Kinetic curves of malignant lesions are not consistent across MRI systems: need for improved standardization of breast dynamic contrast-enhanced MRI acquisition

Abstract

Objective: The purpose of this study was to compare MRI kinetic curve data acquired with three systems in the evaluation of malignant lesions of the breast.

Materials and methods: The cases of 601 patients with 682 breast lesions (185 benign, 497 malignant) were selected for review. The malignant lesions were classified as ductal carcinoma in situ (DCIS), invasive ductal carcinoma (IDC), and other. The dynamic MRI protocol consisted of one unenhanced and three to seven contrast-enhanced images acquired with one of three imaging protocols and systems. An experienced radiologist analyzed the shapes of the kinetic curves according to the BI-RADS lexicon. Several quantitative kinetic parameters were calculated, and the kinetic parameters of malignant lesions were compared across the three systems.

Results: Imaging protocol and system 1 were used to image 304 malignant lesions (185 IDC, 62 DCIS); imaging protocol and system 2, 107 lesions (72 IDC, 21 DCIS); and imaging protocol and system 3, 86 lesions (64 IDC, 17 DCIS). Compared with those visualized with imaging protocols and systems 1 and 2, IDC lesions visualized with imaging protocol and system 3 had significantly less initial enhancement, longer time to peak enhancement, and a slower washout rate (p < 0.004). Only 47% of IDC lesions imaged with imaging protocol and system 3 exhibited washout type curves, compared with 75% and 74% of those imaged with imaging protocols and systems 2 and 1, respectively. The diagnostic accuracy of kinetic analysis was lowest for imaging protocol and system 3, but the difference was not statistically significant.

Conclusion: The kinetic curve data on malignant lesions acquired with one system showed significantly lower initial contrast uptake and a different curve shape in comparison with data acquired with the other two systems. Differences in k-space sampling, T1 weighting, and magnetization transfer effects may be explanations for the difference.

Fig 1. Examples of MR images and kinetic curves obtained with three systems and protocols

A and B, 57-year-old woman with invasive ductal carcinoma (arrow). MR image (A) and kinetic curve (B) acquired with imaging protocol and system 1 have the following quantitative parameters: initial enhancement percentage, 334%; peak enhancement percentage, 350%; signal enhancement ratio, 1.21; time to peak enhancement, 249 seconds. C and D, 54-year-old woman with invasive ductal carcinoma (arrow). MR image (C) and kinetic curve (D) acquired with imaging protocol and system 2 have the following quantitative parameters: initial enhancement percentage, 282%; peak enhancement percentage, 360%; signal enhancement ratio, 0.92; time to peak enhancement, 118 seconds. E and F, 73-year-old woman with invasive ductal carcinoma (arrow). MR image (E) and kinetic curve (F) acquired with imaging protocol and system 3 have the following quantitative parameters: initial enhancement percentage, 107%; peak enhancement percentage, 221%; signal enhancement ratio, 0.55; time to peak enhancement, 120 seconds.

Fig 2. Contrast enhancement of malignant lesions

A and B, Graphs show percentage of lesions with BI-RADS descriptor of kinetic curve shape during initial rise (A) and delayed phase (B) on MR images acquired with imaging protocols and systems 1, 2, and 3.

Fig 3

Graph shows area under curve (A_z) for four kinetic parameters: time to peak enhancement (T_peak), signal enhancement ratio (SER), peak enhancement percentage (E_peak), and initial enhancement percentage (E₁). For each parameter, three A_z values are presented for imaging protocols and systems (IPS) 1, 2, and 3. Error bars indicate 95% CI.