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Biomedical subjects

M Georgi

Publications and source records attributed to M Georgi.

At least 19 recordsLinked to original sources
PubMed2004

[Value of electron beam tomography (EBT)].

Electron beam tomography (EBT) has been scientifically evaluated to a much lesser degree for non-cardiac indications than for cardiac purposes. Therefore, four groups of investigators in Berlin (2), Mannheim and Munchen, which were supported by the Deutsche Forschungsgemeinschaft (DFG), included applications outside the heart in their evaluation of EBT technology. EBT has proven useful to look for pulmonary embolism and to assess other vessels (aorta, aortic branches, and intracranial arteries). Imaging of the lung parenchyma benefits from its intrinsic high contrast and from the fast data acquisition of EBT. Limited photon efficiency, higher radiation exposure, increased noise levels and other artifacts, however, markedly reduce the value of EBT for imaging of low contrast objects compared to conventional spiral CT and multislice CT (MSCT), compromising, in particular, the morphologic depiction of parenchymal abdominal organs and the brain. Consequently, scientific studies to further evaluate EBT for scanning of the brain and parenchymal abdominal organs were not pursued. Radiation exposure for non-cardiac EBT studies is up to three times higher than that for respective spiral CT studies, and in children EBT can only be advocated in select cases. Radiation exposure for the various prospectively triggered cardiac examination protocols of EBT is lower than that for conventional coronary angiography. Radiation exposure in cardiac multislice CT exceeds severalfold that of EBT, but the dose efficiency of EBT and MSCT are similar due to higher spatial resolution and less image noise of MSCT. In addition, modifications of MSCT (ECG pulsing) can further reduce radiation exposure to the level of EBT. Technical improvements of the EBT successor scanner "e-Speed" enable faster data acquisition at higher spatial resolution. Within comparative studies, the "e-Speed" will have to prove its value and competitiveness, particularly in comparison with multislice CT. After profound scientific assessment in a multicenter evaluation supported by the Deutsche Forschungsgemeinschaft (DFG) and regardless of the specific suitability of electron beam tomography for various cardiac and some non-cardiac indications, the investigators unanimously find the electron beam tomograph Evolution C150 XP not suitable as a whole body CT scanner.

Age Factors↗
PubMed2004

[Diagnostic value of electron-beam computed tomography (EBT). I. Cardiac applications].

Electron beam tomography (EBT) directly competes with other non-invasive imaging modalities, such as multislice computed tomography, magnetic resonance imaging, and echocardiography, in the diagnostic assessment of cardiac diseases. EBT is the gold standard for the detection and quantification of coronary calcium as a preclinical sign of coronary artery disease (CAD). Its standardized examination protocols and the broad experience with this method favor EBT. First results with multislice CT indicate that this new technology may be equivalent to EBT for coronary calcium studies. The principal value of CT-based coronary calcium measurements continues to be an issue of controversy amongst radiologists and cardiologists due to lack of prospective randomized trials. Coronary angiography with EBT is characterized by a high negative predictive value and, in addition, may be indicated in some patients with manifest CAD. It remains to be shown whether coronary angiography with multislice CT is reliable and accurate enough to be introduced into the routine work-up, to replace some of the many strictly diagnostic coronary catheterizations in Germany and elsewhere. Assessment of coronary stent patency with EBT is associated with several problems and in our opinion cannot be advocated as a routine procedure. EBT may be recommended for the evaluation of coronary bypasses to look for bypass occlusions and significant stenoses, which, however, can be equally well achieved with multislice CT. Quantification of myocardial perfusion with EBT could not replace MRI or other modalities in this field. EBT has proven to be accurate, reliable and in some instances equivalent to MRI, which is the gold standard for the quantitative and qualitative evaluation of cardiac function. Some disadvantages, not the least of which is the limited distribution of electron beam scanners, favor MRI for functional assessment of the heart.

Adult↗
PubMed2001

[Ultrafast magnetic resonance tomography changes the standard in pancreas diagnosis].

