Brain tumor segmentation from multi-modal magnetic resonance imaging (MRI) is crucial for computer-assisted diagnosis and treatment planning. However, this task remains highly challenging due to substantial image heterogeneity, modality-inherent variability, and severe class imbalance among tumor sub-regions. To address these issues, we propose FRMF-Net , a F eature R ectification and adaptive M odality F usion guided multi-modal brain tumor segmentation Net work, which consists of three key components: a Modality-Specific Feature Rectification (MSFR) module, an Adaptive Modality Fusion (AMF) module, and a Region-Adaptive Loss (RAL). Specifically, MSFR enhances modality-specific representations by jointly modeling shared and private information, thereby mitigating inter-modality noise and reducing feature discrepancies across modalities. Building on this, AMF performs voxel-wise adaptive fusion through modality-, channel-, and spatial-wise attention, enabling the network to dynamically emphasize the most informative features for accurate tumor delineation. In addition, RAL alleviates the class imbalance issue by adaptively reweighting the contribution of each tumor sub-region according to its spatial extent in each sample. Extensive experiments on the BraTS 2019 and BraTS 2020 datasets demonstrate that FRMF-Net consistently outperforms the state-of-the-art methods, achieving superior Dice score and lower Hausdorff distance, particularly in small and challenging tumor regions. These results confirm that FRMF-Net provides a robust and effective solution for multi-modal brain tumor segmentation.

Accurate brain tumor segmentation plays an important role in clinical diagnosis, treatment planning, and therapeutic response monitoring. Multi-modal MRI provides complementary structural and functional information, but existing methods remain limited by their inadequate exploitation of cross-modal complementarity and their inability to effectively handle modality-specific disparities and redundant information. To address these challenges, this paper proposes a novel hierarchical teacher-student learning framework with adaptive cross-modal fusion. MRI modalities are grouped into teacher modalities (Flair and T1c) and student modalities (T2 and T1) based on their intrinsic tumor-related characteristics. Central to this framework is the Modality Guidance Module (MGM), which consists of two key components designed to achieve multi-modal feature distillation. Within MGM, the Modality Enhancement Module (MEM) extracts highly discriminative features from teacher modalities. While the Modality Fusion Module (MFM) leverages these features to guide and refine the learning of student modalities. To further capture inter-modal dependencies, a Cross-Modal Fusion Module (CMFM) is introduced to adaptively integrate complementary information across all modalities. Extensive experiments on the BraTS 2018, 2019 and 2020 datasets demonstrate that the proposed method achieves superior performance compared with state-of-the-art approaches. Beyond brain tumor segmentation, the hierarchical teacher-student paradigm and adaptive fusion strategy also hold potential for broader multi-modal image analysis tasks.

Accurate segmentation of brain tumors from multi-modal MRI is crucial for diagnosis and treatment planning. However, challenges such as severe class imbalance, modality-specific feature heterogeneity, and predictive uncertainty hinder reliable performance. In this work, we propose UTriGate-Net, a novel uncertainty-aware multi-modal brain tumor segmentation framework. First, we design a Triaxial Context Encoding (TCE) block that extracts anisotropic spatial features by applying directional convolutions along the axial, coronal, and sagittal planes, thereby enhancing 3D contextual representation. Second, we introduce a Gated Modality Fusion (GMF) module, which adaptively integrates complementary information across modalities through modality-specific gating weights that suppress redundancy while retaining salient features. Finally, to improve segmentation reliability, we develop an Uncertainty-Regularized Weighted Loss (URWL) that combines dynamic class-specific weighting to mitigate class imbalance with an entropy-based uncertainty penalty to encourage well-calibrated predictions. Experiments on the BraTS 2019 and 2020 datasets demonstrate that UTriGate-Net achieves superior segmentation accuracy and robustness, particularly in challenging subregions. Overall, the proposed framework offers a promising solution for reliable and precise brain tumor delineation in clinical practice.

