Introduction

With the change of lifestyle, the incidence of breast cancer is on the rise. Previous researches showed that magnetic resonance imaging (MRI) is more sensitive to the diagnosis of benign and malignant breast diseases than mammography and ultrasonography [1]. Conventional MRI utilizes dynamic contrast imaging to differentiate benign and malignant breast lesions，and the use of T2 relaxation in differential diagnosis has been previously reported[2].However, few researches have investigated T1 and T2 relaxation time changes before and after contrast injection. And these studies always ignored the T1 relaxation time. Synthetic MRI is a novel imaging technique that may offer simultaneously acquired all the quantitative relaxation maps. In this work, the use of the T1 and T2 mapping in synthetic MR before and after contrast injection in differential diagnosis of benign and malignant cancer is investigated.

Methods

This study was approved by the institutional review board, and written informed consent was obtained from all patients. 186 patients with breast lesions (age 40.15±12.65years, age range 19～79 years) were prospectively enrolled in this study and underwent both of synthetic MR (magnetic resonance image compilation, MAGiC) and pathological biopsy. All data were acquired on a 3T MRI system (Signa Pioneer, GE Healthcare, Milwaukee, USA). Routine scan were performed firstly and then the MAGIC. Both the scan sequences were performed before and after contrast injection. The scan parameters for synthetic MR were: TR = 4000 ms, TE1=19 and TE2=85.5 ms, slice thickness/gap = 5/0 mm, FOV = 36 cm, data matrix = 260*260, echo length = 10, bandwidth = 27.78 Hz. All the regions of interest (ROI) delineation were placed by two experienced radiologists. Firstly,we delineated the the solid lesions of the T1 and T2 quantitative maps avoiding the cystic,necrotic,and hemorrhagic areas(called as “T_local“).And then drawn the outline of the whole tumor(called as“T_tumor“).The mean relaxation values T1、T2、ΔT1、ΔT2(the difference before and after contrast injection)within the ROIs were measured. The “T“ and ”T+“ are used to represent the relaxation time before and after contrast injection respectively. All of the data were recorded as mean ± SD and then analyzed by Wilcoxon signed rank test. Receiver operating characteristic (ROC) analysis and the area under the curve (AUC) statistics were applied to evaluate diagnostic performance of MAGIC in benign and malignant cancer.

Results

The study included 71 benign lesions (46 of fibroadenomas, 10 of inflammatory lesions, 9 of breast adenosis, 4 of intraductal papilloma, 2 of benign phyllodes), and 115 malignancy lesions(5 of intraductal carcinoma in situ, 10 of intraductal carcinoma in situ with invasive carcinoma, 95 of invasive ductal carcinoma, 2 of invasive lobular carcinoma, and 3 of mucinous adenocarcinoma). The T1_local,T1_tumor,ΔT1_tumor,T2_local,T2+local,ΔT2_local,T2_tumor,T2+_tumor, and ΔT2_tumor were all statistically significant differences between benign and the malignant lesions(Table 1). The area under the curve(AUC) of T2local was the largest (AUC=0.819, 95CI%: 0.747~0.891). The T2 relaxation time of the malignant lesions was significantly lower than the benign lesions(78.97±16.95 ms vs 111.79±37.15 ms,p＜0.001) . Using T2 relaxation time of 90.56 ms as a cut-off between the benign and malignant, a sensitivity of 83.1% and a specificity of 80.6% were obtained.The positive predictive value and negative predictive value were 89.6% and 70.4%.The T1_local,T1+_local,ΔT1_local,T1+_tumor,ΔT1_tumor and ΔT2_tumor all had statistically significant differences between the subgroups of benign lesions (Table 2). However,only the T1_local was statistically different between the benign(Table 3). Typical cases of benign and malignant lesions are shown in Figures 1 and 2.

Discussion

Our study show that T2 relaxation time is an effective parameter to distinguish benign and malignant breast lesions, which is concordant with previous study^[2-3]. Prolongation of the T2 relaxation time indicates tissue water content increasing^[4]. Therefore, the higher degree of malignancy, which has the greater density of tumor cells and the less free water content in the the extracellular interstitium will make the T2 relaxation time shorter. However, different to previous studies, our study included the changes between T1 and T2 relaxation times before and after contrast scanning. Compared with benign tumors, malignant tumors have higher capillary network density, greater cell permeability and faster contrast agent outflowing. Therefore, the ΔT value can be used to predict the lesions. In our study, the ΔT1_tumor,ΔT2_local and ΔT2_tumor all have statistically differences between benign and the malignant lesions. Generally speaking, the benign lesions show progressive enhancement and the contrast concentration reaches the peak in the delayed period. Rather, the enhancement pattern of malignant lesions is fast inflow-outflow, and the contrast concentration in the delayed lesions was lower.Therefor, we speculate that the the ΔT values of the malignant lesions are lower than those in the benign lesions in our study, which may be related to the MAGIC scanning in the delayed phase.

Conclusion

T1 and T2 quantitative relaxation time offered by synthetic MR may be effective tools for diagnosis of benign and malignant breast lesions. Our study showed that T2_local had the highest diagnostic efficiency. T2_local of 90.56ms can be used as a cut-off between the benign and malignant with a sensitivity of 83.1% and a specificity of 80.6%.

Acknowledgements

NO Acknowledgements

References

1.Bluemke DA, Gatsonis CA, Chen MH, et al. Magnetic resonance imaging of the breast prior to biopsy[J]. Jama, 2004, 292(22): 2735-2742. 2.Liu L, Yin B, Shek K, et al. Role of quantitative analysis of T2 relaxation time in differentiating benign from malignant breast lesions[J]. J Int Med Res, 2018, 46(5): 1928-1935. 3.Merchant TE, Thelissen GR, de Graaf PW, et al. Application of a mixed imaging sequence for MR imaging characterization of human breast disease[J]. Acta Radiol, 1993, 34(4): 356-361. 4.Bueno MJ, Mouron S, Quintela-Fandino M. Personalising and targeting antiangiogenic resistance: a complex and multifactorial approach[J]. Br J Cancer, 2017, 116(9): 1119-1125.