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PubMedDate not supplied

Diagnostic value of crush artifact in cytologic specimens. Occurrence in small cell carcinoma of the lung.

The occurrence of nuclear crush artifact (NCA) in cytologic specimens of small cell undifferentiated carcinoma (SCUC) and other carcinomas of the lung, lymphoma and benign lymphoid proliferations was studied to determine its diagnostic usefulness. NCA was found to be a common and morphologically distinct feature in SCUC, depending on how the specimen was prepared; it was present in aspirates, washings, brushings and sputum, but not in pleural or cerebrospinal fluids. It was absent in other types of cancer and could be distinguished from other similar-appearing artifacts. These results demonstrate that NCA is a diagnostically useful feature in pulmonary SCUC.

Carcinoma, Small Cell↗
PubMed1990

Evaluation of techniques for the elimination of "hot" bladder artifacts in SPECT of the pelvis.

The purpose of this study was to validate the usefulness of two digital filtering techniques used to eliminate the artifacts caused by rapid bladder filling during SPECT of the pelvis. A dynamic phantom model was used containing two hips and a bladder. The phantom was studied under three conditions--bladder empty, filling, and full. The ability of the pixel truncation and interpolative background replacement techniques to eliminate bladder artifacts was assessed. Both techniques gave similar results and resulted in significant (but not complete) recovery of activity in the hips. Quantitative analysis of pixel counts over each hip shows that the measured activity was variable and approximately 20%-30% less than that seen in the empty bladder study. The use of left/right ratio to quantitate differences in hip activity was highly inaccurate despite the use of these filtering techniques. In summary, while these techniques significantly improve image quality, caution should be exercised, particularly in the evaluation of the medial aspects of the hips.

Data Interpretation, Statistical↗
PubMed1990

[Lead foil artifacts as a result of unintentional bending of dental X-ray films].

The lead foil of dental x-ray film packets may cause a number of artifacts; especially well known are the "tractor treads" and "herringbone patterns" following a backward filmpositioning in the patient's mouth. In the present paper a specific and seldomly occurring lead foil artifact is described which is caused by bending of the film packet. Four cases collected over a 5-year period are presented. Although different the four cases show a number of similarities. They appear as radiopaque areas covering the upper or lower halves of the films. Their borders show the characteristic "sandbar-pattern" previously described by the author. The explanation of their origin is that the patient has been occluding on a part of the film packet which has been bent to a nearly horizontal position. The x-rays directed against the edge of the lead foil will be absorbed causing irregular radiopaque areas on the film lined by "sandbar-pattern". When the film packet is bent, the lead foil will be stretched and drawn a little away from the edges of the films. Consequently the x-rays will be able to expose the edges of the films. Irregularities of the foil will give rise to concentric "bars". The lead foil is only of limited radiopacity, but due to the oblique direction of the x-rays through the foil the absorbing effect is intensified.

Diagnostic Errors↗
PubMedDate not supplied

Artifact formation during smoke trapping: an improved method for determination of N-nitrosamines in cigarette smoke.

Studies in our laboratory revealed artifactual formation of N-nitrosamines during trapping of mainstream and sidestream tobacco smoke by the method of Hoffmann and coworkers (2, 4). Both volatile and tobacco-specific N-nitrosamines were produced. This artifact formation took place on the Cambridge filter, which is part of the collection train used in the previously published procedure. When the filter was treated with ascorbic acid before smoke collection, artifact formation was inhibited. The improved method resulting from these studies was applied to a comparative analysis of N-nitrosamines in smoke from cigarettes that heat, but do not burn, tobacco (the test cigarette) and several reference cigarettes. Concentrations of volatile and tobacco-specific N-nitrosamines in both mainstream and sidestream smoke from the test cigarette were substantially lower than in the reference cigarettes.

Antioxidants↗
PubMed1990

Three-dimensional analysis of averaged electro-retinograms: normal appearance and bioelectric artifacts.

