RESUMO
Objective@#To evaluate the dosimetric difference between carbon ion radiotherapy and photon radiotherapy for treating tumors at lacrimal system.@*Methods@#Using the CT images of 10 patients with tumors at lacrimal system, the carbon ion plan, the photon volume intensity modulation plan (VMAT) and the fixed wild photon intensity modulation radiotherapy (IMRT) plan were generated. The prescription was 54 Gy(RBE) in 18 fractions for clinical target volume (CTV) and 63 Gy(RBE) in 18 fractions for CTV-boost. Dosimetric differences of organ at risks were compared based on the same planning target volumes (PTVs) with similar dose coverages.@*Results@#There was no statistically significant difference in the PTV coverage among three plans (P>0.05). Compared to VMAT and IMRT plans, carbon ion plans reduced the mean doses of eyeballs, mean doses and near-maximum doses of optical nerves of both ipsilateral ( t=7.35, 3.79, 4.66, 8.48, 2.52, 2.76, P<0.05) and contralateral eyes (t=3.87, 10.49, 9.16, 4.43, 6.53, 5.12, P<0.05), while the mean dose of brain was decreased from(5.65±3.58) and (5.76±2.09)Gy(RBE) to (0.81±0.90)Gy(RBE) (t=6.76, 17.33, P<0.05).@*Conclusions@#Compared to photon VMAT or IMRT, carbon ion could reduce the doses to optical critical organs around tumors. Thus, carbon ion radiotherapy has potential to reduce patients′ radiation related side-effects.
RESUMO
Objective To evaluate the dosimetric difference between carbon ion radiotherapy and photon radiotherapy for treating tumors at lacrimal system. Methods Using the CT images of 10 patients with tumors at lacrimal system, the carbon ion plan, the photon volume intensity modulation plan ( VMAT) and the fixed wild photon intensity modulation radiotherapy ( IMRT) plan were generated. The prescription was 54 Gy(RBE) in 18 fractions for clinical target volume (CTV) and 63 Gy(RBE) in 18 fractions for CTV-boost. Dosimetric differences of organ at risks were compared based on the same planning target volumes ( PTVs) with similar dose coverages. Results There was no statistically significant difference in the PTV coverage among three plans ( P>0. 05) . Compared to VMAT and IMRT plans, carbon ion plans reduced the mean doses of eyeballs, mean doses and near-maximum doses of optical nerves of both ipsilateral ( t=7. 35, 3. 79, 4. 66, 8. 48, 2. 52, 2. 76, P<0. 05 ) and contralateral eyes ( t=3. 87, 10. 49, 9. 16, 4. 43, 6. 53, 5. 12, P<0. 05), while the mean dose of brain was decreased from(5. 65± 3. 58) and ( 5. 76 ± 2. 09 ) Gy ( RBE ) to ( 0. 81 ± 0. 90 ) Gy ( RBE ) ( t= 6. 76, 17. 33, P<0. 05 ) . Conclusions Compared to photon VMAT or IMRT, carbon ion could reduce the doses to optical critical organs around tumors. Thus, carbon ion radiotherapy has potential to reduce patients' radiation related side-effects.
