Image Post-processing Techniques Research Articles

Cardiac deformation analysis from orthogonal CSPAMM (OCSPAMM) tagged MRI

Background Magnetic resonance imaging (MRI) is a highly advanced and sophisticated imaging modality for cardiac motion assessment and quantitative analysis. The myocardial tagging techniques have seen wide applications for cardiac deformation analysis (see [1-4] for example). Among different image post-processing techniques, frequency-based methods have played an important role in analysis of heart displacement from tagged MRI images [5,6]. In this abstract, we apply the SinMod technique to data from a new tagging pulse sequence which we have recently developed called Orthogonal CSPAMM (OCSPAMM) [7].

The Rotterdam Scan Study: design and update up to 2012.

Neuroimaging plays an important role in etiologic research on neurological diseases in the elderly. The Rotterdam Scan Study was initiated as part of the ongoing Rotterdam Study with the aim to unravel causes of neurological disease by performing neuroimaging in a population-based longitudinal setting. In 1995 and 1999 random subsets of the Rotterdam Study underwent neuroimaging, whereas from 2005 onwards MRI has been implemented into the core protocol of the Rotterdam Study. In this paper, we discuss the background and rationale of the Rotterdam Scan Study. We also describe the imaging protocol and post-processing techniques, and highlight the main findings to date. Finally, we make recommendations for future research, which will also be the main focus of investigation in the Rotterdam Scan Study.

Unsupervised dealiasing and denoising of color-Doppler data

Color Doppler imaging (CDI) is the premiere modality to analyze blood flow in clinical practice. In the prospect of producing new CDI-based tools, we developed a fast unsupervised denoiser and dealiaser (DeAN) algorithm for color Doppler raw data. The proposed technique uses robust and automated image post-processing techniques that make the DeAN clinically compliant. The DeAN includes three consecutive advanced and hands-off numerical tools: (1) statistical region merging segmentation, (2) recursive dealiasing process, and (3) regularized robust smoothing. The performance of the DeAN was evaluated using Monte-Carlo simulations on mock Doppler data corrupted by aliasing and inhomogeneous noise. Fifty aliased Doppler images of the left ventricle acquired with a clinical ultrasound scanner were also analyzed. The analytical study demonstrated that color Doppler data can be reconstructed with high accuracy despite the presence of strong corruption. The normalized RMS error on the numerical data was less than 8% even with signal-to-noise ratio as low as 10dB. The algorithm also allowed us to recover highly reliable Doppler flows in clinical data. The DeAN is fast, accurate and not observer-dependent. Preliminary results showed that it is also directly applicable to 3-D data. This will offer the possibility of developing new tools to better decipher the blood flow dynamics in cardiovascular diseases.

Decreased-Purgation CT Colonography: State of the Art

In the setting of CT colonography (CTC), decreasing bowel preparation measures may help to optimize colorectal cancer screening compliance without compromising accuracy. Decreased-purgation or wholly noncathartic CTC, known as nonconventional CTC, may be accomplished in conjunction with fecal tagging. Image post-processing technologies such as electronic cleansing and computer-aided detection may boost accuracy and decrease the need for bowel preparation even further. We review pre-study preparation and image post-processing techniques that have been described in nonconventional-preparation CTC studies over the past 10 years. We explore in detail specific aspects of nonconventional cathartic and fecal tagging regimens, including substance, dose, and time frame of ingestion.

Image postprocessing by Non-local Kuan’s filter

Blocking artifacts exist in images and video sequences compressed to low bit rates using block-based discrete cosine transform (DCT) compression standards. In order to reduce blocking artifacts, two image postprocessing techniques, DNLK filter and OCDNLK filter, are presented in this paper. A more accurate DCT domain Kuan’s filter based on Non-local parameter estimation was proposed from the linear minimum mean-square-error (MMSE) criterion. We analyze the required two assumptions for the filter theoretically. Then the DCT domain Kuan’s filter for low frequency coefficients and Non-local mean filter for high frequency AC coefficients constitute the proposed Non-local Kuan’s (NLK) filter. After that, we propose the Dual Non-local Kuan’s (DNLK) filter by applying the proposed filter in dual layer. The DNLK filter is extended to form the Overcomplete Dual Non-local Kuan’s (OCDNLK) filter by applying to the overcomplete DCT coefficients. Experimental results on coded images using test quantization tables and JPEG coded images show the effectiveness of the two methods.

