Biomedical subjects

E Moser

Publications and source records attributed to E Moser.

At least 91 records · Page 5Linked to original sources

PubMed1998

[Clinical value of positron emission tomography in neuromedicine. Position paper on results of an interdisciplinary consensus conference].

To date, positron emission tomography (PET) is the most powerful method for the in-vivo investigation of human brain metabolism. Besides extensive application of this technology in the neurosciences, PET is also being increasingly used as a clinical tool. However, despite its acceptance in clinical practice a major obstacle is its high costs. The present article reviews the literature on the clinical use of PET in neurology, neurosurgery, and psychiatry in order to substantiate the clinical indications for PET in these specialties as established by an interdisciplinary conference.

Brain Diseases↗

PubMed1998

Influence of urinary iodine excretion on thyroid technetium-99m pertechnetate uptake with and without TSH suppression: what happens when iodine supply increases?

This study examines how thyroid pertechnetate uptake with and without thyroid-stimulating hormone (TSH) suppression changes as a function of increasing iodine supply. This is of special interest in countries at the threshold of sufficient iodine supply, where thyroid scintigraphy plays a key role in thyroid examination, especially for the diagnosis of Plummer's disease. From 1995 to 1997, a total of 1069 patients with euthyroid goitre, Plummer's disease or Graves' disease were included in the study. All patients underwent thyroid examination including sonography, scintigraphy with technetium-99m pertechnetate, and determination of free triiodothyronine, free thyroxine, TSH and urinary iodine excretion. Iodine excretion in the range from 0 to 500 microg iodine/g creatinine showed an inverse correlation with thyroid pertechnetate uptake, but no correlation with TSH was observed. There was no correlation between thyroid pertechnetate uptake and iodine excretion when TSH stimulation was eliminated, with two exceptions: thyroid pertechnetate uptake was significantly increased for iodine excretion values below 50 and 100 microg iodine/g creatinine in patients with Graves' and Plummer's disease, respectively. When iodine excretion exceeded 500 microg iodine/g creatinine, pertechnetate uptake was reduced to a basal level independent of the TSH. In conclusion, the influence of TSH on the thyroid pertechnetate uptake seems to be secondary compared with the influence of the iodine supply. It can be concluded further that the reference range of thyroid pertechnetate uptake under TSH suppression will not change significantly when the iodine supply increases from conditions of mild iodine deficiency to iodine sufficiency. Thyroid pertechnetate uptake with and without TSH suppression cannot be reliably interpreted beyond an iodine excretion of 500 microg iodine/g creatinine.

Adolescent↗

PubMed1998

Early-onset Alzheimer's disease due to mutations of the presenilin-1 gene on chromosome 14: a 7-year follow-up of a patient with a mutation at codon 139.

Mutations in the presenilin-1 gene (PS-1 gene) on chromosome 14 have recently been identified as a cause of familial early-onset Alzheimer's disease (EOAD). To our knowledge, only two German EOAD patients with mutations in the PS-1 gene have been identified thus far. Herein we report the case of a German EOAD patient with a family history of dementia and a missense mutation at codon 139 (M139V) of the PS-1 gene. The patient came to our clinic for the first time when he was 44 years old. During the following 7 years, his Mini-Mental State Examination (MMSE) score dropped from 24 to 0. Myocloni were an early neurological symptom that was already present during the first consultation. We could demonstrate that myoclonic activity was of cortical origin using a back-averaging method. Magnetic resonance imaging (MRI) revealed only slight changes in the early stage of the disease. Follow-up MRI studies showed progression of bitemporal ventricular enlargement and progressive frontal and temporal cortical atrophy. Although the majority of EOAD patients belong to the sporadic (non-genetic) type of AD, early-onset dementia, early myocloni and a familial history of AD should direct attention to the possibility of a genetic form of AD.

Adult↗

PubMed1998

Quantification in functional magnetic resonance imaging: fuzzy clustering vs. correlation analysis.

The potential of functional MRI (fMRI) data analysis using the paradigm independent fuzzy cluster analysis (FCA) applied in the time domain compared to frequently used paradigm based correlation analysis (CA) was studied with simulated and in vivo fMRI data. The performance of FCA and CA was investigated in a typical contrast-to-noise range for fMRI, ranging from 1.33 to 3.33. Using simulated fMRI data the methods were quantitatively compared in terms of generation of true positives, false positives, and the corresponding signal enhancement. Even without prior knowledge about the stimulation paradigm and the actual hemodynamic response function the performance of FCA was comparable to that of CA where extensive prior knowledge has to be added. Furthermore, discrimination of nonanticipated hemodynamic responses by FCA, such as different levels of activation and delayed response, are demonstrated in simulated and in vivo fMRI data. We demonstrate that using CA one cannot differentiate between these responses at least without extensive prior knowledge, i.e., FCA yields a more particular description of fMRI data. This may be worthwhile for analysis and optimization of data quality in fMRI as well as in the final data analysis.

