ObjectiveTo compare the dosimetric differences among flattening filter free intensity modulated radiotherapy (3FIMRT), flattening filter free volumetric modulated arc therapy (3FVMAT), filter free intensity modulated radiotherapy (IMRT), and filter free volumetric modulated arc therapy (VMAT) for hyperthyroidism exophthalmus patients.MethodsComputed tomography (CT) scans of 29 patients, who were diagnosed with hyperthyroidism exophthalmus and treated with radiation therapy between September 2016 and September 2017, were selected for study. Four treatment plans with the same dose prescription and objective constrains were designed for each patient based on their images, consisting of IMRT, VMAT, 3FIMRT, and 3FVMAT. The target dosimetric distribution, normal tissue radiation dose, monitor units, and treatment time of each plan were evaluated.ResultsFour types of plans were all able to satisfy the clinical treatment requirements, and there were no significant differences in maximum dose, mean dose (Dmean), homogeneity index of the targets (P>0.05). For the parameters minimum dose, V50%, conformity index (CI), gradient index of the targets, statistically significant differences were observed among the four kinds of technologies (F=10.920, 35.860, 11.320, 17.790; P<0.05). The CI of IMRT and 3FIMRT were superior to those of VMAT and 3FVMAT, but there was no significant difference between IMRT and 3FIMRT. In terms of Lens Dmean and Brain Dmean, statistically significant differences were observed among the four kinds of technologies (F=5.054, 83.780; P<0.05). For Lens Dmean and Brain Dmean, 3FVMAT achieved better sparing effects when compared with the other three plans. The total monitor units and treatment time did not significantly differ between 3FVMAT and VMAT. The mean monitor units of 3FVMAT were 65.07% and 70.22% less than that of IMRT and 3FIMRT respectively. The mean treatment time of 3FVMAT were 48.1% and 35.24% less than that of IMRT and 3FIMRT respectively.Conclusion3FVMAT can bring more dosimetric advantages for hyperthyroidism exophthalmus radiation therapy when compared with IMRT, 3FIMRT, and VMAT.
ObjectiveTo investigate the clinical feasibility of optical surface imaging (OSI) system in guiding thermoplastic body film to fix radiotherapy of pelvic tumors.MethodsFrom January to May in 2019, 20 pelvic tumor patients fixed with thermoplastic films were selected. After the first treatment, cone beam CT (CBCT) was performed to verify and correct the setup errors. OSI was used to collect the patient’s image information as the reference image for the later treatment setup. The later treatment was performed by traditional three-point setup, and OSI was used to record the setup data and monitor the treatment. CBCT scan results were taken as the standard, to calculate the system error (Σ), random error (σ) and margin of three-point and OSI setup. The result of CBCT scan was defined as three-point setup error.ResultsIn lateral-medial, superior-inferior, and anterior-posterior directions, the OSI system errors were 0.14, 0.37, and 0.14 cm, respectively, the random errors were 0.20, 0.57, and 0.23 cm, respectively, and the corresponding margins were 0.49, 1.32, and 0.51 cm, respectively; the three-point setup system errors were 0.13, 0.39, and 0.12 cm, respectively, the random errors were 0.15, 0.43, and 0.13 cm, respectively, and the corresponding margins were 0.43, 1.28, and 0.39 cm, respectively. If the target coverage rate was counted at the 0.8 cm outward margin, the proportions of the three-point setup in lateral-medial, superior-inferior and anterior-posterior were 100.00%, 80.65%, and 100.00%, respectively, and those of the OSI setup were 100.00%, 95.48%, and 99.35%, respectively. Pearson analysis showed that the weakly correlation of lateral-medial, superior-inferior directions had statistical significance (P<0.05), and there was no statistical significance in the other directions (P>0.05).ConclusionsCompared with the traditional three-point setup, OSI cannot improve the setup precision of thermoplastic body film fixation in pelvic tumor radiotherapy. OSI acquired the image of thermoplastic phantom, which is quite different from the actual target location of the patient. OSI application method should be improved in clinical application.
【摘要】 目的 利用不同匹配區域對錐形束CT（CBCT）與定位CT（FBCT）分別配準，測量出鼻咽癌放射治療中頸部的變形誤差。 方法 分析2007年4月-2008年12月收治鼻咽癌患者23例，調整治療床前198次CBCT掃描。將鼻咽部掃描CBCT圖像匹配區域分為上下兩個區域進行對比分析。其中上匹配區域為:上界為蝶竇上緣，下界為頸4下緣，側界包括下頜骨外輪廓，前界為上頜竇1/2，后界為平棘突后緣；下匹配區域為:上界約頸4下緣，下界約胸2-3下緣，側界包括椎體外輪廓，前界包括皮膚，后界平棘突后緣。匹配方式選擇骨，比較匹配結果差異。 結果 選擇上與下匹配區域結果除Y（頭腳）方向旋轉誤差無統計學差異外，余均有統計學差異（Plt;0.05） 。差值在X（左右）、Z（前后）、Y（頭腳）方向平移分別為（1.14±2.80）、（0.47±1.41）、（0.58±3.88） mm，旋轉誤差X、Y、Z方向分別為（0.90±1.98）、（0.80±2.03）、（0.68±1.90）°。 結論 鼻咽癌放射治療中頸部區域存在一定變形誤差，通過CBCT引導發現變形誤差并進行正確糾正是必須的，結合臨床實際及靶區與危及器官的變化為重新計劃提供依據。【Abstract】 Objective To investigate the rotation errors due to neck deformation in nasopharyngeal cancer (NPC) radiotherapy with different match areas to register conebeam CT(CBCT) from image guiding and fanbeam (FBCT) from simulation. Methods A total of 198 pre-correction CBCT data sets from 23 NPC patients from April 2007 to December 2008 were retrospectively analyzed. The matching areas in CBCT images were divided into up and down region of interest (ROI). For the up ROI, the superior, inferior, left and right, anterior, and posterior boundary were set parallel with sphenoid sinus up side, C4 down side, mandible outside, and 1/2 of maxillary air sinus and acanthi. For the down ROI, the lines were set parallel with C4 down side, T2-3 down side, neck outside, skin surface and acanthi respectively in all directions. All registrations were performed automatically by bony anatomy and the results were compared. Results The registration results by the up and the down ROI showed significant difference except Y direction for rotation. The translation error was (1.14±2.80),(0.47±1.41),and (0.58±3.88) mm, respectively; and the rotation error was (0.90±1.98),(0.80±2.03),and (0.68±1.90) ° in X, Y, and Z direction, respectively. 〖WTHZ〗Conclusions〖WTBZ〗There are some significant deformation errors at neck areas in NPC radiotherapy. It is important to find out the deformation and correct it with CBCT image guiding. This kind of error information may provide clues for re-planning in addition to clinical practice and the changes of clinical targets and involved organs.
