ABSTRACT
@#<b>Objective</b> To investigate the dose level of pediatric CT scan in one hospital, and to provide recommendations for optimized scanning. <b>Methods</b> The CT scan data of children were collected from this hospital to analyze the differences in typical dose values and typical scanning parameters between different age groups and different scanning parts. <b>Results</b> The sample size was >10 for routine cranial scan, routine maxillary sinus scan, and routine chest scan in each age group, and the 1-year-old group and the 5-year-old group had the same kV, mA, and CTDIvol values of routine cranial scan and maxillary sinus scan, but with relatively great differences in the parameters of chest scan. <b>Conclusion</b> Scanning parameters in this hospital can be further optimized, and optimization measures should be adopted continuously.
ABSTRACT
Objective:The purpose of current study was to evaluate the interplay effects in intensity-modulated proton therapy (IMPT) for lung cancer and compare the results of different Iso-energy layer repainting techniques in the mitigation of interplay effects.Methods:Eight patients with lung cancer who underwent 4DCT were retrospectively selected. A robust CTV-based IMPT plan was generated for each based on commercial TPS, considering patient setup errors ±5 mm, range uncertainties ±3.5%, and CTV time structure motion in 4DCT image. Monte Carlo dose engines were used for all IMPT plans in the final dose calculation. The 4D static dose (4DSD) and 4D dynamic dose (4DDD) were calculated using a hybrid deformable algorithm and simulated proton delivery system for interplay effects. An index[ΔI(ROI, DVH)] was developed to quantitatively evaluate the interplay effects. We applied Iso-energy layer repainting techniques with different numbers of repainting (3, 4, 5, 6, 7) to the robust IMPT plans and evaluated the difference in the mitigation of interplay effects based on the ΔI(ROI, DVH) index.Results:Due to interplay effects, the mean values of target coverage, conformity and homogeneity index reduced by 13.7%, 12.7% and 24.6%, respectively. The mean values of lung V 5Gy and V 20Gy improved by 0.8%, 3.4% and 2.6%. Compared to the IMPT plans without layer repainting, Multiple iso-energy layers repainting techniques improved the mean values of CTV coverage by 4.5%, 3.8%, 3.8%, 3.6% and 5.7%, respectively. The average values of lung V 20Gy reduced by 1.5%, 1.8%, 1.7%, 1.6% and 1.9%, respectively. Conclusions:In the robust CTV-based IMPT plans, the interplay effects degraded the target dose distribution but were mitigated using iso-energy layer repainting techniques. We recommended to use the layer repainting technique according to the characteristics of the patient.
ABSTRACT
Objective:To demonstrate the concept of planning target volume (PTV) is not suitable for intensity proton therapy (IMPT) in lung cancer, plan differences were compared based on the concept of PTV and Internal target volume (ITV), aiming to provide clinical reference.Methods:Six patients were retrospectively selected and approved by the local ethics committee. Each of the six patients received two IMPT plans based on a synchronous accelerator model, developed by SINAP team (Shanghai Institute of Applied Physics, China Academy Science University) and commercial treatment system: one with the PTV-based robust IMPT (PTV-IMPT) plan and the other with ITV-based robust IMPT (ITV-IMPT) plan. Three beams were set in all plans, and the final dose was calculated using Monte Carlo dose algorithm. The plan quality and robustness of PTV-IMPT and ITV-IMPT plans were evaluated quantitatively.Results:Compared to the PTV-IMPT plan, ITV-IMPT plan showed better target conformity index (conformability index: 0.58 vs.0.43), better homogeneity index (homogeneity index: 0.96 vs.0.92), lower V 5Gy in normal lung tissue (13.1% vs.13.5%) and maximum dose in spinal cord (8.9 Gy vs. 9.5 Gy) as well as plan monitor unit (MU: 338 vs. 401) . In addition, ITV-IMPT plan showed more robust in target coverage (0.003-0.032 vs. 0.02-0.28), and normal lung tissue was also found a bit robust in the ITV-IMPT plan ( 0.06-0.11, 0.07-0.13). Conclusions:Compared with the PTV-IMPT plan, ITV-IMPT plan has the advantages of high planning quality, well robustness and better tumor motion mitigation. Therefore, ITV concept is recommended to be applied in the IMPT plan for lung cancer.
