Search PubMed⌕ Search

Biomedical subjects

T W Kaulich

Publications and source records attributed to T W Kaulich.

15 recordsLinked to original sources
PubMed1996

[Gamma knife versus stereotactic linear accelerator. Utilization, clinical results and cost-benefit relations].

INTRODUCTION: The principles of radiosurgery were developed in 1951 by Leksell. Their technical realization led to the development of the gamma knife and stereotactically modified linear accelerator. METHODS: In addition to the gamma knife, we present the different principles of convergent beam irradiation (radiosurgery with linear accelerator), the further development to fractionated stereotactic conformal radiotherapy, and the necessary quality-assurance steps. RESULTS: The greatest uncertainties in the precision of radiosurgery result from medical imaging (CT 0.7 x 0.7 x 1 mm; DSA 1-5 mm; MR angiography < 2 mm). The focusing accuracy of the gamma knife (+/- 0.3 mm) can also be achieved today by linear accelerators using a stereotactic floorstand. For the same indication and the same dosage for the target volume, there are no clinical differences between the gamma knife and the linear accelerator (AVM: 80% complete obliteration; metastases: 85% local tumor control; AN: 90% tumor control). However, there are greater differences in costs. There is no constellation where the gamma knife is just as expensive or more cost-effective than the linear accelerator treatment. The most cost-effective solution is modification of an available linear accelerator, resulting in treatment costs per patient of 9,201.25 DM (50 patients/year). CONCLUSION: There seem to be no methodological, physical, clinical or cost reasons for using a gamma knife, especially because the trend is going towards fractionated conformation radiotherapy instead of the application of high single doses.

Brain Neoplasms↗
PubMed1994

Fast algorithms for computing and displaying dose-distributions in tomogram-oriented brachy-radiotherapy.

This paper describes in detail a dose calculation algorithm tailored to the needs of tomogram-oriented brachy-radiotherapy and a general-purpose dose visualization for displaying the dose distribution as isolines (or rather interval planes). The verbal description of the algorithms is accompanied by structograms. However, the intention of the authors is to present very fast algorithms that are easy to implement and to give a ready-to-use example formulated in 68020 assembler code. Execution times are estimated theoretically by counting clock cycles and practically by measuring the execution time of sample calculations. It turns out that both the dose calculation as well as the visualization algorithm need less than 1 s when applied to a radioactive point source lying on an arbitrary 320 x 256 grid of three-dimensional space.

Algorithms↗
PubMed1992

Intuitive user interfaces (IUI): a CASE starting point for design and programming.

The acceptance of a software product depends to a considerable extent on the user interface. The class of graphic-oriented user interfaces that are called Intuitive User Interfaces (IUI) is described. These interfaces allow the user to learn to operate software programs quickly. In the following the graphical layout put to use in an IUI is elaborated. All images the layout consists of are created with the aid of a paint program. Using these images, a procedure for creating, programming and linking an IUI to software applications is discussed and recommendations are made concerning software and hardware demands for easily creating IUIs. Practical experience of the authors with this procedure, mainly in the medical area, is described.

Computer Graphics↗
PubMed1992

A Rexx-controlled developing environment for implementing intuitive user interfaces (IUI).

In [our companion paper] intuitive user interfaces as well as a method for developing and programming such interfaces have been described. The present article will improve and simplify this mode of action. The main tool for this undertaking is the programming and script language Rexx. Using Rexx, all software components described in [the companion paper] are linked to form a developing environment, which acts like an integrated software package. Moreover, with the aid of Rexx, source-code and data structure generation is greatly extended, further decreasing the expenditure of programming intuitive user interfaces. This paper first gives a brief introduction to Rexx. A description of the Rexx-controlled developing environment then follows. Finally, there are elucidated the details of the question of how each single software component is linked to the environment using Rexx.

Computer Systems↗
PubMed1991

[The value of NMR tomography in the planning of HDR-afterloading brachytherapy in cervical carcinomas. The experiences with 41 patients].

In 41 patients with inoperable cervical carcinomas, afterloading brachytherapy was used in combination with radiotherapy after planning with MRI (1.5 T spin echo multislice technique). In 27 women, phantoms neutral to MRI were introduced into the uterus to create a topographic situation comparable to that during brachytherapy; at the same time, the position of the applicators was marked. Under the circumstances, MRI demonstrated the position of the uterus and the tumour, the vagina, the bladder, the rectosigmoid and the applicator phantoms in every case. In 88% it was possible to demonstrate the margin of the tumour and normal myometrium. In 18% of the patients, the technique lead to a significant and, in a further 30%, to a marginal improvement in brachytherapy technique.

Brachytherapy↗
PubMed1990

[The use of absorbers to optimize the surface dosage in treatment using ultrahard x-rays].

