Image Post-processing Techniques Research Articles

P 71 Optical coherence tomography – a future imaging technique of peripheral nerves?

Object: Owing to their complex topography, their long courses and their small diameters peripheral nerves are challenging structures for radiological diagnostics. However, imaging techniques in the area of peripheral nerve diseases have undergone unexpected development in recent decades. They include magnetic-resonance imaging (MRI) and high-resolution sonography (HRS). Yet none of those imaging techniques reaches a resolution comparable to that of histological sections. Fascicles are the smallest discernable structure. Optical-coherence tomography (OCT) is the first imaging technique that is able to depict a nerve’s ultrastructure at micrometer resolution. Methods: OCT measurement was performed in 32 patients with different peripheral nerve pathologies, i.e. nerve compression syndromes. The nerves were examined during surgery after exposing. Only the sural nerve was twice examined ex vivo . The OCT systems Thorlabs Callisto and Thorlabs Ganymede were used. For intra-operative use, a hand probe was covered with a sterile foil. Different post-processing imaging techniques were applied and evaluated. Results: The intra-operative use of OCT is easy and intuitive. Image artifacts are mainly caused by motion and the sterile foil. If they are kept at a low level, the hyporeflecting bundles of nerve fascicles and their inner parts can be displayed. In the Haralick evaluation the second angular moment (SAM) is most suitable to depict the connective tissue. Conclusion: OCT is a new imaging technique which has shown to be promising in peripheral nerve surgery for particular questions. Its resolution exceeds that provided by recent radiological possibilities such as MRI and HRS. Since its field of view is relatively small, faster acquisition times would be highly desirable. Currently, the method resembles an optical biopsy and can be a supplement to intra-operative sonography, giving high-resolution insight into a suspect area which has been located by sonography in advance. This could be especially helpful in surgery of peripheral nerve lesions in continuity.

A phenomenological investigation on near-wall bubble behavior close to CHF in flow boiling

The insight information of subcooled flow boiling is very important for the development of boiling crisis mechanistic model. In this paper, visual experiment is carried out in a vertical square channel with a heating rod with diameter of 9.5 mm. Based on the near-wall bubble behavior captured by a high-speed camera, combined with advanced image post-processing technique developed in-house, the qualitative and quantitative analysis of flow boiling behavior near the heating wall are presented when approaching the CHF (Critical Heat Flux). According to the visual experimental study, a detailed discussion on the phenomena before CHF and during the CHF is presented. With high heat flux, periodic large vapor clot passes with relatively constant frequency. Then periodic wavy vapor layer and liquid film clearly appear in the near-wall region when the working condition is extremely close to the CHF. It is found that high thermal-hydraulic parameters, including system pressure, mass flux and inlet subcooling, prevent the formation of thick vapor layer, and this is a significant precursor to trigger boiling crisis. This implies that the possibility of triggering boiling crisis is reduced due to the difficulty in forming thicker vapor layer, and lead to higher CHF value. Additionally, a prediction of wavelength between two-phase layers is proposed by combining visual observations and instability theory. The predicted results show good agreement compared with experimental data. Those results can provide predictions of key interfacial feature parameters for developing CHF mechanistic model.

Noise estimation in 2D MRI using DWT coefficients and optimized neural network

Robust estimation of noise strength in Magnetic Resonance Images (MRIs) is a task of great importance due to its extensive applications in image post-processing techniques. Many noise estimation algorithms have been proposed in the past to retrieve noise characteristics of the magnitude image. These algorithms rely on either the spatial or transform domain information of the image. In this research article, we propose a noise estimation algorithm that utilizes a hybrid Discrete Wavelet Transform (DWT) and edge information suppression based algorithm to estimate the strength of noise in magnitude MR images. The wavelet coefficients corresponding to spatial domain edges are eliminated using a down-sampled complement of the Sobel edge map. The distribution of average noise energy in spatial and transform domain which follows Parseval’s theorem is utilized for calculating the initial noise estimate. Further, the robustness of the proposed algorithm is enhanced using Feedforward Neural Network. The proposed algorithm is observed to be computationally fast and accurate. Results on synthetic and clinical T1- and T2-w brain MRIs following Gaussian or Rician distribution show better performance than the existing benchmark algorithms over a wide range of input noise.