In 10 normal subjects, three-dimensional analysis (X-Y plane and time) was carried out of the dominantly photopic and scotopic components of the electroretinograms (ERG) for the purpose of functional imaging of the retina, after having evaluated bioelectric artifacts. The study of the artifacts had revealed that the major causes of distorting the topographical distribution were blinking, myogenic activities, eye movement, eye position and background activities of the electroencephalograms. In normal subjects, the maximal amplitude of the dominantly scotopic components was located around the lower eyelid, while that of the dominantly photopic components was situated around the upper eyelid. The mechanisms of the equivalent dipole axis of the dominantly photopic and scotopic components were different. However, similar changes in the equivalent dipole axes were found during the periods of eccentric eye positions. Similar topographical characteristics were noted in the latency mapping. The isopotential line of the dominantly scotopic components had a steep gradient and were suggestive of a superficial (peripheral retinal) origin, while that of the dominantly photopic components had a gradual gradient and seemed to be of deep (central retinal) origin. ERG topography would make functional imaging of the retina possible and would be of great diagnostic value.

Adult↗
PubMed1986

D-Phe-Pro-Arg-chloromethylketone: its potential use in inhibiting the formation of in vitro artifacts in blood collected during tissue-type plasminogen activator thrombolytic therapy.

In vitro artifacts due to proteolysis may occur in blood samples containing recombinant tissue-type plasminogen activator (rt-PA) due to continued activation of plasminogen to plasmin by rt-PA. The aim of this study was to identify a rapid inhibitor of rt-PA that would not interfere in assays designed to monitor thrombolytic events. When rt-PA was added at 5 micrograms/ml to whole blood and incubated at 25 degrees C, fibrinogen decreased 50 percent, plasminogen levels decreased 90 percent and alpha 2-antiplasmin decreased below detectable levels. If D-Phe-Pro-Arg-chloromethylketone (PPACK) or aprotinin were added before the addition of rt-PA there was no significant loss of fibrinogen. Only PPACK completely inhibited changes in fibrin degradation products, plasminogen and alpha 2-antiplasmin. PPACK was also found to inhibit the binding of rt-PA to plasma protease inhibitors in vitro. Rhesus monkeys were infused with rt-PA and blood samples were taken with either PPACK or aprotinin in the collection syringe. There was a significant increase in the recovery of immunoreactive rt-PA and consistent measures of fibrinogen, FDPs, plasminogen, and alpha 2-antiplasmin in the PPACK group as compared to the aprotinin group which indicates that PPACK will prevent the in vitro formation of artifacts due to the presence of active rt-PA.

Amino Acid Chloromethyl Ketones↗
PubMedDate not supplied

Importance of absence of CSF pulsation artifacts in the MR detection of significant myelographic block at 1.5 T.

MR imaging was performed on 21 patients who had high-grade myelographic block due to various diseases in all spinal compartments (extradural, intradural/extramedullary, and intramedullary) and in all portions of the spinal canal (cervical, thoracic, and lumbosacral). Loss of CSF pulsation artifacts due to significant compression of the spinal cord was demonstrated on non-motion-compensated T2-weighted examinations in each case. We believe that the absence of such artifacts on these sequences indicates significant spinal cord compression in patients without classic signs and symptoms of cord compression but with intraspinal disease identified on T1-weighted studies.

Adolescent↗
PubMed1989

Optimal specificity of thallium-201 SPECT through recognition of imaging artifacts.

Artifacts are produced in 201TI cardiac single photon emission computed tomography (SPECT) imaging because of a variety of causes including soft-tissue attenuation, overlying abdominal viscera, variable myocardial thickness, left bundle branch block, cardiac rotation, patient motion, and technical errors. Careful attention to quality control, utilization of motion detectors, and familiarization with potential artifacts will improve the specificity and diagnostic accuracy of 201TI SPECT for coronary artery disease.

Abdomen↗
PubMedDate not supplied

Automatic recognition of random artifacts in recordings of slow brain potentials: a bias-free method.

A method for computerized recognition of random artifacts in recordings of slow brain potentials is presented. It is based on systematic comparison of the shape of single trial EEG segments with all other trials obtained in the same experiment. This is possible because, in contrast to short-latency event related potentials, a plateau of EEG negativity during complex tasks can often be detected in single trails. After linear trend removal and subtraction of EOG artifacts, similarity of pairs of single trials is established by point-to-point linear regression analysis, the total score of a trial being defined as the mean correlation coefficient (R) resulting from comparison to all other trials. Selection is then performed by setting a critical value for R, admitting for averaging only trials with a mean correlation coefficient above the critical value. An example is given in which the method is applied to recordings of slow brain potentials during a manual tracking task.

