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At least 739 records · Page 41Linked to original sources
PubMed1997

The comet-tail artifact. An ultrasound sign of alveolar-interstitial syndrome.

Can ultrasound be of any help in the diagnosis of alveolar-interstitial syndrome? In a prospective study, we examined 250 consecutive patients in a medical intensive care unit: 121 patients with radiologic alveolar-interstitial syndrome (disseminated to the whole lung, n = 92; localized, n = 29) and 129 patients without radiologic evidence of alveolar-interstitial syndrome. The antero-lateral chest wall was examined using ultrasound. The ultrasonic feature of multiple comet-tail artifacts fanning out from the lung surface was investigated. This pattern was present all over the lung surface in 86 of 92 patients with diffuse alveolar-interstitial syndrome (sensitivity of 93.4%). It was absent or confined to the last lateral intercostal space in 120 of 129 patients with normal chest X-ray (specificity of 93.0%). Tomodensitometric correlations showed that the thickened sub-pleural interlobular septa, as well as ground-glass areas, two lesions present in acute pulmonary edema, were associated with the presence of the comet-tail artifact. In conclusion, presence of the comet-tail artifact allowed diagnosis of alveolar-interstitial syndrome.

Adolescent↗
PubMed1997

Multifocal brain MRI artifacts secondary to embolic metal fragments.

We report a patient with unusual MRI abnormalities that had the physical characteristics of ferromagnetic artifact. We believe that the MRI artifacts were due to microscopic embolic metal fragments, most likely from a mechanical heart valve prosthesis. Potential sources of metal emboli should be considered in patients with MRI abnormalities compatible with ferromagnetic artifact.

Adult↗
PubMed2004

Artifact in the bispectral index in a patient with severe ischemic brain injury.

UNLABELLED: The electroencephalogram (EEG) has been used to predict neurological outcome in patients with anoxic-ischemic brain injury. The bispectral index (BIS) may be a useful alternative. A persistently low BIS associated with burst-suppression of the raw EEG in the setting of minimal hypnotic drug administration may indicate severe cerebral ischemia. We report a case where a patient with presumed ischemic brain injury and an extremely low BIS had an unexplained increase in BIS that could be attributed to electrocardiogram artifact. Care should be taken when interpreting BIS in the setting of anoxic-ischemic brain injury or brain death. IMPLICATIONS: The bispectral index (BIS) can be prone to artifact. In this report we found that electrocardiogram artifact led to an apparent normal BIS in a patient with complete burst-suppression associated with severe brain injury.

Artifacts↗
PubMed2005

Ki-67 immunoreactivity in the differential diagnosis of pulmonary neuroendocrine neoplasms in specimens with extensive crush artifact.

The aim of the present study was to evaluate the usefulness of immunohistochemical markers in the differential diagnosis of pulmonary neuroendocrine tumors with particular emphasis on the preservation of immunoreactivity in areas showing crush artifacts. Specimens from 9 carcinoid tumors (CTs) and 13 small cell carcinomas (SCCs) with crush artifact were stained with antibodies to Ki-67, chromogranin A, synaptophysin, and cytokeratin. The immunoreactivity was well preserved in the crushed areas. Ki-67 was expressed in the crushed areas of all SCCs. Reactivity was diffuse or at least present in 25% of the crushed areas. In contrast, the immunoreactive areas in CTs never exceeded 10%. Immunoreactivity for Ki-67, synaptophysin, chromogranin A, and cytokeratin is well preserved in tissue with crush artifacts and can be interpreted reliably. The diagnosis of SCC should be questioned if fewer than 25% of cells show reactivity for Ki-67.

Artifacts↗
PubMed2002

Local mean normalization of microarray element signal intensities across an array surface: quality control and correction of spatially systematic artifacts.

Here we present a methodology for the normalization of element signal intensities to a mean intensity calculated locally across the surface of a DNA microarray. These methods allow the detection and/or correction of spatially systematic artifacts in microarray data. These include artifacts that can be introduced during the robotic printing, hybridization, washing, or imaging of microarrays. Using array element signal intensities alone, this local mean normalization process can correct for such artifacts because they vary across the surface of the array. The local mean normalization can be usedfor quality control and data correction purposes in the analysis of microarray data. These algorithms assume that array elements are not spatially ordered with regard to sequence or biological function and require that this spatial mapping is identical between the two sets of intensities to be compared. The tool described in this report was developed in the R statistical language and is freely available on the Internet as part of a larger gene expression analysis package. This Web implementation is interactive and user-friendly and allows the easy use of the local mean normalization tool described here, without programming expertise or downloading of additional software.

