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Biomedical subjects

Harald Kugel

Publications and source records attributed to Harald Kugel.

At least 19 recordsLinked to original sources
PubMed2007

Cognitive coping style modulates neural responses to emotional faces in healthy humans: a 3-T FMRI study.

Repression designates coping strategies that aim to shield the organism from distressing stimuli by disregarding their aversive characteristics. In contrast, sensitization comprises coping strategies that are employed to reduce situational uncertainty such as analyzing the environment. Functional magnetic resonance imaging was used to study neural correlates of coping styles during the perception of threatening and nonthreatening socially relevant information. Pictures of human faces bearing fearful (ambiguously threatening), angry (unambiguously threatening), happy (nonthreatening), and neutral expressions were presented masked and unmasked. Two groups of subjects were examined who were defined as consistent repressors versus consistent sensitizers with the Mainz Coping Inventory. Sensitizers tended to exhibit stronger neural responses in the amygdala to unmasked fearful faces compared with repressors. Overall, repressors were cortically more responsive to fearful (ambiguously threatening) and happy (nonthreatening) facial expressions than sensitizers, whereas sensitizers presented an enhanced responsivity to angry faces in several prefrontal areas, that is, unambiguously threatening expressions. Results from time series analyses suggest that sensitizers could exhibit less top-down cortical regulation of the amygdala than repressors in the processing of fearful faces. An increased responsivity of the amygdala to ambiguously threatening stimuli may represent a biological determinant of sensitizers' feelings of uncertainty.

Adaptation, Psychological↗
PubMed2006

Amygdala reactivity predicts automatic negative evaluations for facial emotions.

The amygdala is a key structure in a limbic circuit involved in the rapid and unconscious processing of facial emotions. In the present study, the role of the amygdala in automatic, involuntary appraisal processes, which are believed to be a crucial component of emotion processing, was investigated in 23 healthy subjects. Amygdala activity was recorded in response to masked displays of angry, sad, and happy facial expressions using functional magnetic resonance imaging (fMRI). In a subsequent experiment, the subjects performed a masked affective priming task that characterizes automatic emotion processing by investigating the biasing effect of subliminally presented emotional faces on evaluative ratings to subsequently presented neutral stimuli. In the affective priming task, significant valence-congruent evaluation manipulation was observed. Subjects rated neutral targets more positively if they were primed by happy faces. Significant correlations were found between amygdala responses to masked negative facial expressions and negative evaluation shifts elicited by the corresponding emotion quality in the affective priming task. Spontaneous amygdala reactivity to facial emotions appears to be a determinant of automatic negative evaluative response tendencies. This finding might shed some light on how amygdala hyperresponsivity contributes to negative cognitive biases commonly observed in affective disorders.

Adult↗
PubMed2006

Detection of colorectal polyps: comparison of multi-detector row CT and MR colonography in a colon phantom.

PURPOSE: To compare multi-detector row (four- and 16-section) computed tomography (CT), including a low-dose protocol, with high-field-strength (1.5- and 3.0-T) magnetic resonance (MR) imaging for reader detection of colorectal polyps in a colon phantom. MATERIALS AND METHODS: A colon phantom with simulated haustral folds and 10 polyps of varying size (2.0-8.0 mm) was imaged at four- and 16-section CT (section thicknesses of 1.25 and 0.75 mm, reconstruction increments of 0.8 and 0.7 mm, and 100 and 10 mAs, respectively, and 120 kV for both) and at 1.5- and 3.0-T MR imaging (three-dimensional gradient-recalled echo sequence, section thickness of 1.4 mm). Three-dimensional endoluminal images were assessed by 10 reviewers for each modality regarding polyp detection. Comparisons of sensitivities were performed by using logistic regression. RESULTS: Overall, polyps were detected with a sensitivity of 87% (95% confidence interval [CI]: 80%, 94%) at four-section CT, 92% (95% CI: 87%, 97%) at 16-section CT, 56% (95% CI: 46%, 66%) at 1.5-T MR imaging, and 55% (95% CI: 45%, 65%) at 3.0-T MR imaging. The detection of polyps at least 4 mm in diameter was not influenced by the modality or radiation dose (sensitivity of 100%). CT performed in low-dose mode depicted all polyps with a diameter of at least 3 mm. Polyps smaller than 3 mm in diameter were detected with a sensitivity of 7.5% (1.5-T MR imaging), 22.5% (3.0-T MR imaging), and 20% (low-dose CT); detection rates were significantly greater (P < .001) with normal-dose CT (four section, 67.5%; 16 section, 82.5%). Increased spatial resolution (with CT) and higher field strength (with MR imaging) had no significant effect on polyp detection. CONCLUSION: With both multi-detector row CT and MR imaging, readers detected polyps above the clinically relevant threshold diameter of 6 mm, with similar sensitivities.