BACKGROUND: Since the introduction of MRI, including imaging of the hepato-pancreatic duct system (MRCP) and 3D-MR angiography (3D-MRA), new pancreatic diagnostic procedures have been developed. METHODS AND PATIENTS: We report on 143 patients with benign and malignant diseases of the pancreas, who only received MRI preoperatively. All radiologic findings were confirmed intraoperatively. RESULTS: For resectability, MRI obtained sensitivity of 96.0% and specificity of 89.5% and for classification sensitivity of 99.1% and specificity of 95.2%. CONCLUSION: Based on our experience, the benign vs malignant nature of the disease, MRI is a safe and reliable method for pancreatic tumors being able to become the standard diagnostic procedure in the future.

Contrast Media↗
PubMed2001

[Autoantigens of subepidermal bullous autoimmune dermatoses].

The dermal-epidermal junction contains a network of structural proteins that link epidermis and dermis. A central component of this complex is the cell membrane-associated hemidesmosomal plaque. Formation of autoantibodies against different components of this hemidesmosomal anchoring complex can lead to subepidermal blisters. Such autoantibodies have been frequently used to characterize the target antigens at the molecular level. Autoimmune subepidermal blistering diseases include bullous pemphigoid, pemphigoid gestationis, lichen planus pemphigoides, linear IgA disease, cicatricial pemphigoid, anti-p450-, anti-p200- and anti-p105-pemphigoid, epidermolysis bullosa acquisita, bullous systemic lupus erythematosus and dermatitis herpetiformis Duhring. Differences in the clinical picture of these diseases can be attributed, at least in part, to the different specificity of the autoantibodies involved. The autoimmune response is further modulated by inflammatory cells and other inflammatory mediators. Native and recombinant forms of the autoantigens are increasingly used for the diagnosis of these diseases.

Autoantigens↗
PubMed2001

Mapping of epitopes on the BP180 ectodomain targeted by IgA and IgG autoantibodies in patients with the lamina lucida-type of linear IgA disease.

Linear IgA disease (LAD) is an autoimmune subepidermal blistering skin disease characterized by the linear deposition of IgA at the dermoepidermal junction. Serum from patients with LAD most commonly contains autoantibodies that are directed against the hemidesmosomal transmembrane glycoprotein BP180 (type XVII collagen). Various antigenic sites on the extracellular domain of this anchoring filament protein have been shown to be targeted by autoantibodies in different autoimmune bullous skin diseases, including bullous pemphigoid and cicatricial pemphigoid (CP). However, little is known about epitopes on BP180 recognized by autoantibodies in LAD. In this study, we used three recombinant GST fusion proteins, together roughly covering the entire BP180 ectodomain, to characterize the autoimmune response in serum from patients with LAD. Interestingly, we found both IgA and IgG reactivity to all three portions of the BP180 ectodomain. The strongest reactivity was observed with the C-terminal portion of BP180. This is also the major region recognized by autoantibodies in patients with CP. This finding correlates with the observation that there may be significant overlap of the clinical and immunopathological findings in LAD and CP.

Adult↗
PubMed2000

Bullous pemphigoid of childhood: autoantibodies target the same epitopes within the NC16A domain of BP180 as autoantibodies in bullous pemphigoid of adulthood.

BACKGROUND: Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease of the elderly that rarely occurs in children. Most adult BP serum samples react with epitopes within the NC16A domain of BP180, a glycoprotein of the cutaneous basement membrane zone. OBJECTIVES: To characterize the autoimmune response in childhood BP using recombinant forms of BP180 and to determine the subclass distribution of autoantibodies and their correlation with disease activity. OBSERVATIONS: Serum samples from 2 infants with BP, aged 4 and 5 months, reacted by immunoblot analysis with 4 epitopes clustered within the N-terminal 45 amino acids of the NC16A domain. The same 4 epitopes have previously been shown to be the target in adult BP. Childhood BP antibodies to BP180 NC16A belonged to IgG1, IgG2, IgG3, and IgG4 immunoglobulin subclasses. IgE reactivity was not detected. Serum levels of antibodies targeting BP180 NC16A paralleled disease activity as detected by enzyme-linked immunosorbent assay. CONCLUSIONS: The fine specificity of autoantibodies to BP180 is the same in BP of childhood and adulthood. Childhood BP is a true variant of BP.

