جستجوی مقالات مرتبط با کلیدواژه « artifacts » در نشریات گروه « پزشکی »

A bone scan was performed on a 69-year-old man with small cell lung carcinoma (limited stage) following 2nd course of adjuvant chemotherapy using etoposide and cisplatin demonstrating extra-osseous tracer accumulation in the right lower abdominal cavity originally thought to be in the ascending colon, was proven to be an ectopically located gallbladder extending to the right lower quadrant (RLQ). Otherwise, the bone scan did not show abnormal skeletal uptake. The precise reason for gallbladder excretion of [99mTc]Tc-MDP derivatives is unknown. None of the other patients injected with the same [99mTc]Tc-MDP kit demonstrated any gallbladder or other abnormal soft tissue tracer accumulation. In the interpretation of non-osseous uptakes in the right abdominal cavity, ectopic and/or abnormal shaped gallbladder should be taken into consideration.

Myocardial perfusion imaging (MPI) is a valuable diagnostic tool for the diagnosis of coronary artery disease (CAD) and is susceptible to a variety of artifacts, which degrade image quality and decrease diagnostic accuracy. Pitfalls and Artifacts in nuclear medicine imaging are not rare and could be classified into issues related to patients, equipment, and technologist. One of these artifacts is unstable PMT gain, which is rare and related to equipment. It is crucial for nuclear physicians to be aware of potential artifacts and their potential effect on image quality. This knowledge helps them to prevent or correct these artifacts if possible and if not, consider the potential effect of these artifacts on image pattern and quality. Some of these artifacts are preventable by routine quality control procedures, but some other artifacts may occur regarding quality control procedures. Three different female subjects 55, 57, and 61 years old with a history of atypical chest pain were referred to our department for myocardial perfusion imaging. MPI was performed according to standard protocols and stress, and rest phases were done. These three cases had different patterns of perfusion abnormalities due to interruption of count detection for a few seconds in some frames during acquisition that was due to voltage drop that leads to unstable PM tube gain. Systematic errors due to voltage drops are not common, and they are not routinely sort of suspicion to artifactual perfusion abnormalities but they may cause misinterpretation of reports of MPI, and we should be aware of them.

 This study assessed the dimensional distortion of four types of intracanal posts on cone-beam computed tomography (CBCT) scans with two different fields of view (FOV) in high and standard resolution modes.

This in vitro study evaluated 40 extracted single-rooted maxillary central incisors that underwent root canal treatment. The teeth were randomly assigned to 4 groups (n=10) for placement of non-tapered brass, silver, titanium and stainless steel (SS) intracanal posts. The diameter of the posts was measured at two reference points by a digital caliper (gold standard). The teeth underwent CBCT with 8 x 8 and 8 x 12 cm FOV with high and standard resolution modes. The post diameters were measured on axial CBCT images at the same reference points and compared with the gold standard. Data were analyzed by ANOVA, and paired and independent sample t-test.

Significant differences were noted between the radiographic diameter of the posts and their actual size (P<0.05). Titanium posts (40.25%) showed minimum percentage of dimensional distortion followed by brass (54%), silver (62.5%) and SS (70.17%) posts. High-resolution images with 8 x 8 cm FOV yielded minimum dimensional distortion (40.6%) followed by high-resolution images with 8 x 12 cm FOV (45.75%), standard-resolution images with 8 x 8 cm FOV (68.75%), and standard-resolution images with 8 x 12 cm FOV (72.1%).

All metal posts showed significant dimensional distortion on CBCT scans, irrespective of the FOV size and resolution mode. SS posts yielded maximum, and titanium posts showed minimum dimensional distortion.

Metal artifacts are the major weak points of cone-beam computed tomography (CBCT) scans. This study aimed to quantify the amount of metal artifacts generated by dental implants placed in different anatomical locations in the mandible on CBCT scans.

In this study, 98 CBCT scans of mandibular dental implants with prosthetic crowns were randomly selected irrespective of the age and gender of the patients. Of all 98 implants, 42 were placed in the anterior mandible and 56 were placed in the posterior mandible. The samples were divided into two groups of single and multiple implants. The CBCT scans of each implant were evaluated in apical and cervical cross-sections. The amount of metal artifacts generated around the implants was calculated. Data were analyzed using the Mann-Whitney U test at 0.05 level of significance.

