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Biomedical subjects

H Seifert

Publications and source records attributed to H Seifert.

At least 109 records · Page 6Linked to original sources
PubMed1995

The radiation exposure of the patient from stable-xenon computed tomography.

For stable-xenon computed tomography (CT), an X-ray examination for measurement of cerebral blood circulation in the brain, the radiation exposure of the patient was determined in order to estimate the risk of inducing cancer. Organ doses of brain, eyelenses, thyroid and gonads have been calculated using the measured air kerma free-in-air on the axis of rotation and organ-specific conversion factors calculated with the Monte Carlo method. Dose measurements with TLD-100 rods using a humanoid Alderson phantom were carried out for verification of the calculated organ doses. In the case of brain partially located in the region of primary radiation a mean organ dose of 39 mSv was calculated. The dose measurements showed dose equivalents between 6 and 68 mSv in different regions of the brain and consequently an inhomogeneous dose distribution. From an estimation of the radiation-induced risk using the effective dose of 1.6 mSv it follows that one additional fatal cancer per 12,500 stable-xenon CT examinations has to be expected. The organ doses of eyelenses and thyroid located in the region of scattered radiation are so low that biological effects are hardly to be expected. The calculated dose equivalents of 6.5 mSv and 0.5 mSv, respectively, are in good agreement with measurements. The organ dose of gonads amounted to less than 0.07 mSv.

Brain↗
PubMed1995

The Tannenbaum stent: a new plastic biliary stent without side holes.

OBJECTIVE: Clogging of plastic biliary stents used in malignant biliary obstruction remains a major problem. In vitro studies have shown that side holes, a standard feature of commercially available stents, may contribute to stent clogging. In a pilot study, we designed and prospectively evaluated a new biliary stent without side holes (Tannenbaum stent). METHODS: Over a 12-month period, 55 consecutive patients (mean age 75 yr) with malignant distal common bile duct obstruction and without papillary or duodenal tumor infiltration underwent endoscopic placement of the Tannenbaum stent for the palliative treatment of jaundice. RESULTS: Tannenbaum stent insertion was technically successful on the first attempt in all patients and was accompanied by a significant reduction in mean serum bilirubin levels (10.1-1.6 mg%). Fifty-one patients were followed until death (median survival of 130 days); the symptomatic occlusion rate was 16%, the dislocation rate was 8%, and the median stent patency was 64 wk. Aside from stent clogging, there were no complications. CONCLUSION: The Tannenbaum stent provided effective palliative biliary decompression in all patients. The patency rate was longer than that reported in the literature for conventional plastic stents with side holes and compared favorably with patency rates that have been reported for the metallic expandable biliary stents. The results of this pilot study are encouraging and warrant further studies.

Aged↗
PubMed1995

[Pancreatic pseudocysts: how and when should they be drained?].

Of 93 endoscopic drainage procedures of pancreatic pseudocysts carried out since 1985, at least 50% were of lasting success. The authors' approach is explained with a review of the literature on various drainage techniques. We consider the puncture of a pseudocyst justified only on clinical grounds: the patient's complaints rather than morphological criteria lead to the decision to perform a drainage procedure. Obligatory in the therapeutic concept are ERCP and endosonography. Visualization of a pancreatico-cystic communication leads to the attempt of transpapillary drainage as the therapy of choice. Visualization of anatomic details, namely vessels, lowers the risk of punctures. Direct punctures even in difficult anatomical conditions can be attempted under direct endosonographic control. In our hands, drainage of pseudocysts is a part of the endoscopic treatment concept for chronic pancreatitis and is generally preferred to surgical techniques.

Adult↗
PubMed1995

[Endoscopic therapy in chronic pancreatitis].

In chronic pancreatitis obstruction of the pancreatic ductal system by strictures, stones or pseudocysts seems to play an important part in pathogenesis. Therefore, therapeutic efforts are directed mainly towards reestablishing a free flow of pancreatic secretion. Endoscopic techniques allow decompression of the organ by stenting or stone extraction, as well as evacuation and drainage of pseudocysts. Thus, interventional endoscopy offers safe and long lasting therapy for many patients suffering from chronic pancreatitis. This paper gives a review of the literature and reports on own clinical data.

Calculi↗
PubMed1994

Complications of adjacent organs in chronic pancreatitis managed by duodenum-preserving resection of the head of the pancreas.

