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="language:en-US">In thoracic tumor radiotherapy, tumor movement with respiration can affect dose distribution, potentially complicating the assessment of dose delivery to organs at risk (OAR). However, no standardized evaluation methods have been reported. We aimed to evaluate the dose&ndash;response effects caused by target movement and propose a more accurate method for assessing spinal cord dose in interstitial brachytherapy. </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">Computed tomography (CT) data from 14 patients with lung cancer undergoing interstitial brachytherapy were used to design a distance-change model: f(d)=a</span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">&times;</span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">e</span></span></span><span lang="en-US" style="font-size:5.9939pt"><span style="font-family:Calibri"><span style="language:en-US">^bd</span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">. In this model, the distance (d) between the spinal cord and the clinical target volume (CTV) was defined, and f(d) represented spinal cord radiation dose parameters, including the maximum spinal cord dose (Dmax), dose to 1 cm&sup3; (D1cc), dose to 0.1 cm&sup3; (D0.1cc), and dose to 1% of the volume (D1%). Each parameter was fitted separately, assuming that the CTV exhibited simple harmonic oscillation. An experiment was designed to measure the effect of radiation source movement on point 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">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">The coefficient of determination (R&sup2;) for the exponential fitting curves of all dose variables exceeded 0.90. Specifically, the R&sup2; value was 0.94 for Dmax and 0.95 for D1cc, D0.1cc, and D1%. The significance of f(d) was evaluated using the F-test, with p<0.05 considered statistically significant. The F-values for Dmax, D1cc, D0.1cc, and D1% were 2,362.63, 3,158.41, 2,705.33, and 2,604.93, respectively, all with p<0.01. </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">Conclusion: </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">Reliance on static CT images in radiotherapy planning systems may result in inaccurate spinal cord dose estimates.</span></span></span></span></span></span></span></span></span></div> Interstitial Radiotherapy, Lung, Neoplasms, Spinal Cords, Target, Movement. 1143 1149 http://ijrr.com/browse.php?a_code=A-10-1-1626&slc_lang=en&sid=1 G. Zhang 7900319475328460035072 7900319475328460035072 No Department of Oncology, The Affiliated Hospital of Southwest Medical University, Luzhou, China J. Zhang 7900319475328460035073 7900319475328460035073 No Department of Oncology, The Affiliated Hospital of Southwest Medical University, Luzhou, China Z. Huang 7900319475328460035074 7900319475328460035074 No School of Medical Information and Engineering, Southwest Medical University, Luzhou, China Y. Han 530018842@qq.com 7900319475328460035075 7900319475328460035075 Yes Department of Oncology, The Affiliated Traditional Chinese Medicine Hospital of Southwest Medical University, Luzhou, China B. Yang yangbo_lz@163.com 7900319475328460035076 7900319475328460035076 No Department of Oncology, The Affiliated Hospital of Southwest Medical University, Luzhou, China