Artifactual Images Research Articles

Contrast-Enhanced Sonography of the Liver: How to Avoid Artifacts.

Contrast-enhanced sonography (CEUS) is a very important diagnostic imaging tool in clinical settings. However, it is associated with possible artifacts, such as B-mode US-related artifacts. Sufficient knowledge of US physics and these artifacts is indispensable to avoid the misinterpretation of CEUS images. This review aims to explain the basic physics of CEUS and the associated artifacts and to provide some examples to avoid them. This review includes problems related to the frame rate, scanning modes, and various artifacts encountered in daily CEUS examinations. Artifacts in CEUS can be divided into two groups: (1) B-mode US-related artifacts, which form the background of the CEUS image, and (2) artifacts that are specifically related to the CEUS method. The former includes refraction, reflection, reverberation (multiple reflections), attenuation, mirror image, and range-ambiguity artifacts. In the former case, the knowledge of B-mode US is sufficient to read the displayed artifactual image. Thus, in this group, the most useful artifact avoidance strategy is to use the reference B-mode image, which allows for a simultaneous comparison between the CEUS and B-mode images. In the latter case, CEUS-specific artifacts include microbubble destruction artifacts, prolonged heterogeneous accumulation artifacts, and CEUS-related posterior echo enhancement; these require an understanding of the mechanism of their appearance in CEUS images for correct image interpretation. Thus, in this group, the most useful artifact avoidance strategy is to confirm the phenomenon's instability by changing the examination conditions, including the frequency, depth, and other parameters.

Human faces and face-like stimuli are more memorable.

We have previously suggested a distinction in the brain processes governing biological and artifactual stimuli. One of the best examples of the biological category consists of human faces, the perception of which appears to be determined by inherited mechanisms or ones rapidly acquired after birth. In extending this work, we inquire here whether there is a higher memorability for images of human faces and whether memorability declines with increasing departure from human faces; if so, the implication would add to the growing evidence of differences in the processing of biological versus artifactual stimuli. To do so, we used images and memorability scores from a large data set of 58,741 images to compare the relative memorability of the following image categories: real human faces versus buildings, and extending this to a comparison of real human faces with five image categories that differ in their grade of resemblance to a real human face. Our findings show that, in general, when we compare the biological category of faces to the artifactual category of buildings, the former is more memorable. Furthermore, there is a gradient in which the more an image resembles a real human face the more memorable it is. Thus, the previously identified differences in biological and artifactual images extend to the field of memory.

Is it real or not? Toward artificial intelligence-based realistic synthetic cytology image generation to augment teaching and quality assurance in pathology.

Urine cytology offers a rapid and relatively inexpensive method to diagnose urothelial neoplasia. In our setting of a public sector laboratory in South Africa, urothelial neoplasia is rare, compromising pathology training in this specific aspect of cytology. Artificial intelligence-based synthetic image generation-specifically the use of generative adversarial networks (GANs)-offers a solution to this problem. A limited, but morphologically diverse, dataset of 1000 malignant urothelial cytology images was used to train a StyleGAN3 model to create completely novel, synthetic examples of malignant urine cytology using computer resources within reach of most pathology departments worldwide. We have presented the results of our trained GAN model, which was able to generate realistic, morphologically diverse examples of malignant urine cytology images when trained using a modest dataset. Although the trained model is capable of generating realistic images, we have also presented examples for which unrealistic and artifactual images were generated-illustrating the need for manual curation when using this technology in a training context. We have presented a proof-of-concept illustration of creating synthetic malignant urine cytology images using machine learning technology to augment cytology training when real-world examples are sparse. We have shown that despite significant morphologic diversity in terms of staining variations, slide background, variations in the diagnostic malignant cellular elements, the presence of other nondiagnostic cellular elements, and artifacts, visually acceptable and varied results are achievable using limited data and computing resources.

Tolerance to geometrical inaccuracies in CBCT systems: A comprehensive study.