Higher amounts of artifacts were noted in the anterior mandible compared to the posterior mandible. Additionally, the amount of artifacts was higher in the cervical cross-section than in the apical cross-section. The difference in the amount of artifacts generated in the cervical cross-section was significant between single and multiple implants (P<0.05). However, this difference was not significant in the apical cross-section (P>0.05).

Dental implants always generate metal artifacts on CBCT scans, and the amount of generated artifacts is influenced by the anatomical location of implants in the mandibular arch.

‘Field of view (FOV) size’ affects the quality of radiographic images and the radiation dose received by patients. In cone-beam computed tomography (CBCT) FOV should be selected according to therapeutic purposes. While aiming for the highest diagnostic image quality, the radiation dose should be kept to a minimum to reduce the risk for patients. The purpose of this study was to assess the effect of different sizes of FOV on contrast-to-noise ratio (CNR) in five different CBCT units.

In this experimental study, CBCT scans were taken from a dried human mandible containing a resin block fixed to the lingual cortex and a resin ring was used to simulate soft tissue during scans. Five CBCT units including, NewTom VGi, NewTom GiANO, Soredex SCANORA 3D, Planmeca ProMax, and Asahi Alphard 3030 were evaluated. Each unit had 3 to 5 different FOVs. Images were obtained and analyzed with ImageJ software and CNR was calculated in each image. ANOVA and T-test were used for statistical analysis (P<0.05).

Comparison among different FOVs of each unit showed significant CNR reductions in small FOVs (P<0.05). Similar FOV sizes of different CBCT devices were also compared and demonstrated significant differences (P<0.05).

A direct relationship between FOV size and CNR was observed in all five CBCT units, but differences in exposure parameters of these units led to variable CNR in FOVs with similar sizes.

Several computer-aided diagnosis systems for depression are suggested for use by clinicians to authorize the diagnosis. EEG may be used as an objective analysis tool for identifying depression in the initial stage to avoid it from reaching a severe and permanent state. However, artifact contamination reduces the accuracy in EEG signal processing systems.

This work proposes a novel denoising method based on Empirical Mode Decomposition (EMD) ( with Detrended Fluctuation Analysis (DFA) and wavelet packet transform. Initially, real EEG recordings corresponding to depression patients are decomposed into various mode functions by applying EMD. Then, DFA is used as the mode selection criteria. Further Wavelet Packets Decomposition (WPD)-based evaluation is applied to extract the cleaner signal. 

Simulations were conducted on real EEG databases for depression to demonstrate the effects of the proposed techniques. To conclude the efficacy of the proposed technique, SNR and MAE were identified. The obtained results indicated improved signal-to-noise ratio and lower values of MAE for the combined EMD-DFA-WPD technique. Additionally, Random Forest and SVM (Support Vector Machine)-based classification revealed the improved accuracy of 98.51% and 98.10% for the proposed denoising technique. Whereas the accuracy of the EMD- DFA is 98.01% and 95.81% and EMD combined with DWT technique equaled 98.0% and 97.21% for the EMD- DFA technique for RF and SVM, respectively, compared to the proposed method. Furthermore, the classification performance for both classifiers was compared with and without denoising to highlight the effects of the proposed technique.

Proposed denoising system results in better classification of depressed and healthy individuals resulting in a better diagnosing system. These results can be further analyzed using other approaches as a solution to the mode mixing problem of the EMD approach.

Myocardial perfusion SPECT is one of the most common imaging techniques performed in nuclear medicine departments. To avoid misleading interpretation, it is necessary to address the quality control and technical problems. The truncation artifact occurs when the patient size is large relative to the field of view of the camera, causing false perfusion defects in the LV myocardium, misinterpreted as myocardial perfusion abnormality. It usually happens in obese patients, who may deviate from the detector field. Here, we present a skinny patient showing myocardial truncation artifact, proved to be because of technical issues.

Artifact refers to an artificial or replaced structure in histopathological slides as a result of an extraneous factor. Given the influence of identification and awareness of the types of artifacts on the correct diagnosis, the frequency of artifacts in oral and maxillofacial histopathological slides was assessed.

In this cross-sectional study, census method was used to assess 119 oral and maxillofacial histopathological slides retrieved from the archive of Zanjan Dental School from 2015 to 2017. Artifacts were divided into three groups arising from the surgeon’s performance, technician’s performance, and specimen transfer to the laboratory. Statistical analysis of data was performed using an independent t test in SPSS software version 18.0.

