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Christopher L Hansen

Publications and source records attributed to Christopher L Hansen.

12 recordsLinked to original sources
PubMed2006

The ratio of the apex/anterior wall: a marker of breast attenuation artifact in women.

BACKGROUND: Breast attenuation artifact is well known for reducing the accuracy of myocardial perfusion imaging in women. We have noticed the particular pattern of relative preservation of apical activity in women with breast attenuation and decreased anterior wall counts. This study was undertaken to see if this finding could be used to improve the accuracy of perfusion imaging in women. METHODS: We identified 295 women referred for exercise stress testing using (201)Tl single photon emission computed tomography (SPECT) of whom 193 had less than 5% probability of coronary disease and 102 had coronary artery disease documented by catheterization within 60 days of stress testing (mean of 1.8+/-0.8 vessels with=50% stenosis). Patients with documented myocardial infarction, pathologic Q waves, left bundle branch block, non-ischaemic cardiomyopathy or prior bypass grafting were excluded. Volume-weighted bullseye plots were generated and normalized to 100; next, regions of interest were drawn over the anterior wall and apex in all patients and the ratio of the mean counts of each region was calculated. The normals were further divided into those with breast attenuation (defined as mean anterior counts <70% maximum) and those without. Defect scores of all patients were calculated; a formula to adjust the score for patients with breast attenuation was developed. Accuracy was assessed by calculating the area under the receiver operating curve. RESULTS: The normals, overall, had a mean ratio of 1.0+/-0.08 vs. 0.9+/-0.16 for those with coronary disease (P<0.0001). In normals with breast attenuation the ratio was 1.1+/-0.08 compared to 0.99+/-0.07 (P<0.0001) without. By adjusting the anterior wall defect score in patients with apex/anterior ratio >1 we were able to improve the accuracy from 0.808+/-0.028 to 0.826+/-0.027 (P<0.01). CONCLUSIONS: A ratio of the apex to the anterior wall >1 is not physiological and suggests the presence of significant breast attenuation artifact. This finding can be used to produce a small but statistically significant improvement in the accuracy of quantitative thallium SPECT in women who have not undergone coronary bypass grafting.

Artifacts↗
PubMed2005

An affective-motivational model of marijuana and alcohol problems among college students.

The study examined models of marijuana (n = 309) and alcohol (n = 731) problems. Impulsivity was directly associated with both marijuana- and alcohol-related problems. Negative mood regulation expectancies were indirectly associated with marijuana problems through coping motives. Sensation seeking was indirectly associated with alcohol problems through enhancement motives. Affect lability and negative affect were indirectly associated with alcohol problems though coping motives. In both models, coping motives were directly associated with use-related problems. A multigroup analysis indicated that the association between negative affect and coping motives as well as use and problems was stronger among participants using both alcohol and marijuana relative to alcohol only. Enhancement motives were a stronger predictor of alcohol use among participants using alcohol only.

Adult↗
PubMed2002

Orthographic neighborhood size, number of word meanings, and number of higher frequency neighbors.

The present lexical decision task experiment examined orthographic (large, medium, small), number-of-meanings (ambiguous, unambiguous), and number of higher frequency neighbors (few, many), factors that have to date not been studied simultaneously. For both mean reaction time and percentage error, the critical three-way interaction between these factors was significant. Breakdown of this interaction revealed that the ambiguity effect (unambiguous-ambiguous) decreased as neighborhood size increased, but only when there were many higher frequency neighbors in the neighborhood. These results appear inconsistent with serial search models but are understandable within the context of interactive-activation models of word recognition.

Adult↗
PubMedDate not supplied

Comparison of pulmonary uptake with transient cavity dilation after dipyridamole Tl-201 perfusion imaging.

BACKGROUND: Elevated lung-heart ratio (LHR) and transient ischemic dilation (TID) have been identified as markers of severe coronary artery disease after both exercise and pharmacologic stress testing. We have previously demonstrated a very weak correlation between elevated LHR and TID after exercise, which suggests that they reflect different pathophysiologic manifestations of coronary disease. Because the physiology of pharmacologic vasodilation with dipyridamole is significantly different than that of physical exercise, we undertook this study to evaluate the relationship between elevated LHR and TID after pharmacologic stress testing with dipyridamole. METHODS AND RESULTS: We identified 1129 consecutive patients who underwent pharmacologic stress imaging with dipyridamole and thallium 201. LHR and a dilation index were calculated and compared with each other and with relevant clinical parameters. Echocardiographic parameters were also compared in a subset of 475 patients who had echocardiography within 2 weeks of pharmacologic stress testing. There was no significant correlation between elevated LHR and TID despite the fact that both were associated with more severe thallium stress and redistribution scores. Patients with elevated LHR were more likely to have a history of myocardial infarction and coronary artery bypass grafting and to have lower ejection fraction. Patients with TID were more likely to have a positive electrocardiographic response (15% vs 7%, P =.0003), which was not seen in patients with elevated LHR (11% vs 8%, P =.23). CONCLUSIONS: Although both elevated LHR and TID were associated with more severe coronary disease, they have no significant correlation. Patients with elevated LHR are more likely to have a history of myocardial infarction or coronary artery bypass grafting, a larger left ventricle, and lower ejection fraction. Our results support the hypothesis that TID is due to diffuse subendocardial hypoperfusion and represents a different pathophysiologic response to ischemia than elevated LHR.

Aged↗