreement calculated using Cohen's kappa statistics.

Results: In the combined reader assessment with equivocal lesions classified as negative, sensitivity rose from 66% (19/29) to 92% (24/26, P < 0.01) and 95% (18/19, P < 0.01) with the specificity also increasing from 65% (32/49) to 87% (40/46, P < 0.01) and 86% (32/37, P = 0.01) corresponding to doses <=0.10, >0.10, >0.13 mmol/kg. With equivocal lesions classified as positive, sensitivity rose from 79% (23/29) to 92% (24/26, P < 0.10) and 95% (18/19, P < 0.10) Specificity also increased from 53% (26/49) to 72% (33/46, P < 0.05) and 70% (26/37, P = 0.05) with increasing dose. Interobserver agreement also improved at the higher doses.

Keywords: breast; contrast dose; diagnostic performance; magnetic resonance imaging.

Fig. 1

Representative DCE‐MR sagittal images of the breast at different gadolinium contrast doses. (a) 0.10 mmol/kg. (b) 0.13 mmol/kg. (c) 0.15 mmol/kg.

Fig. 2

Diagnostic performance as a function of contrast dose. (a,b) Sensitivity and specificity when equivocal lesion were considered a positive finding. (c,d) Sensitivity and specificity when equivocal lesion were considered a negative finding. (e,f) Sensitivity and specificity when equivocal lesion were removed. Performance is shown for each reader and for a combined assessment. Error bars show 95% confidence intervals (Wilson score).