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T Vogl

Publications and source records attributed to T Vogl.

At least 73 records · Page 4Linked to original sources
PubMed1997

[Value of MRI in assessment of cruciate ligament replacement].

To evaluate the predictive value of MRI in the early postoperative course after cruciate ligament replacement, a prospective study was performed. Twenty patients with reconstructed anterior and/or posterior cruciate ligament were examined clinically and with contrast-enhanced MRI 2, 12, 24 weeks, 1 and 2 years postoperatively. The clinical examinations were evaluated according to the scores by Lysholm, OAK and IKDC. The MRI scans (SP 63, 1.5 Tesla) were evaluated regarding the quality and signal intensity of the reconstructed ligament. During the first postoperative year a significant increase in signal intensity and inhomogeneity of the neoligament in MRI was observed in 16 patients with an average value for signal/noise of 1.1 2 weeks postoperatively up to 6.9 1 year postoperatively. In 12 patients the reconstructed ligament could not be evaluated in the 1-year postoperative MRI, whereas none of these patients was suspected clinically of having instability. In the 2-year postoperative MRI, the signal intensity of the neoligament was found to be decreasing again with improvement in judgement.

Adolescent↗
PubMed1997

[Dosage values for characterization of patient exposure in computerized tomography and their significance for risk assessment].

In order to evaluate patients' exposure to radiation in computed tomography, dose quantities such as the computed tomography dose index (CTDI), multiple scan average dose (MSAD) and dose free in air on the axis of rotation are used. The CTDI and the MSAD, derivable from the CTDI, are a good measure for the absorbed doses in the examined volume, but they do not take the biological sensitivity of the organs into account and do not describe the radiogenic risk that is actually relevant for patients and doctors. The dose on the axis of rotation is not an accurate measure of the effective dose and the radiogenic risk. The declaration of a limit for the dose on the axis of rotation should take the different regions into account, in order to guarantee acceptable image quality on one hand and to avoid an unnecessarily high risk on the other side. As physical dose quantities, the CTDI, MSAD and dose on the axis of rotation are useful to characterize and differentiate between programs and systems concerning radiation exposure.

Humans↗
PubMed1997

Clinical significance of magnetic resonance cholangiopancreatography (MRCP) compared to endoscopic retrograde cholangiopancreatography (ERCP).

BACKGROUND AND STUDY AIMS: The clinical importance of magnetic resonance cholangiopancreatography (MRCP) as a noninvasive diagnostic modality for investigation of the biliary tree and pancreatic duct system is under debate. Using endoscopic retrograde cholangiopancreatography (ERCP) as the gold standard, this study determined in a prospective, blinded fashion the sensitivity and further statistic values of MRCP findings for evaluation of the biliary and pancreatic tract. PATIENTS AND METHODS: Seventy-eight patients referred for ERCP were studied prospectively with MRCP and ERCP during a 12-month period. All images were interpreted on a blinded basis by two radiologists. Any dilations, strictures, and intraductal abnormalities were recorded and correlated with the clinical diagnoses. RESULTS: MRCP images of diagnostic quality were obtained in 76 of the 78 patients (97%). Magnetic resonance cholangiography (MRC) showed sensitivities (and positive predictive values) of 71% (62%) for recognition of normal bile ducts, 83% (91%) for recognition of dilation, 85% (100%) for recognition of strictures, 77% (91%) for correct stricture location, and 80% (100%) for diagnosing bile duct calculi. In addition, the sensitivity of MRC in classifying benign and malignant strictures was 50% and 80%, respectively. The statistical values (sensitivity and positive predictive value) for magnetic resonance pancreatography findings were determined for the recognition of normal pancreatic ducts (33% and 50%), recognition of dilation (62% and 100%), recognition of strictures (76% and 87%) and correct location (66% and 100%), diagnosis of benign strictures (87% and 87%) and malignant strictures (60% and 75%), and for diagnosing pancreatic duct stones (60% and 100%). CONCLUSIONS: MRCP is capable of providing diagnostic information equivalent to ERCP in many patients, and should be applied whenever established techniques provide no results, or inadequate results.

Adolescent↗
PubMed1996

[Radiation exposure in interventional radiology as exemplified by the chemoembolization of hepatocellular carcinoma and laser angioplasty of the pelvic arteries].