Brain↗
PubMedDate not supplied

Semiautomatic algorithm to remove resonance artifacts from the direct radial artery pressure.

Resonance artifacts introduced by the catheter-manometer system are removed from the direct radial artery pressure using a three-step algorithm. First, the fast-flush method is used to identify the natural frequency and damping coefficient of the monitoring system by digitizing and analyzing the pressure transient created by the flush. Second, resistor, capacitor, and inductor values are found for an RLC second-order model of the catheter-manometer system in use. Third, the algorithm predicts the undistorted radial artery pressure, removing the resonance artifacts by inverse-filtering the digitized monitored pressure waveform using the RLC circuit derived previously. The algorithm was implemented using a personal computer, but it could also be used without the computer by incorporating an analog-to-digital convertor and a microprocessor in the hemodynamic monitor.

Algorithms↗
PubMedDate not supplied

Attenuation values, volume changes and artifacts in tissue due to freezing.

Freezing of animal and human tissue may change their shape, size and other physical properties such as attenuation of roentgen rays. In correlative radiologic-anatomic studies such artifacts are potential sources of inaccuracy. In fluid phantoms changes of computed tomography (CT) numbers and volume were measured before and after freezing. Frozen saline decreased in attenuation by 80 Hounsfield units (HU) and increased in volume by 9 per cent. Pure soy oil increased in attenuation by 40 HU after freezing and shrank in volume by 4 per cent. Emulsions of 10, 20 and 30 per cent lipid expanded in inverse relationship to the changes in attenuation. In animal and human tissue, changes in CT number of -80 to +55 HU were measured and changes in volume of -6 to +9 per cent were calculated. The attenuation of the vitreous body in the eye decreased by 80 HU and its volume was calculated to increase by 8 to 9 per cent. In the muscle and spinal cord the attenuation decreased by 40 to 60 HU, corresponding to the increase in volume of 4 to 6 per cent. Attenuation of fat was increased by 55 HU after freezing and a decrease in volume of 5 to 6 per cent was calculated. Deformation of soft tissue and herniation of the cerebellar tonsils into the foramen magnum were observed. Most anatomic, freezing artifacts can be avoided by careful preparation.

Adipose Tissue↗
PubMedDate not supplied

"Truncation" artifact in MR images of the internal auditory canal.

Dry skulls and a phantom were studied to determine whether an intracanalicular dark band in MR images of some acoustic neuromas could be artifactual. A "truncation" artifact was detected in the internal auditory canals of the dry skulls and in a simulated internal auditory canal of the phantom when the width of the canal approximately equaled 4 X (field of view) /N, where N equals 128 or 256, depending on the number of gradient steps chosen. The "truncation" artifact should not be confused with CSF between normal nerves when a canal contains tumor.

Humans↗
PubMedDate not supplied

Correction of CSF motion artifact on MR images of the brain and spine by pulse sequence modification: clinical evaluation.

A modification of the standard spin-echo pulse sequence designed to suppress motion artifacts was clinically evaluated on T2-weighted MR images of the cervicocranial region. A retrospective study involving 40 patients, half of whom were examined with a standard T2-weighted multislice spin-echo sequence and half of whom were examined with a gradient waveform modification of the same sequence, uniformly demonstrated restoration of CSF signal intensity on images obtained with the gradient modified sequence. The cervical subarachnoid spaces, cisterna magna, medullary cistern, pontine cistern, fourth ventricle, and aqueduct were more consistently and brightly represented. However, the phase-encoding artifacts arising from CSF motion were not significantly reduced by using the gradient waveform modified pulse sequence. Digital subtraction of an image obtained with the standard sequence from an image of the same slice with the gradient modified sequence provides a direct image representation of CSF flow.

Brain↗
PubMed1988

Tooth mark artifacts and survival of bones in animal scavenged human skeletons.

Animal scavenging activity can result in production of tooth mark artifacts. Such activity can confound interpretation of skeletal material and the identification process. To date, these topics have received limited attention in the forensic science literature. This study discusses the nature of various animal tooth mark artifacts and typical damage to selected bony elements. This study also assesses survivability of various skeletal elements over time. Two major factors that affect which bones are recovered and the amount of damage are circumstances which shelter remains from animals and human population density of the area where the skeleton is recovered.