Live Image Processing Does Not Increase Adenoma Detection Rate During Colonoscopy: A Randomized Comparison Between FICE and Conventional Imaging (Berlin Colonoscopy Project 5, BECOP-5)

Fujinon intelligent chromoendoscopy (FICE) is a post-processing imaging technique for increasing contrast of mucosa and mucosal lesions that might lead to improvement in colonic adenoma detection during colonoscopy. Previous studies on similar contrast-enhancing techniques as well as on dye staining have yielded variable and conflicting results. This large randomized trial was undertaken to determine whether FICE technology enhances adenoma detection rate (ADR). In a prospective study performed in a multicenter private practice and hospital setting, involving 8 examiners with substantial lifetime experience (>10,000 colonoscopies each), 1,318 patients (men 46.7%, women 53.3%; mean age 59.05 years) were randomly assigned to colonoscopy with either FICE or white light imaging on instrument withdrawal. Of the colonoscopies, 68% were screening and 32% were diagnostic examinations. The primary outcome measure was the ADR (i.e., number of adenomas/total number of patients). There was no difference between the two groups in terms of general ADR (0.28 in both groups), the total number of adenomas (184 vs. 183), or detection of subgroups of adenomas. The rate of identification of hyperplastic polyps was also the same in both groups (127 vs. 121; P=0.67). The results were the same for both the screening and the diagnostic colonoscopy subgroups. Withdrawal time was the same in both groups (8.4 vs. 8.3 min, P=0.55). This large randomized trial could not show any objective advantage of the FICE technique over conventional high-resolution endoscopy in terms of improved ADR.

A quantitative measurement of concrete air content using image analyses

A proposed topology method is introduced to measure the air content of fresh cement paste and hardened concrete. The method takes advantage of chromatographic analysis in void areas that are highlighted using different color schemes and later calculated using built-in computer software. The air content measured by the topology method is compared with results obtained from the conventional ASTM methods. It is concluded that the proposed method is reliable, and costs less and is easier to operate compared with the ASTM methods. In addition, 3 dimensional pore models can be created using image post-processing techniques. The proposed method helps researchers in understanding the formation and existence of concrete pores. This paper reports a detailed test program demonstrating the standard operating procedure used for the proposed method and presents a comparison of results between the proposed method and conventional ASTM Specifications. It is also concluded that the air content increases with increasing size of pores and increasing percentage of coarse aggregates.

Non-invasive MRI assessment of the articular cartilage in clinical studies and experimental settings

Attrition and eventual loss of articular cartilage are important elements in the pathophysiology of osteoarthritis (OA). Preventing the breakdown of cartilage is believed to be critical to preserve the functional integrity of a joint. Chondral injuries are also common in the knee joint, and many patients benefit from cartilage repair. Magnetic resonance imaging (MRI) and advanced digital post-processing techniques have opened possibilities for in vivo analysis of cartilage morphology, structure, and function in healthy and diseased knee joints. Techniques of semi-quantitative scoring of human knee cartilage pathology and quantitative assessment of human cartilage have been developed. Cartilage thickness and volume have been quantified in humans as well as in small animals. MRI detected cartilage loss has been shown to be more sensitive than radiographs detecting joint space narrowing. It is possible to longitudinally study knee cartilage morphology with enough accuracy to follow the disease-caused changes and also evaluate the therapeutic effects of chondro-protective drugs. There are also several MRI methods that may allow evaluation of the glycosaminoglycan matrix or collagen network of articular cartilage, and may be more sensitive for the detection of early changes. The clinical relevance of these methods is being validated. With the development of new therapies for OA and cartilage injury, MR images will play an important role in the diagnosis, staging, and evaluation of the effectiveness of these therapies.

