en Radiation Biology Radiation Biology تحقيق بديع Original Research <div style="text-align: justify;"><span style="font-size:10pt"><span style="text-justify:newspaper"><span style="text-kashida-space:50%"><span style="line-height:119%"><span style="font-family:Calibri"><span style="color:black"><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Background</span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-weight:bold"><span style="language:en-US">:</span></span></span></span></span> <span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">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. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Materials and Methods: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">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 volumetric-modulated 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. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Results: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">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. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Conclusions: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">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.</span></span></span></span></span></span></span></span></span></div> Radiotherapy, intensity modulated, radiotherapy planning, radiotherapy dosage, computer-assisted tomography. 263 270 http://ijrr.com/browse.php?a_code=A-10-1-1323&slc_lang=en&sid=1 N. Ayman 7900319475328460031021 7900319475328460031021 No Radiotherapy Department, Nasser Institute, Cairo, Egypt A. Abdelaal 7900319475328460031022 7900319475328460031022 No Radiotherapy Department, Nasser Institute, Cairo, Egypt H.H. Amer 7900319475328460031023 7900319475328460031023 No Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt H.S. Mohammed haitham@sci.cu.edu.eg 7900319475328460031024 7900319475328460031024 Yes Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt