ABSTRACT
Objective@#To explore the intensity of coplanar arc-adjusted radiotherapy with volume-modulated arc therapy (VMAT) and whether the position of the head tilt influences the distribution of radiotherapy dose.@*Methods@#From 2015 to 2017, 500 patients underwent radiotherapy of the head and kept their head tilted. The simulated non-inclined CT images were obtained by rotating the original CT images. The protocol of the coplanar VMAT whole brain irradiation was 30 Gy and the maximum dose of planning target volume in the hippocampus was limited to 16 Gy. The doses of the optic nerve, optic chiasm and eyeball were lower than 37.5 Gy. The dosimetric parameters of two different protocols were statistically compared by paired t-test.@*Results@#The average head tilt angle was (11.12°±0.68°). The homogeneity and the conformal index in the tilted and non-tilted positions were decreased by (8.3±9.6)%(P=0.033) and (5.2±4.1)%(P=0.009). The dose of hippocampus in the tilted position of the head was decreased by (13.6±6.2)% on average compared with that in the non-inclined position (P=0.004). The dose of the lenses was decreased by (15.5±11.1)%(P=0.008) on average. The doses of optic nerve and eyeball were declined by (6.8±5.6)%(P=0.013) and (8.6±6.5)%(P=0.016).@*Conclusions@#By tilting the head at an appropriate angle during VMAT whole-brain radiotherapy, the radiation dose distribution of the target volume can be significantly improved and the radiation dose in the hippocampus and visual system can be reduced simultaneously to maintain the therapeutic effect and minimize the effect upon the cognitive and memory function of patients.
ABSTRACT
Objective To explore the intensity of coplanar arc-adjusted radiotherapy with volume-modulated arc therapy (VMAT) and whether the position of the head tilt influences the distribution of radiotherapy dose.Methods From 2015 to 2017,500 patients underwent radiotherapy of the head and kept their head tilted.The simulated non-inclined CT images were obtained by rotating the original CT images.The protocol of the coplanar VMAT whole brain irradiation was 30 Gy and the maximum dose of planning target volume in the hippocampus was limited to 16 Gy.The doses of the optic nerve,optic chiasm and eyeball were lower than 37.5 Gy.The dosimetric parameters of two different protocols were statistically compared by paired t-test.Results The average head tilt angle was (11.12°±0.68°).The homogeneity and the conformal index in the tilted and non-tilted positions were decreased by (8.3±9.6) ％(P=0.033) and (5.2±4.1)％(P=0.009).The dose of hippocampus in the tilted position of the head was decreased by (13.6±6.2) ％ on average compared with that in the non-inclined position (P=0.004).The dose of the lenses was decreased by (15.5±11.1)％(P=0.008) on average.The doses of optic nerve and eyeball were declined by (6.8±5.6) ％(P=0.013) and (8.6±6.5) ％(P=0.016).Conclusions By tilting the head at an appropriate angle during VMAT whole-brain radiotherapy,the radiation dose distribution of the target volume can be significantly improved and the radiation dose in the hippocampus and visual system can be reduced simultaneously to maintain the therapeutic effect and minimize the effect upon the cognitive and memory function of patients.
ABSTRACT
<p><b>OBJECTIVE</b>To verify the linkage of the candidate regions identified in a previous study (markers D2S168, D2S151, D2S142 on chromosome 2) with hypertension in Chinese families.</p><p><b>METHODS</b>A genetic linkage study focused on chromosome 2 was performed on 240 Chinese families containing 856 patients with essential hypertension. A total of 1080 individuals were genotyped using 9 highly polymorphic microsatellite markers around the candidate regions on chromosome 2 with an average spacing of 5 cM. Non-parametric linkage (NPL), parametric linkage analysis and transmission-disequilibrium test (TDT) with the GENEHUNTER software were used to assess evidence for linkage.</p><p><b>RESULTS</b>Linkage of a region on chromosome 2 around D2S151 and D2S142 with hypertension was confirmed by different statistical methods (NPL, LOD score and TDT). However, the linkage of D2S168 could not be replicated in this extension study.</p><p><b>CONCLUSIONS</b>The data suggest that a region on chromosome 2 at or near the loci of D2S142 and D2S151 may harbor genes responsible for the development of essential hypertension in Chinese.</p>