Search PubMed⌕ Search

Biomedical subjects

W Hundt

Publications and source records attributed to W Hundt.

At least 19 recordsLinked to original sources
PubMed2002

Clinical evaluation of further-developed MRCP sequences in comparison with standard MRCP sequences.

The purpose of this study was the comparison of technically improved single-shot magnetic resonance cholangiopancreatography (MRCP) sequences with standard single-shot rapid acquisition with relaxation enhancement (RARE) and half-Fourier acquired single-shot turbo spin-echo (HASTE) sequences in evaluating the normal and abnormal biliary duct system. The bile duct system of 45 patients was prospectively investigated on a 1.5-T MRI system. The investigation was performed with RARE and HASTE MR cholangiography sequences with standard and high spatial resolutions, and with a delayed-echo half-Fourier RARE (HASTE) sequence. Findings of the improved MRCP sequences were compared with the standard MRCP sequences. The level of confidence in assessing the diagnosis was divided into five groups. The Wilcoxon signed-rank test at a level of p<0.05 was applied. In 15 patients no pathology was found. The MRCP showed stenoses of the bile duct system in 10 patients and choledocholithiasis and cholecystolithiasis in 16 patients. In 12 patients a dilatation of the bile duct system was found. Comparison of the low- and high spatial resolution sequences and the short and long TE times of the half-Fourier RARE (HASTE) sequence revealed no statistically significant differences regarding accuracy of the examination. The diagnostic confidence level in assessing normal or pathological findings for the high-resolution RARE and half-Fourier RARE (HASTE) was significantly better than for the standard sequences. For the delayed-echo half-Fourier RARE (HASTE) sequence no statistically significant difference was seen. The high-resolution RARE and half-Fourier RARE (HASTE) sequences had a higher confidence level, but there was no significant difference in diagnosis in terms of detection and assessment of pathological changes in the biliary duct system compared with standard sequences.

Adult↗
PubMed2001

Case-oriented computer-based-training in radiology: concept, implementation and evaluation.

BACKGROUND: Providing high-quality clinical cases is important for teaching radiology. We developed, implemented and evaluated a program for a university hospital to support this task. METHODS: The system was built with Intranet technology and connected to the Picture Archiving and Communications System (PACS). It contains cases for every user group from students to attendants and is structured according to the ACR-code (American College of Radiology) 2. Each department member was given an individual account, could gather his teaching cases and put the completed cases into the common database. RESULTS: During 18 months 583 cases containing 4136 images involving all radiological techniques were compiled and 350 cases put into the common case repository. Workflow integration as well as individual interest influenced the personal efforts to participate but an increasing number of cases and minor modifications of the program improved user acceptance continuously. 101 students went through an evaluation which showed a high level of acceptance and a special interest in elaborate documentation. CONCLUSION: Electronic access to reference cases for all department members anytime anywhere is feasible. Critical success factors are workflow integration, reliability, efficient retrieval strategies and incentives for case authoring.

Computer Communication Networks↗
PubMed2001

Enhancement of cerebral diseases: how much contrast agent is enough? Comparison of 0.1, 0.2, and 0.3 mmol/kg gadoteridol at 0.2 T with 0.1 mmol/kg gadoteridol at 1.5 T.