Colonic Polyps↗
PubMed2006

Amygdala activation during masked presentation of emotional faces predicts conscious detection of threat-related faces.

It has been argued that critical functions of the human amygdala are to modulate the moment-to-moment vigilance level and to enhance the processing and the consolidation of memories of emotionally arousing material. In this functional magnetic resonance study, pictures of human faces bearing fearful, angry, and happy expressions were presented to nine healthy volunteers using a backward masking procedure based on neutral facial expression. Activation of the left and right amygdala in response to the masked fearful faces (compared to neutral faces) was significantly correlated with the number of fearful faces detected. In addition, right but not left amygdala activation in response to the masked angry faces was significantly related to the number of angry faces detected. The present findings underscore the role of the amygdala in the detection and consolidation of memory for marginally perceptible threatening facial expression.

Adult↗
PubMed2006

fMRI studies of sensitivity and habituation effects within the auditory cortex at 1.5 T and 3 T.

PURPOSE: To assess habituation effects in relation to field strength by fMRI at 1.5 vs. 3.0 T within the auditory cortex of healthy subjects. MATERIALS AND METHODS: fMRI experiments were performed on 19 healthy subjects at 1.5 T (N = 12) and 3 T (N = 12). The auditory cortex was stimulated binaurally by digitally generated pulsed (nu = 5 Hz) 800 Hz sine tones with three alternating on and off periods. RESULTS: The mean activation after stimulation (4.4% +/- 1.2% (1.5 T) and 5.3% +/- 2.3% (3 T)) and number of activated pixels (96.7 +/- 49.8 (1.5 T) and 139.9 +/- 101 (3 T)) were higher at 3 T compared to 1.5 T; however, that difference did not reach statistical significance. A characteristic signal decay with repeated stimuli was revealed at both 1.5 and 3 T, and the response to the second and third stimulation blocks was significantly lower compared to the first. The habituation pattern was the same, independently of field strength and age. CONCLUSION: The mean activation and number of pixels were only modestly higher at 3 T, probably due to higher physiologic noise and higher local macroscopic susceptibility gradients within the temporal lobes at 3 T. Our data reveal that measured auditory habituation is independent of field strength, and data obtained at two different field strengths do not differ fundamentally in this context.

Acoustic Stimulation↗
PubMed2006

Spontaneous acute dissection of the internal carotid artery: high-resolution magnetic resonance imaging at 3.0 tesla with a dedicated surface coil.

