Ultrafast Bilateral DCE-MRI of the Breast with Conventional Fourier Sampling: Preliminary Evaluation of Semi-quantitative Analysis

Abstract

Rationale and objectives: The study aimed to evaluate the feasibility and advantages of a combined high temporal and high spatial resolution protocol for dynamic contrast-enhanced magnetic resonance imaging of the breast.

Materials and methods: Twenty-three patients with enhancing lesions were imaged at 3T. The acquisition protocol consisted of a series of bilateral, fat-suppressed "ultrafast" acquisitions, with 6.9- to 9.9-second temporal resolution for the first minute following contrast injection, followed by four high spatial resolution acquisitions with 60- to 79.5-second temporal resolution. All images were acquired with standard uniform Fourier sampling. A filtering method was developed to reduce noise and detect significant enhancement in the high temporal resolution images. Time of arrival (TOA) was defined as the time at which each voxel first satisfied all the filter conditions, relative to the time of initial arterial enhancement.

Results: Ultrafast images improved visualization of the vasculature feeding and draining lesions. A small percentage of the entire field of view (<6%) enhanced significantly in the 30 seconds following contrast injection. Lesion conspicuity was highest in early ultrafast images, especially in cases with marked parenchymal enhancement. Although the sample size was relatively small, the average TOA for malignant lesions was significantly shorter than the TOA for benign lesions. Significant differences were also measured in other parameters descriptive of early contrast media uptake kinetics (P < 0.05).

Conclusions: Ultrafast imaging in the first minute of dynamic contrast-enhanced magnetic resonance imaging of the breast has the potential to add valuable information on early contrast dynamics. Ultrafast imaging could allow radiologists to confidently identify lesions in the presence of marked background parenchymal enhancement.

Keywords: DCE-MRI; breast imaging; high temporal resolution; lesion kinetics.

Copyright © 2016 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Maximum intensity projections (MIPs) of ultrafast subtractions (a-d) and enhancement gradient images (e-h). Two invasive ductal carcinomas are visible on image right. Images were acquired with a 9s temporal resolution. Arrows point to vessels feeding and draining a lesion in: (f) arterial phase and (g) venous phase.

Figure 2

Examples of time-of-arrival color maps (in seconds) for cases presenting with (lesions marked by arrows): (a) IDC (b) primary and satellite IDC in a case with marked parenchymal enhancement, (c) complex sclerosing lesion and (d) a fibroadenoma. Color scale indicates the time-point at which voxels first began to significantly enhance, relative to time of arrival of the bolus. This image exemplifies the general trend observed, that malignant lesions had shorter TOAs on average.

Figure 3

Scatterplot of average signal enhancement for: malignant lesions, benign lesions and BPE; with their respective average EMM fits.

Figure 4

Plots of the ratio of the signal increase in the lesion to the increase in the background parenchyma for three lesions with marked BPE. The vertical dotted line indicates the approximate time at which the standard clinical protocol would acquire k0. The dashed lines in each curve connect the data points from the ultrafast and standard clinical protocols.

Figure 5

Two examples of lesions (marked by arrows) where background parenchymal enhancement (BPE) reduces conspicuity in later time-points; (a-c) and (e-g) ultrafast acquisitions; (d) and (h) high spatial resolution images acquired at approximately 2 minutes post-injection. Lesions were: (a-d) a fibroadenoma is visible as an oval circumscribed mass in the early images but is isointense with parenchyma in (d), (e-h) a satellite invasive ductal carcinoma clearly defined in (f) and (g) but is less conspicuous in (h).