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Biomedical subjects

M F Müller

Publications and source records attributed to M F Müller.

At least 37 records · Page 2Linked to original sources
PubMed1994

[The value of MR tomography after transsphenoidal hypophyseal resection. A retrospective comparison between endocrinology, operation and MRT].

Postoperative magnetic resonance images of 40 patients after transsphenoidal surgery for pituitary adenoma were evaluated retrospectively. The signal intensities of packing material and residual tumour were analysed. T1-weighted spin-echo sequences were obtained in coronal and sagittal views with and without intravenous injection of contrast media. Residual tumour demonstrated homogeneous or inhomogeneous signal intensity on the native scan with homogeneous or inhomogeneous enhancement. Packing material demonstrated a homogeneous signal intensity on the images obtained without injection of contrast media with a peripheral enhancement or alternate layers of low and intermediate signal intensity with alternate enhancement after injection of contrast media. In 5 of 54 examinations different results were found in MRI, endocrinology and surgery (two false negative and one false positive MRI in correlation with endocrinology; two residual tumours on MRI where surgery was supposed to be complete). Application of intravenous contrast media facilitates the interpretation of postoperative examination of the pituitary gland as well as comparison with preoperative examinations and the knowledge of the intraoperative procedure.

Adenoma↗
PubMed1994

[The role of magnetic resonance angiography prior to the transjugular placement of a portosystemic stent shunt (TIPS)].

The authors employed magnetic resonance angiography (MRA) to guide catheter placement for transjugular intrahepatic portosystemic stent shunt (TIPS) procedures in 14 of 24 patients, and compared the results to the 10 patients who did not have prior planning based on MRA. Two-dimensional time-of-flight venography was performed during breath holding, and projection venograms were formatted in sagittal, coronal and axial planes. MRA defined venous anatomy sufficiently well to shorten the procedure and helped to minimize invasiveness. With MRA guidance, intrahepatic needle punctures were significantly fewer (without MRA guidance: mean 12.1; with MRA guidance: mean 3.5, p < 0.001) and associated complications were absent (without MRA guidance: failed placement, N = 1; bleeding requiring blood transfusions, N = 2; death complicating intraperitoneal haemorrhage with haemobilia, N = 1, and hepatic capsular perforation, N = 1). The average time for the procedure was 2.8 hours without MRA guidance and 1.8 hours with MRA guidance (p < 0.0005). The authors conclude that MR angiography is a useful technique to define portal and hepatic venous anatomy prior to TIPS, and planning based on MRA may decrease the difficulty and length of the procedure.

Adult↗
PubMed1994

[The in-vivo diffusion measurements of the liver, kidneys, spleen and m. erector with an echo-planar imaging system in normal subjects].

A diffusion sensitive pulse sequence using a stimulated echo (STEAM) type excitation and echo-planar (EPI) readout was developed on a 1.5 T echo-planar MR imaging system. Using this sequence the authors measured the apparent diffusion coefficients (ADC) of water in normal human liver, spleen, muscle and kidney in 12 volunteers. ADCs measured in normal volunteers were: liver, 1.39 +/- 0.16 x 10(-3) mm2/s, spleen, 0.95 +/- 0.15 x 10(-3) mm2/s, muscle, 1.99 +/- 0.16 x 10(-3) mm2/s, kidney, 3.54 +/- 0.47 x 10(-3) mm2/s. A large scatter of the ADCs in the kidneys was found in the different degrees of hydration status among the volunteers and also due to inter-subject variability. With further clinical experience, in vivo diffusion measurements of the abdominal organs may prove helpful in the identification and classification of abdominal disease by MRI.

Adult↗
PubMed1994

Abdominal diffusion mapping with use of a whole-body echo-planar system.

