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Biomedical subjects

K Berbaum

Publications and source records attributed to K Berbaum.

At least 19 recordsLinked to original sources
PubMed2001

Impact of graft material configuration on stent-graft endoleak in vitro.

PURPOSE: To assess the effect of different attachment patterns between graft materials and stents on type I endoleak. MATERIALS AND METHODS: Nitinol stents were covered with a coating of Tegaderm in either a straight-edged pattern across the stent cells or a contoured zigzag pattern conforming to the stent skeleton's honeycomb-shaped cells. The stent-grafts were deployed in an ex vivo circuit across a gap of tubing to simulate an aneurysm cavity. Fluid leaking from the gap for more than 30 minutes was recorded as endoleak. Two contoured attachment patterns (short and long necks) and four straight-edged patterns with necks of varying length were tested. Each experiment was repeated 15 times. RESULTS: The length of the aneurysm neck covered by the graft material was inversely related to the rate of endoleak. The zigzag pattern of graft attachment demonstrated significantly less endoleak than the straight-edged pattern in the setting of a short aneurysm neck (0.25 mL vs 47.3 mL). CONCLUSION: Adopting the contoured (zigzag) attachment of graft material to stents minimizes endoleak in vitro, particularly in the setting of a short aneurysm neck.

Aortic Aneurysm, Abdominal↗
PubMed2001

Impact of unilateral common iliac vein occlusion on trapping efficacy of the Greenfield filter: an in vitro study.

RATIONALE AND OBJECTIVES: The purpose of this study was to assess the effect of unilateral common iliac vein occlusion on the capturing efficacy of the Greenfield filter in vitro. MATERIALS AND METHODS: A stainless steel over-the-wire Greenfield filter was placed in the Silastic inferior vena cava module of a pulsatile circuit. Three 30-mm blood clots in sets of five were injected through the module's right iliac limb with the circuit in four experimental conditions: vertical position, both iliac limbs patent (VP); vertical position, left iliac limb occluded (VOC); horizontal position, both iliac limbs patent (HP); and horizontal position, left iliac limb occluded (HOC). Each experiment was repeated 15 times, resulting in 75 clots per condition and a total of 300 clot introductions. RESULTS: Clot trapping efficacy was 36 of 75 (48%) for VP, 41 of 75 (55%) for VOC, 32 of 75 (43%) for HP, and 26 of 75 (35%) for HOC. Cross comparisons of the four conditions revealed a marginally significant difference (P = .0138 with a corrected test-wise alpha = .0125) only between horizontal and vertical positions with unilateral common iliac limb occlusion. CONCLUSION: Unilateral common iliac vein occlusion decreases the capturing efficacy of the Greenfield filter in the horizontal position in vitro. In patients with unilateral common iliac vein occlusion, use of inferior vena cava filters with higher capturing efficacy may be considered.

Dimethylpolysiloxanes↗
PubMed1997

Diagnostic efficacy of compressed digitized real-time sonography of uterine fibroids.

RATIONALE AND OBJECTIVES: The authors investigated the diagnostic efficacy of compression of real-time ultrasound (US) examinations. METHODS: Low- and high-compression recordings (9:1 and 15:1, respectively) of examinations were generated by using Joint Photographic Experts Group algorithms. Seven radiologists used a five-level response scale to answer questions about the presence, number, and location of focal fibroid tumors in 67 randomly sorted uterine examinations. The images were viewed after no, low, and high compression. Results were evaluated by using multipatient, multireader receiver operating characteristic jack-knife analysis. RESULTS: Given the reduction in the US digital video rates from 74 Mbit/sec for uncompressed images to 8 Mbit/sec for low compression and 4.7 Mbit/sec for high compression, there were no statistically significant differences in accuracy between the compression schemes. Confidence intervals suggested that the sample size was adequate. CONCLUSION: Compressed images with compression ratios of 9:1 and 15:1 were diagnostically equivalent to uncompressed images of uterine fibroid tumors.

Female↗
PubMed1995

Influence of prior radiologic information on the interpretation of radiographic examinations.