Multimodal survival analysis aims to combine heterogeneous data sources to improve the prediction quality of survival outcomes. However, this task is particularly challenging due to high heterogeneity and noise across data sources. Additionally, the exact survival time is often censored (partially known) due to incomplete event observation. To address the above challenges, we propose a novel interpretable evidential multimodal survival fusion model, EsurvFusion. This model is designed to combine multimodal data at the decision level using Epistemic Random Fuzzy Sets that jointly handle both data and model uncertainty while incorporating modality-level reliability. Specifically, EsurvFusion first models unimodal data with newly introduced Gaussian random fuzzy numbers, producing possible unimodal survival predictions along with corresponding aleatory and epistemic uncertainty. It then estimates modality-level reliability through a reliability discounting layer to correct the misleading impact of noisy data modalities. Finally, a multimodal evidence fusion layer is introduced to combine the discounted predictions, revealing modality-level influence based on the learned reliability coefficients. Extensive experiments on four multimodal cancer survival datasets demonstrate the effectiveness of our model in handling highly heterogeneous data, establishing a new state-of-the-art performance on several benchmarks.

The comprehensive integration of machine learning healthcare models within clinical practice remains suboptimal, notwithstanding the proliferation of high-performing solutions reported in the literature. A predominant factor hindering widespread adoption pertains to an insufficiency of evidence affirming the reliability of the aforementioned models. Recently, uncertainty quantification methods have been proposed as a potential solution to quantify the reliability of machine learning models and thus increase the interpretability and acceptability of the results. In this review, we offer a comprehensive overview of the prevailing methods proposed to quantify the uncertainty inherent in machine learning models developed for various medical image tasks. Contrary to earlier reviews that exclusively focused on probabilistic methods, this review also explores non-probabilistic approaches, thereby furnishing a more holistic survey of research pertaining to uncertainty quantification for machine learning models. Analysis of medical images with the summary and discussion on medical applications and the corresponding uncertainty evaluation protocols are presented, which focus on the specific challenges of uncertainty in medical image analysis. We also highlight some potential future research work at the end. Generally, this review aims to allow researchers from both clinical and technical backgrounds to gain a quick and yet in-depth understanding of the research in uncertainty quantification for medical image analysis machine learning models.

Brain tumor is one of the leading causes of cancer death. The high grade brain tumors are easier to recurrent even after standard treatment. Therefore, developing a method to predict brain tumor recurrence location plays an important role in the treatment planning and it can potentially prolong patient’s survival time. In this paper, we present a deep learning based brain tumor recurrence location prediction network. Since the dataset is usually small, we propose to use transfer learning to improve the prediction. We first train a multi-modal brain tumor segmentation network on public dataset BraTS 2018. Then, the pre-trained encoder is transferred to our private dataset to extract the semantic features. Following that, a multimodal fusion module and a nonlinear correlation learning module are designed to extract the effective features. To measure the similarity between the distributions of original features of one modality and the estimated correlated features of another modality, we propose to use Kullback-Leibler divergence. Based on this divergence, a correlation loss function is designed to maximize the similarity between the two feature distributions. Finally, two decoders are introduced to jointly segment the present brain tumor and predict its future tumor recurrence location. To the best of our knowledge, this is the first work that can segment the present tumor and at the same time predict future tumor recurrence location, making the treatment planning more efficient and precise. The experimental results demonstrated the effectiveness of our proposed method to predict the brain tumor recurrence sites from limited dataset.

MOTIVATION: Predicting early in treatment whether a tumor is likely to respond to treatment is one of the most difficult yet important tasks in providing personalized cancer care. Most oropharyngeal squamous cell carcinoma (OPSCC) patients receive standard cancer therapy. However, the treatment outcomes vary significantly and are difficult to predict. Multiple studies indicate that microRNAs (miRNAs) are promising cancer biomarkers for the prognosis of oropharyngeal cancer. The reliable and efficient use of miRNAs for patient stratification and treatment outcome prognosis is still a very challenging task, mainly due to the relatively high dimensionality of miRNAs compared to the small number of observation sets; the redundancy, irrelevancy and uncertainty in the large amount of miRNAs; and the imbalanced observation patient samples. RESULTS: In this study, a new machine learning-based prognosis model was proposed to stratify subsets of OPSCC patients with low and high risks for treatment failure. The model cascaded a two-stage prognostic biomarker selection method and an evidential K-nearest neighbors classifier to address the challenges and improve the accuracy of patient stratification. The model has been evaluated on miRNA expression profiling of 150 oropharyngeal tumors by use of overall survival and disease-specific survival as the end points of disease treatment outcomes, respectively. The proposed method showed superior performance compared to other advanced machine-learning methods in terms of common performance quantification metrics. The proposed prognosis model can be employed as a supporting tool to identify patients who are likely to fail standard therapy and potentially benefit from alternative targeted treatments. Availability and implementation: Code is available in https://github.com/shenghh2015/mRMR-BFT-outcome-prediction.

