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Objetivo: disminuir el efecto de artefacto que generan objetos de alta densidad mediante la utilización de filtros de distintos materiales y espesores, ubicados en lugares estratégicos del tomógrafo. Material y métodos: se utilizaron filtros de aluminio y de cobre ubicados en lugares estratégicos en el equipo tomográfico. Se realizaron cortes oblicuos en piezas dentarias con restauraciones metálicas y en implantes; se midió la extensión del artefacto en ancho y alto en cada adquisición tomográfica. Resultados: se hallaron diferencias significativas respecto a la disminución de la dispersión de acuerdo con cada filtro con respecto a la no utilización de estos elementos. Conclusión: la utilización de filtros logró disminuir el efecto de artefacto en estructuras de alta densidad, obteniendo una mejor calidad de imagen para el diagnóstico, permitiendo que el software pueda reconstruir una imagen real (AU)
Objective: to diminish the artifact effect generated by high density objects by using filters of different materials and thickness, located in strategic places of the tomograph. Material and methods: aluminum and copper filters located in strategic places in the tomographic equipment were used. Oblique cuts were made on dental pieces with metal restorations and implants; the extension of the artifact in width and height was measured in each tomographic acquisition. Results: significant differences were found regarding the decrease of the dispersion according to each filter with respect to the non-use of these elements. Conclusion: the use of filters achieves to diminish the artifact effect in structures of high density, obtaining a better image quality for the diagnosis, allowing the software to reconstruct a real image (AU)
Subject(s)
Artifacts , Dental Equipment , Cone-Beam Computed Tomography , Dental Implants , Filters , AluminumABSTRACT
Three-dimensional cone-beam computed tomography (CBCT) has an important role in the detection of vertical root fractures (VRFs). The effect of artifact generation by high-density objects like dental implants on image quality was well documented. This study aimed to assess the effect of tooth-implant distance and the application of metal artifact reduction (MAR) algorithm on the detection of VRFs on CBCT scans. This study was conducted on 20 endodontically treated single-rooted teeth. VRFs were induced in 10 teeth, while the other 10 remained intact. The implant was inserted in the right second premolar socket area, and two teeth were inserted in right canine and right first premolar sockets area randomly and underwent CBCT with and without the application of MAR algorithm. SPSS 21 was used to analyze the results (alpha=0.05). According to the findings of this study, all four variables of sensitivity, specificity, accuracy, and positive predictive values in diagnosis were higher in cases without MAR software at both close(roots in first premolar sockets) and far distances (roots in canine sockets) from the implant. However, the highest rate of diagnosis accuracy of the first and second radiologists was in the far distance group from the implant without MAR, and the lowest rate of diagnosis accuracy in the first and second radiologists was in the close distance to the implant. Applying MAR algorithm had no positive effect on detection of VRFs on CBCT scans in both close and distant scenarios.
La tomografía computarizada de haz cónico tridimensional (CBCT) tiene un papel importante en la detección de fracturas radiculares verticales (VRF). El efecto de la generación de artefactos por objetos de alta densidad como los implantes dentales en la calidad de la imagen está bien documentado. Este estudio tuvo como objetivo evaluar el efecto de la distancia entre el diente y el implante y la aplicación del algoritmo de reducción de artefactos metálicos (MAR) en la detección de VRF en escaneos CBCT. Este estudio se realizó en 20 dientes uniradiculares tratados endodónticamente. Se indujeron VRF en 10 dientes, mientras que los otros 10 permanecieron intactos. El implante se insertó en el área del alveolo del segundo premolar derecho, y dos dientes se insertaron en el canino derecho y en el área del alvéolo del primer premolar derecho al azar y se sometieron a CBCT con y sin la aplicación del algoritmo MAR. Se utilizó SPSS 21 para analizar los resultados (alfa=0,05). De acuerdo con los hallazgos de este estudio, las cuatro variables de sensibilidad, especificidad, precisión y valores predictivos positivos en el diagnóstico fueron más altas en los casos sin el software MAR tanto en distancias cercanas (raíces en las cavidades de los primeros premolares) como lejanas (raíces en las cavidades de los caninos) del implante. Sin embargo, la tasa más alta de precisión diagnóstica del primer y segundo radiólogo fue en el grupo de mayor distancia al implante sin MAR, y la tasa más baja de precisión diagnóstica en el primer y segundo radiólogo fue en la distancia cercana al implante. La aplicación del algoritmo MAR no tuvo un efecto positivo en la detección de VRF en escaneos CBCT en escenarios cercanos y distantes.