RATIONALE AND OBJECTIVES: We examined whether and how the provision of previous radiologic information (previous films and reports) influences the interpretation of radiographs. METHODS: We prospectively studied 35 radiologists' interpretation of 311 plain-film radiology cases in a clinical setting. A radiologist first interpreted the current radiograph with only the information given on the consultation request. Subsequently, the same radiologist received, in random order, either the previous radiographs or the previous written reports, reviewed the diagnosis, changing it when necessary, noted the recognition of new findings, and adjusted his or her degree of confidence. A third interpretation used whichever type of information was not supplied for the second. All three readings of a study were performed at the same sitting by the same radiologist. A diagnosis and degree of confidence were recorded for each reading. RESULTS: The additional information, either radiograph or written report, significantly increased the confidence of the radiologist at each stage of interpretation. The largest increase in confidence occurred whenever previous films were introduced. In group A (second reading, reports; third reading, old films), new observations were made in 17.3% of cases on the second reading and in 19.9% on the third reading. In this group, diagnoses were changed in 14% on the second reading and in 9% on the third reading. In group B (second reading, old films; third reading, old reports), new observations were made in 16.9% of cases on the second reading and 7.3% on the third reading. Diagnoses were changed in 11% on the second reading and in an additional 5% on the third reading. Most changes were toward a more specific diagnosis. CONCLUSION: Prior information significantly increased the radiologists' confidence, facilitated new observations, and allowed more specific diagnoses. Prior radiographs were more valuable than reports in some respects.

Confidence Intervals↗
PubMed1994

The role of previous radiographs and reports in the interpretation of current radiographs.

RATIONALE AND OBJECTIVES: The authors studied radiologists' patterns of using old reports and previous radiographs in the interpretation of current radiographic studies. Supplying information from previous studies is considered necessary for accurate interpretation; however, it is not clear how this information is used. METHODS: Eighteen radiologists interpreted 305 plain-film studies in a general radiologic interpretation area. Radiologists described their perceptions of the use of previous radiographs and reports in film interpretation. RESULTS: Overall, old films were used for 99% of interpretations and previous reports were used for 65%. Prior information increased confidence in 89% of cases, influenced diagnosis in 56% of cases, and assisted in detecting new pathology in 6% of interpretations. Old radiographs were judged most valuable in documenting the progression, regression, or stability of disease in 89% of cases. Previous reports were principally used to obtain patient history (43%). In no cases did the radiologist perceive that the old reports assisted in locating new pathology. CONCLUSIONS: Old films are judged more valuable than reports for documenting disease progress, and radiologists are unlikely to accept written reports as a substitute. Previous reports are used principally to improve clinical histories, a function that might be eliminated if adequate clinical data could be captured by other means.

Attitude of Health Personnel↗
PubMed1992

Effect of antineoplastic agents on smooth muscle cell proliferation in vitro: implications for prevention of restenosis after transluminal angioplasty.

The effect of several antineoplastic agents on vascular smooth muscle cell proliferation was studied in vitro. Both fluorouracil and cytarabine produced significant concentration-dependent inhibition of smooth muscle cell proliferation in cultured porcine pulmonary artery in vitro, while cyclophosphamide stimulated growth. For fluorouracil, inhibition was near maximal at a concentration of 13.0 microgram/mL and was seen with both coincubation and 2-hour preincubation of fluorouracil with quiescent cells. Fluorouracil is a promising agent for inhibition of intimal proliferation. Further work is warranted to determine its effect in vivo.

Angioplasty, Balloon↗
PubMed1990

Effect of conflicting cues on information processing: the 'Stroop effect' vs. the 'Simon effect'.

