A Review Study on the efficacy of Quantitative DCE-MRI in Adnexal Lesion Diagnosis

Abstract

: Ovarian cancer is a leading indication for gynecological surgery. The conventional and widely-accepted imaging modalities, such as ultrasonography (US), fall short of specificity. Thus, advanced imaging modalities such as anatomical along with physiological magnetic resonance imaging, specifically dynamic contrast enhanced (DCE-) MRI could be used successfully as an adjunct to morphological assessment findings. The specificity of diagnosis could benefit from DCE-MRI analysis approach, either semi- or fully quantitative. The aim of this abstract is to give a review on the available scholarly works, in order to investigate the role of quantitative DCE-MRI in ovarian cancer diagnosis and differentiation. US is considered as the primary imaging modality for confirmation of the ovarian origin of the mass and characterization of the nature of the mass as benign or malignant. In a study on 72 patients, Sohaib et al. showed that the sensitivity and specificity of US for differentiating malignant from benign lesions are 100% and 39.5%, respectively. MRI has proved to be most predictive of malignancy. The sensitivity and specificity of anatomical MRI in detecting malignancy are 96.6% and 83.7%, respectively. DCE-MRI has been introduced as a beneficial functional MR imaging technique for improving the tumor diagnosis. In Bernardin et al. study, MRI features of 70 complex adnexal masses with enhancing components in 63 patients were reviewed and correlated with histopathology or radiological follow-up results. Their results showed a significant difference in maximum absolute enhancement of signal intensities (SImax), maximum relative enhancement (SIrel) and wash-in rate (WIR) between benign and borderline/invasive malignant groups. A cut-off of WIR?9.5 l/s had a specificity of 88% and positive predictive value of 86% for predicting malignancy, which was significantly higher than conventional MRI (62%). On the other hand, the pharmacokinetic (or model-based) analysis of DCE-MRI is a feasible and accurate technique to differentiate malignant from benign adnexal tumors. Thomassin-Naggara et al. managed to obtain diagnostic evaluation in 56 women. Microvascular parameters were extracted from high temporal resolution DCE-MRI series, using a two-compartmental model in the solid tissue of adnexal tumors. Malignant tumors displayed higher blood flow (FT), blood volume fraction (Vb), area under the enhancing curve (rAUC) and lower interstitial volume fraction (Ve) than benign tumors. FT was the most relevant factor for discriminating malignant from benign tumors. A tissue blood flow had a high sensitivity of 88.9% for predicting benignity. Diffusion weighted magnetic resonance imaging (DW-MRI) is an alternative functional MR imaging technique. In their study of DW-MRI, Nakayama et al. reported no significant difference in the ADC-values between the benign and malignant cystic ovarian lesions; however, there was a wide variation within the ADC-values of malignant ovarian tumors, which is related to complex morphology of ovarian cancer. DWI can improve characterization of adnexal lesions, especially benign lesions. Ovarian cancer is a genetically heterogeneous disease with a poor prognosis. US is less accurate for complex or indeterminate masses, even when combined with color Doppler imaging. Most MRI studies had higher prevalence of complex (solid, solid/cysts) ovarian lesions than that of US. Semi-quantitative parameters extracted from DCE-MRI are shown to produce promising results for differentiating benign, borderline, and invasive ovarian epithelial tumors and found to correlate with tumor antigenic status, as determined with immunohistochemical staining. Although semi-quantitative DCE-MRI analysis shows rather high sensitivity and specificity (88% and 86%), it lacks reproducibility, because they work based on signal intensity and do not take into account the individual variability of the arterial input function. On the other hand, quantitative DCE-MRI is rather accurate for differentiating borderline from primary invasive ovarian tumors (88.9% of sensitivity). It can be concluded that in order to increase sensitivity and specificity of quantitative DCE-MRI, it seems reasonable to use DWI as an adjunct to PW imaging in combination to conventional MRI, to improve the characterization of complex adnexal masses.