Lower extremity CT angiography in peripheral arterial disease: from the established approach to evolving technical developments.

With the advent of multidetector computed tomography (CT), CT angiography (CTA) has gained widespread popularity for noninvasive imaging of the arterial vasculature. Peripheral extremity CTA can nowadays be performed rapidly with high spatial resolution and a decreased amount of both intravenous contrast and radiation exposure. In patients with peripheral artery disease (PAD), this technique can be used to delineate the bilateral lower extremity arterial tree and to determine the amount of atherosclerotic disease while differentiating between acute and chronic changes. This article provides an overview of several imaging techniques for PAD, specifically discusses the use of peripheral extremity CTA in patients with PAD, clinical indications, established technical considerations and novel technical developments, and the effect of postprocessing imaging techniques and structured reporting.

MAYONNAISE: a morphological components analysis pipeline for circumstellar discs and exoplanets imaging in the near-infrared

ABSTRACT Imaging circumstellar discs in the near-infrared provides unprecedented information about the formation and evolution of planetary systems. However, current post-processing techniques for high-contrast imaging using ground-based telescopes have a limited sensitivity to extended signals and their morphology is often plagued with strong morphological distortions. Moreover, it is challenging to disentangle planetary signals from the disc when the two components are close or intertwined. We propose a pipeline that is capable of detecting a wide variety of discs and preserving their shapes and flux distributions. By construction, our approach separates planets from discs. After analysing the distortions induced by the current angular differential imaging (ADI) post-processing techniques, we establish a direct model of the different components constituting a temporal sequence of high-contrast images. In an inverse problem framework, we jointly estimate the starlight residuals and the potential extended sources and point sources hidden in the images, using low-complexity priors for each signal. To verify and estimate the performance of our approach, we tested it on VLT/SPHERE-IRDIS data, in which we injected synthetic discs and planets. We also applied our approach on observations containing real discs. Our technique makes it possible to detect discs from ADI data sets of a contrast above 3 × 10−6 with respect to the host star. As no specific shape of the discs is assumed, we are capable of extracting a wide diversity of discs, including face-on discs. The intensity distribution of the detected disc is accurately preserved and point sources are distinguished, even close to the disc.

Postprocessing Imaging Techniques of the Computed Tomography Angiography in Trauma Patients for Preprocedural Planning.

Computed tomography provides a wealth of diagnostic information in the trauma patient including the presence of organ, bone, and vasculature injuries for the rapid triage of trauma patients. In the context of interventional radiology, appropriately protocoled studies can be reviewed for vascular injury and help focus the angiographic assessment of bleeding patients to ideally achieve earlier hemostasis. This article outlines various image-processing techniques such as multiplanar reformats, curved planar reformats, maximum intensity projections, and volume rendering to identify and more thoroughly characterize vascular injuries as a preprocedural planning tool to expedite endovascular hemostasis in a case-based format.

An Image Processing Method: Edge-guided Directional Walk Mean Smoothing

Image denoising is an important computer vision task, it is also the basis of many other high-level vision tasks. Recently, various image denoising algorithms have proposed, such as BM3D, sparse representation and deep learning, that have achieved impressive performance in AWGN denoising or blind denoising tasks. However, when dealing with Dongba painting (A traditional painting from China’s ethnic minorities), there are problems that Dongba painting have blurred edges and faded colors, it is important to retain its original style when denoising. In this paper, we propose a novel image post-processing technique termed edge-guided directional walk mean smoothing (EDWMS), it can effectively calculate the mean of pixels along different directions then obtain denoised image with sharp edge. Experiments show that the proposed EDWMS outperforms compared algorithms in both edge sharpness and color saturation.

