Biomedical subjects

R Baumgartner

Publications and source records attributed to R Baumgartner.

246 records · Page 14Linked to original sources

PubMedDate not supplied

Fuzzy clustering of gradient-echo functional MRI in the human visual cortex. Part II: quantification.

Fuzzy cluster analysis (FCA) is a new exploratory method for analyzing fMRI data. Using simulated functional MRI (fMRI) data, the performance of FCA, as implemented in the software package Evident, was tested and a quantitative comparison with correlation analysis is presented. Furthermore, the fMRI model fit allows separation and quantification of flow and blood oxygen level dependent (BOLD) contributions in the human visual cortex. In gradient-recalled echo fMRI at 1.5 T (TR = 60 ms, TE = 42 ms, radiofrequency excitation flip angle [theta] = 10 degrees-60 degrees) total signal enhancement in the human visual cortex, ie, flow-enhanced BOLD plus inflow contributions, on average varies from 5% to 10% in or close to the visual cortex (average cerebral blood volume [CBV] = 4%) and from 100% to 20% in areas containing medium-sized vessels (ie, average CBV = 12% per voxel), respectively. Inflow enhancement, however, is restricted to intravascular space (= CBV) and increases with increasing radiofrequency (RF) flip angle, whereas BOLD contributions may be obtained from a region up to three times larger and, applying an unspoiled gradient-echo (GRE) sequence, also show a flip angle dependency with a minimum at approximately 30 degrees. This result suggests that a localized hemodynamic response from the microvasculature at 1.5 T may be extracted via fuzzy clustering. In summary, fuzzy clustering of fMRI data, as realized in the Evident software, is a robust and efficient method to (a) separate functional brain activation from noise or other sources resulting in time-dependent signal changes as proven by simulated fMRI data analysis and in vivo data from the visual cortex, and (b) allows separation of different levels of activation even if the temporal pattern is indistinguishable. Combining fuzzy cluster separation of brain activation with appropriate model calculations allows quantification of flow and (flow-enhanced) BOLD contributions in areas with different vascularization.

Adult↗

PubMedDate not supplied

Quantification of statistical type I and II errors in correlation analysis of simulated functional magnetic resonance imaging data.

The potential of statistical analyses of functional magnetic resonance images using various threshold strategies in combination with correlation analysis was studied by simulating brain activation. Differences in statistical Type I (alpha) and II (beta) errors are substantial for the various thresholds. Absolute thresholds and individualized thresholds based on the assumption of a gaussian noise distribution are producing constant alpha-errors and thus do not sufficiently improve discrimination of "truly" activated pixels even for very high contrast-to-noise ratios (CNR). Only relative threshold strategies related to the maximum correlation coefficient and thus the individual data quality and activation level, i.e., a data-driven approach, can perfectly discriminate true positives, at least for CNR > 2.5. To further improve discrimination of activated and non-activated pixel in studies with lower CNR, additional prior knowledge would be necessary. From the data presented, one would also expect that the best performing threshold strategy in this simulation study would perform best under in vivo conditions.

Biometry↗

PubMedDate not supplied

Odd-numbered long-chain fatty acids in propionic acidaemia.

UNLABELLED: In patients with propionic acidaemia (PA), the increased intracellular concentration of propionyl-CoA leads to a relative abundance of odd-numbered long-chain fatty acids (OLCFAs) in body lipids. We investigated the relative amount of OLCFA in erythrocyte membrane lipids over a period of 1-8 years in five patients with early onset PA and present their clinical outcome. After extraction from erythrocyte membrane lipids and esterification, fatty acids were analysed by capillary column gas chromatography. The sum of the OLCFA 15- and 17- carbon saturated and 17-carbon monounsaturated fatty acids (C15:0, C17:0, C17:1) was calculated and expressed as a percentage of the total C14-C22 fatty acids in the sample. Three patients (pccBC-complementation group) presented with a stable clinical course and showed OLCFA values usually below 1.9% (median % +/- SD: 1.4+/-0.5, 1.6+/-0.5, 1.8+/-0.5). Two patients (pccA-complementation group) had a more severe course of the disease and showed higher medians and a broader range of OLCFA levels (2.2+/-1.2 and 2.2+/-0.8). CONCLUSION: Our study shows that odd-numbered long-chain fatty acid concentrations are increased in patients with propionic acidaemia and are higher in those with a more severe clinical course. The value of odd-numbered long-chain fatty acids in the assessment of the phenotypic severity and in the management of propionic acidaemia remains to be proven in a prospective long-term study with more patients of differing phenotype.

Amino Acid Metabolism, Inborn Errors↗

PubMedDate not supplied

Lean R value for DXA two-component soft-tissue model: influence of age and tissue or organ type.

Dual-energy X-ray absorptiometry (DXA) is an important new body composition method that is based on tissue attenuation of two main photon energies. When the two photon energies pass through tissue, attenuation at the lower energy compared with that at the higher energy can expressed as a ratio (R), which is used for tissue component identification. We tested whether: (1) the R value of lean tissue is related to age, and (2) the R value of lean tissue differs between soft tissue locations. Elemental content of various tissues from the literature was used. Results show that lean R values for 40 keV and 70 keV are independent of age and tissue type.

Absorptiometry, Photon↗

PubMedDate not supplied

[Propionic acidemia with myelination disorders of the CNS].