Algorithms↗
PubMed1999

Motion artifact seen on slot-scanning direct digital mammography.

OBJECTIVE: Our goal was to determine the appearance of motion artifact when imaging an anthropomorphic breast phantom using a digital slot-scanning system compared with a screen-film system. MATERIALS AND METHODS: Digital and screen-film images were obtained during both brief and continuous manually induced motion of an anthropomorphic phantom in four directions. Continuous motion was further characterized using a syringe pump to induce motion artifact. RESULTS: On screen-film images, brief motion caused degradation of the entire image, simulating a double exposure. Conversely, on digital images using a slot-scanning system, brief motion caused degradation of only a small portion of the image. Continuous motion resulted in smearing of phantom details with both systems, although the smearing was more strongly influenced by the direction of motion when the slot-scanning system was used. With the slot-scanning system, motion in the direction of the detector sweep resulted in elongated distortion, whereas motion in the opposite direction resulted in foreshortening; diagonal smearing was seen with perpendicular phantom motion. The magnitude of distortion for continuous motion at a set velocity was substantially less with the slot-scanning system. CONCLUSION: Motion artifact with a slot-scanning direct digital mammography unit differs significantly from that seen with a conventional screen-film unit and, despite a relatively long overall exposure, may prove to be less of a problem than with conventional units because any given part of an object is exposed only briefly.

Artifacts↗
PubMed2000

Reduction of contrast material dose and artifacts by a saline flush using a double power injector in helical CT of the thorax.

OBJECTIVE: Our objective was to evaluate a combined method of contrast material bolus followed by saline solution flush for thoracic helical CT and statistical comparison with a uniphasic injection protocol. MATERIALS AND METHODS: Fifty patients underwent helical CT of the thorax using 60 ml of contrast material (370 mg I/ml) followed by flushing with 30 ml of physiologic saline solution. These 50 patients had been examined before using our previous protocol, 75 ml of the same contrast material without a subsequent saline solution. Mean attenuation values for both protocols were measured in the superior vena cava, the pulmonary trunk, and the ascending aorta. Image artifacts and mediastinal and hilar depiction were graded and compared. RESULTS: Mean attenuation values in the superior vena cava were considerably higher in the regimen without saline solution flush (459 H versus 352 H) and in the pulmonary trunk and the ascending aorta were almost identical for both protocols. Injection of saline solution diminished surrounding artifacts (p = 0.001). Grading results for the evaluation of mediastinal and hilar structures were not significantly different in the two protocols (p = 0.564). CONCLUSION: Injection of contrast material followed by a saline solution bolus using a double power injector when performing thoracic helical CT allows a 20% reduction of contrast material volume to 60 ml with a similar degree of enhancement. In addition, perivenous artifacts in the superior vena cava are significantly reduced.

Adult↗
PubMed2004

Safety and MRI artifact evaluation at 1.5 T of metallic mounting sheath of a marking clip inadvertently deployed at stereotactic biopsy.

OBJECTIVE: The purpose of our study was to assess the MRI risk factors for the patient after an unusual case of inadvertent deployment of the mounting sheath of a metallic clip used at stereotactic breast biopsy. MATERIALS AND METHODS: We evaluated the materials for ferromagnetic properties, heating, and artifacts. RESULTS: Our analysis showed significant deflection and prominent susceptibility artifacts of the sheath at 1.5 T, although the clip itself showed no deflection and only minimal artifact. Our study shows that a device and its delivery apparatus may have significantly different ferromagnetic properties. CONCLUSION: In case of inadvertent deployment of the sheath, a delay of 6-8 weeks before MRI is recommended as a conservative approach to ensure tissue ingrowth and to minimize the chance of harm to the patient. In the case of metallic clips used for breast biopsy, caution is warranted when a portion of the device unintended for placement is introduced into the breast.

Artifacts↗
PubMed1997

Brain-stem auditory evoked potential monitoring. The increase of the stimulus artifact in the development of brain death: a biological phenomenon?

Brain-stem auditory evoked potentials (BAEPs) were recorded in 12 dead subjects (mean age, 72.6 +/- 14.8 years), 30.6 +/- 19.5 hours (range 9-70) after abolished systemic circulation. Death was due to cardiac failure (n = 10), intracerebral hemorrhage (n = 1) and larynx cancer (n = 1). The presence and amplitude of the stimulus artifact were evaluated. The mean (+/- SD) amplitudes of the stimulus artifact was 0.03 +/- 0.02 microV on the left side and 0.01 +/- 0.02 microV on the right side. These findings in accordance with previous studies on comatose patients and brain dead subjects confirm that the increase of the stimulus artifact in the development of brain death, in spite of stimulation with alternating polarity, seems to reflect a biological phenomenon which is not found in dead subjects after complete cessation of systemic circulation.

