Shape analysis of MR brain images based on the fractal dimension

This paper presents some results concerning the application of the fractal approach to the analysis of shape of white brain matter in the magnetic-resonance (MR) images. The fractal dimension of white brain matter was calculated using the box-counting algorithm

Pseudofractal 2D Shape Recognition

From the beginning of fractal discovery they found a great number of applications. One of those applications is fractal recognition. In this paper we present some of the weaknesses of the fractal recognition methods and how to eliminate them using the pseudofractal approach. Moreover we introduce a new recognition method of 2D shapes which uses fractal dependence graph introduced by Domaszewicz and Vaishampayan in 1995. The effectiveness of our approach is shown on two test databases

Uncertainty Estimation in Classification of MGNT Using Radiogenomics for Glioblastoma Patients

Glioblastoma Multiforme (GBM) is one of the most malignant brain tumors among all high-grade brain cancers. Temozolomide (TMZ) is the first-line chemotherapeutic regimen for glioblastoma patients. The methylation status of the O6-methylguanine-DNA-methyltransferase (MGMT) gene is a prognostic biomarker for tumor sensitivity to TMZ chemotherapy. However, the standardized procedure for assessing the methylation status of MGMT is an invasive surgical biopsy, and accuracy is susceptible to resection sample and heterogeneity of the tumor. Recently, radio-genomics which associates radiological image phenotype with genetic or molecular mutations has shown promise in the non-invasive assessment of radiotherapeutic treatment. This study proposes a machine-learning framework for MGMT classification with uncertainty analysis utilizing imaging features extracted from multimodal magnetic resonance imaging (mMRI). The imaging features include conventional texture, volumetric, and sophisticated fractal, and multi-resolution fractal texture features. The proposed method is evaluated with publicly available BraTS-TCIA-GBM pre-operative scans and TCGA datasets with 114 patients. The experiment with 10-fold cross-validation suggests that the fractal and multi-resolution fractal texture features offer an improved prediction of MGMT status. The uncertainty analysis using an ensemble of Stochastic Gradient Langevin Boosting models along with multi-resolution fractal features offers an accuracy of 71.74% and area under the curve of 0.76. Finally, analysis shows that our proposed method with uncertainty analysis offers improved predictive performance when compared with different well-known methods in the literature

A fractal dimension based optimal wavelet packet analysis technique for classification of meningioma brain tumours

With the heterogeneous nature of tissue texture, using a single resolution approach for optimum classification might not suffice. In contrast, a multiresolution wavelet packet analysis can decompose the input signal into a set of frequency subbands giving the opportunity to characterise the texture at the appropriate frequency channel. An adaptive best bases algorithm for optimal bases selection for meningioma histopathological images is proposed, via applying the fractal dimension (FD) as the bases selection criterion in a tree-structured manner. Thereby, the most significant subband that better identifies texture discontinuities will only be chosen for further decomposition, and its fractal signature would represent the extracted feature vector for classification. The best basis selection using the FD outperformed the energy based selection approaches, achieving an overall classification accuracy of 91.25% as compared to 83.44% and 73.75% for the co-occurrence matrix and energy texture signatures; respectively

Radiomic Texture Feature Descriptor to Distinguish Recurrent Brain Tumor From Radiation Necrosis Using Multimodal MRI

