Comparison of dosimetry in radiotherapy for craniospinal irradiation / 中华放射医学与防护杂志

ABSTRACT

Objective To explore the dosimetry of simplified intensity modulated radiotherapy (sIMRT)in the spinal component of craniospinal irradiation(CSI)compared with conventional plan(3D-CRT).Methods Five previously treated patients were adopted to generate 3D-CRT,3-and 5-field slMRT plans.The prescribed dose was 36 Gy to the planning target volume(PTV)in 20 fractions.The dose distributions of target volume and normal tissues,and homogeneity index(HI)were ananlyzed using the dose volume histogram.The total monitor units(MUs)were also analyzed to compare the delivery time indirectly.Results For 3D-CRT plans,the region of the neighbouring fields only received 70％ of the prescribed dose,and the maximum dose delivered in the normal tissues was increased to approximately 140％ of the prescribed dose.The homogeneity index(HI)of 3-and 5-field sIMRT were 0.09 ± 0.01 and 0.08 ±0.01,respectively,superior to that of 3D-CRT(0.18 ± 0.02,t=7.80,7.65,P＜0.05).The values of V10 for the heart of 3-and 5-field sIMRT were(8.4 ± 1.9)％ and(8.4 ± 2.0)％,respectively,lower than that of 3D-CRT((36.0 ± 6.0)％(t=13.3,13.0,P＜0.05).V20 for the thyroid gland were (12.4±1.5)％ and(12.4±1.6)％,respectively,lower than(69.4±5.7)％ of 3D-CRT(t=26.3,26.4,P＜0.05).V20 for the larynx were(17.2 ± 1.2)％ and(17.9 ± 1.5)％,respectively,lower than that of 3D-CRT[(89.4±7.0)％(t=25.5,26.5,P＜0.05)].V30for the NTwas(4.4±1.4)％,(4.9± 1.9)％,lower than that of 3 D-CRT[(31.9 ± 6.1)％(t=8.5,10.1,P＜0.05)].The averaged values of total MUs for 3-and 5-field sIMRT were 1100 ± 177 and 1160 ±204,respectively,higher than that of 3D-CRT(640 ± 151).Conclusions Compared with the 3D-CRT CSI technique,3-and 5-field sIMRT have better dose distribution and can improve target dose uniformity and protect the organs at risk.