Influencia da Regiao de Interesse nos Mapas de ADC de Sujeitos Normais Usados para Diagnostico de Tumores Cerebrais in vivo

摘要

In diffusion-weighted magnetic resonance imaging (DWI), the contrast is determined by the random microscopic motion of water protons. In general, pathologic processes, such as neoplasic cell changes, tend to alter the structural organization by destruction or reorganization of membranous elements or by a change in cellularity. These changes also have an impact on proton mobility, which can be followed up by DWI. ADC (Apparent Diffusion Coefficient) maps are derived from DWI, being a representation of the magnitude of water diffusion at the points of a given region of interest (ROI). The purpose of this study was to verify the ROI dependence of ADC values in healthy brain tissue, and the influence this could have in the distinction between tumoral (glioblastoma) and healthy brain tissue. ROIs for ADC computation in the control group were selected according to the ROIs specified for the tumor group, with two variants: in one case, the ROIs used in controls were exactly the same as in pacientes, and in another case, the lateral ventricle portions were excluded from these ROIs. Important dependences of ADC values with ROI were not found in the control group for neither case, showing that ROI location in the normal brain is not essential for determination of normal reference ADC values. The mean ADC values found were (2.83±0.45)xl0~(-4) mm~2/s for glioblastoma images, (8.4±1.9)xl0~(-4) for original-ROIs control images, and (8.0±1.2)xl0"4 for ROIs excluding the lateral ventricles portion control images. Both control values allowed the differentiation between this type of tumor and healthy brain tissue.