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F Mehnert

Publications and source records attributed to F Mehnert.

At least 19 recordsLinked to original sources
PubMed2004

Modern MRI tools for the characterization of acute demyelinating lesions: value of chemical shift and diffusion-weighted imaging.

Acute demyelinating lesions occur in various inflammatory disorders of the CNS. Apart from multiple sclerosis, most cases can be attributed to an overshooting immunological response to infectious agents called acute disseminated encephalomyelitis (ADEM). ADEM, which is mostly characterized by a monophasic course, has a multiphasic variant (MDEM). The early application of corticosteroids has been shown to be beneficial for the outcome; thus, an early diagnosis is highly desirable. Furthermore, the differential diagnosis ruling out neoplastic disorders may be difficult using conventional MRI alone. The potential diagnostic value of advanced MR techniques such as chemical shift imaging (CSI) and diffusion-weighted imaging (DWI) was investigated in a patient with MDEM, who had a new lesion in continuity with the initial disease manifestation. CSI was performed at 1.5 T with a long echo time of 135 ms for the evaluation of N-acetyl-aspartate (NAA) and choline (Cho) and with short TE of 30 ms for macromolecules (mm) and myo-Inositol (mI). DWI was performed using a single-shot isotropic EPI sequence. Whereas acute and chronic areas of demyelination were neither distinguishable on T2- nor on contrast-enhanced T1-weighted images, CSI and DWI revealed different metabolite concentrations and diffusion characteristics within the composite lesion, clearly separating acute from chronic areas of demyelination. In conclusion, the addition of CSI and DWI may add to the diagnostic power of MRI in the setting of demyelinating disorders by identifying areas of acute and chronic demyelination, even in the absence of contrast enhancement.

Adult↗
PubMed2002

Large-core needle biopsy for diagnosis and treatment of breast lesions.

PURPOSE: Large-core needle biopsy (LCNB) has become a more widely used technique in the evaluation of breast lesions. This study was undertaken to access the accuracy of percutaneous LCNB on breast lesions and the impact on further proceeding. METHODS: A retrospective review of imaging-guided LCNB of 159 breast lesions was done. 143 LCNB were taken with ultrasound guided automated spring gun biopsy and 16 stereotactic-guided with vacuum-assisted biopsy device. Histology and morphobiological parameters were compared with subsequent material from surgery. RESULTS: In 113 core biopsies (71%), an infiltrating breast cancer was diagnosed, 5 biopsies (3%) yielded in-situ/atypical lesions and a benign lesion was shown in 38 cases (24%). In 3 cases, insufficient/necrotic material was obtained. 108 patients underwent subsequent surgery. In 100/108 cases (93%), histology on LCNB and surgery was identical. LCNB was false negative in 5 core biopsies (5%). Immunhistochemical stains of hormone receptors, bcl-2, c-erbB-2, p53 and MIB-1 was comparable on LCNB and on surgical material. Based on the results of LCNB, 17/113 patients (15%) with infiltrating carcinoma were primarily treated with hormones or with neoadjuvant therapy. 32/38 patients (84%) with benign lesions were followed up by imaging control. CONCLUSIONS: In patients with benign lesions on imaging, open biopsies can be avoided by LCNB. In patients with biopsy proven carcinoma, therapy planning is improved. The addition of morphobiological parameters allows early individual treatment.

Adenocarcinoma, Mucinous↗
PubMed2002

[Imaging diagnosis of solitary pulmonary nodules on an open low-field MRI system--comparison of two MR sequences with spiral CT].

OBJECTIVE: To evaluate and compare two fast gradient-echo sequences (GRE) concerning the visualization of solitary pulmonary nodules with an open low-field MRI system in comparison to computed tomography. MATERIALS AND METHODS: Fourteen patients with solitary pulmonary nodules detected by spiral CT ranging in size from 6 mm to 42 mm (mean 20 mm) underwent MRI on an open 0.2 T scanner using a spoiled 2D GRE (2D FLASH; TR/ TE/Flip = 100 ms/7.5 ms/30 degrees ) and a totally refocused 2D steady-state GRE (True-FISP; TR/TE/FA = 7.3 ms/3.5 ms/80 degrees ). The image quality concerning artifacts (by flow, breathing and susceptibility) and the morphologic characteristics of the nodules were scored and compared with CT by two independent radiologists. The diameters of the nodules measured by MRI were compared with CT measurements. The sequences were also evaluated with regard to the signal-to-noise ratio (SNR) of the lesion. RESULTS: All lesions were detected with the 2D FLASH sequence. True-FISP failed to find a granuloma with a size of 6 mm. The 2D FLASH was rated significantly superior to true FISP concerning image quality artifacts by susceptibility as well as concerning to CT the presentation of nodule characteristics. In MR images, the size of lesions was significantly smaller than in CT images for both sequences: for 2D FLASH the mean difference was 0.9 mm and for true FISP 2.6 mm. The SNR of the nodules was significantly higher for the 2D FLASH than for the true FISP. CONCLUSION: In low field MRI, the 2D FLASH sequence is superior to the 2D true FISP sequence in imaging of pulmonary nodules. With the 2D FLASH sequence nodules of 6 mm or larger in size can be visualized.