The last decades have seen the consolidation of the cone-beam CT (CBCT) technology, which is nowadays widely used for different applications such as micro-CT for small animals, mammography, dentistry, or surgical procedures. Some CBCT systems may suffer mechanical strains due to the heavy load of the x-ray tube. This fact, together with tolerances in the manufacturing process, lead to different types of undesirable effects in the reconstructed image unless they are properly accounted for during the reconstruction. To obtain good quality images, it is necessary to have a complete characterization of the system geometry including the angular position of the gantry, the source-object and detector-object distances, and the position and pose of the detector. These parameters can be obtained through a calibration process done periodically, depending on the stability of the system geometry. To the best of our knowledge, there are no comprehensive works studying the effect of inaccuracies in the geometrical calibration of CBCT systems in a systematic and quantitative way. In this work, we describe the effects of detector misalignments (linear shifts, rotation, and inclinations) on the image and define their tolerance as the maximum error that keeps the image free from artifacts. We used simulations of four phantoms including systematic and random misalignments. Reconstructions of these data with and without errors were compared to identify the artifacts introduced in the reconstructed image and the tolerance to miscalibration deemed to provide acceptable image quality. Visual assessment provided an easy guideline to identify the sources of error by visual inspection of the artifactual images. Systematic errors result in blurring, shape distortion and/or reduction of the axial field of view while random errors produce streaks and blurring in all cases, with a tolerance which is more than twice that of systematic errors. The tolerance corresponding to errors in position of the detector along the tangential direction, that is, skew (<0.2°) and horizontal shift (<0.4mm), is tighter than the tolerance to those errors affecting the position along the longitudinal direction or the magnification, that is, vertical shift (<2mm), roll (<1.5°), tilt (<2°), and SDD (<3mm). We present a comprehensive study, based on realistic simulations, of the effects on the reconstructed image quality of errors in the geometrical characterization of a CBCT system and define their tolerance. These results could be used to guide the design of new systems, establishing the mechanical precision that must be achieved, and to help in the definition of an optimal geometrical calibration process. Also, the thorough visual assessment may be valuable to identify the most predominant sources of error based on the effects shown in the reconstructed image.

Development of a spiral spin- and gradient-echo (spiral-SAGE) approach for improved multi-parametric dynamic contrast neuroimaging.

The purpose of this study was to develop a spiral-based combined spin- and gradient-echo (spiral-SAGE) method for simultaneous dynamic contrast-enhanced (DCE-MRI) and dynamic susceptibility contrast MRI (DSC-MRI). Using this sequence, we obtained gradient-echo TEs of 1.69 and 26 ms, a SE TE of 87.72 ms, with a TR of 1663 ms. Using an iterative SENSE reconstruction followed by deblurring, spiral-induced image artifacts were minimized. Healthy volunteer images are shown to demonstrate image quality using the optimized reconstruction, as well as for comparison with EPI-based SAGE. A bioreactor phantom was used to compare dynamic-contrast time courses with both spiral-SAGE and EPI-SAGE. A proof-of-concept cohort of patients with brain tumors shows the range of hemodynamic maps available using spiral-SAGE. Comparison of spiral-SAGE images with conventional EPI-SAGE images illustrates substantial reductions of image distortion and artifactual image intensity variations. Bioreactor phantom data show similar dynamic contrast time courses between standard EPI-SAGE and spiral-SAGE for the second and third echoes, whereas first-echo data show improvements in quantifying T1 changes with shorter echo times. In a cohort of patients with brain tumors, spiral-SAGE-based perfusion and permeability maps are shown with comparison with the standard single-echo EPI perfusion map. Spiral-SAGE provides a substantial improvement for the assessment of perfusion and permeability by mitigating artifacts typically encountered with EPI and by providing a shorter echo time for improved characterization of permeability. Spiral-SAGE enables quantification of perfusion, permeability, and vessel architectural parameters, as demonstrated in brain tumors.