The average numbers of artifacts arising from the surgeon’s performance, technician’s performance, and specimen transfer to the laboratory were 3.90±1.14, 3.08±1.10, and 0, respectively. The mean number of artifacts arising from the surgeon’s performance was significantly higher compared to the other two groups (P<0.01) and the most common ones included fragmentation, split, and tear. The most common artifacts arising from the technician’s performance were fold/wrinkle, chaffer, and floater. There was no artifact arising from specimen transfer to the laboratory.

The results indicated a high frequency of various artifacts in the studied slides. Therefore, paying more attention to slide preparation protocols and proficient performance during the biopsy procedure as well as further cooperation between the surgeon, pathologist, and laboratory technician can be useful in reducing the frequency of artifacts and achieving a better diagnosis.

Different materials cause artifacts in cone-beam computed tomography (CBCT) images, which, in turn, reduce the quality of images. The aim of this study was to investigate the abundance of artifacts induced by different root canal therapy sealers with two different CBCT resolutions.

Roots of four maxillary central phantom teeth were prepared using rotary files in three steps. In the first step, the first tooth was scanned first without gutta-percha and then with gutta-percha No. 25. Gutta-percha No. 25 with resin, the zinc oxide-eugenol (ZOE)-based sealer and the ceramic-based sealer were placed in the teeth No. 2, 3 and 4, respectively. The second step was performed similar to the first step, except that gutta-percha No. 35 was used in the tooth No. 1 with resin- and ZOE-based sealers in the teeth No. 2 and 3. due to the lack of access to the ceramic-based sealer that was not used to continue the study . In the third step, canal obturation was performed in the teeth No. 2 and 3 with resin and ZOE-based sealers. At each step, three CBCT scans were obtained in high and standard resolution conditions. Contrast-to-noise ratio was obtained in three root plans, and the data were analyzed.

Gutta-percha alone produced more artifacts than gutta-percha with sealers. Moreover, ZOE-based sealers induced more artifacts than other sealers. There was no significant difference between the three steps. Similarly, at different resolutions, there was no significant difference between gutta-percha and sealer artifacts. The ZOE-based sealers had more artifacts at 1/3 apical whereas resin sealers had more artifacts at 1/3 coronal.

The higher artifact of gutta-percha in comparison with gutta-percha and sealer and the artifact decrease in the combination of gutta-percha and resin-based sealer than ZOE-based sealer has led us to recommend the use of resin-based sealer while root canal therapy in order to better evaluation of the CBCT Images of root canal.

To identify and explain different artifacts in macular optical coherence tomography (OCT).

For this comprehensive review, a PubMed and Google Scholar (January 1995–October 2018) search was conducted by the researchers, using the keywords such as OCT, artifacts, artefact, and macula.

We reviewed the main OCT artifacts including software break‑down or misidentification of retinal layers, incomplete segmentation error, complete segmentation failure, mirror artifact (inverted artifact), cut edge artifact, degraded image scan, out‑of‑register artifact, off‑center artifact, motion artifact, foveal duplication, segmentation shift, blink artifact, static or fixed image artifact, linear artifact, and perfluorocarbon liquid‑producing artifact.

There are various artifacts in OCT image scans. The identification of these artifacts may help in accurate interpretations of OCT images in clinical settings that can affect the diagnosis and management of different retinal disorders.

To assess the effect of night shift work on image quality and artifacts when performing optical coherence tomography angiography (OCT-A).

In a prospective case series study, twenty nurses underwent OCT-A in two separate sessions: early in the morning before duty shift and at the end of a night shift. Quantitative measurements of horizontal and vertical saccadic, blink, and stretch artifacts and also signal strength of the images were recorded. Moreover, using visual analogue scale of pain (VAS), the perceived pain and discomfort by blue focus light and red scanning laser were recorded.

Vertical and horizontal saccades, blink, and stretch artifacts were significantly higher after the night shift (P = 0.004, P = 0.015, P < 0.001, and P < 0.001, respectively). Signal strength was not significantly different between the two measurements (P = 0.71). Also, the level of discomfort which was experienced by blue focus light and red scanning laser light was significantly higher after the night shift (P = 0.009 and P = 0.004, respectively).

Our study suggests that night shift may affect image quality of OCT-A by imposing more artifacts.