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OBJECTIVE@#To analyze the malfunction and maintenance process of Carestream digital X-ray machine DRX-NOVA for reference.@*METHODS@#The fault of Carestream digital X-ray machine DRX-NOVA in 2011-2021 was summarized, the fault types were classified, and the maintenance process was summarized.@*RESULTS@#Fault types can be divided into three categories, each of which has its own characteristics and specific solutions.@*CONCLUSIONS@#It is necessary to master the principle of equipment to repair all kinds of equipment failures. Repair the machine should be careful, comprehensive consideration of the cause of the failure. To correctly understand and analyze the operation of the machine under normal conditions, we can accurately analyze the cause of failure, so that we can really solve the problem.
Subject(s)
X-Rays , Radiography , Radiographic Image Enhancement , Equipment FailureABSTRACT
【Objective】 To investigate the value of deep learning image reconstruction (DLIR) in improving image quality and reducing beam-hardening artifacts of low-dose abdominal CT. 【Methods】 For this study we prospectively enrolled 26 patients (14 males and 12 females, mean age of 60.35±10.89 years old) who underwent CT urography between October 2019 and June 2020. All the patients underwent conventional-dose unenhanced CT and contrast-enhanced CT in the portal venous phase (noise index of 10; volume computed tomographic dose index: 9.61 mGy) and low-dose CT in the excretory phase(noise index of 23; volume computed tomographic dose index: 2.95 mGy). CT images in the excretory phase were reconstructed using four algorithms: ASiR-V 50%, DLIR-L, DLIR-M, and DLIR-H. Repeated measures ANOVA and Kruskal-Wallis H test were used to compare the quantitative (skewness, noise, SNR, CNR) and qualitative (image quality, noise, beam-hardening artifacts) values among the four image groups. Post hoc comparisons were performed using Bonferroni test. 【Results】 In either quantitative or qualitative evaluation, the SNR, CNR, overall image quality score, and noise of DLIR images were similar or better than ASiR-V 50%. In addition, the SNR, CNR, and overall image quality scores increased as the DLIR weight increased, while the noise decreased. There was no statistically significant difference in the distortion artifacts (P=0.776) and contrast-induced beam-hardening artifacts (P=0.881) scores among these groups. 【Conclusion】 Compared with the ASiR-V 50% algorithm, DLIR algorithm, especially DLIR-M and DLIR-H, can significantly improve the image quality of low-dose abdominal CT, but has limitations in reducing contrast-induced beam-hardening artifacts.
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Abstract The aim of this study was to compare the influence of endodontic sealers artifacts on the detection of vertical root fracture in cone beam computed tomography (CBCT). Premolars and central incisors were assigned into five different groups: Control, Pulp Canal Sealer, AH Plus, Sealer 26, and BC Sealer (n= 10, per group). VRFs were mechanically induced and the teeth were inserted into an image phantom. Subsequently, CBCT (Cranex 3Dx, Soredex, Tuusula, Finland) images were obtained and two observers were asked separately to identify root fracture, by visual analysis. For both premolar and central incisors, kappa coefficients of intraobserver agreement varied from good to excellent (K: 80% - 87%), and the values for interobserver agreement varied from fair to moderate (K: 30% - 35%). As follows, the area under the curve (AUC) of receiver operating characteristic (ROC) values for VRFs highlighted that the use of BC sealer reduced the observers' ability to discriminate VRFs relative to other sealers. Moreover, sensitivity values for premolars teeth ranged from 20% to 60%, and specificity ranged from 60% to 100%; while sensitivity values for central incisors ranged from 30% to 70%, and specificity ranged from 70% to 100%. In conclusion, the low sensitivity values, mainly for premolars, demonstrated the difficulty in VRF diagnosis. Furthermore, BC Sealer induced significantly more imaging artifacts than other sealers. These results highlighting that endodontic sealers may interfere with the diagnosis of VRFs.
