[en] Uncontrolled tumor growth of pelvic tumors is a very serious problem. To test the possibility of combining intra-operative placement of brachytherapy catheters fixed in a vicryl[reg] mat, patients with pelvic tumors were subjected to surgery followed by brachytherapy plus external radiotherapy. In conclusion: the procedure is feasible

[en] Intraoperative brachytherapy (IOBT) is suggested as a means to deliver a dose to a limited area during surgical resection of the tumor. The single-fraction IOBT is being followed by a series of external radiotherapy (ERT). The ERT dose distribution needs to be adapted to the IOBT dose given. A procedure is demonstrated for conformal treatment of pancoast tumors consisting of surgery combined with IOBT followed by ERT. After resection of the tumor a 'Flexible Intraoperative Template' (FIT) is positioned on the tumorbed. This FIT is a 5 mm thick flexible silicon template containing parallel catheters spaced 1 cm apart and cut into the necessary shape. A dose of 15 Gy is delivered at 1 cm from the surface of the FIT. The overall IOBT procedure (preparation and positioning of the FIT, acquisition of localisation images which are fed into the planning system by a video frame grabber, dose planning, irradiation and removal of the FIT) can be limited to about 2 hours, with the irradiation time varying between 30 and 60 minutes depending on the size of the treated area and the source strength. After recovery of the patient a CT is made for ERT treatment planning. Clips placed during surgery indicate the target and serve as markers to match the IOBT dose distribution (with the geometry recontructed from localisation images) to the CT coordinate system. The ERT treatment plan is determined and the combined ERT and IOBT dose distribution is evaluated, e.g using the dose volume histogram of the spinal cord. The presented procedure offers a method for conformal therapy not only for pancoast tumors but also for e.g. pelvic tumors. It is made possible by the FIT and the ability of combining the IOBT and ERT dose distribution by matching the IOBT dose distribution to the CT coordinate system using surgical clips

[en] The area of the bladder base where late radiation reactions following intracavitary irradiation of a cervix carcinoma most frequently occur is not well indicated by means of the balloon of a Foley catheter which is commonly used as a marker for dosimetry. Therefore, a thin metal chain is inserted and positioned at this part of the bladder base. Dosimetry is performed with the aid of sets of precalculated isodoses on transparencies placed upon the laterally taken radiograph. On the average, the dose predicted with aid of the chain is found at an 11% higher level compared to the dose determined with the balloon. In order to avoid the insertion of a chain, which is less easy than that of a balloon, it has been proposed to replace the marker point of the balloon by another point obtained by shifting over 10 or 15 mm into cranial direction. However, measurements from 50 applications showed that this replacement does not provide reliable results. (Auth.)

[en] Introduction Velotonsillar carcinomas are treated in the CAV and the DDHCC by a similar protocol, that is a combination of external beam radiation therapy (46-50 Gy) and a brachytherapy boost. The techniques of implantation, dosimetry and decision making criteria appear to differ substantially. For a better understanding of the clinical consequences, the brachytherapy procedures in both institutions were critically reviewed. Methods and Results The decision trees followed in the treatments of both institutes will be compared for each of three consecutive patients with localized velotonsillar tumors treated in both CAV and DDHCC. Dose specification in the CAV is based on the Paris system, while in the DDHCC the dose is specified in dose points chosen at a fixed distance from the plane of implantion. See table for treatment parameters for each institute: Discussion and Conclusions The discussion will focus on the question whether the differences in the implant techniques and dose specification methods, lead to recognizable differences in treated volumes which might reflect clinical results. From this comparison, guidelines for relevant dose specification and reporting, e.g. using CT-scans in defining target volumes, will be presented

[en] Using theoretical models based on radiobiological principles for the design of new treatment schedules for HDR and PDR brachytherapy, it is important to realise the impact of assumptions regarding the kinetics of repair. Extrapolations based on longer repair half times in a continuous LDR reference scheme may lead to the calculation of dangerously high doses for alternative HDR and PDR treatment schedules. We used the clinical experience obtained with conventional ERT and LDR brachytherapy in head and neck cancer as a clinical guideline to check the impact of the radiobiological parameters used. Biologically equivalent dose (BED) values for the in clinical practice of LDR brachytherapy recommended dose of 65-70 Gy (prescribed at a dose rate between 30-50 cGy/h) are calculated as a function of the repair half time. These BED values are compared with the biological effect of a clinical reference dose of conventional ERT with 2 Gy/day and complete repair between the fractions. From this comparison of LDR and ERT treatment schedules, a range of values for the repair half times of acute or late responding tissues is demarcated with a reasonable fit to the clinical data. For the acute effects (or tumor control) the best fits are obtained for repair half times of about 0.5 h, while for late effects the repair half times are at least 1 h and can be as high as 3 h. Within these ranges of repair half times for acute and late effects, the outcome of 'alternative' HDR or PDR treatment schedules are discussed. It is predominantly the late reacting normal tissue with the longer repair half time for which problems will be encountered and no or only marginal gain is to be expected of decreasing the dose rate per pulse in PDR brachytherapy

[en] Studies of collisional alignment in molecular beams can yield information about the anisotropic part of the scattering cross section. Here the authors report on measurements of the degree of alignment in Na₂ beams arising from scattering by noble gases. Use is made of the technique of laser-induced fluorescence. (Auth.)

[en] The accuracy of brachytherpy computer planning systems has been investigated by means of an intercomparison of the dose distributions as calculated by these systems for five specific test cases. In this intercomparison, 13 radiotherapy institutions in The Netherlands participated. The planning systems evaluated comprise all commercial systems in clinical use in The Netherlands as well as in-house developed systems. The five test cases were designed in order to quantify the errors introduced by: (a) the calculation algorith including the method of source specificaiton used; (b) the localisation procedure via orthogonal radiographs; and (c) the clinical dose specification system in the case of a geometrically irregular implantion for which no established, rigid dose specification is available. The results of this comparison can be summarized as follows: The accuracy of most calculation algorithms appears to be satisfactory except for the region close to the longitudinal axis of linear sources. Source strength specification in terms of activity or milligram radium equivalent can result in dosimetric errors which may be clinically relevant and therefore specification of the source strength in terms of output, i.e. aire-kerma rate at a specified distance, is to be preferred. This concurs with recent national and international recommendations regarding source strength specification. Localisation via orthogonal radiographs, as commonly used, appears to cause noticeable errors. This uncertainty in clinical dose specification clearly dominates the overall accuracy. This illustrates the need for a consistent dose specification system, which is capable of including interstitial implants with a source geometry deviating from the rules given by the existing specification systems. 20 refs.; 9 figs.; 1 tab

No abstract available

[en] The degree of molecular alignment, due to nozzle expansion, has been determined in supersonic beams of I₂ and Na₂, using the technique of laser-induced fluorescence. It is found that the anisotropic distribution of angular momenta is of the form 1 + a₂P₂(cos theta). The alignment appears to be small for I₂ while for Na₂ a considerably larger effect is measured. Two internal states are studied, v=O,J=28 and v=3,J=43; both under various source conditions. It is found that the alignment depends on the internal state of the molecule and for each state can be described as a unique function of pd, the product of source pressure and nozzle diameter. The results are explained using a model based on scattering between atoms and dimers with different velocity distributions . It is suggested that alignment may be a general feature in seeded molecular beams containing nonspherical components. (Auth.)

[en] Quantitative results have been obtained for the alignment, due to optical pumping, in a beam of Na₂ molecules. This laser-induced alignment offers the possibility of experiments with strongly aligned beams of diatomic molecules in specific internal states. (Auth.)