Cone-beam computed tomography (CBCT) is one of the most important diagnostic tools in maxillofacial imaging. Nowadays different sealers are used in root canal therapy and some of them can create artifact in CBCT images. The aim of this study was to evaluate the effect of different sealers including AH-26, Diadent, and Anyseal in creation of artifact bands in the CBCT images based on voxel size. Methods and Materials: A total of 44 single rooted extracted teeth were selected. The canals were prepared by crown-down technique. All teeth were manually filed up to master apical file (MAF) size 45 and 1 mm shorter than the apical foramen. The teeth were divided into 4 equal groups. The canals were filled with gutta-percha and either of sealers AH-26, Diadent or Anyseal by lateral condensation technique. The control group were filled just with gutta-percha without any sealer. The CBCT images were taken in voxel sizes of 0.3 and 0.15. The Fisher exact and McNemar tests were used for statistical analysis. Although, the control group had the lowest ratio of presence to absence of artifact, the ratio of presence to absence of artifact in voxel size of 0.3 and 0.15 mm were significantly lower in Anyseal than AH-26 (P=0.031, P=0.020) and Diadent (P=0.001, P=0.002). No significant difference was detected between two voxel sizes (P>0.05). In this in vitro study, all evaluated sealers induced artifacts in the CBCT images. Anyseal sealer had the lowest artifact in both evaluated voxel sizes.

The aim of this study was to determine the impact of fixture location and crown restoration on the accuracy of linear measurements by two cone-beam computed tomography (CBCT) systems.

Six dental implants were inserted in a dry human mandible in two stages. CBCT images were obtained in each stage by Alphard VEGA 3030 and Promax 3D Max systems. Imaging procedures were repeated after metallic crown placement. Two observers measured the alveolar height and width using five radiopaque markers. Values were compared to the same measurements made on initial images (prior to implant insertion) using t-test. The linear regression test was used to evaluate the effect of implant location on the accuracy of linear measurements.

The impact of fixture and fixture-crown combination on the accuracy of linear measurements of height (t = -5.2, P=0.0001 and t=-5.98, P<0.0001, respectively) and width (t=-3.42, P=0.004 and t= -2.7, P=0.015, respectively) was significantly underestimated. Metal crowns had no significant effect on measurements of bone height and width (t=-1.38, P=0.19 and t=0, P=1.00, respectively). Although both systems showed some underestimations, Promax 3D Max underestimated bone width significantly more than the other system (Alphard VEGA 3030=- 0.51mm and Promax 3D Max=-0.80). Regarding implant location, the measurements in the canine sites were found to be more accurate than the region between adjacent implants.

CBCT is an accurate and reproducible system for dental implant follow-up examinations. Metal artifacts can lead to underestimation of measurements. However, this was not statistically significant in our study.

Geometric errors in images called image distortion are one of the main problems in magnetic resonance imaging, including 3D imaging, measuring blood flow velocity, functional imaging and treatment planning in radiation therapy. The geometric distortion in MRI images is due to the non-uniformity of the magnetic field and nonlinearity of gradients. In this study, the accuracy and the repeatability of the images were evaluated respectively by phantom measuring and repeating the measurements in the phantom and then we correct these geometric errors.
The magnetic resonance imaging of the phantom was performed on the 3 Tesla Siemens Prisma Model to measure the geometric distortion using the network pattern. The spin echo protocol was repeated three times with T1, T2 and PD weightings to measure the repeatability of image distortion. Image distortion was evaluated by measuring the distance between the edges using a MATLAB program. Furthermore, non-uniformity of the magnetic field and the nonlinearity of the gradients were examined using appropriate phantoms.
The average error obtained in the 25 cm field of view was 1 pixel in both directions x and y (each pixel was 1.024 mm). Given the images by phantom, the device gradient was linear. Furthermore, considering the B1 and B0 fields’ measurements, the B0 of the device was 0.3125 ppm over a 24 cm DSV (diameter of spherical volume).
Since the brain coil displacement was 1 pixel, the device could be used in 3DMRI, velocity MRI, FMRI and RTTP.