PURPOSE: Estimation of radiogenic risks for patient and radiologist in chemoembolisation of hepatocellular carcinoma (HCC) and laser angioplasty of the pelvic arteries. METHODS: In 5 chemoembolisations of HCC (4 males, one female) and 6 laser angioplasties of the pelvic arteries (5 males, one female) the surface doses received by patient and operator were measured using thermoluminescent dosimeters in standardised positions. The organ doses of the patient were derived by conversion factors employed on the measured surface doses. Effective dose was determined according to the recommendations of ICRP 60. RESULTS: The risk of lethal malignant disease and genetic disorder derived from the doses in the patient was found to be of the magnitude of 10(-4)-10(-5). The thresholds for transient erythema of the skin and depression of hematopoiesis can be reached after high expositions. A theoretical maximum of 700 laser angioplasties of the pelvic arteries allowable in one year was calculated based on the dose to the operator's left hand. For chemoembolisation of HCC, the dose to the left eye lens would reach the yearly maximum after approximately 1000 procedures. Remarkable risks for malignant disease of skin and thyroid as well as detectable opacities of the eye lens can occur after frequent interventions for many years. CONCLUSIONS: Because of the lower life expectancy the patient's risk for stochastic effect can be seen as minimal. No clinically relevant deterministic effects will occur. In the case of frequent interventions, the dose absorbed by the radiologist is likely to exceed the prescribed dose limit and to cause remarkable risk for stochastic and non-stochastic effects after many years.

Aged↗
PubMed1996

[Calculated organ doses and effective dosage for computerized tomography examination of the thorax and abdomen: are these doses realistic?].

PURPOSE: To analyse how far dose calculations for the CT examination of the thorax and abdomen can lead to faulty estimations of organ doses and effective dose due to differences in the topographic anatomy between mathematical phantom and man. METHODS: For the CT examination of the thorax, upper abdomen, pancreas, pelvis and the entire abdomen, organ doses were calculated with conversion factors, first with regard to the topographic relation within the phantom, then with additional regard to the real anatomy of the man. RESULTS: In the phantom, the abdomen lies outside the scan volume in case of CT-examination of the thorax and the whole intestine outside the scan volume in case of CT-examination of the upper abdomen and the pancreas, whereas the entire intestine is directly exposed in case of CT-examination of the pelvis. Dependent on whether dose calculations take real anatomy into account, doses of special organs can differ by a factor greater than 15. The calculated effective doses differ by a factor less than 1.5. CONCLUSIONS: Calculations of organ doses for the CT examination of the thorax and abdomen can lead to considerable errors due to different topographic relations between phantom and man. In contrast the calculated effective dose is realistic. Hence, dose calculations with the help of mathematical phantom is an efficient method to estimate the total radiogenic risk.

Female↗
PubMed1996

[Skull injury in childhood: comparison of ultrasonography with conventional X-rays and computerized tomography].

PURPOSE: The purpose of our study was to compare the value of ultrasound, conventional x-ray diagnosis and CT in detecting skull fractures and intracranial haemorrhage in children suffering from a head injury. MATERIAL AND METHODS: We examined 210 children who had a head injury. In all cases the calvarium was investigated by ultrasound using a 7.0 MHz linear transducer. In children with an open fontanel (n = 190) the cerebrum was screened additionally by ultrasound following a standard protocol. The sonographic findings were correlated to the x-ray examination (n = 21) and CT (n = 13). RESULTS: Ultrasound enabled diagnosis of linear calvarial fractures (n = 29), depressed fractures (n = 6) and intracranial haemorrhage (n = 8). X-Ray and CT examination confirmed the diagnosis of linear calvarial fractures in 16 cases, of depressed fractures in 6 cases. CT confirmed the sonographic diagnosis of intracranial haemorrhage in 8 cases. CONCLUSION: Ultrasound as a primary method can replace the conventional x-ray in detecting calvarial fracture and posttraumatic sequelae. Additional CT examination depends on the sonographic and neurological status.

Age Factors↗
PubMed1996

[The efficacy of lead shielding in patient dosage reduction in computed tomography].