Aged↗
PubMed2001

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

The aim of this study was to evaluate the value of automatic bolus tracking for biphasic spiral CT of the liver in comparison with time delay examinations. Forty patients scheduled for a biphasic spiral CT of the liver randomly were examined either with time delay of 25 s for the arterial phase and 55 s for the portal-venous phase (n = 20), or with an automatic scan start triggered by contrast enhancement in the aorta (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 4.0 ml/s. Density measurements of the aorta, of the liver parenchyma, and of the spleen were obtained by means of regions of interest (ROI). The end of the arterial phase was considered when hepatic parenchymal enhancement was greater than 20 HU. In all patients of the group with automatic bolus tracking arterial scanning was completed in the arterial phase of the liver. In 25 % of patients with fixed time delay, however, an enhancement of liver parenchyma during arterial phase greater than 20 HU was observed. During the portal-venous phase there was no significant difference in parenchymal enhancement between both groups. Automatic bolus tracking allows an individualized timing of the arterial phase in biphasic spiral CT of the liver. The timing is more accurate than in time delay scanning.

Adult↗
PubMed2001

Automatic bolus tracking in monophasic spiral CT of the liver: liver-to-lesion conspicuity.

The aim of this study was to evaluate the value of automatic bolus tracking for monophasic spiral CT of the liver and to assess the liver-to-lesion conspicuity in comparison with time-delay examinations. In 40 patients scheduled for therapy control of known hypovascular hepatic metastases a monophasic spiral CT was completed either with time delay of 65 s (n = 20) or with automatic bolus tracking in the liver parenchyma (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 3.0 ml/s. For automatic bolus tracking a parenchymal enhancement threshold of 40 HU was used. Contrast enhancement in the liver parenchyma and in liver lesions was obtained by means of regions of interest (ROI). Mean parenchymal enhancement was not significantly different between time delay and bolus-tracking group. In 4 of 20 patients in the bolus-tracking group the threshold level of 40 HU was not reached. With automatic bolus tracking a significantly higher liver-to-lesion density difference was observed (P < 0.0001). Automatic bolus tracking allows a better liver-to-lesion conspicuity in monophasic spiral CT. Contrary to recent studies, a significantly higher parenchymal enhancement was not found using automatic bolus tracking.

Adult↗
PubMed2000

[High resolution multislice CT of the lung: comparison with sequential HRCT slices].

PURPOSE: To compare the image quality of high-resolution (HR) spiral CT scans from a multislice CT scanner with sequential HRCT scans from a singleslice CT scanner. MATERIALS AND METHODS: 20 patients with diffuse lung disease received a high-resolution spiral CT on a multislice scanner (4 slices) and 5 HRCT single slices (1 mm) on a singleslice scanner. Scan parameters of the multislice scanner were: Collimation 4 x 1 mm, pitch 6, slice thickness 1 mm. 5 HRCT slices were compared to the corresponding HR spiral CT slices using a 5-point scale by 5 radiologists with regard to the image quality and the number of artifacts. The evaluation was performed with a multivariate analysis (MANOVA test). RESULTS: Overall impression of image quality, noise, central vessels and bronchi, and all pathological changes were not significantly different between the two CT methods. Sequential HRCT scans were considered to be significantly better than HR spiral CT scans for spatial resolution (p = 0.02), depiction of peripheral vessels (p = 0.02), and of small bronchi (p = 0.05), and significantly worse for depiction of interlobar septa (p < 0.001). Diagnostically relevant differences were found in only 2.2%. Breathing and heartbeat artifacts each were 3 times higher in the sequential HRCT technique than in the multislice-spiral technique (p < 0.0001). CONCLUSION: HR spiral CT scans performed on a multislice CT scanner provide significantly less artifacts and an equal diagnostic image quality compared to sequential HRCT scans performed on a singleslice CT scanner. Multislice spiral CT in HR technique may replace the common scanning technique with conventional spiral CT and additional HRCT scans for diffuse lung diseases.

Adult↗
PubMed1996

[Complications of percutaneous endoscopic gastrostomy (PEG)].

Percutaneous endoscopic gastrostomy (PEG) is a simple technique for the endoscopic placement of a permanent feeding access. The procedure is relatively safe and the technique well established. PEG can, however, be associated with serious complications and death. Following the rare PEG-related complication of an abdominal dislocation we review technique, indications and complications of this sixteen year old method.

