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Main advancements in radiation treatment in recent years have included the introduction of dynamic techniques and 4D radiotherapy. The treatment of movable tumors relies on two important techniques: gating and tracking. The limitation of the former is the relatively short duration of the respiratory phase during which the radiation can be delivered and the need to teach the patient to breathe in accordance with the correct pattern. At the same time, certain clinical situations require the use of dynamic techniques. Intensity modulated radiotherapy (IMRT), combined with gantry rotation, forms the basis for the VMAT technique. The procedure usually takes a shorter time to complete than other dynamic techniques, which considerably improves patient comfort. The recently introduced True BeamTM accelerator employs all the latest innovations in terms of dose-rate modeling and respiratory gating. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The aim was to provide a dosimetric comparison between IMRT and RapidArc treatment plans with RPI index with simultaneous comparison of the treatment delivery time. Background: IMRT and RapidArc provide highly conformal dose distribution with good sparing of normal tissues. However, a complex spatial dosimetry of IMRT and RapidArc plans hampers the evaluation and comparison between plans calculated for the two modalities. RPI was used in this paper for treatment plan comparisons. The duration of the therapeutic session in RapidArc is reported to be shorter in comparison to therapeutic time of the other dynamic techniques. For this reasons, total treatment delivery time in both techniques was compared and discussed. Materials and methods: 15 patients with prostate carcinoma were randomly selected for the analysis. Two competitive treatment plans using respectively the IMRT and RapidArc techniques were computed for each patient in Eclipse planning system v. 8.6.15. RPIwin® application was used for RPI calculations for each treatment plan. Additionally, total treatment time was compared between IMRT and RapidArc plans. Total treatment time was a sum of monitor units (MU) for each treated field. Results: The mean values of the RPI indices were insignificantly higher for IMRT plans in comparison to rotational therapy. Comparison of the mean numbers of monitor units confirmed that the use of rotational technique instead of conventional static field IMRT can significantly reduce the treatment time. Conclusion: Analysis presented in this paper, demonstrated that RapidArc can compete with the IMRT technique in the field of treatment plan dosimetry reducing the time required for dose delivery. [Copyright &y& Elsevier]

Abstract: Aim: To create a presentation method of TCP and NTCP distributions calculated based on dose distribution for a selected CT slice. Materials and methods: Three 24-bit colour maps – of dose distribution, delineated structures and CT information – were converted into m-by-n-by-3 data arrays, containing intensities of red, green, and blue colour components for each pixel. All calculations were performed with Matlab v.6.5. The transformation function, which consists of five linear functions, was prepared to translate the colour map into a one-dimensional data array of dose values. A menu-driven application based on the transformation function and mathematical models of complication risk (NTCP) and treatment control probability (TCP) was designed to allow pixel-by-pixel translation of colour maps into one-dimensional arrays of TCP and NTCP values. Results: The result of this work is an application created to visualize the TCP and NTCP distribution for a single CT scan based on the spatial dose distribution calculated in the treatment planning system. The application allows 10 targets (PTV) and 10 organs at risks (OaR) to be defined. The interface allows alpha/beta values to be inserted for each delineated structure. The application computes TCP and NTCP matrices, which are presented as colour maps superimposed on the corresponding CT slice. There is a set of parameters used for TCP/NTCP calculations which can be defined by the user. Conclusion: Our application is a prototype of an evaluation tool. Although limited to a single plane of the treatment plan, it is believed to be a starting point for further development. [Copyright &y& Elsevier]

Summary: Background: Quality assurance (QA) in the radiation therapy planning process is essential to ensure accurate dose delivery to the patient and to minimize the possibility of accidental exposure. In recent years, several reports have been developed addressing issues related to the commissioning and quality assurance (QA) of RTPSs. Aim: To evaluate the differences between dose distributions obtained with different dose calculation algorithms implemented in TPSs for stereotactic irradiation. Materials and Methods: BrainLab''s iPlan v. 3.0.2 RT Dose calculates by pencil beam algorithm, while Eclipse v.7.5.18 (Varian Medical Systems) calculates by different types of pencil beam/AAA algorithms (selectable). Results: The largest difference was found in the lung patient, where a difference of 10.3% in the number of monitor units and 8.3% in dose to the isocentre occurred (with calculation by AAA algorithm of Eclipse in relation to iPlan PB algorithm). The average difference in all other cases (AAA compared to iPlan) was 2.2% for MUs and 1.5% for dose to the isocentre. The average difference in all other cases (PB compared to iPlan) was 1.9% for MUs and 3.2% for dose to the isocentre. When data were transferred from iPlan through DICOM RT to Eclipse, for all patients an isocentre shift was observed. Conclusion: The dose distribution calculated by three different photon calculation algorithms results in clinically significant dose differences in isodose distribution, especially in the area of high inhomogeneities. [Copyright &y& Elsevier]

Summary: Aim: The aim of this study was to provide a parameter for treatment plan comparisons in clinical practice. Materials and Methods: 21 patients with brain tumours were selected for analysis. Two alternative treatment plans were calculated for each patient. One of the alternative plans was approved while the second one was rejected by the physician. Alternative plans were compared with the parameter RPI. The computer program RPIWin® was prepared to facilitate the calculation process. Results: Calculations showed that 80% of approved treatment plans had higher RPI than rejected ones. Only 4 cases of approved treatment plans were characterized by lower RPI values than rejected ones. Conclusion: The experiment demonstrated that the Radiation Planning Index formula takes into account the relation between dose distributions calculated for planning treatment volumes and organs at risk and is a convenient tool for treatment plan comparisons in routine clinical practice. [Copyright &y& Elsevier]