PURPOSE: To measure apparent diffusion coefficients (ADCs) of water in liver, spleen, kidney, and muscle. MATERIALS AND METHODS: Ten volunteers (seven women and three men, aged 19-31 years [mean, 24 years]) and nine patients (five women and four men, aged 49-70 years [mean, 62 years]) (liver cyst, n = 3; liver hemangioma, n = 3; liver cirrhosis, n = 2; hepatocellular carcinoma, n = 1; and liver metastasis, n = 1) underwent magnetic resonance (MR) imaging. A stimulated-echo acquisition mode (STEAM)-type excitation and echo-planar imaging (EPI) readout was used in a 1.5-T echo-planar MR imaging system. RESULTS: ADCs measured in volunteers were liver, 1.39 x 10(-3) mm2/sec +/- 0.16; spleen, 0.95 x 10(-3) mm2/sec +/- 0.15; muscle, 1.99 x 10(-3) mm2/sec +/- 0.16; and kidney, 3.54 x 10(-3) mm2/sec +/- 0.47 (mean +/- standard deviation). Distinctive ADC values were found in organs with abnormalities. ADCs in patients with hepatic disease included liver cysts, 3.9-5.3; liver hemangiomas, 2.0-2.8; liver metastases from an islet cell tumor, 1.2; hepatocellular carcinoma, 1.7; and liver cirrhosis, 0.9-1.2 x 10(-3) mm2/sec. CONCLUSION: In vivo diffusion measurements of abdominal organs obtained with MR imaging may prove helpful in the identification and classification of abdominal disease.

Abdomen↗
PubMed1994

Pancreatic tumors: evaluation with endoscopic US, CT, and MR imaging.

PURPOSE: To compare the value of endosonography (endoscopic ultrasound [US]), dynamic computed tomography (CT), and magnetic resonance (MR) imaging in the evaluation of pancreatic tumors. MATERIALS AND METHODS: Forty-nine consecutive patients with clinical suspicion of pancreatic tumor underwent endoscopic US (n = 49), CT (n = 46), and MR imaging (n = 25). The final diagnosis of a malignant (n = 22), benign (n = 2), or inflammatory (n = 9) tumor, or no (n = 16) tumor was made at surgery (n = 28) and/or a combination of biopsy (n = 9) and 9-24-month follow-up (n = 12). RESULTS: The sensitivity was 94% for endoscopic US, 69% for CT, and 83% for MR imaging. Specificity was 100% for endoscopic US, 64% for CT, and 100% for MR imaging. Accuracy was 96% for endoscopic US, 67% for CT, and 84% for MR imaging. The sensitivity for the detection of tumors less than 3 cm in diameter was 93% for endoscopic US (n = 15), 53% for CT (n = 15), and 67% for MR imaging (n = 12). CONCLUSION: Endoscopic US is more accurate than dynamic CT and MR imaging in the diagnosis of pancreatic tumor, particularly for tumors less than 3 cm in diameter.

Carcinoma, Ductal, Breast↗
PubMed1994

Fast MR imaging of the liver: quantitative comparison of techniques.

PURPOSE: To compare several techniques for fast magnetic resonance (MR) imaging of focal liver lesions. MATERIALS AND METHODS: Ninety patients (37 men and 53 women, aged 19-92 years [mean, 54 years]) with 137 focal liver lesions (56 metastases, 13 hepatocellular carcinomas, 52 hemangiomas, 16 cysts) underwent MR imaging with rapid acquisition spin-echo (RASE), T1-weighted fast low-angle shot (FLASH), turboFLASH, segmented turboFLASH, and T2-weighted conventional and turbo spin echo (SE). Images were analyzed for spleen-to-liver and lesion-to-liver signal difference-to-noise ratios (SD/Ns). RESULTS: Turbo SE T2-weighted imaging had the highest SD/N for spleen-to-liver (P < .01) and for lesion-to-liver (P < .02) contrast. Segmented T1-weighted turboFLASH imaging had the second highest SD/N for spleen-to-liver (P < .001) contrast and was better overall than other T1-weighted sequences for depicting liver lesions (P < .01). Results at segmented turboFLASH imaging were second best for hemangiomas (P < .01). For metastases, no significant difference was found for results with the T1-weighted sequences. CONCLUSION: Segmented T1-weighted turboFLASH and turbo SE T2-weighted imaging hae advantages over conventional techniques for liver imaging.

Carcinoma, Hepatocellular↗
PubMed1994

Functional imaging of the kidney by means of measurement of the apparent diffusion coefficient.

PURPOSE: To determine the relationship between the apparent diffusion coefficient (ADC) and renal function. MATERIALS AND METHODS: Twenty-three volunteers and seven pigs underwent diffusion-sensitive magnetic resonance (MR) imaging of the kidneys with a stimulated-echo acquisition mode excitation and echo-planar imaging readout under various physiologic conditions. The effect of hydration and anisotropic diffusion was studied in human subjects, and the effect of renal artery stenosis, ureteral obstruction, and diuresis was studied in the animal model. RESULTS: The renal ADC values of dehydrated subjects were substantially increased with rehydration. Diffusion was highest in the medulla, with a pronounced radial component in the renal collecting system. In the pig model, induced renal artery stenosis resulted in immediate decrease in renal ADC; the degree of change was related to the flow deficit. The ADC also decreased with ureteral obstruction, but diuresis had no meaningful effect. CONCLUSION: In vivo measurement of ADC has the potential for use as a noninvasive means to explore the functional status of the kidney.