Magnetic Resonance Imaging (MRI) is a widely used imaging technique to assess brain tumor. Accurately segmenting brain tumor from MR images is the key to clinical diagnostics and treatment planning. In addition, multi-modal MR images can provide complementary information for accurate brain tumor segmentation. However, it's common to miss some imaging modalities in clinical practice. In this paper, we present a novel brain tumor segmentation algorithm with missing modalities. Since it exists a strong correlation between multi-modalities, a correlation model is proposed to specially represent the latent multi-source correlation. Thanks to the obtained correlation representation, the segmentation becomes more robust in the case of missing modality. First, the individual representation produced by each encoder is used to estimate the modality independent parameter. Then, the correlation model transforms all the individual representations to the latent multi-source correlation representations. Finally, the correlation representations across modalities are fused via attention mechanism into a shared representation to emphasize the most important features for segmentation. We evaluate our model on BraTS 2018 and BraTS 2019 dataset, it outperforms the current state-of-the-art methods and produces robust results when one or more modalities are missing.

In the field of multimodal segmentation, the correlation between different modalities can be considered for improving the segmentation results. In this paper, we propose a multimodality segmentation network with a correlation constraint. Our network includes N model-independent encoding paths with N image sources, a correlation constrain block, a feature fusion block, and a decoding path. The model independent encoding path can capture modality-specific features from the N modalities. Since there exists a strong correlation between different modalities, we first propose a linear correlation block to learn the correlation between modalities, then a loss function is used to guide the network to learn the correlated features based on the linear correlation block. This block forces the network to learn the latent correlated features which are more relevant for segmentation. Considering that not all the features extracted from the encoders are useful for segmentation, we propose to use dual attention based fusion block to recalibrate the features along the modality and spatial paths, which can suppress less informative features and emphasize the useful ones. The fused feature representation is finally projected by the decoder to obtain the segmentation result. Our experiment results tested on BraTS-2018 dataset for brain tumor segmentation demonstrate the effectiveness of our proposed method.

Lymphoma detection and segmentation from PET images are critical tasks for cancer staging and treatment monitoring. However, it is still a challenge owing to the complexities of lymphoma PET data themselves, and the huge memory requirements for 3D volume data. In this work, a prior knowledge integrated scheme based on DBSCAN and GAs is proposed to detect and segment lymphomas in 3D PET images. To reduce memory requirements and add more feature information, billions of voxels in 3D volume data are first aggregated into supervoxels. Then, such supervoxels serve as basic data units for further clustering the supervoxels by using DBSCAN algorithm, in which a new similarity measure based on prior knowledge is proposed. Meanwhile, a genetic algorithm is used to search the most appropriate parameters of DBSCAN to obtain the optimal clustering results. Finally, a series of comparison experiments among various feature attributes and various similarity functions are performed, and the results are encouraging, and show that the proposed scheme by intergrating the prior knowledge of organ distributions can achieve better performance than traditional methods.

Due to the poor resolution and low signal-to-noise ratio in PET images, and especially to the wide variation in size, shape, site and SUV value among different patients or even for the same patient, lymphoma segmentation in 3D PET Images is still a challenging task in the field of medical image processing. In this work, a novel non-self background-based data enhancement method is proposed for the deep learning-based lymphoma segmentation problem. Firstly, a lymphoma pool with 1991 lymphoid lesions is created. Then, some lymphomas from the lymphoma pool are randomly selected and integrated into their non-self images of the patients according to their respective coordinates when training networks. Finally, a series of comparison experiments among various network models and methods are conducted to verify the effectiveness of the proposed method. The results indicated that the proposed method was promising, and could obtain better comprehensive performance than other methods without any data enhancements for the lymphoma segmentation problems.

