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Biomedical subjects

H K Leetz

Publications and source records attributed to H K Leetz.

36 records · Page 2Linked to original sources
PubMed1985

[Experience in the use of face masks for radiotherapy of head and neck tumors].

By means of positioning and fixation aids, the precision and reproducibility of irradiation fields in radiotherapy of malignant tumors of the head and neck can be considerably improved. Face masks made of different synthetic materials have proved to be a practicable solution of this problem. In our hospital we have developed and tested a simple and not expensive possibility of manufacturing the masks with "Baycast" (producer: Bayer AG Leverkusen). The material is generally well tolerated by the patients, and the head is sufficiently fixed. An increased incidence of radiogenic dermatitides is caused by the overlapping of the depth dose of the Co-60 gamma radiation due to additional secondary electrons emanating from the mask material. This effect can be partly prevented by cutting out the irradiation fields in the masks.

Cobalt Radioisotopes↗
PubMed1983

[Deviations in the control of the monitor calibration of a circular accelerator].

The operation of an accelerator requires to perform at regular intervals a control measurement of the basic calibration. This measurement showed a deviation growing from week to week. Finally, the test measurements gave occasion to suppose a defect of the used ionizing chamber, but this was not confirmed by measurements at a gamma irradiation unit. When the chamber had been repaired by the manufacturer, there were no more deviations with respect to the basic measurement.

Particle Accelerators↗
PubMed1979

[An interactive system for recording, storage and processing of treatment data (author's transl)].

For correct radiation treatment and evaluation of treatment a complete recording of data is necessary. With this aim an interactive system was developed. Data recording for every patient is started from a terminal assigned to the physician. After completing the patient file with the data of the physical treatment plan, the file may be displayed on the terminal assigned to the particulr treatment unit, and additional data of the particular treatment session added. If a treatment is finished, a hardcopy of all data is generated by the system. Retrieval of patient data is always possible from the physicians terminal. The system is a contribution towards reducing the work in documentation the radiation treatment. It will be possible not only to carry out epidemiological studies, but also to investigate and perhaps optimate the results of treatment methods.

Computers↗
PubMed1975

[Kidney stress in percutaneous abdominal radiotherapy].

Percutaneous abdominal radiotherapy leads to an obligatory simultaneous stress of the kidneys. This partial stress of the kidneys can be reduced to a bearable minimum if the medicophysical irradiation planning methods, already developed nowadays. are used. The improved irradiation technique basing on these methods was examined, by administering abdominal irradiation, in a corresponding collective of patients. Clinical, laboratory-chemical, roentgenologic, and nucleo-medical examinations were carried out in different intervals. The significant control results certified the kidney protecting method of our radiotherapy.

Cobalt Radioisotopes↗
PubMed1975

[Approach-related dosage calculation in the surroundings of enclosed radium preparations and its combination with dosage calculation].

This study contains discussions about different possibilities of dose calculation with an electronic computer in the environment of radium applicators. First of all, it is demonstrated that no time can be saved in the exact calculation, even if varying mathematical methods are chosen. Therefore, possibilities are discussed in order to save calculation time by approximation procedures; methods are quoted - one less and one more complicated - for realising such a procedure. Furthermore, the reasons are mentioned that are contrary to an immediate inclusion of this calculation into the physical irradiation planning. Possibilities to overcome these difficulties are cited.

Administration, Topical↗
PubMedDate not supplied

Short-term CT and MR changes in brain tumors following 125I interstitial irradiation.

PURPOSE: The study was undertaken to assess characteristic short-term CT and MR changes in brain tumors following 125I interstitial irradiation. METHOD: Sixteen patients were included who had both CT and MR control examinations at regular intervals over a period of 18 months following treatment. Two groups were distinguished: low grade tumors (11 cases) and high grade malignancies (5 patients). 125I seeds were used as temporary implants. The cumulative dose was 50-60 Gy. RESULTS: In some patients of both groups, a low attenuation spheric structure with a contrast-medium-enhanced ring and a diameter of 6-8 mm was observed. There was no edema around the structure, which represents a zone of tissue necrosis at the site of the temporary 125I implant. Tumors in both groups were completely destroyed, some decreased in size, and others were unchanged. Pseudotumor necrosis with accompanying edema occurred in two patients with low grade astrocytoma, the diameter of which was > 4 cm. CONCLUSION: The behavior of cerebral tumors and their appearance on CT and MR images after interstitial irradiation seem to be variable. Decrease in tumor size may take place at different intervals after therapy. Brachytherapy of tumors with a diameter of > 4 cm may produce space-occupying radionecrosis.

Adult↗