ASSESSMENT OF THE WASHING EFFECTIVENESS OF ON-PURPOSE DESIGNED ECO-FRIENDLY CLEANER AGAINST SOOT DEPOSITS

The increment of the industrialization processes led to even more release of carbonaceous particulate into the environment. These airborne contaminants are produced by endothermic machines, coal combustion, heating systems, and production plants. Soot particles suspended into the air can overpass the inlet filters (if present) of gas turbines and deposit onto the internal parts of the compressor. This phenomenon, leading to the modification of the aerodynamic surface of the airfoils, is the main responsible for the gas turbine performance losses over time. This detrimental effect can be partially recovered by washing the compressor unit, frequently. In this work, the assessment of the washing effectiveness against soot deposits of an on-purpose designed eco-friendly cleaner is provided. The removal effectiveness of this water-based cleaner is related to the capability to collect soot particles from surfaces, limiting redeposit phenomena over the stages. The experimental investigation has been carried out by injecting soot particles, under controlled conditions, into a multistage test axial compressor. Using image post-processing techniques, carried out over the entire compressor flow path, a quantitative evaluation of the washing capability has been assessed. Compared with demineralized water, the cleaner was found to be effective if high cleaning performances are expected.

Image-Based Ultrasound Speed Estimation in Isotropic Materials

In Nondestructive Evaluation (NDE), ultrasound imaging is a useful tool for detecting flaws or measuring corrosion in metal pipes. Phased-array systems are becoming standard in NDE, as well as post-processing imaging techniques such as the Total Focusing Method. These techniques require knowledge of parameters such as distance between transducer elements, times of arrival and sound speed to produce sharp images. A deviation in sound speed, for instance, may compromise image accuracy. In this paper, we propose a sound speed estimator based on image quality metrics. The approach consists in generating several reconstructed images from the same acquisition signals, but using a set of candidate sound speeds. The speed value that yields the sharpest image is then chosen as the estimated sound speed. Estimates made on data obtained by simulation of a typical scenario presented relative combined uncertainties as low as 0.0166%. The results, obtained in both simulated and real scenarios, show good agreement with expected speeds. The proposed method can be considered a reference-free sound speed calibration method aimed at field applications.

Methodological Considerations for Neuroimaging in Deep Brain Stimulation of the Subthalamic Nucleus in Parkinson's Disease Patients.

Deep brain stimulation (DBS) of the subthalamic nucleus is a neurosurgical intervention for Parkinson’s disease patients who no longer appropriately respond to drug treatments. A small fraction of patients will fail to respond to DBS, develop psychiatric and cognitive side-effects, or incur surgery-related complications such as infections and hemorrhagic events. In these cases, DBS may require recalibration, reimplantation, or removal. These negative responses to treatment can partly be attributed to suboptimal pre-operative planning procedures via direct targeting through low-field and low-resolution magnetic resonance imaging (MRI). One solution for increasing the success and efficacy of DBS is to optimize preoperative planning procedures via sophisticated neuroimaging techniques such as high-resolution MRI and higher field strengths to improve visualization of DBS targets and vasculature. We discuss targeting approaches, MRI acquisition, parameters, and post-acquisition analyses. Additionally, we highlight a number of approaches including the use of ultra-high field (UHF) MRI to overcome limitations of standard settings. There is a trade-off between spatial resolution, motion artifacts, and acquisition time, which could potentially be dissolved through the use of UHF-MRI. Image registration, correction, and post-processing techniques may require combined expertise of traditional radiologists, clinicians, and fundamental researchers. The optimization of pre-operative planning with MRI can therefore be best achieved through direct collaboration between researchers and clinicians.