Resumo O objetivo deste estudo foi comparar a influência dos artefatos de cimentos endodônticos na detecção de fratura radicular vertical (FRV) em tomografia computadorizada de feixe cônico (TCFC). Pré-molares e incisivos centrais foram divididos em cinco grupos diferentes: Controle, Pulp Canal Sealer, AH Plus, Sealer 26 e BC Sealer (n = 10, por grupo). As FRVs foram induzidas mecanicamente e os dentes inseridos em uma réplica da mandibula humana. Posteriormente, imagens de TCFC (Cranex 3Dx, Soredex, Tuusula, Finlândia) foram obtidas e dois observadores foram solicitados a identificar fratura radicular separadamente, o critério utilizado foi a análise visual. Tanto para pré-molares quanto para incisivos centrais, os coeficientes kappa de concordância intraobservador variaram de bom a excelente (K: 80% - 87%), e os valores de concordância interobservador variaram de regular a moderado (K: 30% - 35%). A seguir, a área sob a curva (AUC) dos valores da característica de operação do receptor (ROC) para FRVs destacou que o uso do cimento BC Sealer reduziu a capacidade dos observadores de discriminar FRVs em relação a outros cimentos endodônticos. Além disso, os valores de sensibilidade para pré-molares variaram de 20% a 60%, e a especificidade variou de 60% a 100%; enquanto os valores de sensibilidade para incisivos centrais variaram de 30% a 70%, e a especificidade variou de 70% a 100%. Em conclusão, os baixos valores de sensibilidade, principalmente para pré-molares, demonstraram uma dificuldade no diagnóstico de FRV. Além disso, o BC Sealer induziu significativamente mais artefatos de imagem do que outros cimentos. Esses resultados evidenciam que os cimentos endodônticos podem interferir no diagnóstico das FRVs.
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@#Introduction: Metal artifacts can degrade the image quality of computed tomography (CT) images which lead to errors in diagnosis. This study aims to evaluate the performance of Laplace interpolation (LI) method for metal artifacts reduction (MAR) in CT images in comparison with cubic spline (CS) interpolation. Methods: In this study, the proposed MAR algorithm was developed using MATLAB platform. Firstly, the virtual sinogram was acquired from CT image using Radon transform function. Then, dual-adaptive thresholding detected and segmented the metal part within the CT sinogram. Performance of the two interpolation methods to replace the missing part of segmented sinogram were evaluated. The interpolated sinogram was reconstructed, prior to image fusion to obtain the final corrected image. The qualitative and quantitative evaluations were performed on the corrected CT images (both phantom and clinical images) to evaluate the effectiveness of the proposed MAR technique. Results: From the findings, LI method had successfully replaced the missing data on both simple and complex thresholded sinogram as compared to CS method (p-value = 0.17). The artifact index was significantly reduced by LI method (p-value = 0.02). For qualitative analysis, the mean scores by radiologists for LI-corrected images were higher than original image and CS-corrected images. Conclusion: In conclusion, LI method for MAR produced better results as compared to CS interpolation method, as it worked more effective by successfully interpolated all the missing data within sinogram in most of the CT images.
