Background: In this study, clinical advantages and the dosimetric accuracy of volumetric modulated arc therapy (VMAT) technique for cranio-spinal irradiation (CSI) were investigated and compared with field in field (FinF) and intensity modulated radiotherapy (IMRT) techniques. Materials and Methods: The organs at risk (OARs) and planning target volume (PTV) were generated on the RANDO phantom computerized tomography (CT) image series. The dose–volume parameters for PTVs and OARs were compared for three techniques. Furthermore, the dose distribution inside the RANDO phantom was measured with thermoluminescent dosimeter (TLD) for all three techniques. Comparisons were done between measured and calculated doses of field junctions, targets and OARs. Results: FinF failed to obtain an adequate dose distribution for the upper spine (US), while VMAT and IMRT provided good dose coverage for all parts of the PTV. The most homogeneous dose distribution at the field junctions was obtained with the VMAT. Although heart, thyroid, intestine, lung, liver and testicular maximum doses were lower for the VMAT, the mean doses were higher except for the heart and thyroid. The absolute volume receiving prescription dose was significantly lower for the VMAT. The median differences between the TLD measurements and TPS calculations were 0.27% (7.8, -9.7; p=0.394), -0.28% (8.1, -10.7; p=0.322) and -0.33% (8.4, -12; p=0.338) for the FinF, IMRT and VMAT, respectively.  These differences were not found statistically significant for the VMAT technique, as were the other two techniques. Conclusion: We conclude that the VMAT technique is the optimal Linac based CSI treatment in regards to dose coverage, dose homogeneity in field junctions and OAR sparing for higher doses. In addition, the VMAT showed dose distribution accuracy as good as the two other techniques in measurements simulating real clinical situations.

Background: We aimed to investigate the relationship between the radiation dose received by the spleen and the hematological parameters of patients who underwent chemoradiotherapy after the diagnosis of locally advanced pancreatic cancer (LAPC).Materials and Methods: Patients with LAPC who were treated with chemoradiotherapy were retrospectively reviewed. Surgical status,chemoradiotherapy details, complete blood count values (baseline, mid-treatment, and end-of-treatment), mean spleen dose, and dose-volume parameters (V5, V10, V15, V20, V25, and V30) were recorded. The relationship between spleen dose-volume parameters and the development of grade 3 lymphopenia was evaluated by Spearman's rank correlation and receiver operating characteristic (ROC) analysis. Results: All dose parameters for the spleen were significantly correlated with the mid-treatment absolute lymphocyte count. In the ROC analysis, mean spleen dose (p=0.011; area under the curve [AUC]: 0.856; 95% confidence interval [CI]: 0.675-0.995), V15 (p=0.020; AUC: 0.938; 95% CI: 0.830-0.997), and V20 (p=0.002; AUC: 0.940; 95% CI: 0.811-0.1000) were significantly associated with mid-treatment grade ≥3 lymphopenia. Conclusion: A significant correlation was found between the dose received by the spleen during chemoradiotherapy in LAPC patients and the development of lymphopenia. Contouring the spleen as an organ at risk (OAR) and documenting doses is important to establish dose limitations.