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R Hofmann

Publications and source records attributed to R Hofmann.

At least 37 records · Page 2Linked to original sources
PubMed1999

Somatotopic mapping of the human primary somatosensory cortex by fully automated tactile stimulation using functional magnetic resonance imaging.

The clinical application of functional magnetic resonance imaging (fMRI) requires time-saving protocols insensitive to artifacts that provide robust localization and important information on brain function. A fully automated, pneumatically driven tactile stimulation is presented, that reproducibly localizes postcentral lip, finger and toe representations in contralateral primary somatosensory cortex (SI) with mean correlation coefficients (cc) and relative BOLD signal changes (dS) of cc approximately 0.59, dS approximately 1.95% (fingers); cc approximately 0.52, dS approximately 1.35% (lips); cc approximately 0.47, dS approximately 1.42% (toes). Bilateral somatotopic mapping requires 21 min of scanning time and has become a clinical routine fMRI application in patients with perirolandic tumors. Normative data may also be useful in monitoring cerebral plasticity and reorganization, e.g. in sensorimotor recovery after cerebral ischemia or in understanding mechanisms of supraspinal pain processing.

Adult↗
PubMed1999

Quality-of-life issues in the treatment of testicular cancer.

Quality of life (QOL) issues in testis cancer have recently assumed great importance for both physicians and patients. Since most of the patients are going to be long-term survivors, with modern therapeutic approaches, psychosocial difficulties and sexual life problems may become one of the major long-term complications of testis cancer treatment. QOL studies available demonstrate that approximately 10% of the patients will suffer from enduring long-term psychological problems, namely anxiety, depression, fatigue, and disrupted intimate relationships. Since these problems develop unrelated to the therapeutic approach, one has to develop risk profiles predicting psychological illness, such as with psychological counseling, prior to the initiation of the therapy. Impairment of sexual life and infertility distress represent other long-term sequelae of testis cancer treatment. The highest incidence of sexual dysfunction develops within the first 6 months following therapy, with most patients recovering within the next 3 years, resulting in a 15% rate of long-term sexual dysfunction. This relatively high frequency of sexual problems warrants an adequate counseling before and after therapy. Future perspectives of QOL research in testis cancer has to concentrate on the development of a site- specific questionnaire. Since the different therapeutic strategies in clinical stage 1 testis cancer result in the same high cure rates but may encounter various levels of psychosocial distress, QOL appears to represent the most important endpoint end of different treatment modalities in the clinical setting of different treatment modalities and QOL documentation must be integrated in all clinical study protocolls. QOL studies are important issues in the evaluation of each new future method of treatment modality going to be established for testis cancer.

Adaptation, Psychological↗
PubMed1999

[Elective stenting of "unprotected" left main coronary stenosis in patients without contraindication to bypass surgery].

Coronary surgery is at this point of time the standard therapy of unprotected left main coronary artery stenosis. Coronary angioplasty (PTCA) is performed only in bail out situations. The number of publications of successful percutaneous intervention in unprotected left main coronary stenosis is increasing because of increasing use of stents and ticlopidine to avoid stent-thrombosis. From 9/96 to 7/98, 13 patients with unprotected left main coronary stenosis were treated with stents. All of them were accepted by the heart surgeon for bypass surgery but were not considered to be optimal candidates due to advanced age of more than 80 years (n = 5), significant co-morbidity (n = 2) or diffuse diseased peripheral coronary segments (n = 6). Mean age of patients was 74 +/- 10 years, 9 were male, and all patients presented with angina III-IV (CCS). Mean ejection fraction was 55 +/- 15%. Localization of stenoses were classified as ostial (n = 5), middle (n = 3), and bifurcational (n = 6). One patient had stenoses both in the ostium and in the bifurcation. In all cases a PTCA of the culprit stenosis was performed prior to stent implantation. The mean diameter of the stents used was 3.3 +/- 0.3 mm and the mean length was 11 +/- 4 mm. In 6 patients a PTCA of either left anterior descendens (LAD) or right coronary artery was performed in the same session. In 4 of these patients it was followed by a stent implantation. All procedures were performed with surgical stand-by, an intraaortal balloon pump was available, but was not uses prophylactically. Stent implantation could be performed successfully in 12 out of the 13 patients (success rate 92%). In bifurcational stenoses stents were positioned with the proximal end in the left main and the distal end in the LAD. Significant injury or occlusion of the circumflex artery was not observed. In one patient with bifurcational stenosis with severe calcification it was not possible to cross the lesion with an accurate sized balloon. Trying to cross with a smaller balloon (2.5 mm) resulted in dissection of the left main coronary artery which could not be reopened again by catheter technique. This patient was transferred to the operating room under conditions of cardiopulmonary resuscitation and a bypass surgery was performed. He was dismissed from the hospital with no evidence of perioperative myocardial infarction. The mean time for follow-up was 12 +/- 7 months, all patients are still alive. In 6 patients an angiography was performed during follow-up because of suspicion of recurrent ischemia. Two patients out of these 6 had restenoses in the left main coronary artery which were re-dilated (17%). Another 2 patients had stenoses in other coronary segments and were also dilated. Thus, stenting of left main coronary artery stenoses is feasible, however, with acceptable risks and could be considered in selected patients as an alternative to coronary artery surgery.

