ObjectivesTo determine the added discriminative value of detailed quantitative characterization of background parenchymal enhancement in addition to the tumor itself on dynamic contrast-enhanced (DCE) MRI at 3.0 Tesla in identifying “triple-negative" breast cancers.Materials and MethodsIn this Institutional Review Board-approved retrospective study, DCE-MRI of 84 women presenting 88 invasive carcinomas were evaluated by a radiologist and analyzed using quantitative computer-aided techniques. Each tumor and its surrounding parenchyma were segmented semi-automatically in 3-D. A total of 85 imaging features were extracted from the two regions, including morphologic, densitometric, and statistical texture measures of enhancement. A small subset of optimal features was selected using an efficient sequential forward floating search algorithm. To distinguish triple-negative cancers from other subtypes, we built predictive models based on support vector machines. Their classification performance was assessed with the area under receiver operating characteristic curve (AUC) using cross-validation.ResultsImaging features based on the tumor region achieved an AUC of 0.782 in differentiating triple-negative cancers from others, in line with the current state of the art. When background parenchymal enhancement features were included, the AUC increased significantly to 0.878 (p<0.01). Similar improvements were seen in nearly all subtype classification tasks undertaken. Notably, amongst the most discriminating features for predicting triple-negative cancers were textures of background parenchymal enhancement.ConclusionsConsidering the tumor as well as its surrounding parenchyma on DCE-MRI for radiomic image phenotyping provides useful information for identifying triple-negative breast cancers. Heterogeneity of background parenchymal enhancement, characterized by quantitative texture features on DCE-MRI, adds value to such differentiation models as they are strongly associated with the triple-negative subtype. Prospective validation studies are warranted to confirm these findings and determine potential implications.

• This study tested the validity of noninvasive electrical conductivity measurements by MRI. • This study also evaluated the electrical conductivity characteristics of diffuse glioma. • Gliomas have higher electrical conductivity values than the normal brain parenchyma. • Noninvasive electrical conductivity measurement can be helpful for better characterisation of glioma.

).q RSNA, 2015 Purpose:To develop and independently validate prognostic imaging biomarkers for predicting survival in patients with glioblastoma on the basis of multiregion quantitative image analysis. Materials and Methods:This retrospective study was approved by the local institutional review board, and informed consent was waived. A total of 79 patients from two independent cohorts were included. The discovery and validation cohorts consisted of 46 and 33 patients with glioblastoma from the Cancer Imaging Archive (TCIA) and the local institution, respectively. Preoperative T1-weighted contrast material-enhanced and T2-weighted fluid-attenuation inversion recovery magnetic resonance (MR) images were analyzed. For each patient, we semiautomatically delineated the tumor and performed automated intratumor segmentation, dividing the tumor into spatially distinct subregions that demonstrate coherent intensity patterns across multiparametric MR imaging. Within each subregion and for the entire tumor, we extracted quantitative imaging features, including those that fully capture the differential contrast of multimodality MR imaging. A multivariate sparse Cox regression model was trained by using TCIA data and tested on the validation cohort. Results:The optimal prognostic model identified five imaging biomarkers that quantified tumor surface area and intensity distributions of the tumor and its subregions. In the validation cohort, our prognostic model achieved a concordance index of 0.67 and significant stratification of overall survival by using the log-rank test (P = .018), which outperformed conventional prognostic factors, such as age (concordance index, 0.57; P = .389) and tumor volume (concordance index, 0.59; P = .409). Conclusion:The multiregion analysis presented here establishes a general strategy to effectively characterize intratumor heterogeneity manifested at multimodality imaging and has the potential to reveal useful prognostic imaging biomarkers in glioblastoma.q RSNA, 2015

M oyamoya disease (MMD) is characterized by the presence of net-like collateral vessels at the brain base that are caused by progressive major cerebral artery occlusion. 1Executive function/attention and working memory, primarily mediated by the lateral prefrontal region, are impaired, suggesting that lateral prefrontal ischemia is responsible for neurocognitive dysfunction.2,3 A recent investigation revealed the association of neurocognitive dysfunction with reduced cerebral blood flow.3 Nevertheless, not all patients with neurocognitive dysfunction had cerebral infarction on conventional MRI. Thus, ischemia-induced subtle microstructural alterations, which are beyond the detectability of conventional MRI, underlie neurocognitive dysfunction in MMD.Subtle gray matter changes, not shown on conventional MRI, are successfully detected in many diseases, such as mild cognitive impairment and schizophrenia, through voxel-byvoxel comparison of gray matter density on 3-dimensional (3D) MRI.4,5 Diffusion tensor imaging (DTI) is reportedly highly sensitive to microstructural alterations in diffusion characteristics of white matter. [6][7][8][9] To the best of our knowledge, no reports have evaluated gray matter changes in MMD using 3D MRI. There are only few reports on DTI assessments of MMD white matter integrity.6-8 Nevertheless, these reports used a specified region-of-interest approach and evaluated only 2 major DTI indices, such as fractional anisotropy (FA) and mean diffusivity (MD). Voxel-based analysis of white matter can provide detailed topographical characteristics of white matter integrity, and tractography can show the integrity of the major white matter tracts that run in anatomic regions. Furthermore, additional information for characterizing chronic ischemia-induced white matter damage can be extracted by incorporating other major DTI indices, such as axial diffusivity (AD) and radial diffusivity (RD).Here, we investigated the brain's microstructure across different regions in adult MMD by a voxel-based analysis of gray and white matter and tractography, and evaluated the relationship of these microstructural alterations with hemodynamic compromise and neurocognitive dysfunction.Background and Purpose-The mechanisms underlying frontal lobe dysfunction in moyamoya disease (MMD) are unknown. We aimed to determine whether chronic ischemia induces subtle microstructural brain changes in adult MMD and evaluated the association of changes with neuropsychological performance. Methods-MRI, including 3-dimensional T1-weighted imaging and diffusion tensor imaging, was performed in 23 adult patients with MMD and 23 age-matched controls and gray matter density and major diffusion tensor imaging indices were compared between them; any alterations in the patients were tested for associations with age, ischemic symptoms, hemodynamic compromise, and neuropsychological performance. Results-Decrease in gray matter density, associated with hemodynamic compromise (P<0.05), was observed in the posterior cingulate cortex of pa...