Chronic pancreatitis frequently generates complications through involvement of adjacent organs. Distal common bile duct stenosis and segmental duodenal stenosis, the most frequent complications, are usually treated by resection or bypass procedures. This study presents experience with duodenum-preserving resection of the head of the pancreas in the treatment of patients with chronic pancreatitis with predominant involvement of the pancreatic head and coexisting complications involving adjacent organs. This procedure preserves the structure and function of the bile duct and duodenum. Sixty-six patients with severe chronic pancreatitis underwent duodenum-preserving resection of the head of the pancreas. Thirty-eight had associated complications of neighbouring organs: 37 had distal common bile duct stenosis, seven had duodenal stenosis, ten had evidence of segmental portal hypertension and one suffered from a pancreatopleural fistula. Details of all patients were documented prospectively; mean follow-up was 4.2 years. The complications of adjacent organs were permanently eradicated in 36 of 38 patients. Two patients required endoscopic stenting for persisting bile duct obstruction. There was substantial or complete relief of all symptoms in 35 patients. Duodenum-preserving resection of the head of the pancreas is effective in the treatment of severe chronic pancreatitis with predominant involvement of the pancreatic head and provides definitive management of associated complications of adjacent organs.

Adult↗
PubMed1994

Outbreak of methicillin-resistant Staphylococcus aureus in a teaching hospital--epidemiological and microbiological surveillance.

An outbreak of methicillin-resistant S. aureus (MRSA) in a large university teaching hospital occurred between December 1991 and May 1992, involving 7 different wards and more than 30 patients. Epidemiological typing was performed to control the epidemic and to identify the MRSA carriers. By a combination of various classical methods (antimicrobial susceptibility, phage typing) and molecular typing procedures (SDS-PAGE of extracellular proteins, plasmid DNA profile, restriction enzyme fragment pattern of chromosomal DNA), three different clones of MRSA could be discriminated. The epidemic clone A was recovered from 30 patients and from 3 staff members. By strict microbiological monitoring together with hygienic measures, the epidemic could be successfully controlled. It is concluded that a combination of phenotypic markers and DNA-based epidemiological markers is extremely useful in the microbiological surveillance of MRSA outbreaks.

Disease Outbreaks↗
PubMed1994

Endoscopic ultrasonography-guided fine-needle aspiration biopsy of lymph nodes.

The recent introduction of convex linear array echoendoscopes equipped with a biopsy channel has made fine-needle aspiration biopsy (FNAB) under direct endosonographic guidance possible. Because the imaging and instrumentation planes overlap, the operator can visualize a biopsy needle lengthwise as it enters the sector-shaped sound field. We performed EUS-guided FNAB of lymph nodes in seven patients who met the following criteria: (1) Lymph node size over > 1 cm; (2) no endoscopic or endosonographic evidence for tumor involvement of bowel wall interposed between the lymph node and the transducer; and (3) absence of coagulopathy or thrombocytopenia. A positive tissue yield was obtained in six patients, of whom five had malignant cells identified on cytology. The patient with an inadequate yield had a dry aspirate, possibly related to prior irradiation treatment for esophageal carcinoma. No procedure-related complications were observed. We conclude that EUS-guided FNAB of lymph nodes is technically feasible, provides a high diagnostic yield, and appears to be safe. Further studies to determine the sensitivity and specificity of this novel procedure are warranted.

Adult↗
PubMed1994

[The determination of the ovarian dosage in defecography on a digital C-arm unit].

When using defaecography as a radiological tool for diagnosing the anorectal function in female patients, the ovaries are inevitably directly exposed. With the aim of minimising the ovarian dose applied both the area-dose product and the surface dose above the ovaries were measured during investigations of female patients with a digital C-arm unit. These values were converted into ovarian doses using tissue-air ratios. From the surface dose measured with TLD-100 a mean ovarian dose of 15.6 +/- 8.6 mGy was derived. The contributions of screening and film exposures were similar. A reduction of screening time by 10 seconds or omission of 60 film exposures results in a decrease of ovarian dose by values between 0.7 and 2 mGy. Employing a greater focus-skin distance during defaecography, however, made it possible to reduce the ovarian dose by 26%.

Anal Canal↗
PubMed1994

Plasmid DNA profiles of Acinetobacter baumannii: clinical application in a complex endemic setting.

OBJECTIVE: To study the epidemiological, microbiological, and clinical features of infections due to Acinetobacter baumannii in a complex endemic situation over an 18-month period and to determine the clinical usefulness of plasmid DNA analysis of A baumannii in epidemiological investigations. DESIGN: Review of medical and laboratory records. Antibiotic resistance patterns, biotyping, and plasmid profile analysis were used to characterize clinical and environmental isolates. Pulsed-field gel electrophoresis (PFGE) of chromosomal DNA was performed to verify results obtained with the other typing methods. SETTING: Four different intensive care units of an 800-bed tertiary care center in Cologne, Germany. RESULTS: 240 patients were colonized or infected with A baumannii during the study period. No seasonal variations were observed. The majority of isolates (53%) were recovered from the respiratory tract. Major infections occurred in 61 patients; these included 48 bacteremias and eight pulmonary infections. Five different epidemic strains were identified: one each was A baumannii biotype 2 and 6, and three were biotype 9. A baumannii biotype 9 accounted for the vast majority of isolates (88%), which were clustered into three epidemic strains demonstrating distinct plasmid profiles. Two of these were considered genetically related as shown by PFGE. Epidemic strains were multidrug resistant, being uniformly susceptible to imipenem only. An epidemiological investigation failed to identify any point source of infection. Barrier precautions and improved handwashing was instituted in three of the four units and significantly reduced the incidence of colonization and infection in these units. Attack rates remained unchanged, however, in the burns unit where control measures were not implemented. CONCLUSION: Acinetobacter strains representing multiple biotypes and plasmid types were present in this endemic setting. Multidrug resistance in A baumannii is an important concern. Plasmid DNA analysis proved to be useful in epidemiological typing of A baumannii strains and may serve as a complementary typing system to traditional epidemiological methods.