PURPOSE: Investigation of the efficacy of lead apron, testis capsule and thyroid collar for dose reduction in uterus, ovaries, testes and thyroid gland in computed tomography examinations. METHODS: At an Alderson-Rando phantom dose of uterus, ovaries, testes and thyroid gland was measured with thermoluminescent dose meters. CT of the upper abdomen, the whole abdomen and the skull were simulated without and with lead shielding. As lead shielding, a lead apron was attached around the pelvis of the phantom in case of CT of the upper abdomen, a testis capsule was used in CT of the whole abdomen and a thyroid collar in CT of the skull. RESULTS: In CT of the upper abdomen the lead apron did not lead to any recognisable dose reduction in uterus and ovaries. In CT of the whole abdomen the testis capsule led to a dose reduction in testes of 95% (1.39 mSv) and in CT of the skull the thyroid collar to a dose reduction in thyroid gland of 23% (0.19 mSv). CONCLUSIONS: In abdominal CT examinations the testis capsule is an important instrument to reduce the dose of the testes whereas the lead apron is not appropriate for a dose reduction in the uterus and ovaries. In CT of the skull the thyroid collar can remarkably reduce the scattered radiation exposure of the thyroid gland and should be recommended.

Female↗
PubMed1996

[Use of MR-controlled laser-induced thermotherapy in recurrent squamous epithelial carcinoma of the head-neck area].

BACKGROUND: The management of patients with recurrent carcinomas of the head and neck that had been treated before by surgery, radiation, and/or chemotherapy presents a considerable problem. The value of the MR-controlled laser-induced thermotherapy (LITT) was analysed as a new palliative treatment modality. METHOD: LITT was used in five patients with recurrent head and neck squamous cell carcinomas, who had undergone established methods of treatment. One patient with a primary laryngeal carcinoma, who refused surgery, was treated by LITT in addition to radiation. A Nd:YAG laser was used to deliver laser light via an applicator directly into the tissue and to produce tumor necrosis. Using two special MR thermosequences (Thermo-TurboFLASH-, modified FLASH-2 D-Sequenfe) the laser process was controlled on line. The necroses were measured by a static and dynamic area calculation program based on a pixel evaluation. RESULTS: The induced tumor necroses ranged from 4 cm3 to 28 cm3. In all cases the MR thermosequences showed a loss of the signal up to 15 mm around the top of the applicator. In the post-interventional T1 sequences with intensified contrast, the coagulation necroses were represented as hypovascular areas. No side effects were seen and five of the patients felt an improvement of clinical symptoms. CONCLUSION: LITT as a minimal invasive, MR-controlled method may be a good alternative in palliative therapy of head and neck carcinomas.

Adult↗
PubMed1996

[Primary extramedullary plasmacytoma of the head-neck area].

BACKGROUND: A primary extramedullary plasmacytoma of the head and neck is a rare neoplasm with an incidence of 1%. The clinical features depend on localization. PATIENTS: The clinical features, the method of diagnosis, and response to treatment of two cases with different localization were analysed. RESULTS: For diagnosis immunohistological and serological investigations are necessary. CONCLUSIONS: The method of treatment is determined by complete staging.

Biomarkers, Tumor↗
PubMed1996

Signal changes on MRI and increases in reactive microgliosis, astrogliosis, and iron in the putamen of two patients with multiple system atrophy.

A correlation of clinical, MRI, and neuropathological data is reported in two patients with multiple system atrophy (MSA). On MRI, patient 1 showed striatal atrophy, reduction of T2 relaxation times within most of the putamen, and a band of hyperintense signal changes in the lateral putamen. In patient 2, MRI disclosed only shortening of the T2 signal in the putamen. Immunohistochemistry showed pronounced reactive microgliosis and astrogliosis in the affected brain regions. In patient 1, the area with the most pronounced microgliosis and astrogliosis most likely correlated with the area of hyperintense signal changes on MRI. This area also contained the highest amount of ferric iron, which was increased in the putamen of patient 1 but not patient 2. It is unlikely that the hypointense signal changes in the putamen are due to an increase of iron alone. Reactive microglial and astroglial cells may play a part in the pathogenesis of MSA.

Adult↗
PubMed1996

[An interstitial miniature antenna for localized in vivo P-31 MR spectroscopy].