Precise delineation of target tumor is a key factor to ensure the effectiveness of radiation therapy. While hybrid positron emission tomography-computed tomography (PET-CT) has become a standard imaging tool in the practice of radiation oncology, many existing automatic/semi-automatic methods still perform tumor segmentation on mono-modal images. In this paper, a co-clustering algorithm is proposed to concurrently segment 3D tumors in PET-CT images, considering that the two complementary imaging modalities can combine functional and anatomical information to improve segmentation performance. The theory of belief functions is adopted in the proposed method to model, fuse, and reason with uncertain and imprecise knowledge from noisy and blurry PET-CT images. To ensure reliable segmentation for each modality, the distance metric for the quantification of clustering distortions and spatial smoothness is iteratively adapted during the clustering procedure. On the other hand, to encourage consistent segmentation between different modalities, a specific context term is proposed in the clustering objective function. Moreover, during the iterative optimization process, clustering results for the two distinct modalities are further adjusted via a belief-functions-based information fusion strategy. The proposed method has been evaluated on a data set consisting of 21 paired PET-CT images for non-small cell lung cancer patients. The quantitative and qualitative evaluations show that our proposed method performs well compared with the state-of-the-art methods.

While hybrid PET/CT scanner is becoming a standard imaging technique in clinical oncology, many existing methods still segment tumor in mono-modality without consideration of complementary information from another modality. In this paper, we propose an unsupervised 3-D method to automatically segment tumor in PET images, where anatomical knowledge from CT images is included as critical guidance to improve PET segmentation accuracy. To this end, a specific context term is proposed to iteratively quantify the conflicts between PET and CT segmentation. In addition, to comprehensively characterize image voxels for reliable segmentation, informative image features are effectively selected via an unsupervised metric learning strategy. The proposed method is based on the theory of belief functions, a powerful tool for information fusion and uncertain reasoning. Its performance has been well evaluated by real-patient PET/CT images.

Nowadays, multi-source image acquisition attracts an increasing interest in many fields, such as multi-modal medical image segmentation. Such acquisition aims at considering complementary information to perform image segmentation, since the same scene has been observed by various types of images. However, strong dependence often exists between multi-source images. This dependence should be taken into account when we try to extract joint information for precisely making a decision. In order to statistically model this dependence between multiple sources, we propose a novel multi-source fusion method based on the Gaussian copula. The proposed fusion model is integrated in a statistical framework with the hidden Markov field inference in order to delineate a target volume from multi-source images. Estimation of parameters of the models and segmentation of the images are jointly performed by an iterative algorithm based on Gibbs sampling. Experiments are performed on multi-sequence MRI to segment tumors. The results show that the proposed method based on the Gaussian copula is effective to accomplish multi-source image segmentation.

Statistical shape models have been widely used to guide the segmentation in an image, thus overcoming noise and occlusions. In this study, the authors present a graph cut‐based segmentation framework, in which multiple objects can be segmented. They design a specific multilabel shape prior, which is integrated into the graph cost function. They also want to enforce spatial constraint between the objects. Towards this aim, they propose a local constraint to forbid the inclusion of an object into another, which is enforced in the regularisation term of the graph energy. They apply the authors’ method to cardiac magnetic resonance images, in which left and right ventricles, and the myocardium are segmented and for which encouraging results are obtained.

The evidential K-nearest-neighbor (EK-NN) method provided a global treatment of imperfect knowledge regarding the class membership of training patterns. It has outperformed traditional K-NN rules in many applications, but still shares some of their basic limitations, e.g., 1) classification accuracy depends heavily on how to quantify the dissimilarity between different patterns and 2) no guarantee for satisfactory performance when training patterns contain unreliable (imprecise and/or uncertain) input features. In this paper, we propose to address these issues by learning a suitable metric, using a low-dimensional transformation of the input space, so as to maximize both the accuracy and efficiency of the EK-NN classification. To this end, a novel loss function to learn the dissimilarity metric is constructed. It consists of two terms: the first one quantifies the imprecision regarding the class membership of each training pattern, while, by means of feature selection, the second one controls the influence of unreliable input features on the output linear transformation. The proposed method has been compared with some other metric learning methods on several synthetic and real datasets. It consistently led to comparable performance with regard to testing accuracy and class structure visualization.

We propose a brain tumor segmentation method from multi-spectral MRI images. First, a large set of features based on wavelet coefficients, is computed on all types of images for a small number of voxels, allowing us to build a training feature base which is not homogeneous due to different types of image. The segmentation task is then viewed as a learning problem where only the most significant features from the feature base should be selected and then a classifier can be used. The new idea is to use Multiple Kernel Learning (MKL) by associating one or more kernels to each feature in order to solve jointly the two problems: selection of the features and their corresponding kernels and training of the classifier. All types of images are then segmented using the trained classifier on the selected features. Our algorithm was tested on the real data provided by the challenge of Brats 2012 and was compared to the resulting top methods. The results show good performance of our method.

