Relationship of temporal resolution to diagnostic performance for dynamic contrast enhanced MRI of the breast

Abstract

Purpose: To investigate the relationship between temporal resolution of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and classification of breast lesions as benign versus malignant.

Materials and methods: Patients underwent T(1)-weighted DCE MRI with 15 s/acquisition temporal resolution using 1.5 Tesla (n = 48) and 3.0T (n = 33) MRI scanners. Seventy-nine patients had pathologically proven diagnosis and 2 had 2 years follow-up showing no change in lesion size. The temporal resolution of DCE MRI was systematically reduced as a postprocessing step from 15 to 30, 45, and 60 s/acquisition by eliminating intermediate time points. Average wash-in and wash-out slopes, wash-out percentage changes, and kinetic curve shape (persistently enhancing, plateau, or wash-out) were compared for each temporal resolution. Logistic regression and receiver operating characteristic (ROC) curve analysis were used to compare kinetic parameters and diagnostic accuracy.

Results: Sixty patients (74%) had malignant lesions and 21 patients (26%) had benign lesions. All temporal-resolution parameters significantly predicted benign versus malignant diagnosis (P < 0.05). However, 45 s/acquisition and higher temporal-resolution datasets showed higher accuracy than the 60 s/acquisition dataset by ROC curve analysis (0.72 versus 0.69 for average wash-in slope; 0.85 versus 0.82, for average wash-out slope; and 0.88 versus 0.80 for kinetic curve shape assessment, for 45 s/acquisition versus 60 s/acquisition temporal-resolution datasets, respectively (P = 0.027).

Conclusion: DCE MRI data with at least 45-s temporal resolution maximized the agreement between the kinetic parameters and correct classification of benign versus malignant diagnosis.

Figure 1

Data analysis method used for systematically reducing temporal resolution. The bottom line shows the 15 second temporal resolution dynamic acquisition (with the high spatial-resolution sequence in the middle). The temporal resolution data acquired at 15 second intervals was systematically reduced to 30, 45, and 60 second as shown (60 second data was similarly done but not shown in the graph).

Figure 2

Method used in this study for kinetic curve shape determination by categorizing the average wash-out slopes. Peak enhancement was considered the reference point (dotted line). Kinetic curves with average wash-out slopes between +0.03%/sec and −0.03%/sec were considered plateau (highlighted grey area). Kinetic curves with average wash-out slopes <−0.03%/sec were considered wash-out. Kinetic curves with average wash-out slopes >0.03%/sec percent/second were considered persistently enhancing.

Figure 3

Comparison between AUC values for the four tested temporal resolution datasets for average wash-in and wash-out slopes and kinetic curve shape. There is a trend of higher AUC values for higher temporal resolutions. The 15 second/acquisition temporal resolution dataset showed significantly greater AUC value than 60 second/acquisition temporal resolution dataset for both wash-in slope kinetic curve shape.

Figure 4

Comparison between AUC values for the wash-in and wash-out slopes for each temporal resolution dataset. AUC values of the wash-out slope were found to be significantly higher than the AUC values of the wash-in slope for all temporal resolution datasets.

Figure 5

ROC curve comparisons between 15 and 60 sec/acquisition temporal resolution datasets. A) Kinetic curve shape was classified based on a 0.03%/sec cut-off to define persistently enhancing, plateau and washout regions as shown in Figure 2. The AUC for the 15 second temporal resolution dataset was greater than that for the 60 second dataset (p < 0.05). B) The average wash-out slope (grey line) showed significantly higher diagnostic performance demonstrated by greater AUC value than the average wash-in slope (black line) (p<0.01).

Figure 6

DCE MRI of 77 year-old female with a history of right breast cancer treated with conservative breast surgery, presented with a new left breast mass. a) High spatial-resolution subtraction image showing a spiculated, rim-enhancing mass lesion at the 6 O’clock position of the Lt. breast. b) A color map of the corresponding 15 sec/acquisition temporal resolution dynamic series showing the lesion exhibiting green and red colors (denoting intermediate and high levels of suspicion for malignancy). C-F) Kinetic curves for different temporal resolution datasets for the lesion. The kinetic curve shape was washout (type III) for the 15, 30 and 45 second/acquisition acquisition data, but was plateau (type II) for the 60 second/acquisition temporal resolution data. Histo-pathologic examination of the lesion revealed infiltrating ductal carcinoma with foci of DCIS.