Stones, Snowflakes, and Insect Eggs

Abstract This paper takes as its broad context the evolution of the place of geometry in ways of thinking about nature and art in early modern Europe. Considering a set of questions about how Nature creates geometric forms, particularly in minerals but also in other kinds of natural beings, the paper explores the concept of “figure” as it appears in Conrad Gessner’s De rerum fossilium, where figure appears as a broad category that cuts across abstract geometry, artifactual images, and shape appearing within natural entities. Gessner is placed within changing ideas about the role of geometry as an intellectual pursuit or, rather, a mechanical property of nature conceived as inanimate and rule-bound.

Diagnostic problems in two-dimensional shear wave elastography of the liver.

Two-dimensional shear wave elastography (2D-SWE) is used in the clinical setting for observation of the liver. Unfortunately, a wide spectrum of artifactual images are frequently encountered in 2D-SWE, the precise mechanisms of which remain incompletely understood. This review was designed to present many of the artifactual images seen in 2D-SWE of the liver and to analyze them by computer simulation models that support clinical observations. Our computer simulations yielded the following suggestions: (1) When performing 2D-SWE in patients with chronic hepatic disease, especially liver cirrhosis, it is recommended to measure shear wave values through the least irregular hepatic surface; (2) The most useful 2D-SWE in patients with focal lesion will detect lesions that are poorly visible on B-mode ultrasound and will differentiate true tumors from pseudo-tumors (e.g., irregular fatty change); and (3) Measurement of shear wave values in the area posterior to a focal lesion must be avoided.

The use of lung ultrasound images for the differential diagnosis of pulmonary and cardiac interstitial pathology.

In recent years, great advances have been made in the use of lung ultrasound to detect pulmonary edema and interstitial changes in the lung. However, it is clear that B-lines oversimplify the description of the physical phenomena associated with their presence. The artifactual images that ultrasounds provide in interstitial pulmonary pathology are merely the ultimate outcome of the complex interaction of a specific acoustic wave with a specific three-dimensional biological structure. This interaction lacks a solid physical interpretation of the acoustic signs to support it. The aim of this paper was to describe the differences between the sonographic interstitial syndrome related to lung diseases and that related to cardiogenic edema in the light of current knowledge regarding the pleural plane's response to ultrasound waves.

Sonographic Appearance of Chromic 2-0 Catgut Sutures in the Parenchyma of a Renal Allograft

A renal transplant recipient had a urinary fistula repaired and a double-pigtail ureteral stent left and later surgically removed. At this same time, an open biopsy was performed and closed with chromic 2-0 catgut sutures. A sonogram revealed an artifactual image that was interpreted as a fragmented piece of the stent that was left in the patient. An exploratory surgery performed, however, was unremarkable, and the renal incision was again closed with chromic 2-0 catgut sutures. A repeated sonogram demonstrated the previous artifact, which raised the suspicion that this appearance should be attributed to the chromic 2-0 catgut sutures. An experiment using a model of coupling gel and chromic 2-0 catgut sutures demonstrated artifacts that matched those seen during sonography of this particular renal allograft. This sonographic artifactual appearance may be seen in hypostenic patients with a high-frequency transducer centered over chromic 2-0 catgut sutures.

Crucial factor causing collapse and aggregation of cultured cells in epon resin.

Ultrastructural artifacts regarding collapse and aggregation of cultured cells have been problematic, especially when investigated apoptotic cells. The infiltration process during sample preparation is considered to be the most crucial factor for this problem. This study was conducted using two culture systems: a suspension culture system of human T-lymphocyte Jurkat cells and rabbit mature dendritic cells and a monolayer culture system of human lung macrophages, human breast cancer cells (A-546 cells) and cat bone-invasive gingival cancer cells (sccf3 cells). Fixation was conducted prior to removing or detaching the cells from the culture dishes. Initial infiltration with a 1 : 3 volume ratio of epon resin : propylene oxide was found to be the most crucial step among these cultured cells. The improved epon-resin infiltration method could eliminate the artifacts. Thus, differentiation between artifactual images and true images is highly possible.