We propose a patient-specific model based on partial differential equation to predict the evolution of lung tumors during radiotherapy. The evolution of tumor cell density is formulated by three terms: 1) advection describing the advective flux transport of tumor cells, 2) proliferation representing the tumor cell proliferation modeled as Gompertz differential equation, and 3) treatment quantifying the radiotherapeutic efficacy from linear quadratic formulation. We consider that tumor cell density variation can be derived from positron emission tomography images, the novel idea is to model the advection term by calculating 3D optical flow field from sequential images. To estimate patient-specific parameters, we propose an optimization between the predicted and observed images, under a global constraint that the tumor volume decreases exponentially as radiation dose increases. A thresholding on the predicted tumor cell densities is then used to define tumor contours, tumor volumes and maximum standardized uptake values (SUVmax). Results obtained on seven patients show a satisfying agreement between the predicted tumor contours and those drawn by an expert.

In this paper, a novel spectrum separation technique based on sparse representation is proposed to deal with Magnetic Resonance Spectroscopy (MRS) quantification which is used to measure the levels of different metabolites in brain tissues. Since a measured MR spectrum contains the spectra of numbers of metabolites and a baseline, the separation and quantification of them becomes difficult. A nonnegative pursuit algorithm based on regularized FOCUSS algorithm is proposed here to decompose a measured spectrum with respect to an overcomplete dictionary. Benefitting from the a priori knowledge, the dictionary is built by Lorentzian and Gaussian basis functions representing different metabolites and baseline. Using this algorithm, not only the baseline is separated from the spectra of interest, but also the spectra of different metabolites are separated. The accuracy of quantification and the robustness are improved, from simulation data, compared with a commonly used estimation method. The quantification on tumor metabolism with in vivo brain MR spectra is also demonstrated.

This article describes a new method for ancient books ornamental letters segmentation and recognition. The pur-pose of our work is to automatically determine the letterrepresented in an ornamental letter image. Our process isdivided in two parts: a segmentation step of the ornamentalletter is followed by a recognition step. The segmentationprocess uses multiresolution analysis to filter backgrounddecorations followed by a binarisation step and a morpho-logic reconstruction of the expected letter. The recogni-tion process use the previously obtained reconstruction andcompares it with capital letters images used as a dictionaryof shapes with the Local Dissimilarity Map (LDM) distance.

In this paper, the multi-kernel SVM (Support Vector Machine) classification, integrated with a fusion process, is proposed to segment brain tumor from multi-sequence MRI images (T2, PD, FLAIR). The objective is to quantify the evolution of a tumor during a therapeutic treatment. As the procedure develops, a manual learning process about the tumor is carried out just on the first MRI examination. Then the follow-up on coming examinations adapts the learning automatically and delineates the tumor. Our method consists of two steps. The first one classifies the tumor region using a multi-kernel SVM which performs on multi-image sources and obtains relative multi-result. The second one ameliorates the contour of the tumor region using both the distance and the maximum likelihood measures. Our method has been tested on real patient images. The quantification evaluation proves the effectiveness of the proposed method.

Face verification and face identification are two main applications for face recognition. Based on the face representation which they use, the current image-based face recognition techniques can be roughly classified into two groups: appearance-based methods and model-based methods. The method presented in this paper focuses on applying model-based methods to face verification. Unfortunately, the existing current model-based schemes are used for the applications of face identification and are not suitable for face verification. A novel scheme, which is custom-built for face verification applications, is therefore proposed in this paper. Active appearance model, a 2D morphable face model, is chosen and applied to realize the proposed scheme.

Image dissimilarity measure is a hot topic. The measuring process is generally composed of an information mining in each image which results in an image signature and then a signature comparison to make the decision about the image similarity. In the scope of binary images, we propose to replace the information mining by a new straight image comparison which does not require a priori knowledge. The second stage is then replaced by a decision process based on the image comparison. The new comparison process is structured as follows: a morphological multiresolution analysis is applied to the two images. Secondly a distance map is constructed at each scale by the computation of the Hausdorff distance, restricted through a sliding-window. A signature is then extracted from the distance map and is used to make the decision. As an application, the algorithm has been successfully tested on an ancient illustration database.