Visualisation of uric acid renal calculi (UARC) using computed radiography (CR)

Aim To investigate the capability of CR to visualise UARC through inverse image post-processing technique. Methods. A patient-equivalent phantom (PEP) consisting of six 2.5-cm thick Perspex layers and one 1-mm thick aluminium layer was used to represent human tissues and bones respectively. A total of eight exposures were made on PEP to radiograph 1 mm, 2 mm and 3 mm UARC located between three layers of 2-cm thick cattle muscle, positioned inside the PEP. After each exposure, a layer of Perspex was removed, and another exposure was made until only one Perspex layer and one layer of muscle (containing the three UARC) remained. For each exposure, two images (a positive and an inverse image) were produced for comparison using Fuji XG1 computed radiography system with IP0 type C-ST-VI Fuji imaging plate (equivalent to 400 speed radiographic screen-film systems). Results In positive image, UARC of all three sizes (1 mm, 2 mm and 3 mm) located in the cattle muscle, cannot be visualised when the PEP consists of more than one layer of Perspex. In inverse image, the 3-mm UARC can be seen even when the PEP consists of five layers of Perspex. Conclusion This study revealed the post-processing capability of CR to increase the visualisation of UARC which has been categorised as radiolucent. A further study of clinical image quality should be performed using blinded observers to test diagnostic accuracy, which was not included in this study.

Advances in Imaging of the Spinal Cord Vascular Supply and its Relationship with Paraplegia after Aortic Interventions. A Review

Introduction: Preoperative knowledge of the spinal cord (SC) vasculature could be useful for stratifying and decreasing the risk of perioperative paraplegia after thoracic and thoraco-abdominal aortic surgery. Recent advances in magnetic resonance (MR) and computed tomography (CT) angiography and post-processing techniques have improved this knowledge. Methods: A search of MEDLINE/Pubmed and SCOPUS databases identified 1414 pertinent abstracts; 123 full-length manuscripts were screened to identify relevant studies with acceptable design and patient numbers. Forty-three were selected. Results: SC circulation was studied in 1196 patients to detect the great radicular artery: 522 by MR-angiography and 674 by CT angiography. Detection rates were 67–100% (mean 80.8%) with MR-angiography being 18–100% (mean 72%) with CT angiography. The side and level of the great radicular artery were consistent between the methods. Several authors tried to use the imaging results to guide clinical management. Conclusions: Non-invasive imaging of the SC blood supply allows preoperative definition of the vasculature in many, but not all, cases. The impact of these findings on clinical management is potentially beneficial but still uncertain. Further improvements in image acquisition and post-processing techniques are needed. Future studies need to be large enough to compensate for inter-individual variability in SC vasculature in health and disease; however, even a partial reduction of paraplegia rate offers a formidable motivation for further research in this area.

Advances in Imaging of the Spinal Cord Vascular Supply and its Relationship with Paraplegia after Aortic Interventions. A Review

Preoperative knowledge of the spinal cord (SC) vasculature could be useful for stratifying and decreasing the risk of perioperative paraplegia after thoracic and thoraco-abdominal aortic surgery. Recent advances in magnetic resonance (MR) and computed tomography (CT) angiography and post-processing techniques have improved this knowledge. A search of MEDLINE/Pubmed and SCOPUS databases identified 1414 pertinent abstracts; 123 full-length manuscripts were screened to identify relevant studies with acceptable design and patient numbers. Forty-three were selected. SC circulation was studied in 1196 patients to detect the great radicular artery: 522 by MR-angiography and 674 by CT angiography. Detection rates were 67-100% (mean 80.8%) with MR-angiography being 18-100% (mean 72%) with CT angiography. The side and level of the great radicular artery were consistent between the methods. Several authors tried to use the imaging results to guide clinical management. Non-invasive imaging of the SC blood supply allows preoperative definition of the vasculature in many, but not all, cases. The impact of these findings on clinical management is potentially beneficial but still uncertain. Further improvements in image acquisition and post-processing techniques are needed. Future studies need to be large enough to compensate for inter-individual variability in SC vasculature in health and disease; however, even a partial reduction of paraplegia rate offers a formidable motivation for further research in this area.