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The non-invasive brain-computer interface (BCI) has gradually become a hot spot of current research, and it has been applied in many fields such as mental disorder detection and physiological monitoring. However, the electroencephalography (EEG) signals required by the non-invasive BCI can be easily contaminated by electrooculographic (EOG) artifacts, which seriously affects the analysis of EEG signals. Therefore, this paper proposed an improved independent component analysis method combined with a frequency filter, which automatically recognizes artifact components based on the correlation coefficient and kurtosis dual threshold. In this method, the frequency difference between EOG and EEG was used to remove the EOG information in the artifact component through frequency filter, so as to retain more EEG information. The experimental results on the public datasets and our laboratory data showed that the method in this paper could effectively improve the effect of EOG artifact removal and improve the loss of EEG information, which is helpful for the promotion of non-invasive BCI.
Subject(s)
Humans , Electrooculography/methods , Artifacts , Brain-Computer Interfaces , Algorithms , Electroencephalography/methods , Signal Processing, Computer-AssistedABSTRACT
Abstract Objectives: To investigate the diagnostic performance of single-source dual-energy computed tomography (DECT) based on gemstone spectral imaging technology (including Discovery CT750HD and Revolution CT) in patients with suspected feet/ankles gouty arthritis, and evaluate the urate deposition with a novel semi-quantitative DECT scoring system. Methods: A total of 196 patients were consecutively included. Feet and ankles were evaluated in all patients by single-source DECT scan. The 2015 EULAR/ACR criteria were used as the reference for the diagnosis of gout. The sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of DECT for the diagnosis of gout in the early (≤1 year), middle (1-3 years), and late (> 3 years) disease durations were calculated. Besides, a novel semi-quantitative DECT scoring system was assessed for the measurement of urate deposition, and the correlation between the scores and the clinical and serological data were also evaluated. Moreover, the influences of artifacts on the diagnostic performance of DECT were also determined. Results: The sensitivity, specificity, and AUC of DECT in 196 patients were 38.10, 96.43%, and 0.673 in the early-stage group; 62.96, 100.00%, and 0.815 in the middle-stage group; and 77.55, 87.50%, and 0.825 in the late-stage group, respectively. The overall diagnostic accuracies in the AUC of DECT (Discovery CT750HD and Revolution CT) in the middle and late stages of gout were higher than that in the early stage of gout. Besides, the monosodium urate crystals were deposited on the first metatarsophalangeal joints and ankles/midfeet. Age, the presence of tophus, bone erosion, and disease duration considerably affected the total urate score. No statistical difference in the positive detection of nail artifact, skin artifact, vascular calcification, and noise artifact was found between the case and control groups. Conclusion: DECT (Discovery CT750HD and Revolution CT) showed promising diagnostic accuracy for the detection of urate crystal deposition in gout but had limited diagnostic sensitivity for short-stage gout. Longer disease duration, the presence of tophus, and bone erosion were associated with the urate crystal score system. The artifacts do not remarkably affect the diagnostic performance of DECT in gout.
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Objective:To compare the quality and diagnostic utility of the three sequences including fast spin echo (FSE), multi-acquisition variable resonance image combination selective (MAVRIC-SL), and isotropic MAVRIC-SL (iso MAVRIC-SL), in evaluating the intervertebral foramen and spinal canal in patients after lateral lumbar interbody fusion (LLIF).Methods:Totally 30 patients after LLIF were enrolled prospectively from May to June 2020 in the Second Hospital of Shanxi Medical University. The patients underwent MRI of the lumbar spine including sagittal MAVRIC-SL and iso MAVRIC-SL sequence three-dimensional volume imaging, and the axial spinal canal level images were reconstructed. FSE sequence sagittal T 1WI and axial T 2WI images were acquired simultaneously. The sagittal and axial images were subjectively graded for visualization of the intervertebral foramen and spinal canal. The artifact area and SNR were measured. The Friedman M test was used to compare the differences in image quality scores, artifact area and SNR among the three sequences. Results:Nonparametric test results showed significant differences in sagittal and axial image quality scores among the three sequences (both P<0.001). Sagittal image quality scores of MAVRIC-SL [4 (4, 4) points] and iso MAVRIC-SL [4 (4, 4) points] were higher than those of FSE T 1WI sequence [3 (3, 3) points, both P<0.001]. The quality scores of MAVRIC-SL and iso MAVRIC-SL showed no significant differences ( P=1.000). The axial image quality score of iso MAVRIC-SL[5 (5, 5) points] were higher than those of MAVRIC-SL [4 (4, 4) points] and FSE T 2WI [3 (3, 3) points, both P<0.05]. The iso MAVRIC-SL images enabled a significantly improved reduction in the artifact area and SNR compared to the MAVRIC-SL and FSE sequence (all P<0.05). Conclusion:The iso MAVRIC-SL acquisitions enhance visualization of the intervertebral foramen and spinal canal and decrease metal artifacts compared with MAVRIC-SL and FSE acquisitions.