RATIONALE AND OBJECTIVES: To determine the clinical dose of gadoteridol (ProHance, Bracco-Byk Gulden) to use for the assessment of blood-brain barrier breakdown on low-field magnetic resonance (MR) scanners that corresponds to a standard dose of gadoteridol on high-field MR scanners. METHODS: This prospective study was carried out at four centers. A total of 138 patients with suspected or known brain diseases underwent a routine head scan comprising precontrast T2-weighted turbo spin-echo and T1-weighted spin-echo sequences on a 1.5-T MR scanner. After administration of a standard dose of 0.1 mmol/kg gadoteridol, the T1-weighted scan was repeated after a delay of 15 to 20 minutes. For continuing the examination on a 0.2-T MR scanner (Magnetom OPEN, Siemens), a standard-dose T1 spin-echo sequence was started within 30 to 50 minutes of the first injection. Then two additional T1-weighted low-field sequences were each started 5 minutes after two additional doses of 0.1 mmol/kg gadoteridol. Eighty patients with enhancing lesions underwent an intraindividual comparison. Evaluation of the overall numbers of lesions detected and of lesion size and character was performed on-site as well as off-site by two independent readers. RESULTS: The single-dose, low-field sequence detected significantly fewer enhancing lesions (80/95 lesions; P < 0.05), particularly metastases and infarctions, than did the standard-dose, high-field sequence. No statistically relevant differences (reader 1: P = 1; reader 2: P = 0.8) were found between the double- and triple-dose, low-field sequences and the standard-dose, high-field sequence. Primary brain tumors were detected by all postcontrast sequences irrespective of the dose. CONCLUSIONS: At low field, the clinically equivalent dose to 0.1 mmol/kg gadoteridol at high field is 0.2 mmol/kg. A dose of 0.1 mmol/kg gadoteridol is less effective and cannot be recommended for use on extremely low-field scanners.

Adult↗
PubMed2001

Neuroendocrine effects of a short-term osmotic stimulus in patients with chronic schizophrenia.

We studied the effects of a short-term hypertonic stimulus on plasma levels of the stress hormones adrenocorticotropin (ACTH), cortisol, prolactin, and the blood volume- and electrolyte-controlling hormones arginine vasopressin (AVP) and atrial natriuretic peptide (ANP). Seven patients suffering from chronic schizophrenia with negative symptoms and ten healthy control subjects were investigated by a 20-minute infusion of 10 ml/kg body weight of hypertonic (2.5%) versus isotonic (0.9%) saline. All patients, who were medication-free for at least one week prior to the study, and all control subjects participated in two investigations in randomized order according to a single-blind cross-over design. During hypertonic infusion, plasma osmolarity and sodium levels were increased similarly in both groups and significantly more than during isotonic saline. Hypertonic saline caused a significant increase of plasma ACTH, cortisol and prolactin in patients in contrast to controls. AVP and ANP plasma concentrations were elevated after infusion of hypertonic saline, however, only patients showed a significant rise in plasma ANP. These results show that a dysregulation of the hypothalamic-pituitary-adrenal (HPA) system in a subset of patients with chronic schizophrenia may become overt during an osmotic stimulation, indicating an increased sensitivity of patients with schizophrenia to osmotic stress.

Adrenocorticotropic Hormone↗
PubMed2001

The combined dexamethasone-suppression/CRH-stimulation test in alcoholics during and after acute withdrawal.

BACKGROUND: Chronic alcoholism is often accompanied by disturbances of the hypothalamic-pituitary-adrenal (HPA) system. Patients with alcoholism frequently show nonsuppression in the dexamethasone (Dex) suppression test and also a blunted increase of adrenocorticotropin (ACTH) after injection of corticotropin-releasing hormone (hCRH). However, the underlying mechanisms have not been fully elucidated. The combined Dex/CRH test (pretreatment with 1.5 mg dexamethasone at 2300 hr, injection of 100 microg hCRH at 1500 hr the next day) has been established as a more sensitive tool to investigate HPA system regulation in depressed patients. METHODS: We studied the effect of the combined Dex/CRH test in 19 alcoholic inpatients (9 male, 10 female) during and after withdrawal along with 19 healthy controls. RESULTS: Compared to normal controls, patients showed a severely dysregulated HPA system during withdrawal, with significantly elevated cortisol and ACTH response to hCRH after pretreatment with dexamethasone. After completed withdrawal, cortisol levels after injection of hCRH were almost normalized while ACTH values were partially lower in patients, compared to controls. CONCLUSIONS: We conclude that the HPA system is severely disturbed during alcohol withdrawal, possibly reflecting an exaggerated release of hypothalamic corticotropin and vasopressin.