Adult↗

PubMed1998

Absolute metabolite quantification by in vivo NMR spectroscopy: II. A multicentre trial of protocols for in vivo localised proton studies of human brain.

We have performed a multicentre trial to assess the performance of three techniques for absolute quantification of cerebral metabolites using in vivo proton nuclear magnetic resonance (NMR). The techniques included were 1) an internal water standard method, 2) an external standard method based on phantom replacement, and 3) a more sophisticated method incorporating elements of both the internal and external standard approaches, together with compartmental analysis of brain water. Only the internal water standard technique could be readily implemented at all participating sites and gave acceptable precision and interlaboratory reproducibility. This method was insensitive to many of the experimental factors affecting the performance of the alternative techniques, including effects related to loading, standing waves and B1 inhomogeneities; and practical issues of phantom positioning, user expertise and examination duration. However, the internal water standard method assumes a value for the concentration of NMR-visible water within the spectroscopic volume of interest. In general, it is necessary to modify this assumed concentration on the basis of the grey matter, white matter and cerebrospinal fluid (CSF) content of the volume, and the NMR-visible water content of the grey and white matter fractions. Combining data from 11 sites, the concentrations of the principal NMR-visible metabolites in the brains of healthy subjects (age range 20-35 years) determined using the internal water standard method were (mean+/-SD): [NAA]=10.0+/-3.4 mM (n=53), [tCho]=1.9+/-1.0 mM (n=51), [Cr + PCr]=6.5+/-3.7 mM (n=51). Evidence of system instability and other sources of error at some participating sites reinforces the need for rigorous quality assurance in quantitative spectroscopy.

Adult↗

PubMed1998

A comparative study on the frequency of prophages among natural isolates of Salmonella and Escherichia coli with emphasis on generalized transducers.

Several collections of natural isolates of the genus Salmonella and of the species Escherichia coli were studied for the release of viable temperate phages. The results indicated that functional prophage genomes may be a common constituent of all bacterial genomes of the investigated strains. About 99% of the Salmonella phages are capable of generalized transduction of chromosomal host markers and plasmids. The ratio of transducing E. coli phages is significantly lower.

Animals↗

PubMed1998

Radioiodine treatment of Plummer's disease.

The presented overview summarizes the results of radioiodine treatment in patients with different forms of Plummer's disease. From the beginning the outcome defined as elimination of autonomy was excellent in the unifocal autonomous adenomas, but unsatisfactory in multifocal and disseminated autonomy using a fixed dose concept. The "dosimetric compromise" (= reducing the dose and defining the total gland as the target volume) yielded in these two variants of autonomy satisfactory results comparable to those of the unifocal form, since the dose was chosen according to the amount of functional autonomy measured by the Tc-99m-uptake in the thyroid gland under TSH-suppression.

Adenoma↗

PubMed1998

Analysis of lymphatic drainage in various forms of leg edema using two compartment lymphoscintigraphy.

The anatomical and functional status of the epifascial and subfascial lymphatic compartments was analyzed using two compartment lymphoscintigraphy in five groups of patients (total 55) with various forms of edema of the lower extremities. Digital whole body scintigraphy enabled semiquantitative estimation of radiotracer transport with comparison of lymphatic drainage between those individuals without (normal) and those with leg edema by calculating the uptake of the radiopharmaceutical transported to regional lymph nodes. A visual assessment of the lymphatic drainage pathways of the legs was also performed. In patients with cyclic idiopathic edema, an accelerated rate of lymphatic transport was detected (high lymph volume overload or dynamic insufficiency). In those with venous (phlebo) edemas, high volume lymphatic overload (dynamic insufficiency) of the epifascial compartment was scintigraphically detected by increased tracer uptake in regional nodes. In patients with deep femoral venous occlusion (post-thrombotic syndrome). subfascial lymphatic transport was uniformly markedly reduced (safety valve lymphatic insufficiency). On the other hand, in the epifascial compartment, lymph transport was accelerated. In those patients with recurrent or extensive skin ulceration, lymph transport was reduced. Patients with lipedema (obesity) scintigraphically showed no alteration in lymphatic transport. This study demonstrates that lymphatic drainage is notably affected (except in obesity termed lipedema) in various edemas of the leg. Lymphatic drainage varied depending on the specific compartment and the pathophysiologic mechanism accounting for the edema. Two compartment lymphoscintigraphy is a valuable diagnostic tool for accurate assessment of leg edema of known and unknown origin.