Introdouction:One of the reasons that cause a pathologist to make an incorrect diagnosis includes artifacts leading to tissue changes and artificial structures in microscopic slides. The aim of this study was to examine the artifacts in histopathological slides in Zahedan School of Dentistry.
In this cross-sectional study, all the available slides in Oral and Maxillofacial Pathology Archive at the School of Dentistry during 1999–2015 were evaluated for existing artifacts. The artifacts found in the slides were divided into the following three categories: 1) caused by a surgeon’s performance, 2) resulting from sample transfer to laboratory, and 3) arising from a technician’s performance. Then, the frequency of each type of artifact was calculated in numbers and percentages and analyzed with the proportions of two populations test.
All the 658 histological slides contained artifacts. Moreover, 96.5% of the artifacts were associated with a technician’s performance, and 90.4% were associated with a surgeon’s performance. The proportion of difference between the two types of artifacts was statistically significant (P value = 0.001). The most common artifacts resulting from technicians’ performances included formalin pigmentation, folding, and bubble. However, the most common artifacts resulting from surgeons’ performances were split, crush, and hemorrhage.
The results of this study indicated that there was a high frequency of artifacts in oral histological slides. Retraining courses seemed to be helpful for practitioners involved in preparation of slides, in addition to increased cooperation of surgeon–pathologist, which can reduce the risk of artifacts.

The aim of this study was to assess the effect of tube current, kilovoltage peak (kVp), metal type, and the position of metal objects on metal artifacts in cone-beam computed tomography (CBCT) images.
Titanium and cobalt-chromium rods were fabricated and placed in a dry human mandible. Samples were scanned using a Promax 3D CBCT unit with different milli-amperages and kVp. The artifacts induced by metal objects were evaluated using the Image J software in four regions of interest (ROIs) on each image.
A higher kVp decreased artifacts of the buccal surface of the rods in 97% of the cases (P=0.046) but did not affect the severity of artifacts between the two metal objects (P>0.05). Increasing the tube current had no effect on metal artifacts in 93% of the cases (P>0.05). Artifacts induced by a cobalt-chromium alloy were more severe than those with titanium (P Tube voltage, metal type and the position of metal objects affected the severity of metal artifacts on CBCT images. The metal type had the greatest effect on metal artifact intensity in this study.

Bidimensional radiographic methods, including periapical, occlusal, panoramic, and cephalometric radiographs, are widely used in dentistry. However, the superimposition of adjacent structures and consequent loss of anatomic details may occur. The purpose of this study is to evaluate the artifacts produced by different cements with different densities using cone-beam computed tomography (CBCT). Samples of five cements with different densities including glass ionomers (or GI, from ChemFil Rock and Fuji IX), mineral trioxide aggregates (MTA), zinc oxide eugenol (ZOE), TempBond and a control sample (polyester) were scanned by CBCT device and analyzed using OnDemand 3D application software. The amount of artifacts was measured by ∆ gray scale value (∆GSV), which was achieved by subtracting the gray level of the samples from the control group. According to the mean GSV of the five different materials, the majority of artifacts produced were as follows: TempBond > ZOE > MTA > GI (ChemFil Dentsply) > GI (GC, Fuji ΙX). The type of materials can influence the obtained GSV. Different materials cause various amounts of artifacts due to differences in density and atomic number.

Subdiaphragmatic activity can produce subdiaphragmatic-related artifacts, which can degrade the quality of myocardial perfusion imaging (MPI).. We examined the impact of drinking milk, water, and lemon juice on different subdiaphragmatic-related artifacts by using 99mTc-sestamibi myocardial single-photon emission computed tomography (SPECT) in order to determine a feasible method for improving the image quality..Patients and A total of 179 patients (age 58 ± 9.6 years) were enrolled in this study. The patients were randomly divided into five groups. Ten minutes after injection of 740 MBq 99mTc-sestamibi in both pharmacologic stress and rest phases, the individuals in group 1 were given water and milk (125 mL of each); those in group 2 were given lemon juice (250 mL); group 3 was given milk (250 mL); and group 4 was given water (250 mL), whereas no intervention was performed in group 5. The study was double-blind for both subjects and data collectors. MPI was performed for all patients and image quality was controlled by 2 experienced nuclear physicians. Interfering activity was determined visually on reconstructed images and categorized as extracardiac normalization artifact, overlapping of activity, scattering of activity, and ramp filter artifact.. There were significant differences in terms of interfering activity among the five groups; group 3 (milk) had significantly lower interfering activity than other groups had, as defined by overlapping of activity (on both stress and rest images), ramp filter artifact (stress images), and scatter artifact (rest images) (P < 0.05). Furthermore, there was a significant difference in the incidence of good-quality images, with no interfering activity in group 3 in the resting state compared with the other groups in the study (P < 0.05).. Drinking 250 mL of milk in either the stress phase or the rest phase of imaging diminishes interfering subdiaphragmatic-related artifacts, particularly overlapping of activity in MPI SPECT, resulting in better-quality images..