Showing papers on "Artifact (error) published in 1980"

DAB cytochemistry: artifact problems in its current uses.

Abstract: the insolubility problem using an enzyme-activated DNA stain, particularly suitable for automated cytology. Any fluorescent substrate with a negative charge or steric hinderance group can prevent the substrate from interacting with DNA. By removing the negative charge or sterically hindered portion of the molecule in an enzymatic reaction, the product can enter the nucleus and act as an enzymeactivated DNA stain.

Site Artifact Density and the Effectiveness of Shovel Probes

Abstract: is a striking resemblance between these malformations and those described by Bennett (1972) for a group of remains of protohistoric Modoc Indians from Night Fire Island, two miles from the Oregon-California border. A very high percentage of these remains showed the four malformations found in the spine of the Los Gavilanes child. Bennett described as an additional feature that the fossae lateral to the first and second sacral tuberosities were unusually large and deep, suggesting a very strong ligament attachment. The same seems to occur in the Los Gavilanes case, although in a child the evidence is less convincing. The rest of the skeleton does not differ in any way from other remains from Peru for the same period, such as those described by Hartweg (1958, 1961) in his studies of skeletons from Culebras, Asia, and Cabezas Largas. It is important in this case that in the first two places, the rule was that the sacrum consisted of six vertebrae. It is very difficult to explain the similarity between the Los Gavilanes child and the remains of the Modoc Indians. Bennett concluded that there was a genetic component. If this is so, it may have involved a mutation producing the same defective gene in both groups, since a close genetic relationship between the two seems very unlikely. The possibility of similar dietary or other external factors affecting spine development in the two cases cannot be overlooked.

Information and artifact in computed tomography image statistics.

Abstract: In conventional computed tomography images only the average CT number, which is a first-order statistical parameter, is used to characterize the tissues by giving an estimate of tissue density. Second order statistical parameters such as the signal variance and cross-correlation function have also been used to obtain additional information to discriminate between certain tissues and lesions. However, the contribution of quantum noise to the signal variance and cross-correlation function creates, for the conventional CT patient dose, a background signal often larger than the signal containing the information about tissue structure. The misleading information, called "artifacts", in second-order image statistics caused by quantum noise, is studied.

Method and apparatus for obtaining a non-cephalic referential electroencephalogram

Abstract: A method and apparatus to provide an electroencephalogram (EEG) measured with respect to a reference which is not on the head and to eliminate the electrocardiographic (EKG) artifact which normally contaminates such a measurement. At least three electrodes are placed at or below the base of the neck. Signals from these electrodes are linearly combined, thereby producing a reference signal. The reference signal is then subtracted from signals derived from scalp electrodes. The linear coefficients are adjusted to eliminate the EKG artifact.

Gated cardiac computed tomography with a motion phantom.

Abstract: CT images of the heart are significantly degraded by the effects of motion during the scanning interval. The use of electrocardiographic (ECG) gating to provide "stop-action" cardiac images remains limited by artifacts. A motion phantom has been constructed to allow systematic study of the artifact structure of ECG-gated images and to isolate the origins of these artifacts. "Stop-action" reconstructed images are presented demonstrating two classes of artifacts: (a) pinwheel artifacts that appear at the edges of high-contrast moving objects; and (b) linear streaks occurring in relation to missing views when an incomplete angular set of projections is used for image reconstruction with the convolution back-projection algorithm. These results underscore the use of the motion phantom for the analysis of image artifacts and stress the need for new CT reconstruction algorithms which are optmized for "stop-action" scanning.

Sputtering positive potentials in the EMG: an artifact resembling positive waves.

Abstract: Sputtering positive potentials (SPPs) in the electromyogram are small, irregularly occurring waveforms recorded in normal distal muscles. They represent cannula-recorded “nerve” potentials, but may be mistaken for the positive waves seen in denervation. Differences in amplitude, regularity, and duration help in distinguishing SPPs.