Adult↗
PubMed2000

Patients with bullous pemphigoid and linear IgA disease show a dual IgA and IgG autoimmune response to BP180.

Bullous pemphigoid (BP) and linear IgA disease (LAD) are autoimmune subepidermal blistering skin diseases associated with autoantibodies against the transmembrane hemidesmosomal protein BP180/type XVII collagen. It has been demonstrated previously that BP is characterized predominantly by IgG autoantibodies, while autoantibodies in LAD mainly belong to the IgA isotype. The aim of the present study was to investigate the hypothesis that there is a significant overlap in the autoantibody isotype profiles associated with these two diseases. Several new recombinant forms of BP180 were generated in the baculovirus expression system, including the full-length protein. IgG autoantibodies to BP 180 were detectable in 39 of 40 (98%) of BP sera; interestingly, 88% of BP sera also contained IgA anti-BP180 autoantibodies. Similarly, anti-BP180 reactivity in LAD sera (n=22) was also attributed to both an IgA (68%) and an IgG (76%) autoantibody response. IgA and IgG autoantibodies to the intracellular portion of BP180 were found in 14% and 28% of BP sera, respectively, and in 8% of LAD sera (same percentage for both isotypes). Our findings clearly demonstrate that both BP and LAD patients have a dual IgA and IgG autoimmune response to BP180 which is directed not only to the ectodomain, but also to the intracellular portion of this protein.

Adult↗
PubMed2000

Teleradiology requirements and aims in Germany and Europe: status at the beginning of 2000.

Specific radiological requirements have to be considered for realization of telemedicine. In this article the goals and requirements for an extensive implementation of teleradiology are defined from the radiological user's point of view. Necessary medical, legal and professional prerequisites for teleradiology are presented. Superior requirements, such as data security and privacy or standardization of communication, must be realized. Application specific requirements, e. g. quality and extent of teleradiological functions as well as technological alternatives, are discussed. Each project must be carefully planned in relation to one's own needs, extent of functions and system selection. Topics like legal acceptance of electronic documentation, reimbursement of teleradiology and liability must be clarified in the future.

Europe↗
PubMed2000

Evaluation of breath-hold contrast-enhanced 3D magnetic resonance angiography technique for imaging visceral abdominal arteries and veins.

RATIONALE AND OBJECTIVES: To evaluate the diagnostic value of breath-hold contrast-enhanced 3D magnetic resonance angiography (MRA) for assessment of the visceral abdominal arteries and veins in patients with suspected abdominal neoplasms. METHODS: Twenty-one patients underwent MR imaging on a 1.5 T unit using a body phased-array coil. MRA was performed with a 3D-FLASH sequence (TR 3.8 ms, TE 1.3 ms, flip angle 25 degrees, acquisition time 20 seconds), 8 to 12 seconds after an intravenous bolus injection of Gd-DTPA. The acquisition delay between the arterial and the portal venous phase was 12 seconds. The image quality and the degree of vascular involvement were evaluated using coronal source images and maximum intensity projection reconstructions. Diagnosis was confirmed by surgery/histology. RESULTS: Image quality was optimal in more than 85% of the patients (19/21 arterial phase and 17/21 portal venous phase). MRA correctly predicted vascular status in 20 of 21 patients (95%), with complete concordance between MRA results and surgical findings. In one patient with chronic pancreatitis, MRA demonstrated a false-positive finding that could not be confirmed surgically. CONCLUSIONS. Breath-hold contrast-enhanced 3D-MRA is a valuable technique for assessing visceral abdominal arteries and veins.