Many practical applications in the field of medical image processing require robust and valid 3D image segmentation results. In this paper, we present a semi-automatic iterative segmentation approach for 3D medical image by combining a 2D boundary tracking algorithm and a boundary mapping process. Upon each of the consecutive slice, the boundary tracking process is accomplished in an alternate procedure of the morphological dilatation and the multi-label front propagation. The multi-label front propagation method is developed based on the minimal path theory and fast sweeping evolution method to ensure the efficiency, and speed of the boundary tracking algorithm. This 3D image segmentation approach can easily extract the close and smooth boundary of the desired object from a 2D medical image series. This approach is efficient and reliable, and requires very limited user intervention. Some experimental results are also presented to demonstrate the efficiency of this approach.

Magnetic resonance image analysis by computer is useful to aid diagnosis of malady. We present in this paper a automatic segmentation method for principal brain tissues. It is based on the possibilistic clustering approach, which is an improved fuzzy c-means clustering method. In order to improve the efficiency of clustering process, the initial value problem is discussed and solved by combining with a histogram analysis method. Our method can automatically determine number of classes to cluster and the initial values for each class. It has been tested on a set of forty MR brain images with or without the presence of tumor. The experimental results showed that it is simple, rapid and robust to segment the principal brain tissues.

We present a fuzzy Markovian method for brain tissue segmentation from magnetic resonance images. Generally, there are three principal brain tissues in a brain dataset: gray matter, white matter and cerebrospinal fluid. However, due to the limited resolution of the acquisition system, many voxels may be composed of multiple tissue types (partial volume effects). The proposed method aims to calculate the fuzzy membership of each voxel to indicate the partial volume degree using a fuzz, Markovian segmentation. Since our method is unsupervised, it first estimates the fuzzy Markovian random field model parameters using a stochastic gradient algorithm. The efficiency of the proposed method is quantified on a digital phantom using an absolute average error, and qualitatively tested on real MRI brain data.

In this paper, we propose a novel automatic method based on fuzzy modeling of knowledge to segment brain structures in MRI (magnetic resonance imaging) images. The segmentation is achieved by the region-wise classification using GAs (genetic algorithms), followed by voxel-wise refinement using parallel region growing. To improve the accuracy of the labeling, we introduce a fuzzy model of ROI (regions of interest) by analogy with the electrostatic potential distribution, to represent more appropriately knowledge of shape, distance and reaction between structures, and to estimate more reliably the statistical moments. This modeling is also used in the design of the fitness function of GAs, and the criteria of region growing. The performance of our proposed method is quantitatively validated by 4 indexes with respect to manually segmented images.

This paper presents an unsupervised segmentation method applied to classify brain tissues in 3D for magnetic resonance (MR) images. An MR image volume may be composed of a mixture of several tissue types due to partial volume effects. The statistical model of the mixtures is proposed and studied by means of simulations. It is shown that it can be approximated by a Gaussian function under some conditions. The D'Agostino-Pearson normality test is used to calculate the risk /spl alpha/ of the approximation. In order to classify a brain into three brain tissues and deal with the problem of partial volume effects, the proposed algorithm classifies firstly the brain into pure classes and mix-classes, it then re-classifies the mix-classes into pure classes by adding the knowledge about the topology of the brain, based on the multifractal dimension. Both steps use Markov random field models. The algorithm is evaluated using both simulated images and real MR images.

This paper presents a fully automatic three-dimensional classification of brain tissues for Magnetic Resonance (MR) images. An MR image volume may be composed of a mixture of several tissue types due to partial volume effects. Therefore, we consider that in a brain dataset there are not only the three main types of brain tissue: gray matter, white matter, and cerebro spinal fluid, called pure classes, but also mixtures, called mixclasses. A statistical model of the mixtures is proposed and studied by means of simulations. It is shown that it can be approximated by a Gaussian function under some conditions. The D'Agostino-Pearson normality test is used to assess the risk alpha of the approximation. In order to classify a brain into three types of brain tissue and deal with the problem of partial volume effects, the proposed algorithm uses two steps: 1) segmentation of the brain into pure and mixclasses using the mixture model; 2) reclassification of the mixclasses into the pure classes using knowledge about the obtained pure classes. Both steps use Markov random field (MRF) models. The multifractal dimension, describing the topology of the brain, is added to the MRFs to improve discrimination of the mixclasses. The algorithm is evaluated using both simulated images and real MR images with different T1-weighted acquisition sequences.