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Objective To compare target dosimetric distribution and normal tissue radiation between different static intensity-modulated radiation therapy (IMRT)plans and volumetric modulated arc therapy (VMAT),and to identify the best IMRT plan for lymphoma patients needed mediastinal radiation. Methods A total of 11 patients with lymphoma who received first course radiotherapy in the mediastinal region after che-motherapy in Cancer Hospital & Shenzhen Hospital,Chinese Academy of Medical Sciences and Peking Union Medical College from March 2017 to January 2019 were included in the study. There were 8 males and 3 fe-males,2 patients were in Ann Arbor stage Ⅰ-Ⅱ,and 9 cases in Ⅲ-Ⅳ stage. There were 6 patients with Hodgkin lymphoma (HL)and 5 patients with non-Hodgkin lymphoma (NHL). Patients with HL and NHL were given prescript doses of 36 Gy and 50 Gy,respectively. Three plans were designed for each patient:static 5F-IMRT,7F-IMRT and VMAT plan. The target dosimetric distribution,normal tissue radiation dose,and effi-ciency of each plan were evaluated. Results The mean conformity index (CI)and homogeneity index (HI) values of plan target volume (PTV)in 5F-IMRT,7F-IMRT,VMAT plan were 0. 64 ± 0. 06,0. 67 ± 0. 05, 0. 76 ± 0. 04 (F = 17. 045,P < 0. 001)and 1. 07 ± 0. 01,1. 07 ± 0. 01,1. 09 ± 0. 01 (F = 9. 258,P =0. 001),respectively. VMAT showed significantly better CI than two static IMRT plans (both P < 0. 001),but worse HI (both P < 0. 001). The lungs low dose irradiation volume (V (V 5 )and high dose irradiation volume 30 )in 5F-IMRT,7F-IMRT,VMAT plan were (43. 98 ± 7. 77)％,(42. 71 ± 4. 98)％,(55. 92 ± 8. 16)％(F = 8. 281,P = 0. 001)and (8. 19 ± 2. 97)％,(8. 25 ± 2. 87)％,(7. 53 ± 3. 16)％ (F = 0. 140,P =0. 870),respectively. The volume of low dose irradiation in lungs of VMAT plan was significantly higher than 5F-IMRT and 7F-IMRT plans (both P < 0. 001),while high dose volume was no significant difference. The left and right breast low dose irradiation volume (V 4 )in 5F-IMRT,7F-IMRT and VMAT plan were (24. 29 ± 8. 14)％,(23. 87 ± 7. 70)％,(80. 17 ± 22. 92)％ (F = 14. 505,P = 0. 005)and (22. 12 ± 13. 28)％, (21. 13 ± 13. 01)％,(81. 77 ± 20. 76)％ (F = 13. 938,P = 0. 006),respectively. VMAT showed signifi-cantly higher breast low dose irradiation volume than static IMRT plan (both P < 0. 05). The number of monitor units and treatment time in 5F-IMRT,7F-IMRT,VMAT plan were (1622 ± 281)MU,(1729 ± 286)MU, (411 ± 75)MU (F = 105. 277,P < 0. 001)and (6. 79 ± 0. 93)min,(7. 42 ± 0. 95)min,(4. 98 ± 0. 00)min (F = 29. 545,P < 0. 001),respectively. VMAT showed significantly less monitor units than static IMRT (both P < 0. 001)and shorter treatment time (both P < 0. 001). Conclusion For lymphoma patients who have the indication of mediastinal radiotherapy,VMAT is highly efficient and has no definite dose advan-tage,the static 5F-IMRT or 7F-IMRT plan has good conformal and uniform target area,and some organs at risk exposure is even lower.