Aged↗
PubMed2001

Peculiar artifacts mimicking carcinoma.

Artifacts that mimic malignancy may lead to diagnostic difficulty and can cause serious consequences. We present 2 cases received in consultation which demonstrated peculiar artifacts that closely mimicked carcinoma. In case 1, contaminating products of conception were confused with squamous cell carcinoma. In case 2, artifactual signet ring cells induced by procedural trauma were suspicious for signet ring cell carcinoma. In both cases, clinical correlation failed to completely exclude carcinoma, and limited tissue prevented use of ancillary studies. Our final resolution of these artifacts required lengthy and detailed morphologic analysis.

Aged↗
PubMed2002

[Experimental study of pseudo-stenosis artifact on three-dimensional DSA].

Rotational three-dimensional digital subtraction angiography (3D-DSA) is very useful for interventional neuroradiology, especially in the endovascular therapy of cerebral aneurysms. However, pseudo-stenosis artifact on the vessel, which runs vertically to the rotational axis, was observed clinically. In this study, this artifact was confirmed in an experiment with 4.5-millimeter diameter vessel phantoms. The attenuation of the phantom at each degree of exposure (44 directions) was measured on the workstation (DSA pixel value). DSA pixel values were plotted from data of 10, 20, 30, 40, and 50 millimeter lengths, respectively. The saturated DSA pixel value of tangent projection on phantoms of 30 millimeters or more in length was observed. This phenomenon induces pseudo-stenosis artifact on 3D-DSA. The maximum reduction in the diameter of the phantom was 27.4% on the length of 50 millimeters. We confirmed that the two-dimensional data vertical to the rotational axis were inaccurate when a straight-coursed, long, segmented vessel was present. Under this special condition, vessels on 3D-DSA were displayed as smaller than their actual diameter.

Angiography, Digital Subtraction↗
PubMed2004

[Basic evaluation of a new technique, tailored contrast truck-fluid-attenuated driven inversion-recovery (TACT-FLADIR), to attenuate the signals of both cerebrospinal fluid and inflow artifacts].

The aim of the present study was to evaluate the new tailored contrast truck-fluid-attenuated driven inversion-recovery (TACT-FLADIR) sequence. Technically, this sequence uses a nonselectively driven inversion (DI) pulse as the inversion pulse. The DI pulse has two parameters, number of refocus pulses (NR) and preparation time (TP). Using normal volunteers, we optimized NR and TP to measure signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) of gray matter (GM) and white matter (WM), and to obtain CSF inflow artifacts. TACT-FLADIR was compared with conventional FLAIR using volunteers and patients. Among the optimized parameters, SNR and CNR were dependent on TP, and inflow artifacts were reduced by increasing NR. In brain imaging, TACT-FLADIR provided improvement in both SNR and CNR compared with conventional imaging with suppressed CSF signal and saturated flow artifacts.

Adult↗
PubMed2002

Twinkling artifact in color Doppler imaging of the orbit.

OBJECTIVE: To show an artifact related to color Doppler flow imaging of the orbit. METHODS: Three patients with strongly reflective structures in the orbit were selected from those routinely referred by clinicians for color Doppler ultrasonography of the orbit. Gray scale and color flow images were obtained with a 7.5-MHz linear array probe for a region with strongly reflective structures. A spectral display was acquired to confirm the presence of blood flow. RESULTS: One patient had a metallic foreign body just behind the bulb; another had calcification within the irregular mass of phthisis bulbi; and the third had hyperechoic drusen in the periphery of the intraocular melanoma. The color mosaic, suggesting the presence of blood flow, was detected beyond all hyperechoic structures. Close vertical bands with no outer wrapping were detected in the spectrum display, obtained by placing the sample volume on the region of color flow. The artificial color flow was recognized as a color Doppler twinkling artifact. CONCLUSIONS: The color flow beyond the strongly reflecting structures in the orbit might be mistakenly interpreted as real blood flow if an examiner is not familiar with the artifact. It should prompt further imaging with spectral Doppler ultrasonography.

Adult↗
PubMed2004

Sonographic duplication artifact of the spinal cord in infants and children.