Adult↗
PubMed1994

Diagnosis of severe birth asphyxia and early prediction of neonatal neurological outcome in term asphyxiated newborns.

Ten indicators available during the first two hours of life, such as clinical criteria of neonatal distress and postnatal arterial blood gases, were compared with the neonatal neurological course in sixty full term newborns with significant birth asphyxia in order to test their value for the diagnosis and the short-term prognosis of severe birth asphyxia. Birth asphyxia was defined as severe when it was followed by symptoms of moderate or severe post-asphyxial encephalopathy. We calculated a sensitivity lower than fifty percent for clinical criteria such as delay in establishing regular respiration and Apgar scores. It was clear that normal delay in establishing regular respiration and normal Apgar scores do not exclude severe birth asphyxia. Arterial pH and base deficit at thirty minutes of life were found to be the best criteria for the diagnosis of severe birth asphyxia, but lacked positive predictive value. The best predictive tool for the short-term neurological prognosis of birth asphyxia was a single score established at 30 minutes of life and based on the evaluation of consciousness, respiration and neonatal reflexes. Some aspects of the pathophysiology of birth asphyxia and the rationale for treatment of post-asphyxial metabolic acidosis are discussed.

Acidosis, Lactic↗
PubMed1993

[Spontaneous rupture of the left hepatic duct].

A previously well 24-year-old man complained of persistent epigastric pain after a session of intensive muscle building exercise especially of the abdominal muscles. The abdomen was diffusely tender without guarding. There was an increased concentration of bilirubin (64.7 mumol/l), GOT (117 U/l), GPT (529 U/l) and alkaline phosphatase (150 U/l). Ultrasound examination showed a widening of the choledochal duct to 11 mm without signs of gallstones. Endoscopic retrograde cholangiography additionally revealed contrast-medium extravasation from the left hepatic duct. Computed tomography, performed immediately afterwards, confirmed the extravasation, while liver and pancreas were unremarkable. Laparoscopy revealed a 5 mm tear in the left hepatic duct, close to the hepatic duct bifurcation with bile effusion into the peritoneal cavity. The latter was rinsed endoscopically with Ringer's solution and drains were placed in the omental bursa and subhepatically in the region of the bile leak. To relax the sphincter Oddi glycerol trinitrate was administered postoperatively, for the first five days 72 mg/24 h intravenously, then for nine days twice daily 20 mg by month. No more bile drained as early as the second postoperative day and the patient was free of symptoms 2 weeks later.

Adult↗
PubMed1993

[Abdominal tumors in children. A comparison between magnetic resonance tomography (MRT) and ultrasonography (US)].

Twenty-one children with predominantly solid tumours detected by US were also examined by MRI (7 neuroblastomas, 2 Wilms tumours, 3 hepatoblastomas, 2 germinal cell tumours, 1 ganglioneuroblastoma, 1 gangliocytoma, 1 Cushing's adenoma, 1 phaeochromocytoma, 1 retroperitoneal rhabdomyosarcoma, 1 diffuse lymphangiectasia of a kidney, 1 splenunculus). The findings from both methods were compared with respect to the identification of the organ involved, extent of the tumour, effect on neighbouring structures and tissue characteristics. US and MRI were of equal value in defining the origin of the lesion and in demonstrating pathological enlargement of lymph nodes. Exact tumour extent could be better demonstrated with MRI because of the ability to perform multiplanar sections and to demonstrate intrathoracic and intraspinal spread. MRI was superior in 9 cases in demonstrating tumour structure and in 6 cases in the evaluation of vascular involvement and vascular anatomy. MRI is therefore recommended as an additional method to US for diagnosis and for treatment planning.

Abdomen↗
PubMed1993

[Radiologic and ultrasound detection of gallstones].