Adolescent↗
PubMed1988

Artifacts in oral biopsy specimens: a case report.

Artifacts in oral surgical specimens could be ascribed to tissue alteration before, during or after biopsy procedures. A case of mandibular ameloblastoma presenting with a series of vacuoles in the subgingival tissue is described. The differential diagnosis and significance of these artifacts are discussed.

Adult↗
PubMed1987

Fast washout of thallium-201 from area of myocardial infarction: possible artifact of background subtraction.

A recent report described a pattern of "reverse redistribution" on poststreptokinase 201Tl studies which was believed to be due to rapid washout of 201Tl from the infarct area related to reperfusion of the infarct vessel. We have also observed the phenomenon of rapid washout of 201Tl from the area of infarction in the absence of thrombolytic therapy. This study was undertaken to test the hypothesis that rapid washout of 201Tl from an area of infarction is an artifact of background subtraction usually employed in analysis of washout. A total of 61 patients with previous myocardial infarction who underwent cardiac catheterization and exercise 201Tl imaging were examined. Thallium-201 images were analyzed using a validated quantitative method employing interpolative background correction. Abnormally increased 201Tl washout was noted in 11 infarct segments in 10 (18%) patients. Infarct segments with rapid washout had significantly less initial uptake, and more severe associated wall motion abnormalities than infarct segments with normal washout. When quantitative analysis was repeated without background subtraction, no segments with rapid washout were observed. A phantom model was constructed to further test our hypothesis. The frequency of observed rapid washout was directly related to the severity of the initial defect and was entirely dependent upon utilizing background correction during the quantitative analysis. Our study suggests that rapid washout of 201Tl in an area of previous infarction reflects an artifact of background subtraction involved with standard quantitative analysis.

Humans↗
PubMed1987

Fetal heart rate measurement during maternal exercise--avoidance of artifact.

The purpose of this study was to investigate the possibility that motion artifact may override the recording of fetal heart rate (FHR) with Doppler ultrasound fetal monitors during maternal exercise on cycle ergometers and treadmills, and to test the efficacy of two-dimensional ultrasound directed M-mode echocardiographs for determining FHR during maternal treadmill exercise. Four pregnant women (26 to 30 yr, means = 28, gestational age = 28 to 34 wk) pedaled a cycle ergometer at 25 to 50 W, while a second group (N = 4) (24 to 36 yr, means = 29, gestational age = 30 to 37 wk) walked on a treadmill at either 1.5 or 2.0 mph. Fetal monitor recordings (Hewlett-Packard 8040A) were consistent with pedal rate in the range of 50 to 70 rpm and with stepping rate in the range of 70 to 76 steps per min at 1.5 mph and 100 to 106 steps per min at 2.0 mph on the treadmill. Actual mean FHRs (audible signal from fetal monitor) were in the normal range [150.5 +/- 10.25 bpm (cycle ergometer) and 148.8 +/- 2.3 bpm (treadmill)]. In a separate session, the cycle ergometer group walked on a treadmill at a maternal heart rate of 140 bpm while FHR was determined by two-dimensional ultrasound directed M-mode echocardiographs. Off-line analysis of fetal cardiac cycle time (clinical graphics analyzer) allowed accurate FHR measurements which were not confounded by motion artifact. Mean FHR during maternal treadmill exercise (158.0 +/- 12.0 bpm) was not different (P greater than 0.05) when compared to pre-exercise standing (140 +/- 3.6) and also during the post-exercise period (sitting) (151 +/- 6.5) compared to the sitting pre-exercise measurements (147 +/- 8.2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

MRI of the upper abdomen using motion artifact suppression technique (MAST).

Magnetic resonance imaging of the upper abdomen has been hampered by motion artifacts that cause suboptimal image quality. A promising software solution to this problem, motion artifact suppression technique (MAST), is described. Using mathematically determined refocussing gradients, it has improved image clarity significantly. Unlike alternate techniques such as respiratory gating, there is no increase in scan time, and patient throughput is expedited.

Abdomen↗