Introduction 1 2 5 6 15 4 12 3 12 16 20 21 4 However, the combination of both dynamic and morphological parameters resulted in the highest diagnostic accuracy in multivariate analysis. 6 22 23 24 6 24 Materials and methods Patient selection 25 Imaging protocol 26 Image evaluation For the evaluation, the MRI data were divided into two sets of dynamic data for each patient. The first dataset contained the high spatial resolution T1-weighted images (FLASH 3D) only. These were used for the evaluation of both lesion morphology as well as signal intensity versus time curves. This method will be further referred to as the ‘slow dynamic’ analysis. The second dataset contained the proton-density-weighted images, the high temporal resolution images as well as the precontrast high spatial resolution sequence. A high-resolution subtraction of the pre- and first postcontrast FLASH3D series prepared on the MRI scanner was also included in this dataset to aid in lesion detection. The proton-density-weighted sequence was necessary for an accurate estimation of the T1 value necessary for the quantitative analyses. The evaluation of this dataset will be further referred to as the ‘fast dynamic’ analysis. In this fast dynamic analysis, the last three postcontrast FLASH 3D series were not used. All cases were evaluated prospectively by two experienced breast MRI radiologists (reader 1 and reader 2). Both readers had over 5 years of experience in dynamic breast MRI. The evaluation on the two workstations was performed independently in different sessions with at least a 2-month time interval between both sessions. 27 28 29 30 1 31 31 32 33 34 e tissue plasma ep tissue plasma trans e ep e trans ep trans ep e trans ep 35 36 Fig. 1 a b Materials and methods 4 5 4 5  Statistical analysis t P Results A total of 870 consecutive clinical breast MRI examinations in 787 patients were performed. In these studies a total of 188 lesions were detected. Eighty-six lesions could not be included due to lack of histological diagnosis or insufficient follow-up. This resulted in a total of 102 lesions in 96 patients; 34 benign and 68 malignant lesions. The mean age was 51 years (range 28–74 years). Ninety-four lesions were included based on histological evaluation, eight lesions based on follow-up. Mean lesion size on MRI for the malignant group was 32 mm (range 9–90 mm) and this was 15 mm (range 5–50 mm) for the benign lesions. A total of 52 lesions were 2 cm or smaller; 25 malignant (mean lesion size 14 mm, range 6–20 mm) and 27 benign (mean lesion size 11 mm , range 5–20 mm). 1 Table 1 IDC DCIS ILC n n Fibroadenoma 11 IDC 47 Fibrosis 4 DCIS 14 Adenosis 3 ILC 7 Inflammation 2   Ductal papilloma 2   Scar tissue 1   Hyperplasia 1   Hamartoma 1   Radial scar 1   Follow-up 8   Imaging results In the slow dynamic analysis reader 1 classified 25 lesions as a BI-RADS 2 (benign:malignant = 22:3), seven as BI-RADS 3 (4:3), 50 as BI-RADS 4 (6:44) and 20 an BI-RADS 5 (2:18). This was respectively 33 (24:9), 12 (4:8), 41 (5:36) and 16 (1:15) for reader 2. The ROC analysis for the slow dynamic analysis resulted in an AUC of 0.85 (95% CI = 0.773–0.918) and 0.83 (95% CI = 0.74–0.89) for reader 1 and 2, respectively. 3 3 3 3 P 2 trans e ep trans 2 trans ep P P Table 2 P   n 95% CI n 95% CI Reader 1 trans a 1.2 0.9–1.4 2.3 2.1–2.6 e 41.6 34.9–48.3 63.9 58.6–69.1 ep a 3.0 2.7–3.3 3.8 3.5–4.0 Reader 2 trans a 1.3 1.0–1.5 2.5 2.2–2.8 e 44.6 37.2–52.0 67.1 62.0–72.3 ep a 3.0 2.6–3.3 3.9 3.7–4.2 a Fig. 2 V K trans a b continuous-line ellipsoid dotted-line ellipsoid  trans ep P P P P P 3 Fig. 3 a b P P P  P P P P P P 4 5 Fig. 4 a b trans c d scalar bar trans 2  Fig. 5 a b trans c d scalar bar trans 2  Discussion 2 27 4 36 36 24 trans 18 trans 1 18 37 37 4 12 18 The results presented in this study are our initial results using this scanning protocol. Therefore, no cut of values for the differentiation between benign and malignant lesions from the pharmacokinetic parameters were used in the evaluation or can be provided at this point. The results presented only show the potential of our method in differentiation between benign and malignant lesions in this group of patients. The value of our method needs to be further studied in a larger group, preferably using a more even distribution between benign and malignant cases and with lesions that can be classified on imaging as a BI-RADS 3 or higher. Unfortunately, the study design used did not allow a multivariate analysis combining the fast dynamic data with morphological characteristics. Also, the possible trade-off between the pharmacokinetic parameters based on initial enhancement and the wash-out based on late dynamic characteristics cannot be derived from these data. Both analyses will need to be performed in future projects in order to evaluate the full potential of the fast dynamic analysis as used in our study.In conclusion, pharmacokinetic parameters derived from fast dynamic imaging during initial enhancement have great potential in classifying enhancing lesions in the breast. In this study, the diagnostic performance for the fast dynamic analysis proved to be equal to the results of experienced radiologists using more common evaluation methods based on morphologic characteristics and slow dynamic enhancement characteristics. An increased diagnostic performance was found in combining both methods. This shows the additional value of this method in further improving the diagnostic accuracy of breast MRI.