Abdomen, Acute↗
PubMed1995

[Quantitative computerized tomography of the lung--respiration controlled diagnosis of diffuse lung diseases].

STUDY OBJECTIVE: Computed tomography provides measurements of lung attenuation which reflect changes in the air to tissue ratio and can thereby be employed for diagnosis of diffuse lung disease. In this prospective study, we quantitatively analyzed lung density by high resolution computed tomography (HRCT) in 26 healthy volunteers, 15 patients with chronic obstructive pulmonary disease (COPD), and 15 patients with idiopathic lung fibrosis (IPF). The procedure was standardized by examination of 3 scans at the carina +/- 5 cm and by defining inflation levels by %VC using an on-line hand held spirometer. RESULTS: Performance of HRCT at 50% VC provides not only significant and distinguishable group data, but is the easiest to carry out for dyspneic patients. The mean lung density at 50% VC for healthy subjects was -820 +/- 4.2 (mean +/- SEM) Hounsfield units (HU). It was significantly lower (p < 0.01) in COPD patients (-865 +/- 9.2 HU), and considerably higher (-697 +/- 17.8 HU, p < 0.001) in the IPF group. At an inflation level of 20% VC, mean lung density values were similarly distributed, at significantly lower values relative to those at 50% VC, but the procedure was more difficult to perform for patients with dyspnea. In contrast, at 80% VC, lung density values for the COPD and control groups were not significantly different (p = 0.08). The sensitivity to detect COPD was improved by selecting HRCT values lower than -900 HU, which represent the part of the lung with an increased air/tissue ratio. For IPF patients an increase of lung density values above -699 HU was characteristic, indicating a decrease of the air/tissue relationship. CONCLUSION: From our data we propose to perform quantitative HRCT measurements at 50% VC. Diagnosis of diffuse lung disease can be further improved by consideration of specific CT -value intervals. Spirometrically controlled quantitative HRCT is a clinically meaningful tool for the assessment of diffuse parenchymal lung disease.

Adult↗
PubMed1992

Monoclonal antipeptide antibodies recognize epitopes upon VP4 and VP7 of simian rotavirus SA11 in infected MA104 cells.

To study morphogenetic events of rotavirus SA11-infected MA104 cells with strictly defined reagents we produced monoclonal antibodies against synthetic peptides from both outer capsid proteins VP4 (aa residues 228-241: QNTRNIVPVSIVSR) and VP7 (aa residues 319-326: SAAFYYRV) of simian rotavirus SA11. Two of the selected monoclonal antibodies proved to be reactive with determinants of SA11-infected MA104 rhesus monkey kidney cells, with purified SA11 as well as with the particular peptides used for immunization. The anti-VP4 antibody had a demonstrable neutralizing titer of 200 (50% focus reduction) whereas the anti-VP7 MuMAb revealed no detectable neutralizing activity. In peptide-inhibition experiments, the corresponding peptide inhibited its MuMAb whereas the noncorresponding peptide had no effect on antibody binding to intracellular viral antigen. Localization of VP7 was preceded by VP4 as shown by immunofluorescence microscopy.

Amino Acid Sequence↗
PubMed1976

[Contributions to the mechanism of the Witebsky-test (author's transl)].

The assumption that immune and normal alloantibodies of the ABO system could be distinguished by partial neutralization with soluble specific blood group substance (Witebsky test) has been reexamined. The following results were presented: 1. ABO alloantibodies in both normal and immune sera as well as their IgG and IgM preparations were inhibited by their homologous soluble specific blood group substances. 2. Anti-A and anti-B immune antibodies as well as normal antibodies of the IgG class were found to be strong hemagglutinins in a saline medium; therefore they have to be called "complete" hemagglutinins as have anti-A and anti-B antibodies of the class IgM too. 3. ABO alloantibodies in both IgG and IgM preparations were able to form precipitation pellets with their homologous soluble specific blood group substances. IgM revealed a stronger precipitation power as IgG. 4. Agglutination reaction in saline was inhibited by the 50-200-fold group substance concentration needed for a optimal precipitation reaction, whereas agglutination of enzyme treated erythrocytes or red cells tested with antiglobulin (Coombs) sera was inhibited by a 20,000-80,000-fold concentration of the blood group substances. 5. Soluble antigen-antibody complexes, prepared from solubilized precipitates or from Witebsky test mixtures using chromatography, ultracentrifuge or ultrafiltration for separation were able to agglutinate erythrocytes in the antiglobulin or papain test. Following conclusions were drawn: A. Soluble antigen-antibody complexes are the main component leading to a positive Witebsky test. B. The mechanism of the Witebsky test as it has to be assumed in respect to our findings do not allow the distinguish immune and normal alloantibodies resp. IgG and IgM alloagglutinins in the ABO system.

ABO Blood-Group System↗