[CyberKnife®: new treatment option for uveal melanoma]. / CyberKnife®: Eine neue Therapieoption bei uvealem Melanom.

BACKGROUND: CyberKnife® stereotactic radiosurgery is a new treatment option for uveal melanoma. OBJECTIVE: This review outlines the technique of robot-assisted CyberKnife® therapy, as well as the pros and cons in the treatment of uveal melanoma. METHODS: The study provides a PubMed literature review and own preliminary clinical experiences. RESULTS: CyberKnife® therapy for choroidal and ciliary body melanomas shows comparable results concerning local tumor control and overall survival matching those of conventional therapies. With only low complication rates, a high level of quality of life can be conserved by possible preservation of visual acuity as well as the ocular globe. CONCLUSION: Stereotactic radiosurgery using CyberKnife® seems to be an efficient and safe therapeutic option for malignant melanomas affecting the choroid and ciliary body. Comparative studies with conventional radiation strategies are now a high priority.

Influence of iodine supply on the radiation-induced DNA-fragmentation.

The protective effect of stable iodide against radiation on thyroid cells was investigated. One physiological effect of stable iodine is well-rooted: stable iodine leads to a reduced thyroid uptake of radioactive iodine. This work wants to focus on an intrinsic effect of stable iodine by which DNA-damage in cells is prevented. To investigate this intrinsic effect thyroid cells (FRTL-5) were externally irradiated by use of a linear accelerator (LINAC) applying energy doses of 0.01 Gy-400 Gy and by incubation with various activity concentrations of 131I (0.1-50 MBq/ml for 24 h). We added stable iodine (NaI) to the cells prior to external irradiation and investigated the effect of the concentration of stable iodine (1, 5, 15 µg/ml). In order to clarify whether thyroid cells have a distinctive and iodine-dependent reaction to ionizing radiation, keratinocytes (HaCaT) without NIS were exposed in the same way. As indicators for the cellular reaction, the extent of DNA fragmentation was determined (Roche, Mannheim, Germany). Both cell types showed distinct ability for apoptosis as proven with camptothecin. The addition of "cold" iodine from 1 to 15 µg/ml without irradiation ("negative control") did not change the response in both cell types. Plausibly, the radio-sensitivity of both cell types did increase markedly with increasing radiation dose but the radiation effect is diminished if iodine is added to the thyroid cells beforehand. The DNA-damage in thyroid cells after addition of cold iodine is reduced by a factor of 2-3. The skin cells did not show an significant change of radio-sensitivity depending on the presence of cold iodine. Elementary iodine possibly acts as a radical scavenger and thus markedly reduces the secondary radiation damage caused by the formation of cytotoxic radicals. This intrinsic radioprotective effect of iodine is seen only in cells with NIS.

[Rules and regulations applying to incidents in radiotherapy]. / Rechtliche Grundlagen für den Umgang mit sicherheitsrelevanten Ereignissen in der Strahlentherapie.

AIMS AND PURPOSE: Radiotherapy is an essential and reliable element of the treatment armamentarium in oncology. Numerous rules, regulations, and protocols minimize the associated risks. It can, however, never be excluded that errors in the treatment delivery chain result in inadequate tumor doses or unnecessary damage to organs at risk. A legal framework governs the management of such incidents. The most important European and North American regulations are reported. RESULTS: Various directives issued by the European Union are differently implemented nationally. This applies particularly to the characterization of incidents that must be reported to authorities. Reporting thresholds, audit systems, and the extent of the integration of voluntary reporting systems vary. CONCLUSION: Radiotherapy incidents are dealt with differently on an international level. Changes are to be expected based on the European Basic Safety Standards Directive that is currently being prepared and will have to be implemented nationally in due course.

A simple and reliable method to simulate multileaf-plans.

To combine conformity of the irradiation with time effectiveness during treatment, the use of multileaf collimators has become more and more common. However, the simulation of the leaf positions is rather difficult compared with metal blocks. We developed a new method, utilizing an acrylic template in which the contour produced by the leaves is machined in the form of a 1 mm groove by a computerized numerically controlled milling machine. This template is then inserted into a mount attached to the simulator. The main advantages are the errorfree, direct communication from the therapy planning system to the milling machine via a network, the possibility to transfer the contour to the skin, and the documentation on the simulation film. The use of templates is reliable and, e.g. the costs of the materials are lower than for block simulation.

[A multileaf collimator: additional quality assurance in a GE linear accelerator]. / Multileafkollimator: erweiterte Qualitätssicherung an einem GE-Linearbeschleuniger.

BACKGROUND: In comparison to a conventional collimator, a multileaf collimator demands a great deal of quality assurance procedures due to its large number of leaves. A concept for daily quality assurance is presented, mainly concerning the positioning accuracy of the leaves. MATERIAL AND METHODS: Two leaf configurations including maximal opening as well as overtravel of single leaves, at a maximal opening of the jaws, are transmitted online in daily exchange from our record- and verify system to the linac. Aiming at a special test phantom a visual control of the positioning accuracy is performed. The leaf positioning is documented by an electronic portal imaging system and is compared with a reference shot by superposition of a grid. RESULTS: This method of quality assurance offers a fast and effective possibility to guarantee the proper function of the whole system by simulating the routine treatment situation. CONCLUSIONS: Compared to a conventional collimator only a slightly greater workload is needed for quality assurance of a multileaf collimator.