OBJECTIVE: To describe the features of sonographic duplication artifacts that we have occasionally seen when imaging the spinal cord of infants and children, mostly with postrepair myelomeningocele. METHODS: Sonography of the spine was performed for the evaluation of neonates with suspected spinal cord abnormalities and of older children in the follow-up of postrepair open-spine defects. RESULTS: Each of our patients had a single spinal cord, but the duplication artifact was seen with 2 brands of scanners and with both linear array and vector array transducers. CONCLUSIONS: The finding of duplication artifacts when imaging the spinal cord of infants and children should be recognized as such and should not be misinterpreted as representing diastematomyelia or diplomyelia.

Artifacts↗
PubMed1999

Reduction of aneurysm clip artifacts on CT angiograms: a technical note.

We describe a head tilt technique for use with CT angiography that reduces beam-hardening artifacts in patients with aneurysm clips. This simple maneuver directs the artifacts away from pertinent anatomy, thus increasing the chances for diagnostic accuracy. No significant changes in the CT angiographic protocol are required, and the maneuver can easily be combined with other artifact-minimizing strategies.

Artifacts↗
PubMed1999

MR imaging artifacts. Challenges and solutions.

A wide variety of artifacts is routinely encountered on MR images. This article reviews the cause, appearance, diagnostic effect, and available remedies for the artifacts that are most frequently observed on MR images and are of greatest clinical significance. Combined with routine preventive maintenance of imaging equipment, consistent quality control, and appropriate selection of imaging parameters, awareness of the manifestations of these artifacts will allow image quality and diagnostic interpretation to be optimized.

Artifacts↗
PubMed2000

Intraventricular CSF pulsation artifact on fast fluid-attenuated inversion-recovery MR images: analysis of 100 consecutive normal studies.

BACKGROUND AND PURPOSE: CSF pulsation artifact is a pitfall of fast fluid-attenuated inversion-recovery (FLAIR) brain MR imaging. We studied ventricular CSF pulsation artifact (VCSFA) on axial FLAIR images and its relationship to age and ventricular size. METHODS: Fast FLAIR axial images were obtained on a 1.5-T unit (8000/150/2 [TR/TE/ excitations], inversion time = 2200, field of view = 24 cm, matrix = 189x256, and 5-mm interleaved sections). Two observers rated VCSFA (hyperintensity on FLAIR images) in the lateral, third, and fourth ventricles by using a three-point ordinal scale in 100 consecutive subjects (ages 20-86 years) with normal brain MR studies. Left-to-right third ventricular width was also measured. RESULTS: Seventy-two subjects had VCSFA in at least one ventricular cavity. The fourth ventricle was the most common site of VCSFA (n = 58), followed by the third ventricle (n = 47) and the lateral ventricles (n = 13). VCSFA was usually severe in the third and fourth ventricles and less severe in the lateral ventricles. Fourth ventricular VCSFA was significantly associated with third ventricular VCSFA. Increasing third ventricular size and, to a lesser extent, increasing age was significantly associated with VCSFA. Ghost pulsation of VCSFA occurred across the brain parenchyma in the phase-encoding direction. VCSFA seen in the fourth ventricle on axial FLAIR images disappeared on sagittal FLAIR images in one subject. CONCLUSION: VCSFA on axial FLAIR images represents inflow artifact caused by inversion delay and ghosting effects. VCSFA might obscure or mimic intraventricular lesions, especially in the third and fourth ventricles. Although common in adults of all ages, VCSFA is associated with advancing age and increasing ventricular size. Thus, altered CSF flow dynamics that occur with ventriculomegaly and aging contribute to VCSFA on axial FLAIR MR images.

Adult↗
PubMedDate not supplied

Applicability and advantages of flow artifact-insensitive fluid-attenuated inversion-recovery MR sequences for imaging the posterior fossa.

We describe a new sequence, flow artifact-insensitive fluid-attenuated inversion recovery (FAIS-FLAIR), that capitalizes on the advantages of fluid-attenuated inversion recovery (FLAIR) while minimizing FLAIR-related artifacts such as those often encountered in the posterior fossa. Twenty-eight patients with posterior fossa disease underwent FAIS-FLAIR, conventional FLAIR, and spin-echo MR studies, and the findings yielded by the three techniques were compared. In this patient population, postcontrast FAIS-FLAIR imaging was obtained in 20 patients and compared with postcontrast T1-weighted images. The images were assessed for lesion conspicuity by three radiologists. FAIS-FLAIR markedly reduces the inflow artifacts from noninverted CSF on FLAIR images. It does so with and without contrast agent administration, and produces higher lesion conspicuity compared with T1- and T2-weighted spin-echo sequences and conventional FLAIR images of the posterior fossa.

Artifacts↗