Differences In Artifacts Research Articles

Image quality assessment of pediatric chest and abdomen CT by deep learning reconstruction

BackgroundEfforts to reduce the radiation dose have continued steadily, with new reconstruction techniques. Recently, image denoising algorithms using artificial neural networks, termed deep learning reconstruction (DLR), have been applied to CT image reconstruction to overcome the drawbacks of iterative reconstruction (IR). The purpose of our study was to compare the objective and subjective image quality of DLR and IR on pediatric abdomen and chest CT images.MethodsThis retrospective study included pediatric body CT images from February 2020 to October 2020, performed on 51 patients (34 boys and 17 girls; age 1–18 years). Non-contrast chest CT (n = 16), contrast-enhanced chest CT (n = 12), and contrast-enhanced abdomen CT (n = 23) images were included. Standard 50% adaptive statistical iterative reconstruction V (ASIR-V) images were compared to images with 100% ASIR-V and DLR at medium and high strengths. Attenuation, noise, contrast to noise ratio (CNR), and signal to noise (SNR) measurements were performed. Overall image quality, artifacts, and noise were subjectively assessed by two radiologists using a four-point scale (superior, average, suboptimal, and unacceptable). A phantom scan was performed including the dose range of the clinical images used in our study, and the noise power spectrum (NPS) was calculated. Quantitative and qualitative parameters were compared using repeated-measures analysis of variance (ANOVA) with Bonferroni correction and Wilcoxon signed-rank tests.ResultsDLR had better CNR and SNR than 50% ASIR-V in both pediatric chest and abdomen CT images. When compared with 50% ASIR-V, high strength DLR was associated with noise reduction in non-contrast chest CT (33.0%), contrast-enhanced chest CT (39.6%), and contrast-enhanced abdomen CT (38.7%) with increases in CNR at 149.1%, 105.8%, and 53.1% respectively. The subjective assessment of overall image quality and the noise was also better on DLR images (p < 0.001). However, there was no significant difference in artifacts between reconstruction methods. From NPS analysis, DLR methods showed a pattern of reducing the magnitude of noise while maintaining the texture.ConclusionCompared with 50% ASIR-V, DLR improved pediatric body CT images with significant noise reduction. However, artifacts were not improved by DLR, regardless of strength.

Comparison and prediction of artefact severity due to total hip replacement in 1.5 T versus 3 T MRI of the prostate

PurposeTo evaluate image quality and diagnostic value of multiparametric prostate MRI (mpMRI) in patients with total hip replacement (THR) at 1.5 and 3 Tesla. MethodsIn this retrospective multicenter cohort study patients with uni- or bilateral THR and 1.5 T or 3 T mpMRI were included. Seventy consecutive, standard-of-care examinations per field strength were evaluated regarding their diagnostic value. The overall diagnostic value and prostate imaging quality score (PI-QUAL) were assessed. Artifact severity in the localizer and mpMRI sequences (T2w, DWI, DCE) was scored on a 3-point scale. Correlation between diagnostic value and artifacts was analysed. Moreover, a subgroup analysis focussed on image quality at different 3 T scanner generations. Results140 consecutive patients (mean age 72, median PSA value 8.3 ng/ml) were included. When comparing 1.5 T to 3 T examinations, no significant differences were observed regarding the artifact severity of DWI and the localizer and the overall diagnostic value of the images. There was a strong correlation between the diagnostic value, PI-QUAL score, and artifact severity in the localizer and DWI. T2w and DCE sequences showed overall low artifacts. Significant improvement in image quality for 3 T at the latest scanner generation was observed, especially for DWI (p < 0.03). ConclusionsMpMRI of patients with THR can be conducted at both field strengths without significant differences in artifacts. The localizer might be useful as an early forecasting feature for diagnostic value and particularly for contrast medium application decision. Patients with THR could benefit from technically advanced scanner generation and rs/ptx-EPI DWI sequences.

Comparative in anatomical information and artifacts between T2W TSE Cartesian sequences and T2W TSE BLADE sequences on axial cervical MRI examinations

Observation of the T2W TSE Cartesian sequence of Axial Cervical MRI Examinations still lacks a blurring on the image. One solution to overcome the blurring problem is using the BLADE trajectory. According to Finkenzeller (2014) states that TSE BLADE is significantly superior with optimum sharpness, depiction of cerebral spinal fluid, and detection of all lesions. In addition, TSE BLADE can suppress motion artifacts. The purpose of this study was to determine differences in anatomic information and artifacts between the T2W TSE Cartesian and BLADE on axial MRI cervical examination and which sequences were more optimal in terms of anatomic information and artifacts. This type of research is a quantitative study with an experimental approach involving 10 volunteers and 2 respondents specializing in radiology. Each voluntary MRI cervical examination was performed using axes T2W TSE Cartesian and BLADE sequences. Image results were examined by respondents to obtain anatomical information and artifact. The data were processed and analyzed using Cohen’s Kappa test and Wilcoxon test. The results showed that there were differences in anatomic information and artifacts between the T2W TSE Cartesian and BLADE on axial MRI cervical examinations with p-values of 0.038 or p <0.05 for differences in anatomic information, and p-values of 0.024 or p <0.05 for differences in artifacts. Sequence test results indicate that the TSE BLADE is more optimal than the TSE Cartesian, using the TSE BLADE sequence can suppress blurring artifacts so as to improve anatomical information. Conlusion: There is a difference in anatomical and artifact information between T2W TSE Cartesian and T2W TSE BLADE on Axial Cervical MRI examination. T2W TSE BLADE is superior compared to T2W TSE Cartesian