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Photoacoustic imaging (PAI) is a rapidly developing hybrid biomedical imaging technology, which is capable of providing structural and functional information of biological tissues. Due to inevitable motion of the imaging object, such as respiration, heartbeat or eye rotation, motion artifacts are observed in the reconstructed images, which reduce the imaging resolution and increase the difficulty of obtaining high-quality images. This paper summarizes current methods for correcting and compensating motion artifacts in photoacoustic microscopy (PAM) and photoacoustic tomography (PAT), discusses their advantages and limits and forecasts possible future work.
Subject(s)
Artifacts , Microscopy , Motion , Photoacoustic Techniques , Tomography, X-Ray ComputedABSTRACT
Aim of Study: The goal of this research was to investigate if application of optimized imaging parameters, recommended in literature, would be effective in producing the image quality required for treatment planning of spinal radiation fields with metallic implants. Materials and Methods: CT images from an anthropomorphic torso phantom with and without spinal implants were acquired using different imaging protocols: raising kVp and mAs, reducing the pitch and applying an extended CT scale (ECTS) technique. Profiles of CT number (CT#) were produced using DICOM data of each image. The effect of artifact on dose calculation accuracy was investigated using the image data in the absence of implant as a reference and the recommended electron density tolerance levels (Δρe). Results: Raising the kVp was the only method that produced improvement to some degree in CT# in artifact regions. Application of ECTS improved CT# values only for metal. Conclusions: Although raising the kVp was effective in reducing metallic artifact, the significance of this effect on Δρe values in corrected images depends on the required tolerance for treatment planning dose calculation accuracy. ECTS method was only successful in correcting the CT number range in the metal. Although, application of ECTS method did not have any effect on artifact regions, its use is necessary in order to improve delineation of metal and accuracy of attenuation calculations in metal, provided that the treatment planning system can use an extended CT# calibration curve. Also, for Monte Carlo calculations using patient's images, ECTS-post-processed-CT images improve dose calculation accuracy for impure metals
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BACKGROUND: CT scan and differential modeling are used to analyze the fracture end, which is an effective method to judge the degree of bone healing. To obtain the high precision of differential modeling and simulation, how to select the optimal CT scanning parameters needs further research and analysis. OBJECTIVE: To compare the effects of different CT scanning parameters on modeling accuracy in personalized differential modeling analysis, to verify the accuracy and effectiveness of personalized differential modeling in the reduction of simulated target bone segments, and to explore the research value of this method in judging the degree of bone healing of long canals of lower extremities. METHODS: The model of internal fixation was established with porcine femur. Four groups of 80 kV-300 mA (group A-low dose), 120 kV-335 mA (group B-automatic tube current control system), 140 kV-300 mA (group C-manual setting comparison) and 140 kV-80 mA (group D-high kV and low mA) were used to scan the same object with the same pitch, slice thickness and environment. The scanning data of each group were selected, the same CT value range was used, and the differential modeling analysis method was used to model the target bone segment. The average area and maximum area of metal artifacts in CT scanning images, the average CT value, volume and maximum wall thickness peak after differential modeling analysis, the radiation amount under four groups of scanning conditions were compared to determine the reduction of metal artifacts, modeling accuracy and radiation, so as to select the optimal CT scanning parameters. RESULTS AND CONCLUSION: (1) Artifact measurement method results: In group A, there were many metal artifacts, which obviously obstructed bone tissue, and had a possibility of missed diagnosis. In group D, there were minimal metal artifacts, less occlusion around bone tissue, but poor image contrast and high fog. The difference between group B and group C lay in the clarity of images, and the accuracy of diagnosis was basically the same. Therefore, the order of artifact size was as follows: group A > group B > group C > Group D. (2) Differential modeling analysis results: In group B, because of the smaller artifact and less loss of CT value, the simulated model was more close to the reality. Moreover, group B adopted the automatic tube current control system, which could obviously show that the radiation amount was smaller and more protective for patients. (3) It is confirmed that the CT scan under the condition of group B can effectively reduce the interference caused by metal artifacts, better retain the original information of CT gray value, and retain the density information of the target bone segment to the maximum extent. Therefore, when establishing differential modeling, the CT automatic tube current control system is used as the optimal CT scanning parameter, which not only improves the simulation accuracy of personalized differential modeling, but also increases the accuracy of calculation.