Ultrasonography (US) is the method of choice for evaluation of gallbladder stones with an accuracy of 96%. Number, size and calcification can be assessed by virtue of US reflection and attenuation. If more than five stones are present, the accuracy decreases. To determine the calcium content of stones more precisely, computed tomography can be used. This allows an assessment of the success rate of lithotripsy and chemolysis. Oral cholecystography is an alternative method of similar accuracy as US. It provides additional information about the patency of the cystic duct. In the presence of ductal stones, the accuracy of US decreases to 30%, mainly because of overlying bowel gas. Since 8 to 16% of all cases of cholecystolithiasis are accompanied by choledocholithiasis and since this entails a change in treatment, intravenous cholecystocholangiography with an accuracy of more than 90% is the method of choice in this case. Additionally, it provides knowledge on the biliary anatomy preoperatively. It does not, however, replace US, because opacification of the gallbladder is limited with this method. If intravenous cholecystocholangiography fails in case of impaired liver function, transcholecystic cholangiography or, in cases of dilated ducts, percutaneous transhepatic cholangiography can be used. Plain film radiography is not a suitable technique, since only 10 to 15% of all gallstones calcify.

Calcinosis↗
PubMed1993

[Monitoring of fontanelle pressure in neonates and infants. Evaluation of a new measuring technique, determination of normal values and clinical usefulness].

The experience with 200 measurements of anterior fontanelle pressure with the Rotterdam Teletransducer in newborns and infants is reported. Statistical analysis of 25 comparative measurements between anterior fontanelle pressure and invasive cerebrospinal fluid pressure showed an excellent correlation (rs = 0.95). Measurements were reproducible and the plot quality allowed visualisation of pulse pressure and pressure waves. Normal values of the anterior fontanelle pressure, pulse pressure amplitude and pressure wave maximal amplitude were established in 15 prematures, 27 term newborns and 10 infants. Anterior fontanelle pressure monitoring was performed in 19 term newborns with post-asphyxial encephalopathy, 18 newborns and infants with hydrocephalus, 8 preterm and term newborns with respiratory distress and 19 patients with subdural haematomas, metabolic diseases, meningitis, subarachnoidal haemorrhage, head trauma, post cardiac arrest encephalopathy and abnormal head growth or bulging fontanelle. Abnormal patterns of anterior fontanelle pressure monitoring were found in moderate or severe neonatal post-asphyxial encephalopathy, evolutive hydrocephalus, subdural haematomas, metabolic diseases with hyperammoniemia and other clinical situations. In contrast, anterior fontanelle pressure monitoring yielded normal values in mild post-asphyxial encephalopathy, arrested hydrocephalus, well functioning ventriculo-peritoneal derivation, and in normal infants with rapid head growth or bulging fontanelle. The Rotterdam Teletransducer provides thus accurate and reproducible values of intracranial pressure. Anterior fontanelle pressure monitoring may be of value in many situations in clinical practice.

Asphyxia Neonatorum↗
PubMed1989

Small-angle X-ray scattering studies of fibrin film: comparisons of fine and coarse films prepared with thrombin and ancrod.

Measurements of small-angle x-ray scattering have been made on films prepared from fine and coarse (i.e., formed at high and low, respectively, pH and ionic strength) clots of bovine fibrin by osmotic shrinkage or compression in one dimension. Intensity profiles were obtained with pinhole geometry on films stretched up to a stretch ratio of 1.43. In unstretched coarse films, repeat spacings were seen at about 245, 120, and 77-80 A. These peaks can probably be identified with the first, second, and third orders of the well-known fibrin repeat of 225 A. In unstretched fine films, only the 77-80 A spacing was seen. In this case, the first two orders may be weak because the half-staggered arrangement of monomer units giving rise to the 225 A reflection is not reinforced by lateral aggregation of protofibrils; the third order may be strong since the molecular subdomains appear to divide the repeat roughly into thirds. After stretching, the 77-80 A spacing persisted in the meridional direction but almost disappeared in the equatorial. Experiments on unstretched films prepared with ancrod substituted for thrombin gave similar results.

Ancrod↗
PubMed1987

Studies on the ultrastructure of fibrin lacking fibrinopeptide B (beta-fibrin).