Flame front tracking in turbulent lean premixed flames using stereo PIV and time-sequenced planar LIF of OH

This paper describes the simultaneous application of time-sequenced laser-induced fluorescence imaging of OH radicals and stereoscopic particle image velocimetry for measurements of the flame front dynamics in lean and premixed LP turbulent flames. The studied flames could be acoustically driven, to simulate phenomena important in LP combustion technologies. In combination with novel image post processing techniques we show how the data obtained can be used to track the flame front contour in a plane defined by the illuminating laser sheets. We consider effects of chemistry and convective fluid motion on the dynamics of the observed displacements and analyse the influence of turbulence and acoustic forcing on the observed contour velocity, a quantity we term as sd2D. We show that this quantity is a valuable and sensitive indicator of flame turbulence interactions, as (a) it is measurable with existing experimental methodologies, and (b) because computational data, e.g. from large eddy simulations, can be post processed in an identical fashion. sd2D is related (to a two-dimensional projection) of the three-dimensional flame displacement speed sd, but artifacts due to out of plane convective motion of the flame surface and the uncertainty in the angle of the flame surface normal have to be carefully considered. Monte Carlo simulations were performed to estimate such effects for several distributions of flame front angle distributions, and it is shown conclusively that sd2D is a sensitive indicator of a quantity related to sd in the flames we study. sd2D was shown to increase linearly both with turbulent intensity and with the amplitude of acousting forcing for the range of conditions studied.

Integrated teaching of anatomy and radiology using three-dimensional image post-processing

This article presents a new way of teaching by integrating both anatomy and radiology using three-dimensional image post-processing tools. One preclinical and one clinical module were developed for integrated teaching of anatomy and radiology. Potential benefits were assessed by anonymous evaluation among the 176 participating students. The students highly appreciated the new approach, especially the high degree of interactivity with the post-processing software and the possibility to correlate the real dissection with the virtual dissection. Students agreed that three-dimensional imaging and postprocessing improved their understanding of difficult anatomical topics and topographical relations. We consider the new approach to provide great additional benefits for participating students regarding preparation for everyday clinical practice. In particular, it imparts familiarity with imaging and image post-processing techniques and may improve anatomical understanding, radiological diagnostic skills and three-dimensional appreciation.

Computed Tomographic Urography Update: An Evolving Urinary Tract Imaging Modality

Multi-detector computed tomography urography (CTU) is now well established as the imaging modality of choice for comprehensive evaluation of the kidneys and urinary tract, having largely replaced excretory urography. Over the past decade, CTU techniques have continued to evolve with the goal of improving urothelial surface visualization. Numerous benign and malignant conditions of the kidneys, ureters, and urinary bladder can be accurately depicted by CTU. This article provides a contemporary review of CTU imaging protocols, image postprocessing techniques, appearances of various urinary tract pathologic conditions, and pitfalls in image interpretation.

On the construction of a ground truth framework for evaluating voxel-based diffusion tensor MRI analysis methods

Although many studies are starting to use voxel-based analysis (VBA) methods to compare diffusion tensor images between healthy and diseased subjects, it has been demonstrated that VBA results depend heavily on parameter settings and implementation strategies, such as the applied coregistration technique, smoothing kernel width, statistical analysis, etc. In order to investigate the effect of different parameter settings and implementations on the accuracy and precision of the VBA results quantitatively, ground truth knowledge regarding the underlying microstructural alterations is required. To address the lack of such a gold standard, simulated diffusion tensor data sets are developed, which can model an array of anomalies in the diffusion properties of a predefined location. These data sets can be employed to evaluate the numerous parameters that characterize the pipeline of a VBA algorithm and to compare the accuracy, precision, and reproducibility of different post-processing approaches quantitatively. We are convinced that the use of these simulated data sets can improve the understanding of how different diffusion tensor image post-processing techniques affect the outcome of VBA. In turn, this may possibly lead to a more standardized and reliable evaluation of diffusion tensor data sets of large study groups with a wide range of white matter altering pathologies. The simulated DTI data sets will be made available online (http://www.dti.ua.ac.be).