Despite multimodal aggressive treatment with chemo-radiation-therapy, and surgical resection, Glioblastoma Multiforme (GBM) may recur which is known as recurrent brain tumor (rBT), There are several instances where benign and malignant pathologies might appear very similar on radiographic imaging. One such illustration is radiation necrosis (RN) (a moderately benign impact of radiation treatment) which are visually almost indistinguishable from rBT on structural magnetic resonance imaging (MRI). There is hence a need for identification of reliable non-invasive quantitative measurements on routinely acquired brain MRI scans: pre-contrast T1-weighted (T1), post-contrast T1-weighted (T1Gd), T2-weighted (T2), and T2 Fluid Attenuated Inversion Recovery (FLAIR) that can accurately distinguish rBT from RN. In this work, sophisticated radiomic texture features are used to distinguish rBT from RN on multimodal MRI for disease characterization. First, stochastic multiresolution radiomic descriptor that captures voxel-level textural and structural heterogeneity as well as intensity and histogram features are extracted. Subsequently, these features are used in a machine learning setting to characterize the rBT from RN from four sequences of the MRI with 155 imaging slices for 30 GBM cases (12 RN, 18 rBT). To reduce the bias in accuracy estimation our model is implemented using Leave-one-out crossvalidation (LOOCV) and stratified 5-fold cross-validation with a Random Forest classifier. Our model offers mean accuracy of 0.967 ± 0.180 for LOOCV and 0.933 ± 0.082 for stratified 5-fold cross-validation using multiresolution texture features for discrimination of rBT from RN in this study. Our findings suggest that sophisticated texture feature may offer better discrimination between rBT and RN in MRI compared to other works in the literature

KONSTRUKCJA WEKTORA CECH W DIAGNOSTYCE SARKOIDOZY NA PODSTAWIE ANALIZY FRAKTALNEJ OBRAZÓW CT KLATKI PIERSIOWEJ

CT images corresponding to the cross-sections of the patients’ upper torso were analysed. The data set included the healthy class and 3 classes of cases affected by sarcoidosis. It was a state involving only the trachea – Sick(1), a state including trachea and lung parenchyma – Sick(2) and a state involving only lung parenchyma – Sick(3). Based on a fractal analysis and a feature selection by linear stepwise regression, 4 descriptors were obtained, which were later used in the classification process. These were 2 fractal dimensions calculated by the variation and box counting methods, lacunarity calculated also with the box counting method and the intercept parameter calculated using the power spectral density method. Two descriptors were obtained as a result of a gray image analysis, and 2 more were the effect of a binary image analysis. The effectiveness of the descriptors was verified using 8 popular classification methods. In the process of classifier testing, the overall classification accuracy was 90.97%, and the healthy cases were detected with the accuracy of 100%. In turn, the accuracy of recognition of the sick cases was: Sick(1) – 92.50%, Sick(2) – 87.50% and Sick(3) – 90.00%. In the classification process, the best results were obtained with the support vector machine and the naive Bayes classifier. The results of the research have shown the high efficiency of a fractal analysis as a tool for the feature vector extraction in the computer aided diagnosis of sarcoidosis.Przeprowadzono analizę obrazów CT górnej części tułowia pacjentów. Zbiór danych zawierał klasę pacjentów zdrowych i 3 klasy przypadków dotkniętych sarkoidozą. Był to stan obejmujący tylko tchawicę – Sick(1), stan obejmujący tchawicę i miąższ płucny – Sick(2) i stan obejmujący tylko miąższ płucny – Sick(3). Na podstawie analizy fraktalnej oraz selekcji cech metodą liniowej regresji krokowej otrzymano 4 deskryptory, które później wykorzystano w procesie klasyfikacji. Były to 2 wymiary fraktalne obliczone za pomocą metod variation i box counting, lakunarność obliczona również za pomocą metody box counting oraz parametr intercept obliczony za pomocą metody widmowej gęstości mocy. W wyniku analizy obrazu szarego otrzymano 2 deskryptory, a 2 kolejne były efektem analizy obrazu binarnego. Skuteczność deskryptorów zweryfikowano za pomocą 8 popularnych metod klasyfikacji. W procesie testowania klasyfikatorów, ogólna dokładność klasyfikacji wyniosła 90,97%, a przypadki zdrowe wykryto z dokładnością 100%. Z kolei, dokładność rozpoznania przypadków chorych była następująca: Sick(1) – 92,50%, Sick(2) – 87,50% i Sick(3) – 90,00%. W procesie klasyfikacji, najlepsze wyniki uzyskano za pomocą maszyny wektorów nośnych i naiwnego klasyfikatora Bayesa. Wyniki badań pokazały wysoką skuteczność analizy fraktalnej jako narzędzia do ekstrakcji wektora cech w komputerowej diagnostyce sarkoidozy

