ABSTRACT
Objective To investigate the optimal treatment planning of intensity modulated radiotherapy (IMRT) for non-small cell lung cancer (NSCLC) .Methods Two types of treatment plans were designed for 11 patients with inoperable NSCLC disease.In the first plan(PTV60 plan) ,60 Gy was prescribed to the planning target volume(PTV) which was created using CTV(GTV +6-8 mm) plus the margin for organ motion and setup uncertainties.In the second plan(PTV70 plan) ,70 Gy was prescribed to the PTV which was created using GTV plus the margin for organ motion and setup uncertainties.The dose-volume histogram,the planning target volume coverage,and other dosimetric parameters of normal structures were compared between the two plans.Results These two plans were not significantly different in the dose heterogeneity,but commpared with the PTV60 plan,the PTV70 plan significantly improved 60 Gy volume with regard to PTV coverage.The values of V_(20) and V_5 of lung were reduced in average by (1.69 ±0.42) % ,and (1.29 ±1.09) % (t ＝ 0.047,0.264,P ＝ 0.002) ,respectively.Conclusions The planning of 70 Gy to the PTV using GTV plus the margin for organ motion and setup uncertainties might be better than that of 60 Gy to the PTV using CTV(GTV +6-8 mm) plus the margin for organ motion and setup uncertainties.
ABSTRACT
Objective To compare the planning systems of the simplified manual intensity modulated (SMIM) irradiation and standard tangential (ST) irradiation,in order to explore the application of SMIM technique in clinic.Methods In 64 cases of breast cancers after breast conserving surgery,each underwent both SMIM and ST planning systems.SMIM planning was designed by copying additional fields for shielding the high dose areas from internal or lateral tangential field.The high dose areas were reduced by adjusting the size of the additional field and open tangential field.To optimize the SMIM planning,3 high dose areas (＞ 103% ,＞ 105% and ＞ 107%) were shielded and 3 protocols carried out.The wedges were also optimized in ST plan.The target coverage and dose homogeneity and dose of organ at risk were compared between SMIM and ST planning systems.Results When the dose was normalized to cover the volume of 95% CTV,85% of the shielded areas in optimal SMIM planning were that of ＞ 103% high dose area,and 94% of target area was covered.The study on the volume of breast CTV showed that,in the large breast group,SMIM could not only significantly reduce the high dose areas,and the maximum dose as well as the dose of organ at risk,but also enhance the dose homogeneity index.However,no such effect was not significant in the small breast group.Conclusions The simplified manual intensity modulated technique can improve target dose homogeneity in the large breast cases instead of the standard tangential technique.
ABSTRACT
Objective To study the altered radiobiological effect of simulative intensity-modulated radiotherapy (SIMR) in cultured human nasopharyngeal carcinoma (NPC) cells and the related mechanism. Methods Single cell suspension of exponentially growing CNE-2 cells, a poor differentiated NPC cell line, was seeded and cultured for 12 hours, then the cells were irradiated in two different models by 6 MV X-ray beams at 3 Gy/min. In single fraction irradiation (SFR) model, cells were irradiated a single fraction of 0, 2, 4, 6 or 8 Gy within 0 to 3 minutes. In S1MR model, cells were irradiated 0, 2, 4, 6 or 8 Gy in 5 frac-tions with interval of 8.0-8.5 minutes between. Clonogenic assay was performed to determine the radiosen-sitivity. Cellular apoptosis was measured by flow cytometry. RT-PCR was used to detect mRNA expressions of Bax and Bcl-2, Respectively. Results Compared with SFR group, the survival fraction in SIMR group was higher at all the dose levels. The values of α, β, D0 and Dq were higher in SIMR group than in SFR group. At dose levels of 2 Gy, 4 Gy and 6 Gy, The early and late apoptotic cells in SIMR group were lower than in SFR group (21.20%: 15.89%, F=18.51, P=0.020;13.00%: 10.20, F=15.67, P=0.040).The mRNA expression of Bax was upregulated in a dose-dependent manner in the both groups. Compared with SFR group, the mRNA expression of Bax in SIMR group was lower at all the dose levels (Mean value of 76.75% : 62.50%, F =36.57, P =0.000). Bcl-2 mRNA expression at every dose level had no significant difference between the two groups (Mean value of 29.25% : 29.75%, F=0.74, P=0.800). Conclusions Prolonged delivery time in SIMR model can decrease the radiobiological effects.