Adult↗

PubMed1998

[First results of radioiodine therapy of multifocal and disseminated thyroid gland autonomy and use of a TcTUs-adapted dose concept].

AIM: The presented study examines prospectively the efficiency of a dose concept for radioiodine therapy (RIT) adapted to the pretherapeutic 99mTc-pertechnetate thyroid uptake under suppression (TcTUs) in patients with multifocal (MFA) and disseminated (DISA) autonomy. This concept considers the total thyroid as target volume and uses target doses from 150 Gy to 300 Gy according to the TcTUs, which is as a measure for the "autonomous volume" of the thyroid. METHODS: The data of 75 patients (54 female, 21 male; age 71 +/- 9 years) with MFA of DISA were evaluated. RIT was performed on patients presenting with normal values for free triiodothyronine and thyroxine and endogenous suppression of the basal thyrotropin (TSH). The following target dose were used for a TcTUs of 1.5-2.5% 150 Gy, for 2.51-3.5% 200 Gy, for 3.51-4.5% 250 Gy, and for > 4.5% 300 Gy. The radiation dose to be administered was calculated using a modified Marinelli formula. The therapy was considered as successful. When the basal TSH was above 0.5 mU/l and autonomous areas had disappeared in thyroid scintigraphy or the TcTU was below 1.5%, respectively. The average follow-up period was 8 +/- 4 months. RESULTS: The success rates average to 92%. Only in one case a subsequent subclinical hypothyroidism and in a further case an immunogenic hyperthyroidism occurred. CONCLUSION: The presented data indicate that even patients with a marked autonomy (TcTUs > 3.5%) can thus expected to be cured by of a one time therapy with success rate of over 90% using the presented dose concept. The rate of early hypothyroidism can altogether be estimated as very low.

Aged↗

PubMed1998

[Change of 99m technetium-pertechnetate uptake by the thyroid under suppression (TcTus) induced by optimization of iodine supply in Germany].

AIM: The present study deals with the change of the 99mTechnetium-pertechnetate thyroid uptake under suppression (TcTUs) in dependence on the urinary iodine excretion. METHODS: The study collective comprises 510 patients with euthyroid goiter (N = 91), with functional thyroid autonomy (N = 361) and with Graves, disease (N = 58), who were examined in the own thyroid ambulance between January 1995 and February 1997 and who presented with endogeneous or exogeneous TSH suppression. All patients received a quantitative thyroid scintigraphy with 99mTechnetium-pertechnetate and a measurement of the urinary iodine excretion. RESULTS: The TcTUs from the whole collective shows an inverse correlation to the urinary iodine excretion for the range of 0 to 500 micrograms iodine/g creatinine. The TcTUs remains constant on a low basal level for iodine excretion values over 500 micrograms iodine/g creatinine. Significant differences occur in dependence on the underlying disease. TcTUs is constantly low in patients with euthyroid goiter, independent of the iodine excretion value. The TcTUs is significantly increased in patients with functional thyroid autonomy or Graves' disease when iodine excretion is below 100 or 50 micrograms iodine/g creatinine respectively, but shows only minor changes when iodine excretion rises up to 500 micrograms iodine/g creatinine. When iodine excretion exceeds 500 micrograms iodine/g creatinine, the TcTUs of patients with thyroid autonomy drops down to a low basal level. CONCLUSION: The reference range of TcTUs for assessing functional thyroid autonomy will not change significantly when the iodine supply in Germany improves. The TcTUs of patients with functional thyroid autonomy might be up to one third higher under conditions of iodine deficiency than in iodine sufficiency. This should be taken into account, when therapeutical consequences were derived from the TcTUs. The TcTUs cannot be interpreted for iodine excretion values over 500 micrograms iodine/g creatinine.

Diet↗

PubMed1997

On the correlation between tissue hydration state and proton NMR relaxation rates in experimental liver transplantation.