Abdomen↗
PubMed1999

[Echo-planar diffusion-weighted MRI in the diagnosis of acute ischemic stroke: characterisation of tissue abnormalities and limitations in the interpretation of imaging findings].

INTRODUCTION: An accurate diagnosis is frequently difficult in early stroke. Diffusion-weighted (DW) magnetic resonance imaging (MRI) allows visualization of ischemic parenchyma and quantitative assessment of tissue changes before unequivocal abnormalities appear on T(2)-weighted MRI. METHODS: We analyzed 105 MRI examinations of patients with acute stroke (<24 h) with regard to patterns of abnormalities in T(2)-weighted and DW MRI. Furthermore we assessed the influence of artifacts related to DW echo-planar single-shot MRI on image interpretation. RESULTS: Depending on the time of patient assessment there were three partly overlapping T(2)/DW patterns: (1) in the very early phase (</=1.5 h after symptom onset) there was no T(2) abnormality and no definite abnormality of diffusion; (2) no T(2) abnormality and restricted diffusion (1.5-4 h); (3) T(2) hyperintensity and restricted diffusion (>/=3 h). Typical artifacts (susceptibility distortions, N/2 artifact, chemical shift artifact and eddy currents artifact) had to be considered when interpreting images. CONCLUSIONS: Provided typical artifacts are taken into consideration, echo-planar DW MRI allows a more precise diagnostic assessment in acute stroke.

Acute Disease↗
PubMed1999

[Long-term follow-up MRI in children with craniocerebral trauma].

PURPOSE: A prospective study was initiated for the correlation of the findings in the initial cranial CT with the long-term follow-up MRI in children with severe head injury. Another aim was the evaluation of frequency and location of lesions, found only in MRI. METHODS: 70 children with severe head injury and initially performed pathological CCT were followed up (mean time 3 years) by MRI. RESULTS: 71% of the children had a pathological MRI. In 43% of the children with subdural bleeding could be found parenchymal lesions in the underlying cortex. All 15 children with epidural bleeding had unsuspicious findings at the former hematoma. All of the contusions were found as parenchymal residual lesions. 44% of the children had evidence of parenchymal lesions in the follow-up MRI initially and retrospectively not revealable. 16 lesions in the corpus callosum were only revealed by MRI. CONCLUSION: This study shows the higher sensitivity of magnetic resonance imaging in non-hemorrhagic parenchymal lesions and in "diffuse axonal injury". A MRI-examination is recommended in children with severe head injury, especially in patients with normal CCT and posttraumatic neurological deficits.

Adolescent↗
PubMed1999

First results of computerised tomographic angiography using electron beam tomography.

The aim of this study was to evaluate the suitability of electron beam tomography (EBT) with fast continuous volume scanning for CT angiography (CTA) in chest and abdomen. An Evolution XP EBT scanner with a new software version (12.34) was used. One hundred forty images per study can be acquired in 17 s using 3-mm collimation and overlapping image reconstruction. Study protocols for five different clinical applications of EBT CTA were established and evaluated. The EBT CTA technique was performed in 155 patients. High- and homogeneous density values were achieved along the whole course of the vessels; the mean density in the aorta was > 240 HU. Coeliac axis, superior and inferior mesenteric artery, renal and lumbar arteries were visualised in all cases. Maximum intensity projection and shaded surface display reconstruction demonstrated the relation between aneurysm and aortic branches very well due to an excellent resolution along the z-axis. In large scan volumes overlapping image reconstruction demonstrated better resolution along the z-axis than is available with helical CT. The EBT CTA technique proved to be very well suited excellent suitability for evaluation of pulmonary vessels. Compared with helical CT, EBT CTA offers a shorter scan time, which allows higher contrast enhancement in pulmonary vessels. The identification of intraluminal emboli and mural thrombi has improved. The EBT CTA technique is a very reliable tool for evaluation of aortic disease and pulmonary vessels.

Angiography↗
PubMed1999

Aortocaval fistula complicating abdominal aortic aneurysm: diagnosis with gadolinium-enhanced three-dimensional MR angiography.

