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Biomedical subjects

J Ranft

Publications and source records attributed to J Ranft.

At least 19 recordsLinked to original sources
PubMed2005

The FLUKA code: new developments and application to 1 GeV/n iron beams.

The modeling of ion transport and interactions in matter is a subject of growing interest, driven by the continuous increase of possible application fields. These include hadron therapy, dosimetry, and space missions, but there are also several issues involving fundamental research, accelerator physics, and cosmic ray physics, where a reliable description of heavy ion induced cascades is important. In the present work, the capabilities of the FLUKA code for ion beams will be briefly recalled and some recent developments presented. Applications of the code to the simulation of therapeutic carbon, nitrogen and oxygen ion beams, and of iron beams, which are of direct interest for space mission related experiments, will be also presented together with interesting consideration relative to the evaluation of dosimetric quantities. Both applications involve ion beams in the AGeV range.

Carbon↗
PubMed2005

The application of FLUKA to dosimetry and radiation therapy.

The FLUKA Monte Carlo code has been evolving over the last several decades and is now widely used for radiation shielding calculations. In order to facilitate the use of FLUKA in dosimetry and therapy applications, supporting software has been developed to allow the direct conversion of the output files from standard CT-scans directly into a voxel geometry for transport within FLUKA. Since the CT-scan information essentially contains only the electron density information over the scanned volume, one needs the specific compositions for each voxel individually. We present here the results of a simple algorithm to assign tissues in the human body to one of four categories: soft-tissue, hard-bone, trabecular-bone and porous-lung. In addition, we explore the problem of the pathlength distributions in porous media such as trabecular bone. A mechanism will be implemented within FLUKA to allow for variable multipal fixed density materials to accommodate the pathlength distributions discovered.

Algorithms↗
PubMed2004

The FLUKA code for space applications: recent developments.

The FLUKA Monte Carlo transport code is widely used for fundamental research, radioprotection and dosimetry, hybrid nuclear energy system and cosmic ray calculations. The validity of its physical models has been benchmarked against a variety of experimental data over a wide range of energies, ranging from accelerator data to cosmic ray showers in the earth atmosphere. The code is presently undergoing several developments in order to better fit the needs of space applications. The generation of particle spectra according to up-to-date cosmic ray data as well as the effect of the solar and geomagnetic modulation have been implemented and already successfully applied to a variety of problems. The implementation of suitable models for heavy ion nuclear interactions has reached an operational stage. At medium/high energy FLUKA is using the DPMJET model. The major task of incorporating heavy ion interactions from a few GeV/n down to the threshold for inelastic collisions is also progressing and promising results have been obtained using a modified version of the RQMD-2.4 code. This interim solution is now fully operational, while waiting for the development of new models based on the FLUKA hadron-nucleus interaction code, a newly developed QMD code, and the implementation of the Boltzmann master equation theory for low energy ion interactions.

Computer Simulation↗
PubMed2003

[DRG-based cost analysis of inpatient conservative treatment of stage III/IV peripheral arterial occlusive disease].

UNLABELLED: DRG-based cost analysis of inpatient conservative treatment of PAD stage III/IV BACKGROUND: In a prospective study carried out by the German Society of Angiology and the DRG Competence Center, Munich, the question was investigated whether the costs of conservative treatment of patients with PAOD stage III/IV (DRG F65) are adequately represented within the current G-DRG system. METHODS UND PATIENTS: Between September 1 and December 16, 2002, a total of 704 patients with DRG F65 (peripheral vascular diseases) were evaluated at 8 angiologic centers in Germany. Apart from the length of hospital stay, the total costs (cost equivalents) were calculated using a method developed by the DRG Research Group at the University of Münster. Moreover, the study population was compared with a German calculation sample for the DRGs F65A/B, as published by InEK. RESULTS: As it turned out, conservatively treated patients with PAOD stage III or IV (DRGs F65A/B) cause significantly (p < 0.001) higher costs and have significantly (p < 0.001) greater lengths of hospital stay than patients who were also assigned to DRG F65 because of other vascular diseases. At the same time it became clear that angiologic centers treat twice as many patients with critical limb ischemia in comparison with the German average. The reimbursement hitherto estimated by InEK covers not even half the cost actually produced by conservative treatment of PAD stage III/IV. CONCLUSION: To ensure a performance-related reimbursement, a new basis DRG for patients with PAD stage III/IV has to be created, as has ben proposed by the German Society of Angiology. Otherwise, adequate conservative therapy in accordance with existing guidelines, of patients who cannot be treated surgically or interventionally will not be possible any more in the future.