Is virtual colonography useful in the diagnosis or management of inflammatory bowel diseases?

V irtual endoscopy is an image postprocessing technique that basically employs sectional volume image data like spiral computed tomography (CT) or magnetic resonance imaging (MRI) for creating virtual 3D models of the colon. Compared to the MRI-based technique the CT-based approach represents a more robust and faster imaging process. The major drawback of CT colonography is exposure to ionizing radiation, the effective dose varying from 0.5–12 mSV.1 MRI colonography reveals superior soft tissue resolution combined with the advantage of a total lack of ionizing radiation, which is a major argument for the mostly young patients with inflammatory bowel disease (IBD). The majority of the data concerning the sensitivity and specificity of virtual colonography in comparison to conventional colonoscopy were generated using the CT technique as a new method of screening for colorectal cancer. A meta-analysis of 33 studies with over 6000 patients demonstrated a heterogeneous sensitivity of polyp detection by CT-colonography ranging from 48%–85%, which improved as polyp size increased.2 However, more recently with more advanced hardand software applications a better sensitivity and specificity especially for polyp sizes 6 mm are reported.3

Measurement and analysis of geometric parameters of human carotid bifurcation using image post-processing technique

Objective To investigate variation in the carotid bifurcation geometry of adults of different age by MR angiography images combining image post-processing technique. Methods Images of the carotid bifurcations of 27 young adults (≤40 years old) and 30 older subjects ( >40 years old) were acquired via contrast-enhanced MR angiography. Three dimensional (3D) geometries of the bifurcations were reconstructed and geometric parameters were measured by post-processing technique. Results The geometric parameters of the young versus older groups were as follows: bifurcation angle (70.268°± 16.050° versus 58.857°±13.294°), ICA angle (36.893°±11.837° versus 30.275°± 9.533°), ICA planarity (6.453°±5.009° versus 6.263°±4.250°),CCA tortuosity (0.023°0.011 versus 0.014± 0.005), ICA tortuosity (0.070±0.042 versus 0.046±0.022), ICA/CCA diameter ratio (0.693± 0.132 versus 0.728±0.106), ECA/CCA diameter ratio (0.750±0.123 versus 0.809±0.122), ECA/ ICA diameter ratio (1.103±0.201 versus 1.127±0.195), bifurcation area ratio (1.057±0.281 versus 1.291±0.252). There was significant statistical difference between young group and older group in bifurcation angle, ICA angle, CCA tortuosity, ICA tortuosity, ECA/CCA and bifurcation area ratio (F= 17.16,11.74,23.02,13.38,6.54,22.80,respectively, P<0.05). Conclusions MR angiography images combined with image post-processing technique can reconstruct 3D carotid bifurcation geometry and measure the geometric parameters of carotid bifurcation in vivo individually. It provides a new and convenient method to investigate the relationship of vascular geometry and flow condition with atherosclerotic pathological changes. Key words: Imaging process, computer-assisted; Carotid arteries; Magnetic resonance imaging

Functional malcentering of the humeral head and asymmetric long-term stress on the glenoid: Potential reasons for glenoid loosening in total shoulder arthroplasty

We tested the hypothesis that functional malcentering of the humeral head during arm elevation exists in patients with glenohumeral osteoarthritis and influences long-term glenoid loading. Twenty-eight healthy volunteers and 10 patients with primary osteoarthritis, 10 with cuff-arthropathy, and 1 with dysplastic glenoid were examined. Open magnetic resonance imaging and 3-dimensional (3D) digital postprocessing techniques were applied in various arm positions. Osteoabsorptiometry was used to determine 3D subchondral mineralization patterns of the glenoid as an indicator of integral long-term stress distribution. At 30 degrees of abduction, 5 patients demonstrated malcentering of the humeral head posteriorly; all patients with cuff arthropathy had malcentering superiorly. At 90 degrees, most patients displayed significant (P < .001) malcentering in the superior and posterior direction. The shoulders showed maximal subchondral mineralization patterns in the direction of malcentering. Most patients with glenohumeral osteoarthritis displayed functional malcentering, which might be responsible for postoperative glenoid loosening in shoulder arthroplasty if not corrected intraoperatively.