Comparison of artifacts between paste and collodion method of electrode application in pediatric EEG

ObjectivesChildren pose challenges to obtain quality EEG data due to excessive artifact. Collodion is used in EEG electrodes due to its water resistance and strong adhesive qualities. This study was done to evaluate differences in artifacts between the collodion and paste method. Methods115 subjects (children age >3 years) were randomized into paste and collodion groups and artifacts evaluated at baseline and every hour over 30 s increments. Age, sleep state, and number of electrodes with artifact were also documented. T-test was performed to determine differences in the various parameters between the two groups. Results61 subjects were in the paste group and 54 in the collodion group. Mean of total seconds of artifact from 0 to 24 h were 41.8 s in paste group versus 30.3 s in collodion group (P = 0.02). Children >11 years old had less artifact than younger children from 0 to 24 h (24.3 versus 41.2 s, P = 0.03), and from 24 to 48 h (33.1 versus 43.1 s, P = 0.03). There was a significant effect of sleep vs. awake state recordings on artifact from 0 to 24 h (30.3 versus 50.2 s, P = 0.01). ConclusionElectrode problems are common with both collodion and paste in prolonged AEEG monitoring. However, for studies less than 24 h, collodion may be a better alternative. SignificanceOur study provides evidence that in some cases collodion may be a better alternative to paste in terms of decreased artifacts.

Target volume and artifact evaluation of a new data-driven 4D CT

PurposeFour-dimensional computed tomography (4D CT) is often used to define the internal gross target volume (IGTV) for radiation therapy of lung cancer. Traditionally, this technique requires the use of an external motion surrogate; however, a new image, data-driven 4D CT, has become available. This study aims to describe this data-driven 4D CT and compare target contours created with it to those created using standard 4D CT. Methods and materialsCine CT data of 35 patients undergoing stereotactic body radiation therapy were collected and sorted into phases using standard and data-driven 4D CT. IGTV contours were drawn using a semiautomated method on maximum intensity projection images of both 4D CT methods. Errors resulting from reproducibility of the method were characterized. A comparison of phase image artifacts was made using a normalized cross-correlation method that assigned a score from +1 (data-driven “better”) to –1 (standard “better”). ResultsThe volume difference between the data-driven and standard IGTVs was not significant (data driven was 2.1 ± 1.0% smaller, P = .08). The Dice similarity coefficient showed good similarity between the contours (0.949 ± 0.006). The mean surface separation was 0.4 ± 0.1 mm and the Hausdorff distance was 3.1 ± 0.4 mm. An average artifact score of +0.37 indicated that the data-driven method had significantly fewer and/or less severe artifacts than the standard method (P = 1.5 × 10-5 for difference from 0). ConclusionsOn average, the difference between IGTVs derived from data-driven and standard 4D CT was not clinically relevant or statistically significant, suggesting data-driven 4D CT can be used in place of standard 4D CT without adjustments to IGTVs. The relatively large differences in some patients were usually attributed to limitations in automatic contouring or differences in artifacts. Artifact reduction and setup simplicity suggest a clinical advantage to data-driven 4D CT.

Differences in Manufacturing Traditions and Assemblage-Level Patterns: the Origins of Cultural Differences in Archaeological Data

A relationship between behavioral variability and artifactual variability is a founding principle of archaeology. However, this relationship is surprisingly not well studied empirically from an explicitly “microevolutionary” perspective. Here, we experimentally simulated artifactual variation in two populations of “artifact” manufacturers, involving only a single behavioral difference in terms of their “tradition” of manufacturing tool. We then statistically analyzed shape variation in the resultant artifacts. In many respects, patterned differences might not have been expected to emerge given the simple nature of the task, the fact that only a single behavioral variable differed in our two populations, and all participants copied the same target artifact. However, multivariate analyses identified significant differences between the two “assemblages.” These results have several implications for our understanding and theoretical conceptualization of the relationship between behavior and artifactual variability, including the analytical potency of conceiving of artifacts as the product of behavioral “recipes” comprised of individual “ingredient” behavioral properties. Indeed, quite trivial behavioral differences, in generating microevolutionarily potent variability, can thus have long-term consequences for artifactual changes measured over time and space. Moreover, measurable “cultural” differences in artifacts can emerge not necessarily only because of a strict “mental template” but as the result of subtle differences in behavioral ingredients that are socially learned at the community level.