Evolution of anodic erosion components and heat transfer efficiency for W and W80Ag20 in atmospheric-pressure arcs

Based on the in situ diagnostic system and the digital image post-processing technique, quantifications of the anodic erosion components and heat transfer efficiency for tungsten and the W80Ag20 material in arcs of argon, helium, and nitrogen were achieved. The leading vaporization of silver has been found to result in evidently lower anodic heat transfer efficiency and much smaller molten pools compared with those of the tungsten anode, but the intensive generation of silver vapor under the melt layer causes higher splashing erosion of the W80Ag20 anode. However, these characteristics can be strongly changed by the cathodic blowing, which leads to a much higher splashing erosion of tungsten anode but a lower erosion rate of W80Ag20 anode. Through the visualization of the erosion behavior and the post microanalysis of the anode surface, the possible driving mechanisms for the generation of the splashing droplet were discussed. The result indicates that the local high pressure caused by the vapor blasting during the bubble explosion plays a key role in the detachment of splashing droplets. Furthermore, as for the tungsten-based anode, the comparison of erosion behavior between the W80Ag20 anode and the previous-studied W70Cu30 anode makes it clear that increasing the temperature difference between the melting point (MP) of tungsten and the boiling point (BP) of the other material has the pros and cons. It is effective for the decrease of the anode erosion when the anode heat energy is relatively weak, while it can promote the splashing erosion when the liquid tungsten layer has been formed on the anode tip. These results are beneficial for the optimal design of the electrode system in circuit breakers.

Analyzing capacity of a consumer-grade infrared camera in South Africa for cost-effective aerial inspection of building envelopes

Prohibitive equipment cost and certain export regulations are the major obstacles to the widespread adoption of infrared (IR) thermography when evaluating building envelopes. In this work, we propose the use of an affordable and easily available camera as a first step of making the technology accessible. Combined with image post-processing, we hypothesize that a low-cost, low-resolution, and consumer-grade device can provide an economic alternative for the periodic evaluation of building envelopes. Following a market survey, the Seek Thermal Compact (STC) was chosen for evaluation. The STC was able to accurately measure the temperature of surfaces and distinguish small thermal anomalies (3 mm in diameter), and the IR images can be post-processed to reasonably estimate the anomaly areas. The STC was particularly effective when images were taken within 1.75 m from the surface. The 1.75 m distance did not pose a challenge in this study, as the goal was to mount the selected IR camera on an unmanned aerial vehicle for the surveys. The small size and weight of the STC were also useful. The results from the analysis of the capability of the STC and the image post-processing techniques may help form the basis of future investigations aiming at lowering the cost of building thermographic surveys.

Coronary computed tomography angiography derived flow fractional reserve: the state of the art

Coronary computed tomographic angiography (CCTA) is an effective examination with high sensitivity to rule out obstructive coronary artery disease (CAD). It can provide anatomical information of coronary artery disease, such as the degree of stenosis, plaque characteristics, but has poor discriminatory power for hemodynamically significant lesions, which may lead to unnecessary referrals for invasive coronary angiography (ICA). Invasive fractional flow reserve (FFR) is generally considered as the gold standard for the functional evaluation of CAD. However, high cost and invasive characteristics of FFR limit its wide clinical application. Recently, non-invasive CT-derived fractional flow reserve (CT-FFR), a novel image post-processing technique combining the advantages of CCTA and FFR, allows us to obtain both anatomic and functional information of a coronary lesion. CT-FFR has been used in diagnosing and guiding clinical management of CAD patients. This review introduces the basic principles, key points of CT-FFR analysis, and current research progress of CT-FFR.

Application value of 16-slice spiral CT multi-planar reconstruction, surface occlusion display and other image post-processing techniques in the diagnosis of peripheral lung cancer

Objective To explore the application value of 16-slice spiral CT multi-planar reconstruction(MPR), surface occlusion display and other image post-processing techniques in the diagnosis of peripheral lung cancer. Methods From April 2017 to April 2019, a total of 98 patients with peripheral lung cancer admitted to the Affiliated Hospital of Hangzhou Normal University and the First People's Hospital of Jiashan County were selected.The detection rates of various signs of MPR, surface occlusion display and other image post-processing techniques in the diagnosis of peripheral lung cancer were analyzed and compared. Results MPR in the diagnosis of peripheral lung cancer, the lobulated sign was 94.9%(93/98), the vascular bundle sign was 85.7%(84/98), the fine and short burr was 93.9%(92/98). The detection rate of vascular bundle sign and fine burr sign was higher than that of thin layer scan (χ2=5.351, 5.023, 5.777, all P 0.05). The surface occlusion in the diagnosis of peripheral lung cancer, showed 90.8%(89/98) lobulated sign and 74.5%(73/98) pleural indentation.The detection rates of lobulated sign and pleural sag were higher than those of thin layer scanning (χ2=5.450, 6.002, all P 0.05). Conclusion In the diagnosis of various signs of peripheral lung cancer, the detection rate of 16-slice spiral CT MPR technique is high and worthy of application. Key words: Tomography, spiral computed; Lung neoplasms; Image processing, computer-assisted; Multi-plane reconstruction technology; Surface occlusion display