BACKGROUND: Phosphorus spectroscopy can be used to assess response in tumor therapy and to monitor response. An additional response parameter would be useful for individualization in oncological therapy. Methodical problems of localisation and contamination make it more difficult to interpret and reproduce the spectra. Interstitial and endoluminal spectroscopy antennas placed directly within or close to the tumor could provide help in this problem. MATERIAL AND METHOD: We developed an interstitial 31P MRS antenna together with a tuning network which can be used in thermometry catheters for hyperthermia within an internal lumen of 1.1 mm in diameter. A prototype of this type of miniature antenna suitable for use in Siemens MRI scanners at 1.5 T was described spectroscopically with regard to excitation profile, range and SNR. RESULTS: In terms of quality, the excitation profiles of the interstitial antennas in relation to orientation correspond to those of comparable but considerably larger endocavitary antennas and catheter coils for MR imaging and spectroscopy. Maximum sensitivity was achieved by aligning the coil normal perpendicular to the B0 field. Signal losses of up to 50% have to be reckoned with when using other orientations. The maximum range of the interstitial antenna was determined using spectroscopy and was found to be 5 mm, i.e. 9 times coil radius. The sensitivity (SNR, detection sensitivity) of the studied type of interstitial antenna allows in vivo 31P spectroscopy to be performed despite the unusually low axial dimension (coil radius r = 0.55 mm). The prototype of the described interstitial antenna was used to measure an in vivo spectrum from the back muscle of a rabbit in 10 min. Nevertheless, the detection volume of at least some ml necessary for 31P spectroscopy results mainly from the large antenna length. CONCLUSION: The sensitivity (SNR, detection sensitivity) of the interstitial antenna needs to be further improved in order to assess treatment response in patients. However, the construction principle is suitable for intracavitary 31P spectroscopy antenna with larger diameters, which can be used for advanced rectal, cervical and prostate carcinomas.

Animals↗
PubMed1995

Mechanism of protein stabilization by disulfide bridges: calorimetric unfolding studies on disulfide-deficient mutants of the alpha-amylase inhibitor tendamistat.

The present differential scanning calorimetry and circular dichroism studies on the mechanism of protein stabilization by disulfide bonds were concerned with two questions: is the increase in unfolding entropy upon removal of disulfide links sufficient for the explantation of the general stability decrease of disulfide-deficient mutants? Is it immaterial by which residue cysteine residues are replaced when disulfide bridges are to be opened? To answer these questions we investigated two disulfide bridge mutants of the alpha-amylase inhibitor Tendamistat where the large loop (C45A/C73A) or the small loop (C11A/C27A) had been opened by recombinant DNA techniques, and we compared the stability of the mutated proteins with that of wild-type Tendamistat published previously. To elucidate the significance of the nature of the group that replaces Cys we introduced in position 27 of the small loop four different amino acids instead of Cys: Ala, Leu, Ser and Thr. Surprisingly, opening of the small loop (17 residues) causes larger destabilization than opening of the large loop comprising 29 residues. The thermodynamic parameters at pH 7.0 are: wild-type: t1/2 = 81.6 degrees C, delta Hcal = 296 kJ mol-1, large loop mutant (C45A/C73A): t1/2 = 58.6 degrees C, delta Hcal = 225 kJ mol-1 and small loop mutant (C11A/C27A): t1/2 = 42.7 degrees C, delta Hcal = 135 kJ mol-1. This finding is at variance with the entropy hypothesis. The relative contributions to stability of enthalpic and entropic terms can be varied by a proper choice of substitutions. While the destabilization originating from C45A/C73A exchanges in the large loop turns out to be purely entropic, the stability decreases of the small loop mutants are caused by changes in both enthalpic and entropic terms. Leu or Ser in position 27 leads to an overall enthalpic destabilization. Thr in position 27 increases the transition enthalpy of this mutant to the value of the wild-type protein but increases at the same time the value of the transition entropy with the result of an overall entropic destabilization. Finally, in the C11A/C27A small loop mutant of lowest stability a very large enthalpic destabilization occurs, which is, however, partly counterbalanced by a reduction in the transition entropy. The preferential perturbation of the native state by the mutations is manifest in the increase of the native state heat capacity relative to that of the wild-type protein and the identity of the heat capacity of the unfolded state.(ABSTRACT TRUNCATED AT 400 WORDS)

Calorimetry, Differential Scanning↗
PubMed1995

Extreme thermostability of tarantula hemocyanin.

