Fractal Dimension Analysis of High-Resolution X-Ray Phase Contrast Micro-Tomography Images at Different Threshold Levels in a Mouse Spinal Cord

Evaluation of the mandibular condyles trabecular structure in patients with severe class III pattern: a computed tomography (CT) fractal analysis study

Class III malocclusion is a combination of dental and skeletal disorders that causes discrepancies in occlusion. Malocclusion can affect the structure of the Temporomandibular joint (TMJ) resulting in many problems, one of which is affecting the internal structure of the bone. This study aimed to examine the morphological features of class III patients' trabecular structure of the mandibular condyle in comparison with normal class I individuals using fractal analysis (FA). To study the internal structure of the mandibular condyle bone, Computed Tomography (CT) scans of 45 severe class III patients (age: 16-46) who were the candidates for orthognathic surgery were selected and matched by age and sex with 45 normal class I individuals. The trabecular bone structure of the left and right mandibular condyles in three CT planes of the study group and control group were evaluated employing the FA. The result of the present study indicated that the fractal dimensions (FD) values of class III patients were lower than those of the normal class I individuals in axial (class I: 1.31 ± 0.02, class III: 1.28 ± 0.02), sagittal (class I: 1.25 ± 0.03, class III: 1.19 ± 0.08), and coronal (class I: 1.5 ± 0.06, class III: 1.45 ± 0.07) planes (P < 0.001). There were no significant differences between the FD values of the males and females. The intra-group evaluation revealed that there was no correlation between age and FD values. No evidence of laterality was found regarding the FD values of the right and left condyles. Given the noticeable differences between the FD values, it can be implied that severe class III malocclusion may affect the trabecular pattern of the cancellous bone of the mandibular condyle compared to class I individuals. Therefore, due to the altered trabecular structure, clinicians should be cautious when planning treatments for these patients.

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.

Apparent scaling of virus surface roughness-An example from the pandemic SARS-nCoV

This paper investigates the scaling of the surface roughness of coronavirus, including the SARS-nCoV based on fractal and spectral analyses of their published electron microscopy images. The box-counting fractal dimensions obtained are subjected to ANOVA tests for statistical significance. Results show that the SARS-nCoV particles could not statistically be resolved by their shape on the basis of the fractal dimension values, but they could be distinguished from the earlier SARS-CoV particles. MANOVA test results require interaction of factors used for classifying virions into different types. The topological entropies, a measure of randomness in a system, measured for the images of varying size show correlation with the fractal dimensions. Spectral analyses of our data show a departure from power-law self-similarity, suggesting an apparent scaling of surface roughness over a band of maximum an order of magnitude. The spectral crossover that corresponds to characteristic length scale may represent average viral size. Our results may be useful in inferring the nature of surface-contact between the viral and human cell, causing infection and also in providing clues for new drugs, although it is too early to say. In addition, limitations of this study, including possible ways to avoid the bias in scaling exponents due to the use of different techniques are discussed.

Controlled fractal growth of transition metal dichalcogenides

We report controlled fractal growth of atomically thin transition metal dichalcogenides (TMDCs) by chemical vapor deposition, with morphological evolution from dendritic to triangular. Several important growth parameters controlling the fractal dimensions were identified, including the relaxation rate, adhesion coefficient, diffusion anisotropy and growth time. A model based on nucleation, diffusion limited aggregation and relaxation was proposed to explain the morphological evolution. The results of the computational simulation based on this model are in good agreement with the experimental results. Our study sheds light on the growth mechanism of TMDCs and paves the way for growth of TMDCs with improved controllability.