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OBJECTIVE: To demonstrate that human visual illusion can contribute to sub-endocardial dark rim artifact in contrast-enhanced myocardial perfusion magnetic resonance images.MATERIALS AND METHODS: Numerical phantoms were generated to simulate the first-passage of contrast agent in the heart, and rendered in conventional gray scale as well as in color scale with reduced luminance variation. Cardiac perfusion images were acquired from two healthy volunteers, and were displayed by the same gray and color scales used in the numerical study. Before and after k-space windowing, the left ventricle (LV)-myocardium boarders were analyzed visually and quantitatively through intensity profiles perpendicular the boarders.RESULTS: k-space windowing yielded monotonically decreasing signal intensity near the LV-myocardium boarder in the phantom images, as confirmed by negative finite difference values near the board ranging −1.07 to −0.14. However, the dark band still appears, which is perceived by visual illusion. Dark rim is perceived in the in-vivo images after k-space windowing that removed the quantitative signal dip, suggesting that the perceived dark rim is a visual illusion. The perceived dark rim is stronger at peak LV enhancement than the peak myocardial enhancement, due to the larger intensity difference between LV and myocardium. In both numerical phantom and in-vivo images, the illusory dark band is not visible in the color map due to reduced luminance variation.CONCLUSION: Visual illusion is another potential cause of dark rim artifact in contrast-enhanced myocardial perfusion MRI as demonstrated by illusory rim perceived in the absence of quantitative intensity undershoot.
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Objective: To investigate the metal artifact reduction effect of orthopedic metal artifact reduction (O-MAR) techonology and its improvement effect on the image quality in CT examination in the patients with arthroplasty, and to elaborate the significance of the technology in clinical diagnosis and treatment of arthroplasty. Methods: The CT data of 20 patients with hip or knee prostheses was collected. There were two tube voltages in each group of CT data : 120 and 140 Kev. There were also two groups of CT data in each tube voltage group: Non- O-MAR group and O-MAR group; there were four subgroups of CT data of each case: 120 Kev/ O-MAR. 120 Kev/ + 0-MAR, 140 Kev/ O-MAR, 140 Kev/ + 0-MAR. After data collection. Mimics software was applied to conduct three-dimensional (3D) reconstruction for purpose of the qualitative and quantitative analysis of CT data. Qualitative analysis mainly included the grade of severity of metal artifact and quality of data. Quantitative analysis included the volume of metal artifact, the average CT value and standard deviation (SD) in region of interest (KOI). ROI 1 and ROI 2 were chosen at the location of beam hardening artifact (radial high-density metal artifact) and photon starvation artifact (band low-density metal artifact), respectively. Results: According to the result of 3D measurement, the volumes of artifact had no significant difference between 120 Kev/ O-MAR group and 140 Kev/O-MAR group (P=0.062) but there were siginificant differences in the volumes of artifact between other groups (P<0. 05); OMAR technology decreased the volume of beam-hardening artifact obviously ( P< 0.05). According to the results of two-dimensional (2D) measurement, there was no significant difference in the average CT values in ROI 2 between 120 Kev/ O-MAR group and 140 Kev/ OMAR group (P= 0.069), but there were significant differences in the average CT values between other groups ( P
