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During the past decade planning of adjuvant radiotherapy (RT) of early breast cancer has changed from two-dimensional (2D) to 3D conformal techniques. In the planning computerised tomography (CT) scan both the targets for RT and the organs at risk (OARs) are visualised, enabling an increased focus on target dose coverage and homogeneity with only minimal dose to the OARs. To ensure uniform RT in the national prospective trials of the Danish Breast Cancer Cooperative Group (DBCG), a national consensus for the delineation of clinical target volumes (CTVs) and OARs was required. Material and methods. A CT scan of a breast cancer patient after surgical breast conservation and axillary lymph node (LN) dissection was used for delineation. During multiple dummy-runs seven experienced radiation oncologists contoured all CTVs and OARs of interest in adjuvant breast RT. Two meetings were held in the DBCG Radiotherapy Committee to discuss the contouring and to approve a final consensus. The Dice similarity coefficient (DSC) was used to evaluate the delineation agreement before and after the consensus. Results. The consensus delineations of CTVs and OARs are available online and a table is presented with a contouring description of the individual volumes. The consensus provides recommendations for target delineation in a standard patient both in case of breast conservation or mastectomy. Before the consensus, the average value of the DSC was modest for most volumes, but high for the breast CTV and the heart. After the consensus, the DSC increased for all volumes. Conclusion. The DBCG has provided the first national guidelines and a contouring atlas of CTVs and OARs definition for RT of early breast cancer. The DSC is a useful tool in quantifying the effect of the introduction of guidelines indicating improved inter-delineator agreement. This consensus will be used by the DBCG in our prospective trials. [ABSTRACT FROM AUTHOR]

Introduction. Cone beam CT is a powerful tool to ensure an optimum patient positioning in radiotherapy. When cone beam CT scan of a patient is acquired, scan data of the patient are compared and evaluated against a reference image set and patient position offset is calculated. Via the linac control system, the patient is moved to correct for position offset and treatment starts. This procedure requires a reliable system for movement of patient. In this work we present a new method to characterize the reproducibility, linearity and accuracy in table positioning. The method applies to all treatment tables used in radiotherapy. Material and methods. The table characteristics are investigated on our two recent Elekta Synergy Platforms equipped with Precise Table installed in a shallow pit concrete cavity. Remote positioning of the table uses the auto set-up (ASU) feature in the linac control system software Desktop Pro R6.1. The ASU is used clinically to correct for patient positioning offset calculated via cone beam CT (XVI)-software. High precision steel rulers and a USB-microscope has been used to detect the relative table position in vertical, lateral and longitudinal direction. The effect of patient is simulated by applying external load on the iBEAM table top. For each table position an image is exposed of the ruler and display values of actual table position in the linac control system is read out. The table is moved in full range in lateral direction (50 cm) and longitudinal direction (100 cm) while in vertical direction a limited range is used (40 cm). Results and discussion. Our results show a linear relation between linac control system read out and measured position. Effects of imperfect calibration are seen. A reproducibility within a standard deviation of 0.22 mm in lateral and longitudinal directions while within 0.43 mm in vertical direction has been observed. The usage of XVI requires knowledge of the characteristics of remote table positioning. It is our opinion that the method presented meets the requirements in high precision IGRT. [ABSTRACT FROM AUTHOR]