Clinical course and special diagnostic procedures in a 7 1/2 weeks old dystrophic infant with propionic acidemia are described. The disorder manifested with vomiting and diarrhea within the first week of life when the child was on a cow milk formula. Parenteral nutrition with glucose and electrolytes led to improvement. When oral nutrition with a cow milk formula was implemented again, an acute deterioration with diarrhoea and vomiting occurred. Thus, a diagnosis of cow milk allergy was suggested. There was also a severe muscular hypotony. Oral nutrition with a soybean formula did not prevent further clinical deterioration. At 7 1/2 weeks of age the patient died with symptoms of cardiogenic shock. The correct diagnosis was considered too late and confirmed post mortem. Clinical symptoms in the neonatal period like vomiting, muscular hypotony and failure to thrive should alert the physician to a possible diagnosis of a hereditary organic aciduria. Gas chromatography-mass spectrometry of urinary organics acids, in the present case, established the diagnosis. On autopsy, spongy degenerations were found in CNS.

Acidosis↗

PubMedDate not supplied

[Asymmetry of posture and truncal musculature following unilateral arm amputation--a clinical, electromyographic, posture analytical and photogrammetric study].

Unilateral upper limb amputation causes changes in statics of the spine. As a result asymmetrical posture of the spine, muscular asymmetries follow. In this study a population of upper limb amputees (above and below elbow amputees) is examined by clinical, electromyographical analysis and gait analysis. Upper limb amputations cause in correlation to weight loss a shift of the trunk to the side of the amputation, a scoliosis with a bowing to the side of the amputation, an elevation of the shoulder on the amputation side and a torsion of the trunk. Muscular asymmetries result from loss of function (muscles of the arm, M. latissimus, M. trapezius) and by shifting of the center of gravity. In order to get the center of gravity over the legs, the amputee compensates the loss of weight by shifting the upper trunk to the side of the amputation. As a result the shift of the segmental center of gravity at the lumber height to the side of the normal arm with muscular asymmetry in the erector trunci lumbalis results. As well we saw an overactivity of musculus glutaeus medius and resulting stress of the amputation sided hip joint. There was a remarkable difference between above and below elbow amputees caused by differences in weight loss. Muscular and static asymmetries in amputees who lost their arm only a short period before could be reduced by compensating the weight loss. Results for technical orthopaedic fitting and stress on gymnastic procedures to compensate these statistical problems are discussed.

Adult↗

PubMedDate not supplied

[Special case report: Gangrene of all 4 extremities caused by disseminated intravascular coagulation in pneumococcal sepsis].

The rare case of a child with gangrene of all extremities following intravascular coagulation in pneumococcus septicaemia is described. The two years old spanish girl showed a gangrene of all four extremities and accompanying celloid scars. The operative treatment, the orthopaedic technical fitting as well as the problems are discussed.

Amputation, Surgical↗

PubMedDate not supplied

[Prosthesis edge nodule and verrucous hyperplasia in leg amputees].

Dermatologic problems in leg amputees mainly result from their specific prosthetic supply. As this relationship is not well documented in the German language literature, we try to illustrate important pathophysiologic aspects of lower and upper limb prostheses in two highly characteristic dermatoses, epidermoid cysts and verrucous hyperplasia (papillomatosis cutis lymphostatica). Their management includes improvements in prostheses' workmanship and conceptional changes (e.g. CAT-CAM-technique). Interdisciplinar diagnostic and therapeutic efforts particularly between orthopedic surgeons, prosthetists and dermatologists should prevent immobility of the amputee at an early stage.

Adult↗

PubMedDate not supplied

[Charcot's elbow joint in syringomyelia].

Neuropathic arthropathy is a rare case in daily orthopedic practice. The case of a 43 year old technician is reported, who developed severe destruction of both elbow joints as a result of syringomyelia. The diagnostical problems as well as the therapeutical considerations are discussed.

Adult↗

PubMedDate not supplied

[Prosthetics-orthotics and related surgery].

Only in German speaking countries, prosthetics/orthotics are still considered as being a part of orthopaedic surgery (and not of physical and rehabilitation medicine). Thus, patient management is an overall task for the orthopaedic surgeon from diagnostics to surgical and conservative treatment up to rehabilitation programs. This special issue is dedicated to prosthetics, orthotics and related surgery as a part of orthopaedics. It is one of the results of a '93 campaign in order to promote this specialty.

Humans↗

PubMedDate not supplied

[Indications for the Krukenberg hand based on long-term results].

The object of the Krukenberg procedure invented in 1916 is to convert the forearm stump into an active pincer with two opposable branches covered with skin and with normal sensibility. The procedure was devised during World War I and particularly used and developed on further war amputees. Whereas functional results are mostly excellent, the cosmetic appearance of a Krukenberg hand nowadays is considered to be obsolete by most surgeons. The authors have reexamined 20 patients, 13-45 years after surgery and have studied the relevant literature. All but one patient are satisfied with their Krukenberg hand as its performance is superior compared to the even most modern prosthetic devices. Therefore, the principles of the operative techniques are recalled and, based on the analysis of results, today's indications for the Krukenberg procedures are specified.

Amputation, Surgical↗

PubMedDate not supplied

[Technical surgical possibilities for preserving an end-bearing knee exarticulation stump in skin necrosis].

Disarticulation of the knee results in an excellent end-bearing stump. Operative technique is easy, fast and gentle. The muscular balance in the femur is not disturbed. The shape of the stump provides excellent rotation control in the prosthesis. New socket designs and prosthetic knee mechanisms have eliminated the former cosmetic problems concerning this amputation level. Nevertheless--because of external rotation of the femur, poor skin quality or wound closure under tension skin necrosis can occur, most of the times concerning the lateral condyle region. Several operative possibilities to get a satisfactory wound closure while preserving the advantages of this stump are presented.

Artificial Limbs↗