Adrenocorticotropic Hormone↗
PubMed2000

Functional consequences of reduction in NMDA receptor glycine affinity in mice carrying targeted point mutations in the glycine binding site.

We have used site-directed mutagenesis in conjunction with homologous recombination to generate two mouse lines carrying point mutations in the glycine binding site of the NMDAR1 subunit (Grin1). Glycine concentration-response curves from acutely dissociated hippocampal neurons revealed a 5- and 86-fold reduction in receptor glycine affinity in mice carrying Grin1(D481N) and Grin1(K483Q) mutations, respectively, whereas receptor glutamate affinity remained unaffected. Homozygous mutant Grin1(D481N) animals are viable and fertile and appear to develop normally. However, homozygous mutant Grin1(K483Q) animals are significantly lighter at birth, do not feed, and die within a few days. No gross abnormalities in CNS anatomy were detected in either Grin1(D481N) or Grin1(K483Q) mice. Interestingly, in situ hybridization and Western blot analysis revealed changes in the expression levels of NMDA receptor subunits in Grin1(D481N) mice relative to wild type that may represent a compensatory response to the reduction in receptor glycine affinity. Grin1(D481N) mice exhibited deficits in hippocampal theta burst-induced long-term potentiation (LTP) and spatial learning and also a reduction in sensitivity to NMDA-induced seizures relative to wild-type controls, consistent with a reduced activation of NMDA receptors. Mutant mice exhibited normal prepulse inhibition but showed increased startle reactivity. Preliminary analysis indicated that the mice exhibit a decreased natural aversion to an exposed environment. The lethal phenotype of Grin1(K483Q) animals confirms the critical role of NMDA receptor activation in neonatal survival. A milder reduction in receptor glycine affinity results in an impairment of LTP and spatial learning and alterations in anxiety-related behavior, providing further evidence for the role of NMDA receptor activation in these processes.

Animals↗
PubMed2000

Effect of superparamagnetic iron oxide on bone marrow.

The goal of this study was to compare the effects of SPIO particles on the signal intensity of the bone marrow of the vertebra spine in patients with and without liver cirrhosis. Forty-eight patients with normal liver tissue and 56 patients with liver cirrhosis were examined before and after intravenous SPIO administration, using a 1.5-T system (Magnetom Vision, Siemens, Erlangen, Germany) with a semiflexible cp-array coil. Three different pulse sequences were applied: a T1-weighted gradient-echo sequence, a T2-weighted fast spin-echo sequence with spectral fat suppression and a T2*-weighted gradient-echo sequence. The signal-to-noise ratio (SNR) of the liver, vertebra bone and paraspinal muscle were obtained. The SNR value change in each patient group and the SNR value difference between the two groups were evaluated. For assessment of statistical significance, Student's t-test with a level of p < 0.05 was applied. No significant differences in the SNR values of the liver and bone marrow between the two groups could be seen with any of the three sequences precontrast. Using the T1-weighted gradient-echo sequence in the noncirrhotic liver group, pre- and postcontrast comparisons of the SNR values of the liver and bone marrow indicated a decrease of approximately -44.3% (p = 0.02) and increase of approximately 15.3% (p = 0.04), respectively. No significant change was seen in the cirrhotic liver group. With the T2-weighted fast spin-echo sequence, a significant decrease of the SNR value of the liver and the bone marrow in both groups was seen. With the T2*-weighted gradient-echo sequence, the signal intensity decrease of the normal liver tissue was approximately -65.6% (p = 0.00), in cirrhotic liver tissue the decrease was -29.9% (p = 0.02). The SNR values of the bone marrow showed a decrease of -27.8% (p = 0.04) in the noncirrhotic liver group, whereas in the cirrhotic liver group it was only -11.3% and statistically not significant. The effect of SPIO particles on the liver and bone marrow is significantly less in patients with liver cirrhosis.

