註釋 This project is realized at the hospital Landesklinikum Wiener Neustadt and consists of two parts. The first part contains the measurements of small fields with different detectors. A water phantom is used for these detectors: Semiflex, Pinpoint, Micro-Diamond and Micro-Lion. The main task of this part is to find a proper detector to obtain the highest measurement accuracy. In the second part, a comparison is made between the dose of the measurements and the dose calculated in the treatment planning system, to evaluate the results. Finally, it should be justified whether a more precise determination of doses for small fields translates into a higher accuracy for the dose modelling in the treatment planning system (TPS) for volumetric modulated arc therapy (VMAT), intensity-modulated radiation therapy (IMRT) or stereotactic treatments. In conclusion, the detector microDiamond shows good behaviour for small fields and the deviations between measurements and calculations of larger fields are still smaller.*****This project is realized at the hospital Landesklinikum Wiener Neustadt and consists of two parts. The first part contains the measurements of small fields with different detectors. A water phantom is used for these detectors: Semiflex, Pinpoint, Micro-Diamond and Micro-Lion. The main task of this part is to find a proper detector to obtain the highest measurement accuracy. In the second part, a comparison is made between the dose of the measurements and the dose calculated in the treatment planning system, to evaluate the results. Finally, it should be justified whether a more precise determination of doses for small fields translates into a higher accuracy for the dose modelling in the treatment planning system (TPS) for volumetric modulated arc therapy (VMAT), intensity-modulated radiation therapy (IMRT) or stereotactic treatments. In conclusion, the detector microDiamond shows good behaviour for small fields and the deviations between measurements and calcula 