PURPOSE: Magnetic Resonance Imaging (MRI) has become the method of choice in the evaluation of patients with suspected cervical artery dissection (CAD). However, reliable identification of acute CAD might be impaired by the limited spatial resolution of standard 1.5 T MRI. In this preliminary study, we implemented a multicontrast high-resolution noninvasive vessel wall imaging approach at 3.0 T in patients with spontaneous CAD. METHODS AND MATERIALS: Ten patients with CAD of the internal carotid artery (ICA) were included in the study. 3.0 T MRI (Gyroscan Intera, Philips) was acquired using a dedicated phased-array coil. MRI-protocol consisted of: (1) bright blood 3D inflow MRA (TR/TE/FA = 25 milliseconds/3.1 millisecond/16 degrees , 120 slices, reconstructed voxel size 0.3 x 0.3 x 0.8 mm); (2) black blood cardiac-gated water-selective T1w 3D spoiled GE (TR/TE/FA = 31 milliseconds/7.7 milliseconds/15 degrees , 36 slices, 0.3 x 0.3 x 1.0 mm); and (3) black blood cardiac triggered fat suppressed T2w TSE (TR/TE/ETL = 3 heart beats/44 milliseconds/7, 18 slices, 0.3 x 0.3 x 2 mm). Three observers in consensus performed image analysis. Special attention was paid to the integrity of the luminal and adventitial vessel boundary and the presence of a communicating intimal tear or flap. RESULTS: 3.0 T MRI provided excellent delineation of vessel lumen and vessel wall as a result of the nearly complete suppression of arterial blood signal. An intramural hematoma could be identified in all patients, confined between the luminal and adventitial vessel boundary. In no patient a communicating intimal tear could be identified. Clear distinction between intramural hematoma and thrombus was possible. CONCLUSION: High-resolution vessel wall imaging in patients with acute CAD is feasible. The increased signal-to-noise ratio at 3.0 T can be invested to obtain a higher spatial resolution, permitting depiction of intimal and adventitial vessel wall boundary and the intramural hematoma in the diseased vessel segment. The morphologic information that is gained is helpful in the understanding of the underlying pathomechanismen of CAD.

Adult↗
PubMed2005

FLAIR imaging for multiple sclerosis: a comparative MR study at 1.5 and 3.0 Tesla.

The purpose of this study was (1) to identify the optimal TE for FLAIR-imaging at 3.0 T assessing three different echo times qualitatively and quantitatively and (2) to evaluate the diagnostic efficacy of high-field 3.0-T FLAIR imaging in comparison to conventional 1.5-T MRI in patients with multiple sclerosis (MS). Twenty-two patients with clinically definite MS underwent axial FLAIR imaging at 1.5 and 3.0 T. In 15 of these patients further FLAIR images with a TE of 100, 120 and 140 ms were acquired at 3.0 T. Imaging protocols were modified for 3.0 T using the increased SNR to acquire more and thinner slices while maintaining a comparable scan time. FLAIR images of either different TEs or different field strengths were ranked for each patient qualitatively by two observers. Signal intensity measurements were obtained in the gray and white matter, CSF and representative white matter lesions (WML). At 3.0 T, a TE of 100 and 120 ms proved superior in all qualitative categories when compared to 140 ms. In the quantitative assessment CNR of WML was highest for 120 ms (CNR: 19.8), intermediate for 100 ms (17.2) and lowest for 140 ms (15.3) (P<0.003). For lesion conspicuity and overall image quality, 3.0 T was judged superior to 1.5 T, whereas no difference was found for gray-white differentiation and image noise. With regard to artifacts, 3.0 T was inferior to 1.5 T. The CNR for WML was slightly lower at 3.0 T, but the difference was not significant (22.6 vs. 28.0, P=ns). However, significantly more WML were detected at 3.0 T than at 1.5 T (483 vs. 341, P<0.0001). The optimal echo time for FLAIR imaging at 3.0 T is 120 ms due to the significantly higher CNR of WML. By trading the higher SNR at 3.0 T for better spatial resolution, nearly the same CNR level could be maintained, increasing lesion detectability at 3.0 T compared to 1.5 T. Thus, high-field MRI may further strengthen the role of MRI as the most sensitive paraclinical test for the early diagnosis of MS.

Adult↗
PubMed2005

Abnormal brain activation during movement observation in patients with conversion paralysis.

Dissociative paralysis in conversion disorders has variably been attributed to a lack of movement initiation or an inhibition of movement. While psychodynamic theory suggests altered movement conceptualization, brain activation associated with observation and replication of movements has so far not been assessed neurobiologically. Here, we measured brain activation by functional magnetic resonance imaging during observation and subsequent imitative execution of movements in four patients with dissociative hand paralysis. Compared to healthy controls conversion disorder patients showed decreased activation of cortical hand areas during movement observation. This effect was specific to the side of their dissociative paralysis. No brain activation compatible with movement inhibition was observed. These findings indicate that in dissociative paralysis, there is not only derangement of movement initiation but already of movement conceptualization. This raises the possibility that strategies targeted at reestablishing appropriate movement conceptualization may contribute to the therapy of dissociative paralysis.