This study examined the relationship between two sources of interference in human information processing: the Stroop effect and the Simon effect. Forty subjects pressed a left- or right-hand key in response to a Stroop color word located on the left or right side of a screen. For one group, ink color was the relevant cue and, for another group, word meaning was the relevant cue. Independent variables were: congruence, i.e., agreement or lack thereof between the ink color and meaning of the Stroop word; spatial correspondence, i.e., agreement or lack thereof between the location of the Stroop word and the location of the key used to make the response; and stimulus duration, i.e., 400 or 100 ms. Each of these variables had a significant effect on RT, and there were no significant interactions. According to Sternberg's additive-factor logic, these findings suggest that the Stroop effect (congruence) and the Simon effect (spatial correspondence) involve separate stages of processing. If one assumes that manipulation of stimulus duration effects the encoding stage, then results also suggest that neither the Stroop effect nor the Simon effect involves the stimulus encoding stage.

Attention↗
PubMed1990

The incidence of serious hemodynamic changes in physically-limited patients following oral dipyridamole challenge before thallium-201 scintigraphy.

Dipyridamole has liberalized referrals for stress TI-201 chloride (thallium) studies at the Iowa City Veterans Administration Medical Center. Seventy-five percent of referrals now receive dipyridamole and, unlike patients who tolerate conventional exercise testing, these patients are often quite debilitated. Therefore, the hemodynamic consequences of dipyridamole were reviewed in 120 consecutive, physically-limited patients referred for thallium scintigraphy following an average oral dose of 5.4 mg/kg. Each patient's blood pressure was measured every 5 minutes for 1 hour after dipyridamole and compared with several clinical factors to determine if blood pressure change was predictable. In all patients, blood pressure changed from 136 +/- 21/83 +/- 15 (mean +/- 1 SD) to 117 +/- 25/72 +/- 15 following dipyridamole administration. One hundred nine of the 120 patients had a blood pressure decline from 137 +/- 21/82 +/- 12 to 113 +/- 21/70 +/- 13. Of the 109, 43% (N = 47) had a systolic blood pressure decline greater than 20 mmHg, 16% (n = 18) greater than 40 mmHg, and 13% (n = 14) greater than 50 mmHg. Thirteen percent (n = 14) required emergent reversal of the dipyridamole with aminophylline. Significant hypotension is relatively common but generally unpredictable after oral dipyridamole. Therefore, patient eligibility criteria should be carefully considered; strict hemodynamic monitoring must be routine in the usual patient undergoing thallium scintigraphy after oral dipyridamole challenge.

Administration, Oral↗
PubMed1988

Small bowel enteroclysis survey.

A survey questionnaire was sent to 125 radiology programs to determine the frequency and indications for the use of small bowel enteroclysis. Sixty-seven of the 84 respondents perform small bowel enteroclysis while 17 do not. The 3 most common indications for enteroclysis are detection of unexplained gastrointestinal bleeding, partial small bowel obstruction, and Crohn's disease. We conclude that although small bowel enteroclysis is a well-established examination, there are wide differences in the frequency with which it is performed, the techniques of examination, and indications for its use.

Barium Sulfate↗
PubMed1985

Reaction time to word meaning and ink color of laterally-presented stroop stimuli: effects of handedness and sex.

In two experiments, subjects pressed a key labeled Red or Green in response to a 100 msec duration stimulus presented to the left or right visual field. In Experiment I, subjects responded to the meaning of Stroop words; the stimulus was the word Red or Green printed in red, green, or white ink. In Experiment II, subjects responded to ink color; the stimulus was either the word Red or Green printed in red or green ink or a red or green color patch. In each experiment, there were 20 strongly right-handed subjects and 20 strongly left-handed subjects. Half the subjects in each handedness group were male and half were female. In both experiments, RT was faster when words were presented to the right visual field than to the left visual field, suggesting that both meaning and ink color of Stroop words were processed more quickly in the left hemisphere. Results of both experiments revealed faster reactions when meaning and ink color of the Stroop words were congruent than when they were not. A comparison with baseline trials indicated that the RT difference between responses to congruent and incongruent Stroop words was due to the incongruent cue interfering with information processing rather than to the congruent cue facilitating processing. Hypothesized interactions between stimulus position, congruence, handedness and sex were not significant.

Adolescent↗
PubMed1984

Form and depth in global stereopsis.