The surface dose in megavoltage x-ray therapy can be modified using two different techniques: either varying the thickness of an absorber positioned directly on the surface of the patient or varying the distance to the surface of an absorber with constant thickness. Surface dose as a function of distance and absorber thickness has been measured at 4 MV and 8 MV x-rays. Both methods yield sufficiently and well-defined dose enhancements at the surface of the patient as desired clinically. The variation of the absorber-surface distance however has been proved to be the more simple and practicable method, offering the additional advantage of no contacting the patients skin.

Humans↗
PubMed1990

[2 years' experience with a monitoring and recording system for gynecological afterloading irradiation].

A computer program running on a simple desk calculator has been developed for monitoring and recording gynecological high-dose afterloading therapy. For treatment monitoring the multiple-probe AM6-system (PTW-Freiburg) is used which allows for dose measurements in the urinary bladder and the rectum. The probe signals are processed on line in order to indicate the actual dose at the measuring points. After completing the irradiation the treatment is documented. Performing fractionated treatment the measuring data are stored in the computer memory for calculating total accumulated dose. The above-described monitoring and recording [correction of protocolling] system has proven its usefulness during two years of clinical work.

Brachytherapy↗
PubMed1989

[Correlation of blood pressure and cadmium and lead content of the hair in nonsmoking males].

In developed countries, hypertension represents one of the most frequent diseases and is one of the most important risk factors of arteriosclerotic vascular disease e.g. to myocardial infarction or cerebral apoplexy. The etiology of hypertension is unknown in about 90% of cases. The heavy metals cadmium and lead occur in increasing amounts in the human environment. Numerous epidemiological studies and investigations using experimental animals have dealt with the putative relationship between cadmium and lead, and hypertension. The results to date have been quite controversial; thus the issue appears to be unresolved at present. In the present study scalp hair samples were collected from 100 non-smoking 30-to-50-year-old men. After washing, the samples were digested with a mixture of nitric and sulfuric acid in a teflon bomb and analyzed by flameless atomic absorption spectroscopy. For 90% of the test persons the cadmium hair values were in the range of 0 to 1400 micrograms/kg; the corresponding range for hair lead was 0 to 13,000 micrograms/kg. Correlation with diastolic or systolic blood pressure was neither found for cadmium or lead. The test persons with the highest cadmium or lead load were not hypertensive. Some factors should be considered when comparing the present results with those of other investigators reporting a positive correlation in the question under consideration. 1. Previous studies in man frequently did not sufficiently take smoking habits into account. This is essential, however, because, in addition to cadmium and lead, nicotine and carbon monoxide are also constituents of tobacco smoke and contribute to an increase in blood pressure. 2. Previous investigations generally employed blood samples, which is disadvantageous in comparison with the analysis of hair because blood samples do not reflect long-term exposition, which is important in the etiology of chronic diseases. Correlation between hypertension and levels of long-term cadmium and lead exposure in man seem to be unlikely in light of the present results. Nevertheless, numerous potential effects should be considered to obtain further insight in the complex pathogenesis of hypertension.

Adult↗
PubMed1985

[Experimental studies of the scatter behavior of fast electrons in the use of electron applicators in radiotherapy].

When using high energy electrons in radiotherapy, there is frequently undesirable electron scatter, which is derived from the applicators used to delimit the field. In order to improve our understanding of the factors which influence scatter, this was studied using fast electrons and a variety of materials to reduce this scatter. The geometry and angulation of the scattering plate and the electron energies were varied during these experiments.

Electrons↗
PubMed1984

[Possibilities and limits of practice-oriented daily control measurements of linear accelerators].

Daily control measurements of the dose taken at a linear accelerator are described in order to present a practice-oriented measurement and evaluation method rendering possible a long-term quality control. This method allows to establish sudden parameter variations as well as to determine in a simple and precise manner long-term drifting effects with an amplitude within the range of measurement variations and a period of many months. During the time of six months, not only a drifting effect with a long period and an amplitude within the range of pro mille, but also a variation coefficient smaller than 0,3% could be determined.

Humans↗
PubMed1983

[Optimization of the isodosis in case of radiotherapy with asymmetric target volumes].

By superimposing only two moving fields, it is nearly always possible to adapt an 80% isodose to asymmetric target volumes. By means of wedge filters, it is possible to create asymmetric 80% isodoses with only one irradiation field. The authors compare four different moving field techniques for the irradiation of the left kidney region with regard to the radiation exposure of various transverse body regions. If wedge filters are used for moving field therapy, the average dose values of the different organs are generally significantly inferior to those measured in case of conventional moving field therapy. The reduction of the total volume exposure by 20% and of the liver exposure by nearly 50% is most favorable. Another great advantage is the complete sparing of the remaining kidney. These quantitative advantages are supplemented by the qualitative factor concerning the considerably simplified therapy planning and the easy focussing.

Filtration↗