Adult↗
PubMed2005

Excellent cognitive performance despite massive cerebral white matter changes.

Marked cerebral white matter changes are a frequent finding in the daily routine of magnetic resonance imaging of elderly patients. These findings are often equated with a decrease of cognitive function. Here we present a case of massive white matter changes but excellent cognitive performance, to avoid the automatism of drawing conclusions on intellectual ability by just interpreting the imaging data of elderly patients.

Aged↗
PubMed2005

Association of the functional -1019C/G 5-HT1A polymorphism with prefrontal cortex and amygdala activation measured with 3 T fMRI in panic disorder.

Serotonergic genes have been implicated in the pathogenesis of panic disorder and amygdala function in response to fearful stimuli. Regional brain activation on visual presentation of emotional facial stimuli was investigated in 20 patients with panic disorder by means of fMRI at 3 T. All patients were genotyped for the functional -1019C/G 5-HT1A and 5-HTTLPR polymorphisms. In patients homozygous for the 5-HT1A -1019G risk allele (n=5), fearful stimuli were associated with a decreased activation of right prefrontal cortex regions. Patients homozygous for the 5-HT1A -1019G risk allele or patients carrying the short risk allele of the 5-HTTLPR (n=13) showed higher amygdala activation in response to happy faces. This exploratory study suggests a role of the functional -1019C/G 5-HT1A and 5-HTTLPR polymorphisms on prefrontal cortex and amygdala activation patterns in response to emotional facial stimuli. These serotonergic polymorphisms might increase the risk for panic disorder by contributing to an altered processing of emotional stimuli.

Adult↗
PubMed2005

3.0 T vs. 1.5 T MR angiography: in vitro comparison of intravascular stent artifacts.

PURPOSE: To evaluate the signal characteristics of different iliac artery stents in MR angiography (MRA) at 3 T in comparison with 1.5 T. MATERIALS AND METHODS: Sixteen iliac artery stents were implanted in plastic tubes filled with a solution of Gd-DTPA and imaged at 3 T and 1.5 T using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis included a subjective assessment of artifact characteristics, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements in stented and unstented vessel parts, and quantitative measurements of total artifact size. RESULTS: The pattern of stent artifacts inside the stents evidently did not differ at 3 T and 1.5 T. The average total size of the artifact areas surrounding the stents was significantly larger at 3 T (P < 0.03). However, within the stented part of the vessel phantom, the signal of the lumen and its contrast to modeled surrounding tissue was significantly higher at the higher field. The mean SNR of the lumen increased from 95.5 at 1.5 T to 127.3 at 3 T, and the CNR of the vessel increased from 70.3 to 93. CONCLUSION: Assessment of the stent lumen in iliac artery stents in a phantom model is not compromised by imaging at 3 T compared to 1.5 T. The signal gain inside the stented part of the vessel lumen at higher field compensates for the higher degree of stent artifacts seen in stents made of steel or cobalt.

Artifacts↗
PubMed2005

Safe performance of magnetic resonance imaging on a patient with an ICD.

This is a report on a patient with an implanted cardioverter defibrillator (ICD) who intentionally underwent magnetic resonance imaging (MRI) of a malignant brain tumor. To avoid inadequate detection of ventricular tachycardia (VT) or ventricular fibrillation (VF), the ICD was inactivated by programming the VT-detection and VT/VF-therapy status off. The patient came through the protocol safely and without any difficulty or discomfort. There was no arrhythmic event. MRI affected neither programmed data nor the function of the ICD system.

Brain Neoplasms↗
PubMed2005

Nonlinear responses within the medial prefrontal cortex reveal when specific implicit information influences economic decision making.