An automated method for comparing motion artifacts in cine four‐dimensional computed tomography images

The aim of this study is to develop an automated method to objectively compare motion artifacts in two four‐dimensional computed tomography (4D CT) image sets, and identify the one that would appear to human observers with fewer or smaller artifacts. Our proposed method is based on the difference of the normalized correlation coefficients between edge slices at couch transitions, which we hypothesize may be a suitable metric to identify motion artifacts. We evaluated our method using ten pairs of 4D CT image sets that showed subtle differences in artifacts between images in a pair, which were identifiable by human observers. One set of 4D CT images was sorted using breathing traces in which our clinically implemented 4D CT sorting software miscalculated the respiratory phase, which expectedly led to artifacts in the images. The other set of images consisted of the same images; however, these were sorted using the same breathing traces but with corrected phases. Next we calculated the normalized correlation coefficients between edge slices at all couch transitions for all respiratory phases in both image sets to evaluate for motion artifacts. For nine image set pairs, our method identified the 4D CT sets sorted using the breathing traces with the corrected respiratory phase to result in images with fewer or smaller artifacts, whereas for one image pair, no difference was noted. Two observers independently assessed the accuracy of our method. Both observers identified 9 image sets that were sorted using the breathing traces with corrected respiratory phase as having fewer or smaller artifacts. In summary, using the 4D CT data of ten pairs of 4D CT image sets, we have demonstrated proof of principle that our method is able to replicate the results of two human observers in identifying the image set with fewer or smaller artifacts.PACS number: 87.57.cp; 87.57.N‐

Voltage-Pulsed and Laser-Pulsed Atom Probe Tomography of a Multiphase High-Strength Low-Carbon Steel

The differences in artifacts associated with voltage-pulsed and laser-pulsed (wavelength = 532 or 355 nm) atom-probe tomographic (APT) analyses of nanoscale precipitation in a high-strength low-carbon steel are assessed using a local-electrode atom-probe tomograph. It is found that the interfacial width of nanoscale Cu precipitates increases with increasing specimen apex temperatures induced by higher laser pulse energies (0.6-2 nJ pulse(-1) at a wavelength of 532 nm). This effect is probably due to surface diffusion of Cu atoms. Increasing the specimen apex temperature by using pulse energies up to 2 nJ pulse(-1) at a wavelength of 532 nm is also found to increase the severity of the local magnification effect for nanoscale M2C metal carbide precipitates, which is indicated by a decrease of the local atomic density inside the carbides from 68 ± 6 nm(-3) (voltage pulsing) to as small as 3.5 ± 0.8 nm(-3). Methods are proposed to solve these problems based on comparisons with the results obtained from voltage-pulsed APT experiments. Essentially, application of the Cu precipitate compositions and local atomic density of M2C metal carbide precipitates measured by voltage-pulsed APT to 532 or 355 nm wavelength laser-pulsed data permits correct quantification of precipitation.

Evaluation of Image Quality of a 32-Channel versus a 12-Channel Head Coil at 1.5T for MR Imaging of the Brain

Multichannel phased-array head coils are undergoing exponential escalation of coil element numbers. While previous technical studies have found gains in SNR and spatial resolution with the addition of element coils, it remains to be determined how these gains affect clinical reading. The purpose of this clinical study was to determine if the SNR and spatial resolution characteristics of a 32-channel head coil result in improvements in perceived image quality and lesion evaluation. Twenty-one patients underwent MR imaging of the brain at 1.5T sequentially with both a 12-channel and a 32-channel receive-only phased-array head coil. Axial T2WIs, T1WIs, FLAIR images, and DWIs were acquired. Anonymized images were compared side-by-side and by sequence for image quality, lesion evaluation, and artifacts by 3 neuroradiologists. Results of the comparison were analyzed for the preference for a specific head coil. FLAIR and DWI images acquired with the 32-channel coil showed significant improvement in image quality in several parameters. T2WIs also improved significantly with acquisition by the 32-channel coil, while T1WIs improved in a limited number of parameters. While lesion evaluation also improved with acquisition of images by the 32-channel coil, there was no apparent improvement in diagnostic quality. There was no difference in artifacts between the 2 coils. Improvements in SNR and spatial resolution attributed to image acquisition with a 32-channel head coil are paralleled by perceived improvements in image quality.

Image quality of spiral CT versus conventional CT in routine brain imaging

Objective: Aim of the study was to compare image quality of spiral (helical) versus conventional (sequential) routine brain scans obtained on a spiral CT scanner of the latest generation. Materials and methods: In a prospective study 60 patients scheduled for cranial CT were examined in spiral (27 cases) or conventional technique (33 cases) after randomization. Two blinded observers rated artifacts, gray–white-matter contrast and overall image quality. Results: No significant differences in artifacts were detected. Concerning gray–white-matter contrast and overall image quality, none or small differences in favour of conventional scans were found depending on the observer. Conclusion: On a modern scanner image quality of spiral brain scans in adults is nowadays comparable to or only slightly less than that of conventional scans. On such a machine, spiral mode can be recommended if, for example, rapid scanning or high-quality secondary reconstructions are needed.