Aged↗
PubMed1999

Aortic valve replacement: is the stentless xenograft an alternative to the homograft? Midterm results.

BACKGROUND: This study was performed to assess the midterm clinical results after aortic valve replacement (AVR) with stentless xenograft (SX) compared with cryopreserved aortic or pulmonary homografts (HX). METHODS: In 139 patients (<60 years) undergoing elective AVR, 59 HX and 80 SX were inserted. All patients were followed clinically and by color flow Doppler echocardiography for 45+/-12 months (range 31-58 months). RESULTS: There were 5 in-hospital deaths (3.5%): 4 HX and 1 SX (p = NS). The mean gradient was 6+/-2 mm Hg in HX versus 13+/-6 mm Hg in SX (p<0.001) and remained unchanged during follow-up. Actuarial survival (HX 77%, SX 80%), freedom from endocarditis (HX 91%, SX 99%), freedom from thromboembolic events (HX 98%, SX 90%), and freedom from reoperation (HX 98%, SX 100%) were comparable between groups after 58 months. CONCLUSIONS: Despite slightly higher transvalvular gradients, the stentless aortic valve achieved excellent midterm results, when compared with homografts.

Actuarial Analysis↗
PubMed1999

Minimal leptin elimination into ultrafiltrate during continuous venovenous haemofiltration in patients with sepsis.

Intensive care patients with organ failure often suffer an acute catabolic state. Leptin is a 16-kDa hormone which is produced by mature adipocytes and correlates with human energy expenditure. We investigated whether continuous venovenous haemofiltration, which may eliminate molecules up to 20-30 kDa, is capable of removing human leptin. Leptin measurements were made in the plasma of 15 patients with sepsis before continuous venovenous haemofiltration (T0) and during the procedure at 24 h (T1), 48 h (T2), and 72 h (T3), using samples taken before and after haemofiltration. In addition, measurements were made in the ultrafiltrate at T1-T3. The plasma leptin level at T0 was 17.6 ng mL-1. The concentration at T1 was 17.5 ng mL-1 pre-filter and 26.5 ng mL-1 post-filter (T2: 14.2/23.2 ng mL-1; T3: 12.4/16.3 ng mL-1). This concentration effect after haemofiltration was also seen with albumin. The values measured at T3 tended to be lower than those recorded at T1. The mean leptin levels in the ultrafiltrate were 0.15-0.18 ng mL-1. The range of leptin levels in the ultrafiltrate was thus only 0.5-3% of that measured in plasma. We conclude that human leptin is only minimally elimininated into the ultrafiltrate by continuous venovenous haemofiltration and that plasma leptin levels may decrease during sepsis.

Aged↗
PubMed1999

Model-independent mean-field theory as a local method for approximate propagation of information.

We present a systematic approach to mean-field theory (MFT) in a general probabilistic setting without assuming a particular model. The mean-field equations derived here may serve as a local, and thus very simple, method for approximate inference in probabilistic models such as Boltzmann machines or Bayesian networks. Our approach is 'model-independent' in the sense that we do not assume a particular type of dependences; in a Bayesian network, for example, we allow arbitrary tables to specify conditional dependences. In general, there are multiple solutions to the mean-field equations. We show that improved estimates can be obtained by forming a weighted mixture of the multiple mean-field solutions. Simple approximate expressions for the mixture weights are given. The general formalism derived so far is evaluated for the special case of Bayesian networks. The benefits of taking into account multiple solutions are demonstrated by using MFT for inference in a small and in a very large Bayesian network. The results are compared with the exact results.

Child↗
PubMed1999

[Detection of airborne cultivatable microorganisms from compost sites--emissions and imissions].

The statement presented here gives an overview and assessment of the procedures and concepts currently used for the collection and determination of airborne, culturable microorganisms at sources of emission within composting plants and in their near vicinity. The paper focuses on "classical" methods, which involve cultivation as an intermediate step for the determination of viable, airborne microorganisms. The theoretical and practical requirements on such methods are discussed. Results and experiences from recent investigations are described.

Air Microbiology↗
PubMed1999

['Microbial air pollutants'. Emission sources and preventive measures].

Already in the planning or monitoring phase, measures have to be realized for the reduction in emissions of bio-aerosols in biological waste treatment plants. For this purpose, operation-related measures (in open and partially closed plants) and technology-related measures (in closed plants with automatic ventilation) can be taken. A survey on the currently feasible measures for reduction is submitted. The realization has to be adapted to the individual site and type of plant. An enormous demand for examinations is envisaged in order to enable a qualified assessment of the emission behaviour of diverse waste air systems or process steps.