BACKGROUND AND PURPOSE: The authors used functional magnetic resonance imaging (fMRI) to investigate how individual economic decisions are influenced by implicit memory contributions. METHODS: Twenty-two participants were asked to make binary decisions between different brands of sensorily nearly undistinguishable consumer goods. Changes of brain activity comparing decisions in the presence or absence of a specific target brand were detected by fMRI. RESULTS: Only when the tar get brand was the participant's favorite one did the authors find reduced activation in the dorsolateral prefrontal, posterior parietal, and occipital cortices and the left premotor area (Brodmann areas [BA] 9, 46, 7/19, and 6). Simultaneously, activity was increased in the inferior precuneus and posterior cingulate (BA 7), right superior frontal gyrus (BA 10), right supramarginal gyrus (BA 40), and, most pronounced, in the ventromedial prefrontal cortex (BA 10). CONCLUSIONS: For products mainly distinguishable by brand information, the authors revealed a nonlinear winner-take-all effect for a participant's favorite brand characterized, on one hand, by reduced activation in brain areas associated with working memory and reasoning and, on the other hand, increased activation in areas involved in processing of emotions and self-reflections during decision making.

Adult↗
PubMed2004

Acute and subacute intracerebral hemorrhages: comparison of MR imaging at 1.5 and 3.0 T--initial experience.

PURPOSE: To assess and describe the appearance of intracerebral hemorrhage (ICH) at 3.0-T magnetic resonance (MR) imaging as compared with the appearance of this lesion type at 1.5-T MR imaging. MATERIALS AND METHODS: Sixteen patients with 21 parenchymal ICHs were examined. ICHs were classified as hyperacute, acute, early subacute, late subacute, or chronic. Patients underwent 1.5- and 3.0-T MR imaging with T2-weighted fast spin-echo, fluid-attenuated inversion-recovery (FLAIR), and T1-weighted spin-echo (1.5-T) and gradient-echo (3.0-T) sequences within 4 hours of each other. The central (ie, core) and peripheral (ie, body) parts of the ICHs were analyzed quantitatively by using contrast-to-noise ratio (CNR) calculations derived from signal intensity (SI) measurements; these values were statistically evaluated by using the Mann-Whitney U test. Two readers qualitatively determined SIs of the cores and bodies of the ICHs, degrees of apparent susceptibility artifacts, and lesion ages. The chi(2) test was used to determine statistically significant differences. RESULTS: With the exception of the bodies of late subacute ICHs at 3.0-T T2-weighted imaging, which had increased positive CNRs and SI scores (P </=.05), all parts of the ICHs at all stages showed increased negative CNRs and SI scores at 3.0-T FLAIR and T2-weighted imaging, as compared with these values at 1.5 T (P </=.05). No significant CNR or SI score differences at any ICH stage were observed between 1.5-T spin-echo and 3.0-T gradient-echo T1-weighted imaging (P >.05). With the exception of minor susceptibility artifacts seen in acute and early subacute ICHs at 3.0-T T1-weighted gradient-echo imaging, no susceptibility artifacts were noticed. The ages of most lesions were identified correctly without significant differences between the two field strengths (P >.05), with the exception of the ages of acute ICHs, which were occasionally misinterpreted as early subacute lesions at 3.0 T. CONCLUSION: At 3.0 T, all parts of acute and early subacute ICHs had significantly increased hypointensity on FLAIR and T2-weighted MR images as compared with the SIs of these lesions at 1.5 T. However, 1.5- and 3.0-T MR images were equivalent in the determination of acute to late subacute ICHs.

Acute Disease↗
PubMed2004

3.0 Tesla magnetic resonance angiography of endovascular aortic stent grafts: phantom measurements in comparison with 1.5 Tesla.