Imaging plays an important role in the diagnosis and staging of cancer, as well as in radiation treatment planning and evaluation of therapeutic response. Recently, there has been significant interest in extracting quantitative information from clinical standard-of-care images, i.e. radiomics, in order to provide a more comprehensive characterization of image phenotypes of the tumor. A number of studies have demonstrated that a deeper radiomic analysis can reveal novel image features that could provide useful diagnostic, prognostic or predictive information, improving upon currently used imaging metrics such as tumor size and volume. Furthermore, these imaging-derived phenotypes can be linked with genomic data, i.e. radiogenomics, in order to understand their biological underpinnings or further improve the prediction accuracy of clinical outcomes. In this article, we will provide an overview of radiomics and radiogenomics, including their rationale, technical and clinical aspects. We will also present some examples of the current results and some emerging paradigms in radiomics and radiogenomics for clinical oncology, with a focus on potential applications in radiotherapy. Finally, we will highlight the challenges in the field and suggest possible future directions in radiomics to maximize its potential impact on precision radiotherapy.

Purpose: To investigate the correlation between perfusion-related parameters obtained with intravoxel incoherent motion (IVIM) and classical perfusion parameters obtained with dynamic contrast-enhanced (DCE) MRI in patients with head and neck squamous cell carcinoma (HNSCC), and to compare direct and asymptotic fitting, the pixel-by-pixel approach, and a region of interest (ROI)-based approach respectively for IVIM parameter calculation. Materials and Methods:Seventeen patients with HNSCC were included in this retrospective study. All MR scanning was performed using a 3T MR unit. Acquisition of IVIM was performed using single-shot spin-echo echo-planar imaging with three orthogonal gradients with 12 b-values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800, 1000, and 2000). Perfusion-related parameters of perfusion fraction 'f' and the pseudo-diffusion coefficient 'D*' were calculated from IVIM data by using least square fitting with the two fitting methods of direct and asymptotic fitting, respectively. DCE perfusion was performed in a total of 64 dynamic phases with a 3.2-s phase interval.The two-compartment exchange model was used for the quantification of tumor blood volume (TBV) and tumor blood flow (TBF). Each tumor was delineated with a polygonal ROI for the calculation of f, f･D* performed using both the pixel-by-pixel approach and the ROI-based approach. In the pixel-by-pixel approach, after fitting each pixel to obtain f, f･D* maps, the mean value in the delineated ROI on these maps was calculated. In the ROI-based approach, the mean value of signal intensity was calculated within the ROI for each b-value in IVIM images, and then fitting was performed using these values. Correlations between f in a total of four combinations (direct or asymptotic fitting and pixel-by-pixel or ROI-based approach) and TBV were respectively analyzed using Pearson's correlation coefficients. Correlations between f･ D* and TBF were also similarly analyzed. Results:In all combinations of f and TBV, f･D* and TBF, there was a significant correlation. In the comparison of f and TBV, a moderate correlation was observed only between f obtained by direct fitting with the pixel-by-pixel approach, whereas a good correlation was observed in the comparisons using the other three combinations. In the comparison of f･D* and TBF, a good correlation was observed only with f･D* obtained by asymptotic fitting with the ROI-based approach. In contrast, moderate correlations were observed in the comparisons using the other three combinations. Conclusion:IVIM was found to be feasible for the analysis of perfusion-related parameters in patients with HNSCC. Especially, the combination of asymptotic fitting with the ROI-based approach was better correlated with DCE perfusion.

Objectives:To evaluate the diagnostic value of intravoxel incoherent motion (IVIM) and diffusional kurtosis imaging (DKI) parameters in nasal or sinonasal squamous cell carcinoma (SCC) patients to determine local control/failure. ･Especially, the D-value's histogram 25th percentile has high diagnostic accuracy. Methods

Maps of changes in OEF generated from SW phase images revealed changes in OEF corresponding to anticipated changes in CBF induced by various conditions; SW phase imaging might, in the future, be applied to evaluate cerebrovascular and other cerebral disorders in which changes in oxygen metabolism are important for planning therapeutic strategies.