Biotops with extreme temperatures such as deserts force animals to avoid or escape high temperatures by biochemical, behavioural or morphological adaptation. In this context we tested the resistance to heat of the oxygen carrier hemocyanin from the ancient tarantula Eurypelma californicum, which is found in arid zones of North America. Differential scanning calorimetry, light scattering, crossed immunogelelectrophoresis and oxygen binding experiments show that the 24-meric hemocyanin is conformationally stable and fully functioning at temperatures up to 90 degrees C. Our results demonstrate that the cation-mediated state of oligomerization is not only crucial for the high cooperativity of oxygen binding of this hemocyanin, but also for its extreme stability in the physiological temperature and pH range.

Adaptation, Physiological↗
PubMed1995

Partial molar heat capacities and volumes of Gly-X-Gly tripeptides in aqueous solution: model studies for the rationalization of thermodynamic parameters of proteins.

The thermodynamics of protein unfolding can be rationalized if the temperature dependence of the partial molar volumes and heat capacities of their constituent groups are known reliably. Despite many experimental and theoretical studies there are still several inconsistencies in the published thermodynamic data. We have investigated some of these inconsistencies by applying high sensitivity scanning densimetry and microcalorimetry to aqueous solutions of tripeptides of the structure Gly-X-Gly, where X is one of the amino acids Met, Asn, Gly and Ile. For these side-chains either no direct data have been determined or serious discrepancies exist between the values published by different laboratories. Partial molar heat capacities and volumes have been determined for the peptides in pure water, in water adjusted to pH = 4 and in 0.5 M sodium acetate buffer at pH = 4. The results obtained are critically compared with those in the literature.

Amino Acid Sequence↗
PubMed1995

[Spiral CT of the pancreas. A clinical comparison with conventional CT and dynamic CT].

PURPOSE: Spiral CT is compared with the dynamic CT and the conventional CT with regard to the enhancement of the pancreas and peripancreatic vessels and the visualisation of anatomic details. METHODS: In 15 patients spiral CT of the pancreatic region was performed in the arterial phase followed by spiral CT of the upper abdomen in the arterial-venous phase. In 30 patients dynamic CT (n = 15) and spiral CT (n = 15) of the pancreatic region was performed in the arterial phase followed by conventional CT of the upper abdomen. RESULTS: Compared with dynamic CT, spiral CT of the pancreatic region in the arterial phase (flow 4 ml/s, delay 15-18 s) leads to a stronger contrast of the peripancreatic vessels (p < 0.001) and the pancreas (108 vs. 86 HU) (p < 0.05). In the following spiral CT of the upper abdomen (flow 1 ml/s, delay 70 s), a high enhancement of both arteries and veins could be achieved. Intrapancreatic structures and peripancreatic vessels were better seen in the spiral CT than in the conventional CT (p < 0.05) and p < 0.005, respectively). CONCLUSION: The combination of spiral CT of the pancreatic region in the arterial perfusion phase and spiral CT of the upper abdomen in the arterial-venous phase enables an optimal enhancement of the pancreas and the abdominal vessels and a reliable visualisation of anatomic details.

Artifacts↗
PubMed1995

Cervical lymphadenopathy: ratio of long- to short-axis diameter as a predictor of malignancy.

The purpose of this study was to evaluate short- and long-axis diameters of enlarged cervical lymph nodes with ultrasonography and to determine whether the long-to-short axis (l/s) ratio is a valid diagnostic parameter in the differentiation between benign and malignant nodal disease. 730 enlarged cervical lymph nodes in 285 patients were examined with ultrasound. The short- and the long-axis diameters of each enlarged node were measured and the l/s ratio calculated. Definite diagnoses of the nodes were obtained by histological examination following neck dissection. 95% of enlarged cervical nodes shown on ultrasound to have a l/s ratio of more than 2 were correctly diagnosed as benign. Nodes presenting with a more circular shape and a l/s ratio of less than 2 were diagnosed correctly as metastases with 95% accuracy. The l/s ratio of lymph nodes thus provides an excellent criterion for differentiation between benign and malignant enlargement in cervical lymphadenopathy.

Adult↗