Tissue- and water-equivalent materials (TEMs) are widely used in quality assurance and calibration procedures, both in radiodiagnostics and radiotherapy. In radiotherapy, particularly, the TEMs are often used for computed tomography (CT) number calibration in treatment planning systems. However, currently available TEMs may not be very accurate in the determination of the calibration curves due to their limitation in mimicking radiation characteristics of the corresponding real tissues in both low- and high-energy ranges. Therefore, we are proposing a new formulation of TEMs using a stoichiometric analysis method to obtain TEMs for the calibration purposes. We combined the stoichiometric calibration and the basic data method to compose base materials to develop TEMs matching standard real tissues from ICRU Report 44 and 46. First, the CT numbers of six materials with known elemental compositions were measured to get constants for the stoichiometric calibration. The results of the stoichiometric calibration were used together with the basic data method to formulate new TEMs. These new TEMs were scanned to validate their CT numbers. The electron density and the stopping power calibration curves were also generated. The absolute differences of the measured CT numbers of the new TEMs were less than 4 HU for the soft tissues and less than 22 HU for the bone compared to the ICRU real tissues. Furthermore, the calculated relative electron density and electron and proton stopping powers of the new TEMs differed by less than 2% from the corresponding ICRU real tissues. The new TEMs which were formulated using the proposed technique increase the simplicity of the calibration process and preserve the accuracy of the stoichiometric calibration simultaneously.

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On average, automatically created plans are superior to manually created treatment plans. For particular plans, experienced physicists were able to perform better than scripts or AP; thus, the benefit is greatest when time is short or staff inexperienced.

Tissue-equivalent materials are used for simplifying quality control and quality assurance procedures, both in diagnostic and therapeutic radiology. Important information to formulate a tissue-equivalent material is elemental composition of its base materials. However, this information is not easily obtained. Therefore we propose a stoichiometric analysis method to investigate the elemental composition of the base materials that can potentially be used for manufacturing tissue-equivalent materials. In this technique, we combined the stoichiometric calibration and the basic data method to obtain the elemental composition of materials from measured computer tomography (CT) numbers. The elemental composition, with the maximum number of the elements of the material in question up to the available number of different tube voltages at the CT scanner, was analysed using the proposed approach. We tested eight different cylinders in this study. The estimated elemental compositions of unspecified materials in the cylinders were evaluated by comparing the calculated and the simulated CT numbers to the measured ones; the results showed good correlation with maximum absolute differences of 1.9 and 3.7 HU, respectively. The accuracy of the stoichiometric analysis method to estimate the elemental composition was influenced by the accuracy of the measured CT numbers. The method proposed allows for determining the elemental composition of the base materials which can then be applied further to formulate tissue-equivalent materials.

A deeper understanding of biological mechanisms to promote more efficient treatment strategies in proton therapy demands advances in preclinical radiation research. However this is often limited by insufficient availability of adequate infrastructures for precision image guided small animal proton irradiation. The project SIRMIO aims at filling this gap by developing a portable image-guided research platform for small animal irradiation, to be used at clinical facilities and allowing for a precision similar to a clinical treatment, when scaled down to the small animal size. This work investigates the achievable dosimetric properties of