With approximately 150 reported cases, fistulas between the abdominal aorta and inferior vena cava are rare. Preoperative clinical diagnosis of aortocaval fistula is difficult because the classical triad of abdominal pain, pulsatile abdominal mass, and abdominal machinery-like bruit may be absent in up to 50 % of patients. We report a case of aortocaval fistula complicating abdominal aortic aneurysm which was diagnosed preoperatively using breath-hold gadolinium-enhanced three-dimensional MR angiography.

Aorta, Abdominal↗
PubMed1999

MRI with superparamagnetic iron oxide: efficacy in the detection and characterization of focal hepatic lesions.

The purpose of this study was to evaluate the potential of superparamagnetic iron oxide particles (SPIO) as tissue specific contrast agent in magnetic resonance (MR) imaging in detection and characterization of focal hepatic lesions. We investigated 45 patients with focal hepatic lesions. T1-weighted SE (TR 650/TE 15 ms) and T2-weighted SE (TR 2015-2030/TE 45 and 90 ms) unenhanced images were obtained. After SPIO application we performed T1-weighted images with and T2-weighted images with and without fat suppression using the same image parameters. Liver signal intensity decreased by 74% (min 47%, max 83%) on T2-weighted images after application of the contrast agent. Benign lesions (FNH, adenoma) showed an average signal drop of 40% (min 20%, max 47%) whereas malignant lesions showed no significant change of signal intensity on post-contrast images. The mean tumor-to-liver contrast-to-noise ratio (C/N) was improved in all post-contrast sequences irrespective of the lesion type. An additional increase of tumor-to-liver contrast by use of fat suppression technique could be established in the slightly T2-weighted sequence (TE 45 ms). In metastases, divided in different size groups, we could determine a significant size relation of tumor-to-liver C/N. After SPIO application the number of detected lesions increased distinctly, especially small foci are more easily demonstrated. SPIO particles are a efficacious contrast agent for MR examinations of the liver. For tumor characterization T1- and T2-weighted pre- and post-contrast images are necessary. The T1-weighted sequences are helpful to differentiate benign lesions such as cysts and hemangiomas from malignant lesions. Detection and differential diagnoses of hepatic lesions are improved by use of the SPIO-particles.

Adult↗
PubMed1999

Autoantibodies in a subgroup of patients with linear IgA disease react with the NC16A domain of BP1801.

Linear IgA disease is an autoimmune subepidermal blistering disease characterized by IgA deposits at the cutaneous basement membrane zone. IgA antibodies from linear IgA disease sera react with antigens of 97 kDa (LABD97) and 120 kDa (LAD-1), both of which appear to be fragments of the extracellular domain of bullous pemphigoid 180 (type XVII collagen). The aim of this study was to determine whether linear IgA disease sera react with the immunodominant region of BP180 (NC16A domain), which is a major target of IgG autoantibodies produced by patients with bullous pemphigoid. Indeed, 11 of 50 linear IgA disease sera were found to contain IgA autoantibodies that recognized a recombinant form of NC16A by immunoblotting. The same sera also reacted with NC16A by enzyme-linked immunosorbent assay. An epitope mapping analysis uncovered four linear IgA disease-associated epitopes located within the 45 amino acid N-terminal stretch of NC16A, all of which were previously identified as antigenic sites targeted by bullous pemphigoid autoantibodies. Eight of the linear IgA disease sera that were reactive with NC16A also recognized LAD-1 secreted by the SCC-25 cell line, and five sera recognized BP180 extracted from keratinocytes. Linear IgA disease sera depleted of reactivity to NC16A by immunoadsorption continued to react with both the LAD-1 antigen and BP180 by immunoblotting and with the basement membrane zone by indirect immunofluorescence microscopy. Our results demonstrate that IgA autoantibodies from a subset of linear IgA disease patients react with the same sites on BP180 that are targeted by IgG autoantibodies in bullous pemphigoid.

Aged↗