Both the measurement of the dose and the measurement of its distribution, like any other measurements, are subject to measurement uncertainties. These uncertainties affect all dose calculations and dose distributions in a patient’s body during treatment planning in radiotherapy. Measurement uncertainty is not a medical physicist’s error, but an inevitable element of their work. Planning the dose distribution in a patient’s body, we often try to reduce it in the volume of critical organs (OaR - Organ at Risk) or increase the minimum dose in the PTV region by a few percent. It is believed that the measurement uncertainty should be taken into account in these calculations at the stage of treatment planning. The paper presents the method of calculating the measurement uncertainty for different physical quantities in radiotherapy as percentage depth dose, profile function and output factor, due to the fact that these quantities have a particular impact on the calculated dose distributions in a patient’s body. The uncertainties that must be taken into account in planning treatment the planned dose per fraction and real in PTV, maybe different up to 4%.

Introduction. Medical physicists planning radiation treatment are increasingly confronted with situations that require special attention. Undoubtedly, one such situation is the postoperative irradiation of a patient with breast cancer in which there is a prosthesis or an expander. In recent years, expanders have appeared in this location, which, due to the density of the device's valve makes it difficult to prepare an acceptable treatment plan. The study aims to present treatment planning in these situation in various Polish cancer centres and to compare overall patient preparation for the treatment. Material and methods. A questionnaire was prepared and sent to more than 20 radiotherapy departments, which included basic questions regarding the preparation of an irradiation plan for patients treated for breast cancer after a subcutaneous mastectomy with immediate reconstruction with a prosthesis or expander. The survey encompassed eight radiotherapy departments. Results. Not all radiotherapy departments require a manufacturer's certificate, which shows that the manufacturer does not prohibit the use of a prosthesis/expander during treatment with ionizing radiation. The X 6MV photons and the supine position, total and fraction doses: from 40 to 60 Gy and from 2 to 2.67 Gy, respectively, are the most commonly used. The way of defining them also depends on the oncological centre. The most commonly used irradiation technique is VMAT. Conclusion.The conclusion from the questionnaire -no standardisation of treatment planning -should encourage the community, at least medical physicists, to develop rules of conduct in this case. Irradiation techniques are mainly dynamic ones. The expander or prosthesis does not significantly affect the dose distributions.

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