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Purpose: The study aims at investigating how far image quality (MTF and NPS) differs in between CT, CBCT and DVT units and how far the geometrical 3 D accuracy and the HU calibration differ in respect to surgical or radio therapeutic planning., Materials and Methods: X ray image stacks have been made using a new designed test device which contains structures for measuring MTF, NPS, the 3 D accuracy and the Hounsfield calibration (jaw or skull program). The image stacks of the transversal images were analyzed with a dedicated computer program., Results: The MTF values are correlated with the physical resolution (CT and DVT) and are influenced by the used Kernel (CT). The NPS values are limited to an intra system comparison due to the insufficient HU accuracy. The 3 D accuracy is comparable in between the system types., Conclusions: The values of image quality are not yet correlated with dose values: NPS. Investigations to an appropriate dosimetry are ongoing to establish the ratio between dose and image quality (ALARA principle). No fundamental difference between the systems can be stated in respect radio therapeutic planning: improper HU calibration accuracy in CBCT and DVT units. The geometric 3 D accuracy of high performance DVT systems is greater than that of CT Systems., (© Georg Thieme Verlag KG Stuttgart · New York.)

Compared with conventional radiation treatment techniques, quality assurance for dynamic techniques has to consider additionally the variability of the movement parameters of the treatment unit. In this context the exactness and the reliability of the computer control are of special interest. In this paper the results of quality assurance for dynamic treatment techniques are reported. At first investigations concerning the reproducibility are carried out. Another test is the simulation of conventional moving beam techniques by external computer control. Further the differences between measured dose distributions of dynamic techniques and the distributions resulting from the sequence of fixed fields approximating these techniques are determined. Finally we compared measured and calculated dose distributions. The results of the investigations justify the introduction of dynamic radiation treatment techniques into clinical use.