Acinetobacter↗
PubMed1994

Plasmid DNA fingerprinting of Acinetobacter species other than Acinetobacter baumannii.

During the last years Acinetobacter species have emerged as clinically significant pathogens. Most infections are nosocomially acquired and mainly due to Acinetobacter baumannii. Little is known about the epidemiology and clinical significance of unnamed Acinetobacter species 3 (the second most often encountered member of the genus Acinetobacter) and other Acinetobacter species such as A. johnsonii, A. junii, and A. lwoffii. Seventy-five clinical isolates of Acinetobacter species other than A. baumannii (Acinetobacter species 3, n = 37; A. johnsonii, n = 20; A. junii, n = 8; A. lwoffii, n = 10) recovered from 66 patients over a period of 12 months were analyzed by plasmid DNA fingerprinting. Plasmids were found in 84.4% of Acinetobacter species 3 isolates and in all A. johnsonii, A. junii, and A. lwoffii isolates. Strains harbored up to 15 plasmids each. Almost every isolate gave a unique plasmid pattern. With one exception, identical plasmid profiles were detected only in corresponding isolates recovered from blood cultures and intravascular catheters from a given patient. Plasmid DNA fingerprinting proved to be useful for typing Acinetobacter species other than A. baumannii. There was no evidence of patient-to-patient transmission or hospital outbreaks due to these species. This finding is in contrast to the results obtained in studies of the hospital epidemiology of A. baumannii.

Acinetobacter↗
PubMed1994

Comparison of four different methods for epidemiologic typing of Acinetobacter baumannii.

A set of 103 epidemiologically well-defined Acinetobacter baumannii isolates obtained from nine hospital outbreaks and 21 unrelated strains were characterized by pulsed-field gel electrophoresis (PFGE) of total genomic DNA digested with ApaI. Among outbreak strains, eight different patterns and five possible variants were identified by PFGE. Results were compared with those from traditional typing methods such as plasmid profile analysis, antimicrobial susceptibility, and biotyping. Plasmid analysis revealed six different and two related patterns; one outbreak strain lacked plasmids. A total of 16 of the 21 unrelated strains harbored plasmids and exhibited unique patterns. Epidemiologically unrelated strains were placed into only two biotypes and had similar antimicrobial susceptibility patterns but were clearly distinguished by PFGE. PFGE of A. baumannii chromosomal DNA yielded reproducible and easily readable results and showed excellent discriminatory power. However, plasmid profile analysis may provide a cost-effective first step in epidemiological typing of A. baumannii isolates obtained from well-defined hospital outbreaks.

Acinetobacter↗
PubMed1994

[Endoscopic techniques in therapy of choledocholithiasis].

Endoscopically, approximately 85% of all bile duct stones can be removed immediately after successful papillotomy. For the remaining cases, complete clearance of the bile duct is achieved by lithotripsy techniques. Due to the lower risks, endoscopic treatment is preferable.

Cholecystectomy, Laparoscopic↗
PubMed1994

[Computer-assisted dosimetry system for the monitor calibration of accelerators].

PURPOSE: A computerized dosimetry system for calibration of the dose monitor of a medical accelerator was developed with the aim of saving time and reducing errors during measurement and analysis of measured data. METHOD: The PC-based part of the programme system controls measurements with dosimeters of type Dosimentor using an interface IF4. After transmission of the measured data to an UNIX-network the other part of the programme system serves as a tool for analysis. That means in particular the calculation of the absorbed dose in water per monitor unit and the conversion of measured data to basic data for treatment planning. RESULTS: In the case of the compact ionization chamber M233641 the relative uncertainty of the monitor calibration amounts to 3.5% and 3.3% for photons and electrons, respectively. Using the flat ionization chamber of Markus type M23343 for measuring electrons a relative measuring uncertainty of 2.1% results. CONCLUSIONS: For high-energy photons and electrons with energies above 10 MeV the greatest contribution to the relative uncertainty of the monitor calibration is caused by the uncertainty of the calibration factor for the compact ionization chamber M233641. If it is possible to reduce this error to a value of 2% the relative measuring uncertainty would be smaller than 3%. In the case of high-energy electrons it can be concluded that the precision of the monitor calibration is higher with a flat ionization chamber of Markus type M23343 than with a compact ionization chamber M233641.

Calibration↗