Motivation for whole-heart perfusion CMR: a simulation study based on retrospective comparison of the diagnostic performance of 3-slice vs. whole-heart SPECT

Background There is an ongoing debate on the merit of whole-heart 3D CMR perfusion imaging in terms of improving the overall diagnostic accuracy of myocardial perfusion CMR [1]. Whole-heart imaging is technically more challenging [2] and requires a compromise in terms of the spatial resolution [2] and temporal footprint (hence, potentially leading to more instances of artifactual images). The purpose of this work was to evaluate the potential incremental diagnostic value of whole-heart myocardial perfusion imaging compared to 3-slice imaging. The presented results are based on on a simulation of 3-slice imaging with myocardial perfusion SPECT (MPS) in a retrospective quantitative analysis of a large cohort who underwent stress MPS [3,4].

Elucidation and Identification of Double-Tip Effects in Atomic Force Microscopy Studies of Biological Structures

While atomic force microscopy (AFM) has been increasingly applied to life science, artifactual measurements or images can occur during nanoscale analyses of cell components and biomolecules. Tip-sample convolution effect is the most common mechanism responsible for causing artifacts. Some deconvolution-based methods or algorithms have been developed to reconstruct the specimen surface or the tip geometry. Double-tip or double-probe effect can also induce artifactual images by a different mechanism from that of convolution effect. However, an objective method for identifying the double-tip/probe-induced artifactual images is still absent. To fill this important gap, we made use of our expertise of AFM to analyze artifactual double-tip images of cell structures and biomolecules, such as linear DNA, during AFM scanning and imaging. Mathematical models were then generated to elucidate the artifactual double-tip effects and images develop during AFM imaging of cell structures and biomolecules. Based on these models, computational formulas were created to measure and identify potential double-tip AFM images. Such formulas proved to be useful for identification of double-tip images of cell structures and DNA molecules. The present studies provide a useful methodology to evaluate double-tip effects and images. Our results can serve as a foundation to design computer-based automatic detection of double-tip AFM images during nanoscale measuring and imaging of biomolecules and even non-biological materials or structures, and then personal experience is not needed any longer to evaluate artifactual images induced by the double-tip/probe effect.

“Synthetic” Comets: A New Look at Lung Sonography

Ultrasound interstitial syndrome is an echographic pattern of the lung characterized by the presence of multiple acoustic artifacts called “comets” or B-lines. It correlates to increase in extravascular lung water and to interstitial lung disease. From the physical and genetic point of view, the characteristics and the entity of this correlation have not yet been studied. The purpose of this study was to extrapolate past observations and demonstrate how comets or B-lines are artifactual images whose formation is linked to ultrasound interactions on discretely aerated tissues of variable density. Echographic comets were studied by scanning a wet synthetic, partially aerated polyurethane sponge (phantom). Density of the phantom in different drying phases was measured and correlated to the presence of echographic artifacts. Artifacts (comets) showed a different concentration from a completely white artifactual field to presence of rare comets. Their density correlates with porosity and geometry of the phantom. In our opinion, comets represent superficial, artifactual, density and geometry correlated phenomenon due to the acoustic permeability of a broken (collapsed) specular reflector, normally present when the phantom is dry.

Imaging Artifacts in MRI Simulators

Artifactual images are created in the process of imaging. They are images that distort reality, i.e. they do not correspond to the image but they arise from them and are false. This paper describes image artifacts in MR that can lead to misdiagnosis, analyzes their causes and reviews the most common imaging artifacts.