Release of fibrinopeptide B from fibrinogen by copperhead venom procoagulant enzyme results in a form of fibrin (beta-fibrin) with weaker self-aggregation characteristics than the normal product (alpha beta-fibrin) produced by release of fibrinopeptides A (FPA) and B (FPB) by thrombin. We investigated the ultrastructure of these two types of fibrin as well as that of beta-fibrin prepared from fibrinogen Metz (A alpha 16 Arg----Cys), a homozygous dysfibrinogenemic mutant that does not release FPA. At 14 degrees C and physiologic solvent conditions (0.15 mol/L of NaCl, 0.015 mol/L of Tris buffer pH 7.4), the turbidity (350 nm) of rapidly polymerizing alpha beta-fibrin (thrombin 1 to 2 U/mL) plateaued in less than 6 min and formed a "coarse" matrix consisting of anastomosing fiber bundles (mean diameter 92 nm). More slowly polymerizing alpha beta-fibrin (thrombin 0.01 and 0.001 U/mL) surpassed this turbidity after greater than or equal to 60 minutes and concomitantly developed a network of thicker fiber bundles (mean diameters 118 and 186 nm, respectively). Such matrices also contained networks of highly branched, twisting, "fine" fibrils (fiber diameters 7 to 30 nm) that are usually characteristic of matrices formed at high ionic strength and pH. Slowly polymerizing beta-fibrin, like slowly polymerizing alpha beta-fibrin, displayed considerable quantities of fine matrix in addition to an underlying thick cable network (mean fiber diameter 135 nm), whereas rapidly polymerizing beta-fibrin monomer was comprised almost exclusively of wide, poorly anastomosed, striated cables (mean diameter 212 nm). Metz beta-fibrin clots were more fragile than those of normal beta-fibrin and were comprised almost entirely of a fine network. Metz fibrin could be induced, however, to form thick fiber bundles (mean diameter 76 nm) in the presence of albumin at a concentration (500 mumol/L) in the physiologic range and resembled a Metz plasma fibrin clot in that regard. The diminished capacity of Metz beta-fibrin to form thick fiber bundles may be due to impaired use or occupancy of a polymerization site exposed by FPB release. Our results indicate that twisting fibrils are an inherent structural feature of all forms of assembling fibrin, and suggest that mature beta-fibrin or alpha beta-fibrin clots develop from networks of thin fibrils that have the ability to coalesce to form thicker fiber bundles.

Blood Coagulation↗
PubMed1985

Effects of fibrinogen-binding tetrapeptides on mechanical properties of fine fibrin clots.

The tetrapeptides Gly-Pro-Arg-Pro and Gly-His-Arg-Pro, analogs of the amino termini of the alpha and beta chains of fibrin monomer, respectively, were introduced by diffusion into fine unligated fibrin clots. Gly-Pro-Arg-Pro decreased the shear modulus of elasticity progressively and at a concentration of 5.8 mM the clot was eventually liquefied. The decrease in elastic modulus was accompanied by enormously enhanced viscoelastic creep under shear stress and irrecoverable deformation after removal of stress. However, the differential compliance (or modulus) for clots containing the tetrapeptide remained constant during creep and creep recovery, so the structure rearranged under stress without any permanent damage. Ligation with factor XIIIa and calcium largely eliminated these effects. From these changes in mechanical properties, it appears that Gly-Pro-Arg-Pro competes for binding sites, with consequent depolymerization. The tetrapeptide Gly-His-Arg-Pro at comparable concentrations decreased the modulus and increased the creep to a lesser degree; when combined with Gly-Pro-Arg-Pro it enhanced the effectiveness of the latter.

Binding, Competitive↗
PubMed1984

Electron microscopy of fine fibrin clots and fine and coarse fibrin films. Observations of fibers in cross-section and in deformed states.

Fine fibrin clots and coarse and fine fibrin films (both ligated and unligated), formed by shrinkage of clots in one dimension, were examined by electron microscopy. Specimens of clots were prepared by critical point drying and by embedding and sectioning; specimens of films were prepared by embedding and sectioning only. In the fine clots, network junctions appeared to be formed by fiber segments in which two or more protofibrils were gently twisted around each other for distances of the order of 200 nm and then diverged to give trifunctional branch points. This topology appeared to be preserved in the fine films. It is proposed that the strength of the junctions is primarily provided by the twisting topology, though reinforced by non-covalent bonding involving the B sites uncovered by thrombin. In coarse films, bundles of protofibrils, lying primarily in the film plane, had diameters of 40 to 200 nm and were gently twisted around each other to form thicker cables. Uniaxial stretching, up to 100%, of either fine or coarse film before fixing caused suprisingly extensive orientation of the protofibrils or bundles. However, random orientation was recovered if a stretched ligated film was allowed to retract to its original dimensions before fixing. In a stretched coarse film sectioned perpendicular to the stretch direction, fiber bundles could be seen in cross-section; these were roughly circular with scalloped edges. The changes with stretching and recovery are discussed in relation to possible mechanisms of deformation and elastic energy storage.

Animals↗