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Objective To study the adverse effect of mirror artifacts generated from the specular reflection of trachea wall on microwave ablation (MWA) treatment of thyroid nodules and the causes. Methods Perioperative ultrasound imaging data of 304 patients who received MWA of thyroid nodules in Shanghai International Medical Center from Jan. 2018 to Oct. 2018 were systemically studied. The occurrence rate, sources, acoustic characteristics of the mirror artifacts and the adverse effects of mirror artifacts on MWA were summarized. The factors contributing to specular reflection of trachea were analyzed. Results A total of 169 cases (55.59%) presented tracheal mirror reflection artifacts in this study. The sources of mirror artifacts included thyroid nodules (20 cases, 11.83%), injection needle (133 cases, 78.70%), ablation electrode (16 cases, 9.47%), hydro-dissection zone (137 cases, 81.07%), and remote ablated area of thyroid nodule (8 cases, 4.73%). We also found that 88.17% (149/169) of mirror artifacts were during the MWA operative period. Conclusion Mirror artifacts generated from the specular reflection of trachea wall are commonly seen in the perioperative period of thyroid nodule MWA. Lesion close to the trachea, flattened tracheal wall, and flat interface linearity larger than the real source dimension are the important causes of mirror artifacts. Direct compression on the tracheal wall caused by thyroid nodules, ablated areas and hydro-dissection zone are the main causes of flattened tracheal wall.
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Objective@#To investigate the effect of simple artifacts on the calculation of radiation dose in actual clinical operations by the aid of artificially caused CT artifacts.@*Methods@#The phantom was scanned using CT before and after replacing the titanium alloy component. Then, the CT values were measured at different distances before and after replacement. After correcting the CT value of the titanium alloy region to the CT value of the water phantom, the doses to the phantom were calculated by using Varian′s AAA algorithm, AXB algorithm and Pinnacle system′s CCC algorithm. The absolute dose values at different distances were furtherly analyzed.@*Results@#Varian system was consistent with Pinnacle system in evaluating the CT values. When the CT value deviated by less than 30 HU for a uniform phantom, the dose deviations of the three different algorithms were within 6.0 %-12.0 % at a distance of 0.5 cm from the body surface, and less than 1.0% at a distance of more than 1.5 cm from the body surface. When the CT value deviated by 15 HU for the lung phantom, both Varian′s AAA algorithm and Varian′s AXB algorithm showed about 1.0% dose deviation. However, the CCC algorithm of the Pinnacle system had a significant difference (5.0%) in dose values under the same conditions.@*Conclusions@#CT artifacts have noticeable effects on the calculation of radiation dose and change tissue dose distribution which may result in insufficient or excessive exposure doses.
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Objective@#To explore the mechanism and influencing factors of mirror-image artifact of color blood flow (MACBF) due to longitudinal strong echo big interface (LSEBI).@*Methods@#Fifty suspicious patients with MACBF beside the main pulmonary artery and/or the left pulmonary artery undergoing echocardiography examination from November 2018 to April 2019 in Shengjing Hospital of China Medical University were chosen as the subjects. Image characteristics of the MACBF were observed, and mechanism and influence factors of the MACBF were explored with Doppler imaging principle.@*Results@#Of all the subjects with MACBF, 36 subjects occurred only on the left side of the main pulmonary artery, 14 subjects occurred on both the left side of the main pulmonary artery and the left pulmonary artery. The LSEBI was found between the real color blood flow (RCBF) and the MACBF, there was a mirror relationship between the RCBF and the MACBF. The LSEBI on the left of the main pulmonary artery and the left pulmonary artery were the interface of the left lung and pleural. The signal strength of MACBF enhanced as the distance between the blood flow and the LSEBI got closer or the gain of the color blood flow got bigger.@*Conclusions@#MACBF may caused by LSEBI beside vessel. The formation of MACBF and its signal strength are influenced by the distance between blood flow and LSEBI and the gain of the color blood flow.