Voxel‐based 3D MRI analysis helps to detect subtle forms of subcortical band heterotopia

To evaluate the potential diagnostic value of a novel magnetic resonance image (MRI) postprocessing technique in subtle forms of subcortical band heterotopia (SBH). The method was introduced to improve the visualization of blurred gray-white matter junctions associated with focal cortical dysplasia but was found to be applicable also to SBH. In the voxel-based MRI analysis presented here, T1-weighted MRI volume data sets are normalized and segmented using standard algorithms of SPM5. The distribution of gray and white matter is analyzed on a voxelwise basis and compared with a normal database of 150 controls. Based on this analysis, a three-dimensional feature map is created that highlights brain areas if their signal intensities fall within the range between normal gray and white matter and differ from the normal database in this respect. The method was applied to the MRI data of 378 patients with focal epilepsy in three different epilepsy centers. SBH was diagnosed in seven patients with five of them showing subtle forms of SBH that had gone unrecognized in conventional visual analysis of MRI and were only detected by MRI postprocessing. In contrast to distinct double cortex syndrome, these patients had partial double cortex with SBH mostly confined to posterior brain regions. The results of this study suggest that a considerable part of cases with SBH might remain unrecognized by conventional MRI. Voxel-based MRI analysis may help to identify subtle forms and appears to be a valuable additional diagnostic tool in the evaluation of patients with cryptogenic epilepsy.

Direct and Indirect Measurement of Temporal Horn Volume and Temporal Horn Index and its Neuropsychological Correlation in Mild Cognitive Impaired and Alzheimer Diseased Patients

Objectives: Clear, objective, quantitative and early indicators of Alzheimer disease (AD) are important for clinical assessment and monitoring of therapeutic interventions. In this article, we present a recently developed post processing technique to segment and visualize the ventricular system and measure ventricular volumes in patients with mild cognitive impairment (MCI) and AD. We applied this method to quantify temporal horn volumes (THV) and the temporal horn index (THI, ratio of temporal horn volume to lateral ventricular volume) and compared the results with both a direct measurement of the hippocampal formation, and neuropsychological test performance. The aim of this article is to present the two most common methods of direct and indirect measurement and their possible limitations in comparison to the neuropsychologic scoring. Methods and materials: All subjects (21 healthy controls, 21 patients with MCI and 10 patients with AD) underwent extensive neuropsychological testing and were scanned using a 1.5 T MRI (Magnetom Vision, Siemens, Germany). A direct measurement of the hippocampal formation was produced via high-resolution T1-weighted volume imaging, while indirect temporal horn volume (THV) was calculated using a watershed algorithm-based software package (MeVis, Germany). Results: In all subjects, a successful direct and indirect quantification of the hippocampus was performed or the THV and THI were calculated. For both the manual and the semi-automated approach, a significant volume difference was found between healthy volunteers and AD patients (p < 0.001). Group analysis also showed a significant difference between the THV as well as THI of AD patients compared to MCI subjects and controls (p < 0.005). There was a significant negative correlation between the neuropsychological performance and both THV and THI (p < 0.01) as well as a significant correlation of direct and indirect measurement (p < 0.001). Conclusion: The fast and rapid development of post processing imaging techniques now allow an easy and objective method of performing hippocampal volumetry. These recently developed post processing techniques presented accurate results which are comparable to the conventional direct approach, while offering a faster and more automated technique of assessing THV and THI that could be used as an indicator of AD in a clinical context and may be helpful in studying therapeutic intervention.