Physical Dependence on Ethanol: Methodological Considerations

Abstract: An ethanol-induced biological change may be: 1) cause, 2) effect, 3) unrelated covariate of physical dependence, or 4) an experimental artifact. The first three possible relationships are shown in the Figure and have been discussed in detail elsewhere (Freund, in press, b). In addition to correlation, other criteria were listed to establish the significance of an observation to the pathogenesis of physical dependence. This discussion deals with the fourth possible relationship—the experimental artifact.

Effusion artifact: a chronic problem in DAB cytochemistry.

Abstract: I share Novikoff’s concern, expressed in two Letters to the Editor (14, 16), regarding artifacts caused by diffusion of reaction product and enzyme or antigen, adsorption to nonreactive sites and poor preservation of tissue, and I would like to call attention to two related 3, 3’-diaminobenzidine (DAB) artifacts. Subtle staining artifacts can also be seen in tissues that appear to be very well preserved. For example, one likely adsorption artifact that has gone unchallenged is the staining ofouter mitochondrial membranes, which has been attributed to cytochrome b5, in tissues incubated in various DAB media ( 1 , 1 5). Such staining is seen only in small segments that are adjacent to reactive inner mitochondrial membrane (see inset to Figure 9 in ref. 1) and is not present when only the cristae are reactive (see Figure 1 3 in ref. 1 ). Staining of the entire inner mitochondrial membrane yields a complex three-dimensional view of the membrane ( 1 5 ). Images of the two reactive cut surfaces of the inner membrane usually do not overlap and have been misinterpreted as representing inner and outer membrane staining (Figure 8b in ref. 17). In addition to artifactual localization of enzymes and antigens, cytochemists should be equally concerned with artifactual attributions in the citation of original research. For example, in his recent Letter (14), Novikoff quotes from a 1972 Letter to the Editor from his own laboratory ( 16) that praises DAB because “the product ofits oxidation is a highly insoluble polymer that is osmiophihic and homogeneous when viewed by electron microscopy.” His own Letter (16) is the only reference given for this fundamental observation. However, neither the cited Letter nor any other publication from his laboratory has ever presented any evidence for the polymeric nature of oxidized DAB. The evidence concerning the nature of oxidized DAB came from other investigators. Karnovsky (1 1), in a 1965 abstract, first reported that DAB reaction product was “non-crystalline, insoluble, and extremehy electron opaque after fixation in osmium tetroxide. “ The following year Graham and Karnovsky (7) described the reaction products as a “dense, more or less homogeneous mass . . . not extracted by the organic solvents used in Epon embedding. “ They noted that its chemical nature was unknown and suggested that osmium was reduced by oxidized DAB. The evidence that oxidized DAB was an osmiophihic polymer came from a 1968 report by Sehigman et al. (18) that Novikoffdoes not cite in his recent Letter (14) and did not credit in this regard in his 1972 Letter (16).’

The Schilling Test

Abstract: Excerpt To the editor: In the October 1979 issue Drs. Jacobson and Onstad (1) described a Schilling test artifact caused by inactive commercial intrinsic factor. That report is an important reminde...

Pacemaker artifact on ENG tracing.

Abstract: The electronystagmogram (ENG) of this 76-yearold female, who was referred for diagnostic evalua­ tion of vertigo, demonstrates an electronic artifact secondary to the signal generated by a cardiac pace­ maker. The patient had complaints of dizziness, staggering and tinnitus associated with visual \"grayouts\" lasting 15-20 seconds almost daily for several months . Three years prior to her evaluat ion, a Medtronic® endocardial pacemaker had been placed in the t rabecular system of the right ventricle via the right cephalic vein for correction of a complete heart block.

Cephalic Electromyographic Artifact During Electrocerebral Silence

Abstract: (1980). Cephalic Electromyographic Artifact During Electrocerebral Silence. American Journal of EEG Technology: Vol. 20, No. 1, pp. 25-28.