Computer-aided diagnosis (CAD) is considered one of the major research subjects in medical imaging and diagnostic radiology [1, 2]. With CAD, radiologists use the computer output as a "second opinion" and make the final decisions. The ability to produce high contrast medical images has its importance in diagnosing, evaluation and computer based simulation for a certain tissue or organ.
Medical imaging such as CT-scan and MRI are usually accomplished in anisotropic manner where the planer resolution spacing and slice to slice spacing are (usually) different [3]. This makes the 2D based segmentation process of scans not able to provide the accurate 3D bounds of the tissues, where this show the necessity for estimating some intermediate plans to solve that problem. The estimation of some intermediate plans requires 3D image resizing to be involved in the process.
In addition to the anisotropic spacing problem, it is only possible to obtain macroscale images because of scanners’ limited resolution, where each sample represents the average property of the corresponding group of tissues for each zone [4, 5]. This limitation is the main reason for boundary-overlapping problem between neighbor tissues in medical images [6–8], and as a result, automatic medical image segmentation is difficult to be achieved. With those 2 problems, the estimation of accurate 3D tissue’s boundary becomes in demand.
When only 2D images of the original scans are employed for processing of tissue in 3D, it would act like resizing this image using nearest interpolation method. However, by applying other interpolation methods such as Linear, Cubic, Lanczos2 or Lanczos3 [9, 10], more accurate estimation for the intermediate plans would be expected. Linear interpolation estimates intermediate states over a tangent line between two measured states while Cubic uses Gaussian smoothing curve and Lanczos methods depends on the Sinc function.
The most important image segmentation techniques are: threshold based methods, clustering based methods, edge based methods, region based methods, watershed based methods, Partial Differential Equation (PDE) based methods and Artificial Neural Network (ANN) based methods [11]. Clustering base methods such as Otsu [12], K-Means [13], Expectation Maximization (EM) [14], C-Means, Fuzzy C-Means (FCM) and Fuzzy C-Means algorithm with spatial constraints (SFCM) [15], Markov Random Field (MRF) and Iterated Conditional Modes (ICM) [16] are widely used with medical images.
It was reported that there is no unique solution for the segmentation problem, because of the effect of the used imaging modality on the segmentation process; different results are obtained by changing clustering method and/or the selected numbers of clusters [5, 7, 8, 15, 16]. One solution in a former research [17] has been developed to produce Uni-stable images where segmentation results are relatively stable regarding the change of the clustering method. However, this was tested for the 2D images and need to be improved to cover the 3D images as well.
Human brain is taken as case study for this research. Brain is composed of three main components: White Matter (WM), Gray Matter (GM) and Cerebrospinal Fluid (CSF). CSF contains the largest amount of water among WM and GM. Arrangement of water particles for each of these components differs as water particles of CSF are completely free; however, water contents of WM are arranged in very restricted order inside the myelinated axons and for GM, water particles are arranged in axons but not very restricted as in WM. In other terms, CSF is isotropic material with larger amount of water particles, GM is anisotropic material with relatively low amount of water and finally WM is highly-anisotropic material with relatively the lowest amount of water. Among different medical imaging modalities, DTI is capable of providing more information about different tissues structures, and hence the ability to segmenting these structures from each other for further processing such as diagnosing and simulation.
Many models have been represented for 3D brain segmentation. Duy M. H. Nguyen et. al. produces a 3D brain tissues segmentation using Gaussian Mixture Models (GMMs), Convolution Neural Networks (CNNs) and Deep Neural Networks (DNNs)[18]. Yuankai Huo et.al. proposed the Spatially Localized Atlas Network Tiles (SLANT) method to distribute multiple independent 3D Fully Convolutional Networks (FCN) for high-resolution whole brain segmentation[19]. Fareeen Ramzan et.al. employ a network for the segmentation of multiple brain regions has been proposed that is based on 3D convolutional neural networks and utilizes residual learning and dilated convolution operations to efciently learn the end-to-end mapping from MRI volumes to the voxel-level brain segments[20]. Youyong Kong et.al. presents a novel algorithm for brain tissue segmentation based on supervoxel and graph filter. Firstly, an effective supervoxel method is employed to generate effective supervoxels for the 3D MRI image. Secondly, the supervoxels are classified into different types of tissues based on filtering of graph signals [21]. Kamarujjaman represnt a novel 3D unsupervised spatial fuzzy-based brain MRI volume segmentation technique in the presence of intensity inhomogeneity and noise. Instead of static masking, dynamic 3D masking has been proposed to measure the correlation among neighbors [22]. Results from stated methods targeting either high resolution scans or depends on one segmentation technique. The main aspect of this research is to generate 3D images which are universal and stable for segmentation process.