Three experiments were performed to investigate the role of vergence and the relationship between form and depth processes in global steropsis by comparing global and classical stereopsis. In the first experiment, the speed of stereoscopic resolution as a function of initial fixation-target distance was measured to discover the role of vergence in stereopsis with the random-dot and contoured stereograms. In the second experiment, the accuracy of form and depth discrimination as a function of fixation-target distance was measured using brief stimulus exposure (150 ms) to examine the nature of form and depth processing in global stereopsis. In the third experiment, the speed of resolving random-dot stereograms in the presence or absence of juxtaposed contoured stereograms was observed to examine the interaction of global stereopsis and classical stereopsis. The conclusions of these studies are summarized as follows: First, vergence plays a critical role in the solution of the random-dot stereograms but not in the solution of contoured stereograms. Second, performance with the contoured stereograms is better than with the random-dot stereograms in terms of both speed and accuracy. Third, in random-dot stereograms, discrimination of form is independent of and more accurate than discrimination of depth. Fourth, again for random-dot stereograms, the disparity of target relative to fixation systematically affects discrimination of form but not discrimination of depth. Fifth, a rapid reduction in reaction time over practice occurs for both types of stereograms. Finally, strong interference with the solution of the random-dot stereograms by the monocular contour occurs when the two kinds of stimuli are present simultaneously.

Cues↗
PubMed1984

Extending the perception of shape from known to unknown shading.

Two experiments are reported which demonstrate the effects of light-source position as an intervening variable upon the perception of relief in pictures. In the first experiment, it is shown that the pattern of light (attached shadow) falling upon forms that can be recognized as having unambiguous surface relief (concave and convex parts) influences the perception of forms with ambiguous surface relief. In the second experiment it is demonstrated that cast shadows may also determine the interpretation of ambiguous relief. These findings suggest that light-source position, implicitly or explicitly, mediates the interpretation of surface relief in pictures.

Cues↗
PubMed1984

Measures of displacement and type of background in apparent motion with random-dot cinematograms.

The primary purpose of the studies presented was to determine whether stimulus displacement in random-dot cinematogram apparent motion should be measured in terms of relative or absolute distance, while taking into account the effect of number of displaced elements. Support for each measure has been reported in the literature (Braddick, 1974; Lappin & Bell, 1976). A secondary purpose was to test a basic assumption about the generalizability of results in the random-dot cinematogram literature by determining whether the same results may be obtained using cinematograms with a constant-background field as with cinematograms with a varied-background field. For varied-background cinematograms, the clarity of apparent motion decreased as relative displacement increased. The number of elements in the target square was also found to affect the ratings. These findings support a global rather than strictly local process for perceptually segregating areas of random-dot texture based upon motion. For constant-background cinematograms, factors different from those affecting varied-background cinematograms determined the clarity of apparent motion.

Discrimination Learning↗
PubMed1983

Depth perception of surfaces in pictures: looking for conventions of depiction in Pandora's box.

The perception of depth in monocularly viewed pictures has been investigated with the use of a binocular rangefinder developed by Gregory. Two experiments are reported which focus upon stimulus conditions that were identified by Haber as conventions for rendering depth in pictures. Several conclusions, which concern assumptions that must be made in interpreting pictures according to such conventions, are supported by the results. There is a default or assumed layout of background space. The interpretation of a point in a depiction depends upon the interpretation of neighboring points, so that interpretations of local features influence the interpretations of nearby 'empty' areas. In photographs, the magnitude of apparent depth depends upon the degree of discrepancy between the position of the illuminating source and the observer's supposed light-source position. Also in photographs, apparent depth increases as the contrast between highlights and attached shadows increases.

Cues↗
PubMed1983

Light source position in the perception of object shape.

The apparent relief of monocularly viewed surfaces reversed when the order of light and shade was reversed relative to the position of a lamp observed the moment earlier. The pattern of shading was reversed either by illuminating from a direction opposite to that of the apparent direction of illumination or by inverting the illuminating image relative to the light source. The combination of both of these manipulations restores the original juxtaposition of light source and shading and reestablished accurate perception of relief. These results demonstrate that the perception of the relief of physical surfaces depends upon the remembered position of an apparent light source.

Adult↗