Air Microbiology↗
PubMed1998

Nonlinear Time&hyphenSeries Prediction with Missing and Noisy Data

We derive solutions for the problem of missing and noisy data in nonlinear time&hyphenseries prediction from a probabilistic point of view. We discuss different approximations to the solutions &hyphen in particular, approximations that require either stochastic simulation or the substitution of a single estimate for the missing data. We show experimentally that commonly used heuristics can lead to suboptimal solutions. We show how error bars for the predictions can be derived and how our results can be applied to K&hyphenstep prediction. We verify our solutions using two chaotic time series and the sunspot data set. In particular, we show that for K&hyphenstep prediction, stochastic simulation is superior to simply iterating the predictor.

Journal Article↗
PubMed1998

[Alternative endourologic methods for treatment of urethral stricture].

Advances in endoscopic instrumentation and techniques offer new alternatives for safe and effective treatment of urethral strictures. Visual internal urethrotomy, the standard treatment modality, is associated with new scar formation with stricture recurrence. This experience has led to the investigation of alternative techniques which would avoid or ameliorate this result. This article reviews the current literature and discusses these newer approaches, including balloon dilatation, laser urethrotomy, endoscopic urethroplasty, "cut to the light" and "core through" procedures, and urethral wallstent implantation.

Catheterization↗
PubMed1998

Dysfunctional voiding in women: which muscles are responsible?

OBJECTIVE: To analyse the striated external urethral sphincter (EUS) and pelvic floor muscles using two different electromyography (EMG) techniques in women with dysfunctional voiding and/or urinary retention. PATIENTS AND METHODS: Fifteen women (mean age 38.2 years, range 18-61) with dysfunctional voiding and/or unexplained voiding dysfunction associated with urinary retention were examined neurologically and urologically; urodynamics and kinesiological EMG of the bilateral pubococcygeal and external urethral striated sphincter muscles were obtained. In an additional neurophysiological session, concentric-needle EMG of the external urethral sphincter was performed. RESULTS: Kinesiological EMG recordings revealed inappropriate pelvic floor muscle activation during voiding in 11 and EUS activation in four women. Concentric needle EMG of the EUS revealed complex repetitive discharges in the four women with inappropriate urethral sphincter activation recorded by kinesiological EMG during voiding. Biofeedback training led to improvement in women with inappropriate pubococcygeal activation but not in those with urethral sphincter complex repetitive discharges. CONCLUSION: Urodynamic examinations in combination with kinesiological EMG examination of the pubococcygeal and external urethral sphincter muscles revealed two groups of women with dysfunctional voiding. Further diagnostic evaluation of such patients with concentric-needle EMG is mandatory. The differentiation of the two groups is therapeutically relevant.

Adolescent↗
PubMed1997

Sensitivity of combined DNA/immunophenotype flow cytometry for the detection of low levels of aneuploid lymphoblastic leukemia cells in bone marrow.

By simultaneous DNA staining and immunophenotyping, the aneuploid blasts of acute lymphoblastic leukemia (ALL) can be quantitated by flow cytometry. The present study evaluates the application of this method for the detection of minimal residual disease (MRD). For this purpose leukemia cells with known aneuploidy were serially diluted with diploid bone marrow cells obtained after chemotherapy. These mixed samples were immunophenotyped using antibodies CD34, CD10, or CD19 and processed for DNA staining with propidium iodide. Fifty thousand cells were measured for each experiment and the results were compared with the analysis of control sample without added aneuploid cells. Aneuploid cells diluted to 1% were not detectable in 6/15 cases when DNA content analysis was used alone, and in dilutions of < 1%, these cells were not detectable. When DNA content and immunophenotype were simultaneously measured, aneuploidy was detectable in 15/15 cases at 1.00%, 6/6 at 0.50%, 16/16 at 0.10%, and 16/17 at 0.05%. Therefore this method may be useful for the detection of minimal residual disease in cases of aneuploid lymphoblastic leukemia.

Aneuploidy↗
PubMed1997

Iridium 192 high-dose-rate brachytherapy--a useful alternative therapy for localized prostate cancer?

We report on a novel protocol involving iridium 192 high-dose-rate brachytherapy and follow-up of up to 130 months in patients with prostatic carcinoma. Using regional anesthesia, five to seven hollow needles are placed within the prostate by perineal puncture under ultrasound guidance. A 9-Gy prostate dose is applied followed by 30 min of hyperthermia (since 1991). This treatment is repeated once after 7 days; 2 weeks later, 18 x 2-Gy external beam radiation (small-field prostate) is added as percutaneous dose saturation. Since 1984 we have treated 40 patients with this protocol. Local tumor control was achieved by means of prostatic biopsy at 18 months after therapy and determination of prostate-specific antigen (PSA) values in about 70% of the patients; after a mean follow-up period of more than 6 years (16-130 months), 80% of the patients show either no evidence of disease or stable disease. We therefore conclude that iridium 192 high-dose-rate brachytherapy is a useful alternative in the treatment of localized prostate cancer in patients who are not eligible for radical prostatectomy.

Adult↗