Adult↗
PubMed2000

Signal changes in liver and spleen after Endorem administration in patients with and without liver cirrhosis.

The goal of this study was compare the effect of Endorem on the signal intensity of the spleen in patients with normal liver tissue and in patients with liver cirrhosis. Thirty patients with normal liver tissue and 47 with liver cirrhosis were examined before and after i.v. Endorem administration. The patients were examined with a 1.5-T magnet system (Magnetom Vision) using a semiflexible cp-array coil. Three different pulse sequences were used: a T1-weighted gradient-echo sequence, a T2-weighted fast spin-echo sequence with spectral fat suppression, and a T2*-weighted gradient-echo sequence. The signal-to-noise ratios (SNRs) of two areas of the liver and spleen were determined. The mean SNRs of the liver and spleen in patients with and without liver cirrhosis were compared. For assessment of statistical significance, the t-test at a level of P < 0.05 was applied. After i.v. administration of Endorem, no differences were seen with the T1-weighted gradient-echo sequence for the liver and spleen and, with the T2-weighted fast spin-echo sequence, no differences were found for the spleen. Significant differences between both groups were seen for the liver with the T2-weighted fast spin-echo sequence. The SNR in the noncirrhotic liver group was 57.4% lower than the SNR in the cirrhotic liver group. With the T2*-weighted gradient-echo sequence, the SNRs of the liver and spleen in the noncirrhotic liver group, compared with the cirrhotic liver group, were 126.8% and 45.6% less, respectively. The effect of Endorem on the liver in patients with Child C-stage liver cirrhosis was 32.1% less than in patients with Child B-stage liver cirrhosis. Likewise, the Endorem effect on the spleen was 27.1% less in patients with Child C-stage compared with Child B-stage liver cirrhosis. Hepatic and splenic uptake of Endorem is significantly decreased in patients with liver cirrhosis.

Adult↗
PubMed1999

[Kidney spiral CT. Indication, method, results].

The introduction on spiral computed tomography (spiral CT) has vastly enriched the methodological diversity of computer-tomographic scans. It allows for the recording of different perfusion or excretion stages of the kidney parenchyma of the urine draining paths by carrying out long-distance, phase-identical multiple examinations of the retroperitoneum. The description of the findings which are characterized by their local and contrasts behavior is possible. The following report describes the indications and technological process of kidney spiral CT using kidney-typical intravenous contrast media. Special emphasis is put on the advantages and limits of multiple phase spiral CT. Decisive preconditions are: 1. specific clinical query, 2. selection of the corresponding phase contrasts of the kidneys and uretra or bladder, 3. exact technical and temporal adjustment of the acquisition parameters. Scanning times are in the range of seconds. The overall examination can be carried out quick and without any major strain on the part of the patient. A sound proof and a general differentiation of focal kidney lesions can be derived from the acquired data. This is also true for kidneys and ureters findings. Bladder findings can be localized and differentiated according to stage. More than two "spiral acquisitions" should be carried out with re-straint taking exposure to radiation into account. Due to the sound registration of focal lesions, its capability of reproduction and its short-time examination, the spiral CT of the kidneys can be said to be the most effective current scanning method of the retroperitoneum following clinical examinations and sonography.

Female↗
PubMed1999

Assessment of gastric cancer: value of breathhold technique and two-phase spiral CT.

The purpose of this study was to evaluate the capabilities of subsecond spiral CT in detecting and staging of gastric cancer. Our study included 40 patients with endoscopically detected gastric carcinomas. Two-phase spiral CT was performed within one breathhold each. Distension of the stomach was achieved by intravenous application of scopolamine and drinking of 500 ml water. After bolus injection of contrast medium, scanning was performed in the arterial and venous phase. Gastric tumour extention and lymph node involvement was assessed. Gastric cancer was detected in 39 of 40 cases (sensitivity 97.5%). Location of the tumour was correctly assessed in all cases. In 31 of the 39 cases (79.4%) CT staging was accordant with pathological staging. One hundred two (70%) of 145 nodes infiltrated by tumour tissue were detected and 144 (42.8%) of 336 nodes free of metastatic involvement were found. The predictive values of positive and negative results for the detection of lymph node metastases were 67.1 and 75%, respectively. Spiral CT is recommended for staging of gastric cancer.