Film and Archaeology in the Indigenous and Industrial American West

Phenomenological and postcolonial archaeologies of film bracket the artifactual images and historical narratives in two films depicting hydraulic industrialization in the 20th-century Native American West of the United States. The documentary Echoes of Yesterday [Ball and Gibby 1939, 1979] consists of industrial and archaeological footage shot in 1939 and remixed in 1979 which depicts the building of the Grand Coulee Dam in Washington State, the relocating of indigenous villages there, and disinterring of Native American dead. The independent magical realism film Northfork [Polish 2003] is based on the building of the Fort Peck Dam on the Missouri River in Montana and the subsequent relocation of people and graves in that area. Both films animate the historic Modern period (1934–1975) and present the cultural losses, nostalgia and redemption attendant in a transition to a Supermodern period (1975–present).

Error signal artifact in apertureless scanning near-field optical microscopy

Apertureless scanning near-field optical microscopy is a method for obtaining subwavelength optical images of nanostructures. However, great care must be taken to avoid artifactual images. We report on one artifact related to the error signal in cantilever vibration amplitude when operating in tapping mode atomic force microscopy. The artifact is described experimentally and modeled by electromagnetic calculations based on the finite element method. We report specific steps to identify and avoid this artifact with experimental results on gold nanostructures. It is suggested that future apertureless scanning near-field optical microscopy studies verify that optical image does not correlate with error signal.

Imagen artefactual por inyección intra-arterial de 99mTc-MDP simulando un proceso patológico osteoarticular

Imagen artefactual por inyección intra-arterial de 99mTc-MDP simulando un proceso patológico osteoarticular

Spin echo entrapped perfusion image (SEEPAGE). A nonsubtraction method for direct imaging of perfusion.

Arterial spin-labeled perfusion imaging is increasingly being applied to the study of the brain and other organs. To date, perfusion information has invariably been obtained by subtraction of images with and without spin-labeling of inflowing water. Due to the relatively small amount of blood which enters tissue over a typical inflow period (1-1.5 sec), subtraction errors due to image instability or, in certain circumstances, magnetization transfer effects, can lead to very significant amounts of artifactual image intensity. These problems are avoided in the nonsubtraction method described here. Initially, spins in the imaging slice are selectively saturated, leaving other spins unaffected. A subsequent spin-echo train traps these magnetizations irrespective of flow. Finally, an imaging module generates intensity only from those spins which have entered the imaging slice during the inflow period. A slight modification of the sequence facilitates validation by detecting any contaminating signal in a control image.

Diffusion-weighted multiple shot echo planar imaging of humans without navigation.

A new method is proposed for reducing the artifacts produced in diffusion-weighted imaging. When data are acquired using multiple shot echo planar acquisitions, conventional reconstruction methods produce artifactual images as a consequence of diffusion weighting and small amounts of bulk motion of the subject. If the amount of motion can be determined, it is possible to correct the data before reconstruction, which removes the artifact. A method for estimating the motion from the acquired data has been developed and evaluated. This method assumes that ghost image effects will be minimized when motion has been correctly compensated. By considering the amount of signal in the background of the image, appropriate corrections to the data can be made, and the accuracy of the motion compensation may be estimated. This technique has been evaluated by computer simulation, and its performance has been demonstrated in a phantom and humans with both two- and four-shot echo planar acquisitions and using both "mosaic" and "interleaved" sampling schemes.

Topography of ribosomes and initiation complexes from rat liver as revealed by atomic force microscopy.

Atomic force microscopy (AFM) was used to image ribosomes and ribosomal subunits (60S, 40S and native 40S ribosomal subunits) isolated from rat liver. A variety of topographic images were obtained directly and found to be consistent with models established by other biophysical methods. In addition, the ternary complex of eIF-2 x GTP x Met-tRNA(i) and the 43S preinitiation complex have been discerned by AFM directly. Detailed information about the binding sites for eIF-1A, eIF-2, eIF-3, and Met-tRNA(i) on the 40S ribosomal subunit was derived from the AFM images. Finally, factors which may give rise to artifactual images, namely, convolution of the AFM tip on ribosomes, surface tension collapse effect and dehydration, are discussed. This work demonstrates that AFM is useful for imaging ribosomes and translational complexes and provides valuable information that can be used to complement other well-established techniques.