Post mortem computed tomography meets radiomics: a case series on fractal analysis of post mortem changes in the brain

Estimating the post-mortem interval is a fundamental, albeit challenging task in forensic sciences. To this aim, forensic practitioners need to assess post-mortem changes through a plethora of different methods, most of which are inherently qualitative, thus providing broad time intervals rather than precise determinations. This challenging problem is further complicated by the influence of environmental factors, which modify the temporal dynamics of post-mortem changes, sometimes in a rather unpredictable fashion. In this context, the search for quantitative and objective descriptors of post-mortem changes is highly demanded. In this study, we used computed tomography (CT) to assess the post-mortem anatomical modifications occurring in the time interval 0–4 days after death in the brain of four corpses. Our results show that fractal analysis of CT brain slices provides a set of quantitative descriptors able to map post-mortem changes over time throughout the whole brain. Although incapable of producing a direct estimation of the PMI, these descriptors could be used in combination with other more established methods to improve the accuracy and reliability of PMI determination

Prediction of Molecular Mutations in Diffuse Low-Grade Gliomas Using MR Imaging Features

Diffuse low-grade gliomas (LGG) have been reclassified based on molecular mutations, which require invasive tumor tissue sampling. Tissue sampling by biopsy may be limited by sampling error, whereas non-invasive imaging can evaluate the entirety of a tumor. This study presents a non-invasive analysis of low-grade gliomas using imaging features based on the updated classification. We introduce molecular (MGMT methylation, IDH mutation, 1p/19q co-deletion, ATRX mutation, and TERT mutations) prediction methods of low-grade gliomas with imaging. Imaging features are extracted from magnetic resonance imaging data and include texture features, fractal and multi-resolution fractal texture features, and volumetric features. Training models include nested leave-one-out cross-validation to select features, train the model, and estimate model performance. The prediction models of MGMT methylation, IDH mutations, 1p/19q co-deletion, ATRX mutation, and TERT mutations achieve a test performance AUC of 0.83 ± 0.04, 0.84 ± 0.03, 0.80 ± 0.04, 0.70 ± 0.09, and 0.82 ±0.04, respectively. Furthermore, our analysis shows that the fractal features have a significant effect on the predictive performance of MGMT methylation IDH mutations, 1p/19q co-deletion, and ATRX mutations. The performance of our prediction methods indicates the potential of correlating computed imaging features with LGG molecular mutations types and identifies candidates that may be considered potential predictive biomarkers of LGG molecular classification

Prediction of Rapid Early Progression and Survival Risk with Pre-Radiation MRI in WHO Grade 4 Glioma Patients

Recent clinical research describes a subset of glioblastoma patients that exhibit REP prior to start of radiation therapy. Current literature has thus far described this population using clinicopathologic features. To our knowledge, this study is the first to investigate the potential of conventional ra-diomics, sophisticated multi-resolution fractal texture features, and different molecular features (MGMT, IDH mutations) as a diagnostic and prognostic tool for prediction of REP from non-REP cases using computational and statistical modeling methods. Radiation-planning T1 post-contrast (T1C) MRI sequences of 70 patients are analyzed. Ensemble method with 5-fold cross validation over 1000 iterations offers AUC of 0.793 with standard deviation of 0.082 for REP and non-REP classification. In addition, copula-based modeling under dependent censoring (where a subset of the patients may not be followed up until death) identifies significant features (p-value <0.05) for survival probability and prognostic grouping of patient cases. The prediction of survival for the patients cohort produces precision of 0.881 with standard deviation of 0.056. The prognostic index (PI) calculated using the fused features suggests that 84.62% of REP cases fall under the bad prognostic group, suggesting potentiality of fused features to predict a higher percentage of REP cases. The experimental result further shows that mul-ti-resolution fractal texture features perform better than conventional radiomics features for REP and survival outcomes