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.

[Importance of sonotomography in radiation therapy (author's transl)]

Ultrasound tomography provides true scale representation of body contours and organ structures. The image supplies substantial, individual geometrical data, essential for computerized radiation treatment planning. The mehtod is described. Typical planning examples for therapy are demonstrated. The value of follow up sonograms for radiation therapy is described. The limitations of the method are pointed out.

Kinetics of binding of bovine trypsin-killikrein inhibitor (K unitz) in which the reactive-site peptide bond Lys-15--Ala-16 is cleaved, to alpha-chymotrypsin and beta-trypsin

Equilibrium measurements of the binding of reactive-site-cleaved (modified) bovine trypsin-kallikrein inhibitor (Kunitz) to alpha-chymotrypsin and beta-trypsin show a stoichiometric 1:1 association with high binding constants. At least in the case of chymotrypsin much evidence is presented that the reaction with modified inhibitor leads to the same complex as the reaction with virgin inhibitor does. The association rate constant of modified inhibitor with chymotrypsin at pH 7, 22.5 degrees C is 15.8 M-1 S-1. This is about 2 x 10(4) times slower than the binding of virgin inhibitor to that enzyme. In the analogous reaction of modified inhibitor with beta-trypsin, however, the association rate constant (1.2 x 10(4) M-1 s-1 at pH 6.9, 22.5 degrees C) is of about the same order of magnitude as it is in the reaction of virgin inhibitor and trypsin. These and analogous phenomena observed in the reactions of virgin and modified soybean trypsin inhibitor (Kunitz) with alpha-chymotrypsin and beta-trypsin suggest that the specificity of both inhibitors to trypsin is strongly reflected in the association rate constants of the modified forms. The dissociation rate constants of the complexes of trypsin-kallikrein inhibitor with chymotrypsin or with trypsin towards the modified inhibitor are estimated to be unmeasurably slow (half-life times of 45 or 1.5 x 10(4) years, respectively).

The effect of cleaving the reactive-site peptide bond Lys-15--Ala-16 on the conformation of bovine trypsin-kallikrein inhibitor (K unitz) as revealed by solvent-perturbation spectra, circular dichroism and fluorescence

Spectroscopic measurements of virgin bovine trypsin-kallikrein inhibitor and its modified species (in which the reactive-site peptide bond Lys-15--Ala-16 is split) indicate a conformational difference between both proteins. The inhibitor contains four tyrosines but no tryptophan. In the modified inhibitor a tyrosyl blue shift is seen in the difference absorption spectrum of modified against virgin inhibitor. The solvent perturbation spectra show an increase of the fraction of exposed tyrosyls from 0.45 in the virgin inhibitor to 0.59 in the modified form. Comparison of the circular dichroism spectra of the modified and virgin inhibitors reveals a decrease of the mean residue ellipticity in the tyrosine and peptide bond region of the modified inhibitor. In the fluorescence spectra a 50% increase in the quantum yield of the tyrosine fluorescence is observed in the modified inhibitor. All these spectroscopic data support the idea, which is also evidenced by the X-ray crystallographic model, that in the modified inhibitor up to five residues from Ala-16 to Arg-20 gain rotational freedom.

[The cast structure after vacuum-pressure casting and centrifugal casting]

Evaluation of polished sections revealed the following: 1. Grain size in marginal areas of the crown is, in general, smaller than it is in the occlusal region. 2. Grain size varies depending on the casting method applied. Differences in hardness were found only to a limited extent. They were not always in line with the grain structure. This phenomenon deviating from the rule cannot satisfactorily be explained. The piping distribution was in accordance with observations made so far.