RATIONALE AND OBJECTIVES: This study evaluated different stent grafts by 3 T magnetic resonance angiography (MRA) with respect to lumen visibility, susceptibility-induced signal loss, and type of stent artifacts compared with 1.5 T MRA in a phantom model. METHODS: Six different stent-grafts (tube: n = 3, bifurcated: n = 3) were evaluated by 3 T and 1.5 T MRA using a tube phantom. MRA was performed using T1-weighted sequences at both systems with comparable parameters (3T: TR 5.4/TE 2.0/FA 30 degrees, 1.5 T: TR 6.2/TE 2.2/FA 30 degrees). A blind study of the image quality, including artifacts, was performed by 3 radiologists. Furthermore, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values were calculated. Statistical analysis was performed with Student's t test (P < 0.05). RESULTS: One Elgiloy stent graft showed almost a complete intraluminal signal loss at 1.5 and 3 T. All other models could be evaluated by both systems by MRA, resulting in a favorable lumen visibility (score: 1) for prostheses made of nitinol. Scores for overall image quality and artifacts were the same for both MR systems. SNR and CNR values of the stented part of the vessel phantom increased from 320 +/- 33 to 618 +/- 40 and from 306 +/- 34 to 596 +/- 40 at 3 T when compared with 1.5 T, resulting in a significant signal gain of 93% at the higher field strength. CONCLUSIONS: 3 Tesla MRA of aortic stent grafts in a phantom model demonstrates an increase in SNR and CNR when compared with 1.5 T. However, the magnitude of imaging artifacts as well as coherent intraluminal signal loss within the stent does not increase equally in both MR systems.

Aorta↗
PubMed2003

Hazardous situation in the MR bore: induction in ECG leads causes fire.

There is a potential hazard during examinations of patients with attached or implanted long conductors, e.g. ECG leads: an MR exam of the lumbar spine of a patient was performed in a 1.5-T scanner under ECG monitoring using equipment marked as MR compatible. Standard cabling of 370-cm length was guided without loops from the electrodes through the caudal opening of the magnet bore. During a sagittal T1-weighted turbo-spin-echo scan suddenly a flame of approximately 3 cm arose from the patient's shirt, close to the position of the electrodes. The supervising anaesthesiologist extinguished the flames with his hands. A subsequent physical examination revealed second- to third-degree burns. The analysis of the incident revealed that high voltages can be induced in straight conductors without loops as ECG cables by coupling with the electric component of the HF field. Local heating or sparking can cause an open flame at the position of the electrodes. This danger exists even with ECG equipment that is specifically marked as MR compatible.

Electrocardiography↗
PubMed2003

Proton spectroscopic metabolite signal relaxation times in preterm infants: a prerequisite for quantitative spectroscopy in infant brain.

PURPOSE: To determine relaxation times of metabolite signals in proton magnetic resonance (MR) spectra of immature brain, which allow a correction of relaxation that is necessary for a quantitative evaluation of spectra acquired with long TE. Proton MR spectra acquired with long TE allow a better definition of metabolites as N-acetyl aspartate (NAA) and lactate especially in children. MATERIALS AND METHODS: Relaxation times were determined in the basal ganglia of 84 prematurely born infants at a postconceptional age of 37.8 +/- 2.2 (mean +/- SD) weeks. Metabolite resonances were investigated using the double-spin-echo volume selection method (PRESS) at 1.5 T. T1 was determined from intensity ratios of signals obtained with TRs of 1884 and 6000 msec, measured at 3 TEs (25 msec, 136 msec, 272 msec). T2 was determined from signal intensity ratios obtained with TEs of 136 msec and 272 msec, measured at 2 TR. Taking only long TEs reduced baseline distortions by macromolecules and lipids. For myo-inositol (MI), an apparent T2 for short TE was determined from the ratio of signals obtained with TE = 25 msec and 136 msec. Intensities were determined by fitting a Lorentzian to the resonance, and by integration. RESULTS: Relaxation times were as follows: trimethylamine-containing compounds (Cho): T1 = 1217 msec/T2 = 273 msec; total creatine (Cr) at 3.9 ppm: 1010 msec/111 msec; Cr at 3.0 ppm: 1388 msec/224 msec; NAA: 1171 msec/499 msec; Lac: 1820 msec/1022 msec; MI: 1336 msec/173 msec; apparent T2 at short TE: 68 msec. CONCLUSION: T1 and T2 in the basal ganglia of premature infants do not differ much from previously published data from basal ganglia of older children and adults. T2 of Cho was lower than previous values. T2 of Cr at 3.9 ppm and Lac have been measured under different conditions before, and present values differ from these data.

Adult↗