In this study, we conducted a randomized controlled study on preoperative high-temporal resolution and low-temporal resolution DCE-MRI texture features, including the lesion central area, surrounding peripheral area, and background enhancement area. The quantitative parameters were measured by volume measurement, and the ROI area was selected to be larger, which was more comprehensive and accurate than the data measured at a single level in most previous studies. Neoadjuvant chemotherapy patients were excluded to avoid the effect of therapy on lesions. These results in this study indicated that high-temporal resolution DCE-MRI may be more helpful than low-temporal resolution DCE-MRI in the differentiation of breast disease from background enhancement.
Most previous studies have focused only on the disease itself [8–18, 21, 22] or the peripheral interstitial areas [19, 23, 24]. The lesion center, periphery and background enhancement area may be related to the differentiation of benign and malignant lesions. Few studies have comprehensively focused on the aforementioned area by volume measurement. The region of interest in this study included the lesion central area, surrounding peripheral area and background enhancement area. Therefore, the data were as comprehensive. It was found that the three ROI’s hemodynamic characteristics (Ktrans, Kep, Ve, Vp, TTP) obtained from two different temporal resolution DCE-MRI had a statistical difference. Particularly, the joint Ktrans texture features of three areas may be helpful for the differentiation of benign and malignant breast disease. These results indicated that the comprehensive measurement of lesions and background enhancement area could be more accurate in the diagnosis and differentiation of benign and malignant lesions.
In this study, the ROC curve showed that models from the high-temporal resolution DCE-MRI group were slightly higher than those of the low-temporal resolution DCE-MRI group, which meant that DCE-MRI with high temporal resolution had high application value in the diagnosis of breast diseases. Conventional breast dynamic enhanced MRI mainly observed the characteristic of time signal intensity curve of breast disease (i.e curve shape, time to peak, early enhancement rate, etc.) and allowed for semiquantitative analysis of tumor characters. But these semiquantitative parameters were influenced by the cardiac output, imaging sequences, contrast medium injection rate, blood flow and so on, which were prone to error [30]. This study used quantitative analysis based on breast DCE - MRI by the Extended Tofts model and obtained multiple hemodynamic parameters, such as the endothelial transfer constant of Ktrans, reflux rate of Kep, fractional EES volume of Ve and fractional plasma volume of Vp. The extended Tofts model was applicable to the time resolution of < 12 seconds, as high temporal resolution can more accurately measure the lesion and observe subtle pharmacokinetic changes in tissue for a very short time. This allows the sequence to accurately capture characters of the lesion, even including subtle differences of contrast agent concentration changes. Thus, high-temporal resolution may extract more texture features than low-temporal resolution for accurate diagnosis of breast lesions [31, 32].
Although pathology is the gold standard for disease analysis and classification, it is limited by invasiveness and local sampling, which may cause inaccurate pathological results and the limited pathological classification of diseases. DCE-MRI has become an important method of diagnosis and observation of breast diseases due to its noninvasive, radiation-free and high-resolution nature with soft tissue. In this study, we analyzed the correlation between DCE-MRI and pathological grading of malignant lesions (invasive ductal carcinoma, IDC). The results showed that only the Ktrans-mean of lesion central area on the high-temporal resolution DCE-MRI was significantly correlated with pathological grade [33]. In this study, invasive ductal carcinoma was only included in the malignant group because the number of patients with other malignant types was too small (less than 5 cases) to be excluded by correlation statistics of pathological grade. These indicated that high-temporal resolution DCE-MRI may offer more diagnostic information in a lesion.
It was determined that Ktrans-mean reflects the hemodynamic characteristics of the disease and was related to the number and immaturity degree of blood vessels in the central tumor and peritumor regions in different pathological grades. Tumor angiogenesis increased in most malignant lesions, and there were a large number of immature tumors with high permeability of their vessel walls. Therefore, low molecular weight contrast agents were able to enter the EES through the thin vessel walls. Some previous studies also support that high-temporal resolution DCE-MRI can more accurately evaluate the hemodynamic microenvironment of tissues, through high-throughput extracted image texture features and quantitative evaluation. For example, the gray level co-occurrence matrix with the quantitative enhancement of heterogeneity can predict breast cancer invasion, prognosis and curative effect [7, 9–15].
Interestingly, this study found that the performance of Ktrans texture feature models of lesion, peripheral and background enhancement area based on high-temporal resolution DCE-MRI had more slightly high than low resolution, particularly joint textural feature model of three areas better than others. Background enhancement (BE) of the breast reflects an increase of T1 relaxation after enhancement, which directly reflects the blood supply and permeability of breast tissue. Hormones, especially estrogen, increase the microvascular permeability and vasodilation of breast tissue, causing vascular hyperplasia and ductal gland epithelial proliferation. Progesterone increases metabolic activity by promoting mitosis and leads to increased perfusion of the breast tissue, resulting in background enhancement of the breast. Tissue enhancement in MR imaging is related to vascular distribution, the permeability of contrast agents and T1 relaxation of the tissue [28]. In breast tissue, the anatomy of the vascular system and the effect of hormones on breast tissue are factors affecting the morphology and degree of BE [29]. High resolution dynamic enhanced MR texture can quantitatively evaluate disease and tissue heterogeneity, which is helpful for accurate assessment and early diagnosis of breast diseases and BE [4, 10, 27]. Thus, not only can high-temporal resolution DCE-MRI provide a high application value in the diagnosis of breast disease and background enhancement, but also allows for joint texture features of the lesion.
There were several limitations in this study: First, the sample size was relatively small. When the number of texture features to be extracted and screened was large, the sample size was challenged, which needs further study with large samples. Second, malignant breast lesions of other pathological types of the breast were not included in the group, which needs to be further studied. Third, high time resolution DCE-MRI scan still needs to be further improved to further optimize the scanning time. Fourth, the textural features model in this study was not further outside this center. Therefore, a multi-center validation can be implemented and add clinical characteristics to the model in the future.