Impact of Slice Thickness and Grid Size on Dose Calculation in Intensity Modulated and Volumetric-Modulated Arc Radiotherapy in Head and Neck Cancer

Background:The grid size in radiotherapy can have an impact on dose values.When calculating the dose, slice width is a crucial component to consider.A thinner slice provides for a more precise mean dose estimate than a thicker slice.Materials and Methods: For this study, 35 patients with Head and Neck (H&N) cancer were chosen.Planning Target Volume (PTV) and Organ At Risks (OARs) were optimized using the same criteria.Intensity Modulated Radiation Therapy (IMRT) and volumetricmodulated arc therapy (VMAT) plans, which were designed with slice thicknesses (3,5,7 mm) and grid sizes (2,3,5, 7 and 8 mm).Homogeneity (HI) and Conformity Index (CI), dose points, such as D2%, D50%, and D98% for each OAR, assessed in relation to slice thickness and grid size.Results: There is a substantial difference (p<0.05) between grid sizes 3mm, 5mm, 7mm, and 8mm in IMRT and VMAT, but no significant difference (p>0.05) in target and OAR dose between grid sizes 2mm and 3mm.Conversely, the target dosage and OAR dose are significantly affected by variations in the Computed Tomography (CT) slice thickness, with a significant difference (p<0.05)seen in the target dose between 3mm, 5mm, and 7mm slice thickness and an insignificant difference (p>0.05) between 5mm and 7mm in OAR dose.Conclusions: According to this study, using the grid size of 2 mm is not recommended because it generates memory issues in the treatment planning system (TPS) and takes a lot of time, neither of which have a practical clinical effect.