ABSTRACT
Objective To conduct simulation analysis on support performance of the stent by using finite element method, and optimize structure parameters of the stent by using Kriging surrogate model, so as to provide more scientific guidance for clinical treatment with design and development of the stent. Methods The contact model was established by penalty function method. The generalized variational principle was selected as theoretical basis of the numerical simulation, and the theory of Kriging surrogate model was used for finite element optimization on support stiffness of the stent, so as to study the effect from the number of circumferential support, the length of the support and the initial diameter on support performance of the stent. Results With the increase of the number of circumferential support or the length of the support, the support performance showed the decreasing tendency; with the increase of the initial diameter, the support performance showed the increasing tendency. From seven stents by using the theory of Kriging surrogate model, it was concluded that structural parameters of the optimal stent were: the number of circumferential support was six, the length of the support was 1.15 mm, and the initial diameter was 1.65 mm. Conclusions The numerical result agreed well with the experimental data and the error was smaller than 5%, and the error rate of experimental repeatability was within 0.5%, which verified effectiveness and rationality of the finite element analysis. The optimization of support performance provides an important reference for design and exploration of new magnesium alloy stent.
ABSTRACT
Objective To reduce the dose to organ at risk ( OAR) by script-based optimizing the gantry angles of tangential beams for forward-planned intensity-modulated breast radiotherapy ( fIMRT ) plans. Methods A total of 46 patients with breast cancer (26 in left and 20 in right) after conservative surgery who were treated with manually planned fIMRT were retrospectively re-planned using a script to place the tangential beams automatically. The script program was developed using Pinnacle3 scripting language as imbedded in the Pinnacle3 treatment planning system, and the Python scripting language. Dosimetric indices, including V20 of the ipsilateral lung, D1 of the contralateral breast and V10 of the heart were extracted by the script for plans of different gantry angles. Then the optimal tangential angles were selected by a penalty function. Results For the 26 left breast cancer cases, V20 of the ipsilateral lung for manual and script were (18.2 ±3.4)% and (18.1 ±3.4)%, respectively(P>0.05), while D1 of the contra-lateral breast(249. 2 ± 88. 4) cGy and (230. 4 ± 80. 2) cGy, respectively( t=2. 27, P<0. 05), V10 of the heart (13. 7 ± 5. 7)% and (13. 1 ± 5. 7)%(t=2. 82, P<0. 05). The V20 of the ipsilateral lung of the 20 right breast cancer cases were (19. 8 ± 3. 8)% and (19. 8 ± 3. 9)%, respectively(P>0. 05). The script plans achieved better V10 of the heart[(298. 0 ± 239. 7) cGy] than the manual plans[(340. 0 ± 286. 2) cGy] (t =2. 53, P <0. 05). Conclusions Compared with the manualmethod, the script can assess of the impact of tangential beam angles on the OAR dose, patient-specifically and quantitatively, hence make better trade-offs and improve the plan quality.
ABSTRACT
Objective To reduce the dose to organ at risk ( OAR) by script-based optimizing the gantry angles of tangential beams for forward-planned intensity-modulated breast radiotherapy ( fIMRT ) plans. Methods A total of 46 patients with breast cancer (26 in left and 20 in right) after conservative surgery who were treated with manually planned fIMRT were retrospectively re-planned using a script to place the tangential beams automatically. The script program was developed using Pinnacle3 scripting language as imbedded in the Pinnacle3 treatment planning system, and the Python scripting language. Dosimetric indices, including V20 of the ipsilateral lung, D1 of the contralateral breast and V10 of the heart were extracted by the script for plans of different gantry angles. Then the optimal tangential angles were selected by a penalty function. Results For the 26 left breast cancer cases, V20 of the ipsilateral lung for manual and script were (18.2 ±3.4)% and (18.1 ±3.4)%, respectively(P>0.05), while D1 of the contra-lateral breast(249. 2 ± 88. 4) cGy and (230. 4 ± 80. 2) cGy, respectively( t=2. 27, P<0. 05), V10 of the heart (13. 7 ± 5. 7)% and (13. 1 ± 5. 7)%(t=2. 82, P<0. 05). The V20 of the ipsilateral lung of the 20 right breast cancer cases were (19. 8 ± 3. 8)% and (19. 8 ± 3. 9)%, respectively(P>0. 05). The script plans achieved better V10 of the heart[(298. 0 ± 239. 7) cGy] than the manual plans[(340. 0 ± 286. 2) cGy] (t =2. 53, P <0. 05). Conclusions Compared with the manualmethod, the script can assess of the impact of tangential beam angles on the OAR dose, patient-specifically and quantitatively, hence make better trade-offs and improve the plan quality.