Απεικόνιση σταθμισμένης διάχυσης στη [sic] τομογραφία πυρηνικού μαγνητικού συντονισμού του μαστού

by Σοφία Τσέκα

Institution: University of Patras
Year: 2014
Keywords: Diffusion weighted imaging; Magnetic Resonance Imaging (MRI); Breast; Apparent diffusion coefficient (ADC); ADC map; Benign tumors; Malignant tumor; Texture analysis; Receiver operating characteristic (Roc) analysis; First order statistics; 618.190 757 2; Απεικόνιση σταθμισμένης διάχυσης; Τομογραφία πυρηνικού μαγνητικού συντονισμού; Μαστός; Φαινόμενος συντελεστής διάχυσης; Χάρτης ADC; Καλοήθεις όγκοι; Ανάλυση υφής; Χαρακτηριστικά υφής πρώτης τάξης
Record ID: 1152970
Full text PDF: http://hdl.handle.net/10889/8003


Breast cancer is a major global health problem and the most common form of cancer among women. Major advances in the technologies of imaging provide improved detection and sensitivity with fewer unnecessary biopsies. Commonly used imaging modalities include mammography, ultrasonography, magnetic resonance imaging (MRI), scintimammography, single photon emission computed tomography (SPECT) and positron emission tomography (PET). The current study is focused on breast MRI imaging, especially one of the most promising recent techniques, i.e. the Diffusion Weighted Imaging breast MRI (DWI). DWI is an unenhanced MRI technique, based on volume sequences on various b values (the b value identifies the measurement's sensitivity to diffusion and determines the strength and duration of the diffusion gradients) measuring the mobility of water molecules (Brownian motion) in vivo (in tissues) and provides different and potentially complementary information to Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) technique. As DWI based on the diffusive properties of water molecules, reflects their random motion resulting from thermal agitation. Water diffusion on breast can be quantified by measuring the mean diffusivity, which is the average of Apparent Diffusion Coefficient (ADC). The ADC can be calculated by making measurements at a low b factor, b1, and a higher b factor, b2. DWI allows the mapping of the diffusion process of molecules by the ADC map. ADC maps are calculated by collecting images with at least 2 different values, b1 and b2, of the b factor. The ADC map is a parametric image whose color scale or gray scale represents the ADC values of the voxels and is usually generated by proprietary or in house software. DWI apart from the 3D anatomical information, provides a noninvasive investigation of tissue vascularity, a novel contrast mechanism in MRI and has a high sensitivity in the detection of changes in the local biologic environment due to a pathologic process. Therefore, in addition to contrast enhancement-based characterization (DCE-MRI), measurement of the motion of water molecules in DWI provides an additional feature for lesion characterization that may further increase the specificity of MRI for classifying breast lesions. The diagnostic task that the current study deals with, accounts for the diagnosis of mass-like lesions in Diffusion Weighed Magnetic Resonance Imaging, based on low ADC values compared to high once in case of benign versus normal tissue. The hypothesis is that diffusivity of water molecules is restricted in environments of high cellularity, intracellular and extracellular edema, high viscosity, and fibrosis, such as malignant tumors, because these conditions become barriers to the movement of water molecules. Therefore, most of breast cancers show low ADC values compared with benign and normal tissue. Many studies have revealed the usefulness of ADC values in the differential diagnosis of breast lesions; however, the clinical effect remains limited because of the substantial…