Adenocarcinoma↗
PubMed1999

Evaluation of spiral CT in staging of colon and rectum carcinoma.

The purpose of our study was to evaluate the capability of a subsecond spiral-CT scanner using two contrast medium phases in staging of colorectal cancer. In our study we included 37 patients with proven rectum or colon carcinoma. Spiral CT was performed following tap-water enema of the colon in the arterial and venous phases of contrast medium enhancement. Our results were compared with the findings of pathological examination after surgery. The tumor's size and extension were evaluated in the arterial and venous phases, the lymph nodes in the venous phase of the CT scan. The tumor was in the rectum (n = 14), sigma (n = 11), descending colon (n = 6), and cecum (n = 6). Two-phase spiral CT had a sensitivity of 97.2% in the arterial phase and 89.1% in the venous phase in detecting the carcinoma. The staging results were in the arterial phase in 30 of 37 cases (81.0%) and in the venous phase in 24 of 37 cases (64.8%) according to pathology. In 27 of 32 patients (84.3%) lymph nodes were detected. The correct classification of the N-stage was possible in 23 of 34 cases (67.6%). The combined use of arterial and venous phases in staging of colorectal cancer can improve the T- and N-stage classification in comparison with using only one contrast medium phase. The arterial phase is superior compared with the venous phase for local tumor staging and the venous phase is used for lymph node assessment.

Adult↗
PubMed1999

Diffuse metastatic infiltration of a carcinoma into skeletal muscle.

Skeletal muscle is one of the most unusual sites of metastasis from any malignancy. We report a patient with rapidly progressive contractures due to metastatic infiltration of a carcinoma of unknown origin into the skeletal muscle. This 61-year-old man presented with a 1-month history of rapidly evolving, painful restriction of mobility of his right arm and his legs. Computed tomography showed diffuse metastatic nodules in all muscles, particularly in the hip abductors. Muscle biopsy revealed extensive infiltration of the muscle with carcinoma cells.

Biopsy↗
PubMed1999

MRI findings of muscle involvement in idiopathic hypereosinophilic syndrome.

A 40-year-old white man presented with fever, muscle pain, skin nodules and persistent hypereosinophilia over a period of 1 year. In addition, he had ventricular arrhythmias with episodes of tachycardia. Besides a lack of response to antiparasitic therapy, laboratory and pathological data excluded the diagnosis of trichinosis or any other parasitic infection. The patient's course of the disease over the previous 1(1)/2 years was compatible with hypereosinophilic syndrome. In a muscle biopsy several eosinophilic perivascular and leucocytic intravascular infiltrates were found, indicative of muscle involvement by the disease. This is a report on the MRI findings of muscle involvement in idiopathic hypereosinophilic syndrome.

Adult↗
PubMed1999

Speech processing in radiology.

The goal of this study was to evaluate the recognition rate, learning potential and amount of time needed to complete a report with the Philips speech recognition system SP 6000 (Philips, Best, The Netherlands). Four radiologists dictated reports of interventional radiology, MRI examinations of the musculoskeletal system and CT examinations of the thorax and abdomen with the Philips system using the German language. The recognition rate of each report and improvement rate after each learning phase of the Philips system was assessed. The time needed to complete a report using the Philips system was then compared with the time needed to complete a report using the tape-based system via a time analysis. The average recognition rate for the four radiologists using the Philips system was 79.6 %, which improved to 92.5 % after the third adaptation. Initially, the average time demand to dictate and correct one report was approximately 16.8 min, but this time decreased to 8.1 min after the third adaptation. In contrast, only 3. 6 min were needed to dictate and correct one report using the tape-based system. However, with the speech recognition system, dictation, correction and transcription of the report can be completed within 15 min, whereas with the tape-based system, it takes nearly 1 day. With the Philips system, speech recognition can reach as high as 95 % since each adaptation of the system improves the recognition rate by approximately 5 %. While the Philips system is associated with longer dictation times than the tape-based system, turn-around time for a complete report is substantially shorter with the Philips system than the tape-based system.