Arterial Occlusive Diseases↗
PubMed2002

Evaluation of long-term toxicity in patients after cisplatin-based chemotherapy for non-seminomatous testicular cancer.

BACKGROUND: Because of the increasing number of long-term survivors of metastatic testicular germ-cell cancer, a general concern has been secondary morbidities, especially cardiovascular risk factors. PATIENTS AND METHODS: Thirty-two patients treated with cisplatin- and doxorubicin-containing chemotherapy > or = 13 years before the time of analyses were evaluated for neuro-, oto-, pulmonary-, vascular- and gonadal toxicity including evaluation of myocardial damage and cardiovascular risk factors and analysis of microcirculation. RESULTS: Thirty percent of the patients showed abnormal left ventricle function. Elevated follicle stimulating hormone (FSH) and luteinising hormone (LH) levels in 75% of patients were often associated with low testosterone levels. Elevated total cholesterol levels were found in 82% and higher triglyceride levels in 44% of patients, most of them were overweight. About 25% of the patients developed diastolic arterial hypertension after chemotherapy. Reduced hearing was confirmed in 23% of patients, especially at frequencies higher than 3000 Hz. Moreover, 53% of patients presented transient evoked otoacoustic emissions. In 38% of patients non-symptomatic neuropathy was detected, in 28% symptomatic neuropathy, and in 6% disabling polyneuropathy. In 80% of patients with neuropathic symptoms additional morphological and functional abnormalities were found by nailfold capillary videomicroscopy, compared to only 57% of the patients without neuropathic symptoms. CONCLUSIONS: Patients cured by cisplatin-based chemotherapy for metastatic testicular cancer have to be cognizant of their unfavorable cardiovascular risk profile, that might be a greater risk than developing a relapse or second malignancy.

Adolescent↗
PubMed2001

The FLUKA radiation transport code and its use for space problems.

FLUKA is a multiparticle transport code capable of handling hadronic and electromagnetic showers up to very high energies (100 TeV), widely used for radioprotection and detector simulation studies. The physical models embedded into FLUKA are briefly described and their capabilities demonstrated against available experimental data. The complete modelling of cosmic ray showers in the earth atmosphere with FLUKA is also described, and its relevance for benchmarking the code for space-like environments discussed. Finally, the ongoing developments of the physical models of the code are presented and discussed.

Aerospace Medicine↗
PubMed1996

Duplex sonography of venous atheromatosis found in the venous part of hemodialysis fistula.

Manifestation of atherosclerosis is one of the alterations in venous bypass grafts. Its progression and morphology usually cannot be described by sonography. The venous part of a hemodialysis fistula can be compared to a venous bypass graft. The authors investigated the venous part of hemodialysis fistula in 16 patients. They found atherosclerosis in 7 patients. The morphologic findings were similar to arterial atherosclerosis. Looking at the venous part of hemodialysis fistulas may be an adequate model to investigate the initiation and progression of atherosclerotic lesions in venous bypass grafts.

Adult↗
PubMed1995

[Reactive hyperemia after arterial occlusion: comparison of infrared telethermography and laser Doppler flowmetry].

Before, during and after arterial occlusion we measured Laser-Doppler Flux (LDF) and skin temperature using Infrared-Thermographie (IRT) in 40 healthy adults (20 female, 20 male). In the region of the hypothenar eminence of the left hand LDF and skin temperature showed significantly higher values in male compared with female subjects prior to occlusion (p < 0.01 resp. p < 0.05). After arterial occlusion for 120 seconds LDF showed a significant overshoot of 71.3% (+/- 39.5%) above baseline. During this phase of hyperemia skin temperature rose from 33.5 to 34.8 degrees C (p < 0.0001). This reaction was similar in men and in women. Changes in skin temperature were slower and more prolonged compared with the rapid changes of LDF. The absolute temperatures were significantly higher when we used IRT compared with temperatures measured by resistance thermometry. Both methods showed a close correlation (p < 0.0001, r = 0.891). Using the IRT technique a large number of skin temperatures can be measured simultaneously and temperature changes can be detected and visualized by colour thermograms. Postocclusive cutaneous hyperemia induces similar responses in LDF parameters and in skin temperatures. IRT therefore could be used as an additional tool for the assessment of physiological and pathological functions of the cutaneous microcirculation.

Adolescent↗