As the tissue hydration state is one of the most important parameters to predict viability cold stored livers before transplantation, we investigated the correlation between the tissue inverse total water fraction, reflecting the hydration state, and proton relaxation times in cold stored rat liver and orthotopic liver transplantation in a pig model. In cold stored rat liver excellent linear correlations between relaxation rates R1 (= 1/T1) and R2 (= 1/T2) and inverse total water fraction 1/Pw were obtained. In pig liver transplants, the slope and intercept obtained from a linear regression model are twice as high for R1 and almost identical for R2; however, correlation coefficients are lower due to increased biological variation and a smaller range in storage conditions, reflected by the range of water content. Proton nuclear magnetic resonance relaxation times measured during the cold storage on the whole organ non-invasively show also linear correlation with the inverse total water fraction, but the method is presently not accurate enough to estimate the hydration state of the liver tissue with sufficient precision. NMR relaxation times obtained from liver biopsies have the potential to predict tissue viability in experimental liver transplantation independent of species, strain and gender, and thus may be useful in estimating the viability of human donor livers (or at least add a new complementary information to the information gained by standard liver selection and function test before and after transplantation).

Adenosine↗

PubMed1997

Brain glucose utilization in systemic lupus erythematosus with neuropsychiatric symptoms: a controlled positron emission tomography study.

In contrast to morphological imaging [such as magnetic resonance imaging (MRI) or computed tomography], functional imaging may be of advantage in the detection of brain abnormalities in cases of neuropsychiatric systemic lupus erythematosus (SLE). Therefore, we studied 13 patients (aged 40+/-14 years, 11 female, 2 male) with neuropsychiatric SLE who met four of the American Rheumatism Association criteria for the classification of SLE. Ten clinically and neurologically healthy volunteers served as controls (aged 40+/-12 years, 5 female, 5 male). Both groups were investigated using fluorine-18-labelled fluorodeoxyglucose brain positron emission tomography (PET) and cranial MRI. The normal controls and 11 of the 13 patients showed normal MRI scans. However, PET scan was abnormal in all 13 SLE patients. Significant group-to-group differences in the glucose metabolic index (GMI=region of interest uptake/global uptake at the level of the basal ganglia and thalamus) were found in the parieto-occipital region on both sides: the GMI of the parieto-occipital region on the right side was 0.922+/-0.045 in patients and 1.066+/-0.081 in controls (P<<0.0001, Mann Whitney U test), while on the left side it was 0.892+/-0.060 in patients and 1. 034+/-0.051 in controls (P=0.0002). Parieto-occipital hypometabolism is a conspicuous finding in mainly MRI-negative neuropsychiatric SLE. As the parieto-occipital region is located at the boundary of blood supply of all three major arteries, it could be the most vulnerable zone of the cerebrum and may be affected at an early stage of the cerebrovascular disease.

Adult↗

PubMed1997

[Indications for nuclear medicine diagnosis in trauma surgery].

Skeletal scintigraphy is the most frequently utilized nuclear medicine imaging procedure in traumatology. Concerning any skeletal abnormality associated with changes in local perfusion, exudation and metabolism, it is a sensitive functional imaging procedure to detect bony disease. However, because of the varying causes of bony disease, it is characterized by a low specificity. Further, specificity may be enhanced, when patient history, clinical and lab results as well as results obtained from other diagnostic imaging procedures are combined with the result of skeletal scintigraphy. On the other hand, it is known that metabolic abnormalities of the skeleton depicted by radionuclide imaging occur much earlier than structural changes visible on X-ray imaging. Beside skeletal scintigraphy, antigranulocyte antibody or labelled leucocyte imaging may greatly assist in the detection of inflammation or infection following joint replacement surgery, respectively. Ultimatively, a combination of clinical, lab and imaging results including radionuclide imaging may represent the best approach to answer some questions asked by surgical traumatologists.

Bone and Bones↗

PubMed1997

[Involvement of the lymphatic system in primary non-lymphogenic edema of the leg. Studies with 2-compartment lymphoscintigraphy].

Two-compartment lymphoscintigraphy was developed to examine the sub- and epifascial lymphatics of the leg. Digital images were evaluated visually and semiquantitatively by calculating the uptake of activity within the lymph nodes. The data from patient groups with four different types of leg edema were compared with those of the control group to prove the involvement of the lymphatics in the non-lymphatic edema. The cyclic idiopathic edema demonstrated an accelerated transport of the lymph consistent with a high volume insufficiency. In phlebedema the high volume insufficiency was epifascially so distinct, that it could be detected scintigraphically. In post thrombotic syndrome the transport of the lymph was reduced dramatically corresponding to a safety valve insufficiency. Epifascially however, an accelerated lymph flow was observed due to compensatory mechanisms. The lipedema did not show any scintigraphic abnormalities. These results show that two-compartment lymphoscintigraphy can detect alterations in lymphatic function secondary to non-lymphogenic leg edema. The lymphatic function is changed according to the underlying pathophysiology which may be facilitate the differential diagnosis of such a leg edema.