An Efficient Hybrid Fuzzy-Clustering Driven 3D-Modeling of Magnetic Resonance Imagery for Enhanced Brain Tumor Diagnosis

Brain tumor detection and its analysis are essential in medical diagnosis. The proposed work focuses on segmenting abnormality of axial brain MR DICOM slices, as this format holds the advantage of conserving extensive metadata. The axial slices presume the left and right part of the brain is symmetric by a Line of Symmetry (LOS). A semi-automated system is designed to mine normal and abnormal structures from each brain MR slice in a DICOM study. In this work, Fuzzy clustering (FC) is applied to the DICOM slices to extract various clusters for different k. Then, the best-segmented image that has high inter-class rigidity is obtained using the silhouette fitness function. The clustered boundaries of the tissue classes further enhanced by morphological operations. The FC technique is hybridized with the standard image post-processing techniques such as marker controlled watershed segmentation (MCW), region growing (RG), and distance regularized level sets (DRLS). This procedure is implemented on renowned BRATS challenge dataset of different modalities and a clinical dataset containing axial T2 weighted MR images of a patient. The sequential analysis of the slices is performed using the metadata information present in the DICOM header. The validation of the segmentation procedures against the ground truth images authorizes that the segmented objects of DRLS through FC enhanced brain images attain maximum scores of Jaccard and Dice similarity coefficients. The average Jaccard and dice scores for segmenting tumor part for ten patient studies of the BRATS dataset are 0.79 and 0.88, also for the clinical study 0.78 and 0.86, respectively. Finally, 3D visualization and tumor volume estimation are done using accessible DICOM information.

Multiparametric Imaging for the Locoregional Follow-up of Rectal Cancer

To discuss the potential of multiparametric imaging for the locoregional follow-up of rectal cancer by outlining the strengths/weaknesses of anatomical imaging in specific MRI and highlighting the potential of the most relevant functional imaging and novel image post-processing techniques In addition to anatomical imaging, diffusion-weighted imaging (DWI) and PET have been most extensively studied for the locoregional follow-up of rectal cancer. Fewer (and more recent) studies have focused on the use of other functional MRI techniques, advanced post-processing methods such as Radiomics and hybrid imaging (PET-MRI). Anatomical imaging experiences difficulties in the locoregional assessment of rectal cancer after chemoradiotherapy and surgery. Addition of DWI to anatomical MRI has proven its benefit for qualitative response assessment after neoadjuvant chemoradiotherapy. PET mainly has a role for the detection of recurrent disease after surgery and may be valuable for early response prediction. Evidence for multiparametric assessment of PET combined with MRI or hybrid PET-MRI is sparse. More quantitative functional imaging techniques including DCE-MRI and advanced post-processing techniques such as Radiomics have shown potential in research settings to render biomarkers of response but require standardisation and large-scale validation, preferably in trial settings.

Digital image post processing techniques for taxonomic publications with reference to insects

There exists substantial literature for capturing digital images of insect specimens for taxonomy purposes but very few papers are available on post processing of these images. We present a few techniques for editing digital images of insects using Adobe® Photoshop® which can be performed in a relatively short amount of time. The results clearly show that techniques using a combination of options like Curves, Dodge/Burn, Hue/Saturation and Lab Color mode in the software, enhance the quality of the original image without changing any taxonomic information. These methods applied in different combinations can be used for taxonomy of any insect taxon. We also caution the readers of the abuse of such techniques in context of taxonomy.

