The use of the ophthalmological services during the preschool age, ocular findings and family background

The series consists of 12,059 children followed-up since their mothers' pregnancy. Of these children, 5.2 percent had visited an ophthalmological department during their first five years. Visits were significantly more frequent among the children of social classes I to III than among those of class IV and the farmers', and thus the frequencies of the diseases based on diagnoses given in the ophthalmological departments were also higher in social classes I to III. These children clearly had the best opportunities to have their diseases diagnosed at an early age. Squint was the most common diagnosis with the prevalence being 18.4 per thousand for the children in social classes I to III and 15.9 for the total series. The second largest group consisted of children without any positive ocular finding. These were mainly risk children having some other disease. The third most common diagnosis was dacryostenosis--its incidence in social classes I to III being 9.4 per thousand and that in the total series 7.9 per thousand. Squint correlated negatively with birth weight and was more common among children with some other disease, especially some nervous or mental disease. Dacryostenosis correlated positively with gestational age. If the mother smoked during the pregnancy she was more likely to give birth to a child with squint and less likely to bear a child with dacryostenosis.

New individual tissue compensators for high-energetic photons. Part I. Principle and procedure

Part I. The inhomogeneity of absorbed dose caused by irregular body surface contour in the treatment port for external photon radiation is shown as a problem. The discussion of the physical fundamentals and technical possibilities of missing tissue compensators leads to a practical solution. A new handy procedure is presented allowing easy and rapid preparing of geometrically minified as well as absorption- and stray radiation corrected individual compensators. The achievable dose homogeneity within the target volume is shown as better than +/-5%. Systematical errors are investigated for the different parameters. In Part II systematical preclinical tests and first practical clinical experiences will be discussed.

[Contribution to deep electron pendulous therapy. VIII. Communication: concerning the problem of diverging contours in telecentric electron pendulous irradiation using the electron energies 10 MeV and 20 MeV (author's transl)]

The mode of correction of the isodose curves from telecentric electron pendulous technique using a constant patient radius rp = 30 cm (Isodosenatlas, Siemens, 1973) is represented with regard to its application in patients with diverging surface contours. Correction is possible by two different methods: 1st by experimental determination of an air gap factor for the shift of isodoses, and 2nd by two factors depending on the focus-skin distance and on the angle of incidence of the electron beam. Determination of the factors is performed either by means of fixed fields measured by vertical and at oblique incidence of the beam and a depth dose distribution measured at the central axis, with oblique incidence of the electrons.

On a simple method for routine check of the constancy of radiation quality of bremsstrahlung emitted by therapeutic particle accelerators

The constancy of radiation quality of therapeutically employed particle accelerators has to be checked at weekly intervals. Any change in radiation quality may have considerable therapeutic effects owing to its influence on dose distribution. It can be recommended to make measurements instead of, or in addition to, the axial reference-point measurement at 5 and 15 cm depth in the phantom, at 5 cm depth in the beam axis and at a reference-point about 1 cm within the geometric edge of the field, for checking the constancy of the radiation quality of bremsstrahlung. Only then, if routine checks carried out for the axial and the lateral reference-point dose ratios do not show any deviations greater than e.g. +/- 2%, radiation quality is deemed to have remained sufficiently constant for radiotherapeutical applications.

Procedure for field axes measurement, beam indication adjustment, and figure of convergence determination within performance tests for radiation therapy equipment

A routine measuring procedure for the verification of radiation field axes and figure of convergence within a spatial resolution of +/- 0.5 mm is described. Measurements are done in two parallel planes in a certain distance before and behind the presumed isocentre. The used test arrangement permits rapid check and controlled adjustment of the alignment of beam or isocentre indicating devices for all isocentic radiation therapy equipment.