Adult↗

PubMed1997

Nonlinear motion artifact reduction in event-triggered gradient-echo FMRI.

Event-triggered FMRI was designed to yield good spatial and time resolution on conventional hardware. However, due to longer overall measurement time this method is even more prone to motion artifacts than regular FLASH-based methods. We demonstrate a simple and efficient method to detect and reduce linear and non-linear motion artifacts by manipulating k-space MR data. Results show that (a) motion artifacts may be reduced from typically 10% to noise level (2-3%); (b) small, well-localized hemodynamic changes may be differentiated from motion artifacts; and (c) are visualized with high contrast using an appropriate model function. This way, hemodynamic changes detected by event-triggered FMRI can be quantitated reliably in the lower percent range.

Adult↗

PubMed1997

Quantification of signal changes in gradient recalled echo FMRI.

Understanding and quantifying the various contributions to functional magnetic resonance imaging (FMRI) signal changes in activated cortical areas is paramount for a clinical application of brain mapping by FMRI. Therefore, all significant contributions to FMRI signal changes, both extra- and intravascular, from macrovessels down to the capillary network, should be taken into account. We present a gradient-recalled-echo FMRI model based on in-flow effects described by the Bloch equations, adding susceptibility effects empirically via T2* differences measured in vitro in human blood samples. Results of these calculations (by systematically varying alpha, echo time (TE), repetition time (TR), as well as blood velocity and T2* upon stimulation) may be used to (a) simulate functional MRI experiments with different measurement protocols and (b) estimate realistic values for important anatomical and physiological details that influence local signal changes in FMRI (i.e., size and distribution of vessels, effective relaxation times of blood, etc.). The excellent agreement between our model calculations and experimental results from conventional gradient recalled echo fMRI in vivo suggests a significant contribution from very slow flow and oxygenation changes, predominantly in small vessels (vblood = 1-4 mm/s). The actual contribution of T1- and T2-related effects is strongly dependent on sequence design and actual sequence parameters used. Thus, the model simulations presented may also be used to optimize measurement protocols for investigating various neurophysiological phenomena.

Adolescent↗

PubMed1997

Modulation of signal changes in gradient-recalled echo functional MRI with increasing echo time correlate with model calculations.

Based on systematic in vivo studies analysed by fuzzy clustering, we prove the complex dependence of functional magnetic resonance imaging (fMRI) signal changes on echo time (TE) (ranging from 42 ms up to 160 ms) in the human visual cortex at 1.5 Tesla. We obtain a steady increase of signal enhancement with increasing TE, except at TE = 130 ms where the signal increase is significantly less than at 100 and 160 ms, respectively, caused by signal dephasing of spins in the vascular environment of the cortical region imaged. A comparison with model calculations reveals that vessels with a diameter of about 0.5 to 1 mm may be the main source of gradient-recalled echo fMRI signal changes at 1.5 Tesla at the given spatial resolution. In addition to conventional correlation analysis, fuzzy cluster analysis has been applied to evaluate fMRI data sets. Our results also indicate that, despite the similar temporal pattern of the functional response, it is possible to differentiate between areas which show higher signal enhancement (cluster 1, higher blood volume fraction) and lower signal enhancement (cluster 2, lower blood volume fraction), reflecting the different vascular environment. Therefore, fuzzy cluster analysis may help to extract functional information from activated areas closer to the actual neuronal activation.

Adolescent↗

PubMed1997

Incidental appendix carcinoid. Value of somatostatin receptor imaging.

PURPOSE: Somatostatin receptor scintigraphy is used to diagnose carcinoid of the gastrointestinal tract. Its sensitivity ranges from approximately 75%-100%. Therefore, it was hypothesized that it can be used in the postsurgical follow-up to detect residual carcinoid, recurrence, and metastatic disease. RESULTS: This article is concerned with the findings of somatostatin receptor imaging performed on a 12-year-old girl 8 weeks after appendectomy. Histologic examination showed an incidental appendix carcinoid. Somatostatin receptor scintigraphy performed for detection of lymph node metastatic spread of the carcinoid showed focal tracer accumulation at the former operative site; subsequently, a right hemicolectomy was performed. However, histologic examination of the surgical tissue showed no evidence for carcinoid. CONCLUSION: It is concluded that there are some potential pitfalls for somatostatin receptor imaging at least soon after surgery. Therefore, it should not be used to aid in reoperation.

Appendiceal Neoplasms↗