Gradient-based fibre detection method on 3D micro-CT tomographic image for defining fibre orientation bias in ultra-high-performance concrete

Ultra-high-performance fibre reinforced concrete (UHPC) is a class of advanced cementitious composites characterized by its high compressive and flexural strengths, toughness and enhanced durability. The mechanical properties of the UHPC are to a great extent dependent on fibre volume fraction, orientation and distribution within the cementitious matrix. However, determination of the true three-dimensional fibre orientation and distribution is challenging. In this paper micro-computed tomography (micro-CT) is used to determine these parameters. Cylindrical samples of UHPC were extracted from a dogbone tension test specimen and from a pretensioned bridge girder, and high-resolution micro-CT images were then acquired. Using the scanned data, and following three-dimensional image reconstruction and image processing, quantitative fibre information was obtained via a novel image post-processing technique based on local-intensity gradient significantly improving cross-fibre detection compared to existing techniques. The estimated fibre volume fraction is close to design and experimentally measured values. Straight and hooked end fibres in UHPC sample were successfully identified and segmented using this novel technique. The test results show the fibre arrangement to be highly anisotropic with fibres aligned predominantly in one direction, which is attributed to the casting processes and flow.

The utility of computed tomography and diffusion-weighted magnetic resonance imaging fusion in cholesteatoma: illustration with a UK case series.

Post-processing imaging techniques allow high-resolution computed tomography and diffusion-weighted magnetic resonance imaging of the temporal bone to be superimposed and viewed simultaneously (fusion imaging). This study aimed to highlight the practical utility of fusion imaging for disease localisation and evaluation in a UK case series of primary and post-operative cholesteatoma. Fusion of computed tomography and diffusion-weighted magnetic resonance b1000 images was performed using specific software. Axial computed tomography images and coronal b1000 images were selected for fusion. A case series of primary and post-operative cholesteatoma in which computed tomography and magnetic resonance imaging fusion assisted the management of both the patient pathway and surgical approach is reviewed. Computed tomography and magnetic resonance imaging fusion can assist in pre-operative surgical planning and patient counselling through assessment of disease in both primary and revision scenarios. Computed tomography and magnetic resonance imaging fusion can assist the operative surgeon through accurate localisation that can influence both the operative technique and optimise operation theatre utilisation.

MR Neurography: Current Several Issues for Novice Radiologists

말초신경병증의 진단을 위해 MR neurography의 사용이 점차 증가하고 있다. 고대조도와 고해상도로 말초신경을 직접 영상화한 MR 영상을 MR neurography라고 하고, 지방억제 T2 강조영상과 확산강조영상이 흔히 사용되는 시퀀스이다. 작은 직경, 복잡한 해부학적 구조를 가진 말초신경을 합리적 시간 안에 영상화하기 위해서 최신의 isotropic 3차원 기법, 다양한 고속영상기법, post-processing 영상 기법 등이 사용된다. 이런 발전들로 인해 MR neurography가 유용하게 사용되지만 항상 적절한 MR neurography 영상을 얻을 수 있는 것은 아니다. 적절한 MR neurography 영상을 얻기 위해 영상의학과 의사가 고려해야 할 다음의 몇가지 쟁점들이 있다. 이에는 적절한 표준 프로토콜의 선책, 지방억제 기법의 선택, 해상도와 field of view와 slice thickness 간의 상호 관계의 이해, 적절한 post-processing 영상 기법의 적용, 2차원 영상획득 기법과 3차원 영상획득 기법의 장단점, 근위부 말초신경과 말단부 말초신경의 T2 대조도의 차이, 말초신경에 인접한 정맥이 MR neurography에 미치는 영향, 확산강조영상에서 기하학적 왜곡의 발생과 적절한 b value의 선택 등이다. 이런 쟁점들을 잘 이해하는 것이 경험이 적은 영상의학과 의사가 적절한 MR neurography 영상을 얻고, 말초신경병증을 정확히 평가하는 데 많은 도움이 될 것이다.