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Objective To preliminarily investigate the optimum scheme of thyroid CT flat scanning plan,to reduce the artifacts and the radiation dosage.Methods Patients who were involved in this research with thyroid CT flat scanning were divided into three groups:group A (conventional scan group),group B (dosage- reduced group)and group C (a combination of body posture change and dosage reduction).In group A (50 patients),the patients’bilateral arms were naturally drooped on both sides of the body during scanning (scan parameters:120 kV,250 mA).In group B (50 patients),the patients were scanned under the same circumstance with group A,but difference in scanning condition (scan parameters:100 kV,280 mA).In group C (50 patients),the patients kept one arm rise upward,another arm reach firmly toward the contralateral iliac bone during CT scan(scan parameters:100 kV,250 mA).CT attenuations,noise and SNR values around the soft tissue of thyroid gland,which was in the most severe thyroid artifacts (seventh cervical vertebrae to the first thoracic vertebrae level),were measured among the three groups.Meanwhile,the patient’s dose length product (DLP)and effective dosage (ED)were calculated.The images of the three groups were measured by double-blind method,i.e. severe artifacts,moderate artifacts,mild artifacts,and no artifacts.Results The image quality in group C was significantly higher than that of group A and group B (P＜0.05).There was no difference in subj ective quality between group A and group B (P＞0.05).The CT and noise values of group C were better than those of group A and group B (P＜0.05),while the radiation dosage was lower than that of group A and group B (P＜0.05).Conclusion When the thyroid CT scan is performed with the unilateral limb lifting and the other arm extending to the contralateral iliac bone,the thyroid band artifacts can be effectively reduced and decreasing the kV can reduce the radiation dosage.
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Objective To explore the mechanism and influencing factors of mirror-image artifact of color blood flow (MACBF) due to longitudinal strong echo big interface (LSEBI).Methods Fifty suspicious patients with MACBF beside the main pulmonary artery and/or the left pulmonary artery undergoing echocardiography examination from November 2018 to April 2019 in Shengjing Hospital of China Medical University were chosen as the subj ects.Image characteristics of the MACBF were observed, and mechanism and influence factors of the MACBF were explored with Doppler imaging principle.Results Of all the subjects with MACBF,36 subjects occurred only on the left side of the main pulmonary artery,14 subj ects occurred on both the left side of the main pulmonary artery and the left pulmonary artery.The LSEBI was found between the real color blood flow (RCBF) and the MACBF,there was a mirror relationship between the RCBF and the MACBF.The LSEBI on the left of the main pulmonary artery and the left pulmonary artery were the interface of the left lung and pleural.The signal strength of MACBF enhanced as the distance between the blood flow and the LSEBI got closer or the gain of the color blood flow got bigger.Conclusions MACBF may caused by LSEBI beside vessel.The formation of MACBF and its signal strength are influenced by the distance between blood flow and LSEBI and the gain of the color blood flow.
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The hardware and software faults in the image guidance system may cause ring-shaped artifacts,which is more commonly induced by the aging of the hardware.During troubleshooting,the first step should be checking whether there are obvious faults in the basic hardware.Subsequently,OBI background image is collected to confirm the bad point status.If the bad point is not shielded,it can be compensated by updating the image processing bad point.The invoked Pixel Correction Maps are adopted compensate for the bad point and calibrate the image.If it is still unable to repair,replacing the detection board can be considered.Cone-beam CT (CBCT) image guidance system is an important approach to verify the position orientation and positioning accuracy in modem radiotherapy,which effectively guarantees for the safety and accuracy of radiotherapy.We should fully understand its law of aging,maintain the equipment on a regular basis and verify the image quality to ensure the normal operation of the equipment.