Computer Communication Networks↗
PubMed1998

Ethanol and N-methyl-D-aspartate receptor complex interactions: a detailed drug discrimination study in the rat.

The discriminative stimulus properties of compounds that interact with the NMDA receptor complex were investigated in rats trained to discriminate ethanol from saline. Male Wistar rats were trained in a two-lever operant drug discrimination paradigm to make differential responses [fixed ratio 10 (FR10)] for food after ethanol (1 g/kg i.p.; 12% v/v ethanol solution) and saline vehicle injections. Drug effects were assessed by means of generalization and antagonism tests. In the generalization tests, the noncompetitive NMDA antagonists acting at the ion channel dizocilpine, memantine, phencyclidine (PCP) and the sigma1 receptor agonists (+)-pentazocine and (+)-N-allyl-normetazocine (NANM) dose-dependently generalized for ethanol, whereas the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) antagonist GYKI 52466, the glycine antagonists L-701,324 and MRZ 2/502, the polyamine site antagonist arcaine and the polyamine site ligand spermidine, did not. Our results show that the noncompetitive NMDA antagonists fully substitute dose-dependently for ethanol in a drug-discrimination task. The ethanol-like discriminative stimulus effects of PCP, pentazocine and NANM, which are also sigma receptor ligands, are likely to be attributed to their activity at NMDA receptors. We therefore assume that some of the acute effects of ethanol are mediated via NMDA receptor antagonism at the PCP binding site.

Animals↗
PubMed1998

A computer-based reporting system in radiology of the chest.

The aim of this study was to compare our computer-aided report writing system to standard techniques. A computer-aided reporting system for reporting on chest X-rays was developed and linked with a UNIX-based radiology information system. The reporting system consists of different text modules which can be composed to a complete radiological report. The quality of the report, the system's efficiency, flexibility and availability at the radiology information system (RIS), as well as its acceptance by the users, were criteria we took as a basis of evaluation. Acceptance and flexibility of the system were tested by assessing necessary changes and additions performed to text modules and by subjective evaluation. The time spent on working with the reporting system was evaluated by performing a time-analysis study comparing the new system to the two conventional methods, the tape system and handwriting. On average, the readers needed 22.6 text modules for each report. For the users the most important advantages of the new system are that primarily fewer changes to or additions to the text are necessary, and when they cannot be avoided they can be performed more easily. In comparison with the tape system and handwritten reports, it took on average two and a half to three times longer to report on a chest X-ray. The printed report had left the department within 6.4 h using the tape system within 0.4 h when handwritten and within 1.4 h when recorded by the reporting system. The completeness of the set of modules and the logical order were positively assessed by the users. The demand of time for reporting increases, but the final report is available sooner.

Humans↗
PubMed1998

Discriminative stimulus effects of glutamate release inhibitors in rats trained to discriminate ethanol.

In a drug discrimination paradigm with rats trained to discriminate ethanol (1 g/kg IP) from saline we studied two substances, lamotrigine and riluzole, which are regarded as glutamate release inhibitors concerning their ability to substitute for ethanol. Both substances have been shown to act primarily on voltage-gated sodium channels; however, Lamotrigine dose dependently generalized to the ethanol cue, whereas riluzole did not. These results reflect the different high-dose effects of both sustances at voltage-gated calcium channels, where lamotrigine has inhibitory effects, but not riluzole, and provide further evidence for a role of voltage-gated calcium channels in the mediation of the effects of ethanol.

Animals↗