Dose Distribution Differences of IMRT and Helical Tomotherapy for Patients with Multiple Brain Metastases

Objective To analyze dose distribution differences of IMRT and helical tomotherapy(HT) plan for tumor and organs at risk in patients with multiple brain metastases receiving whole brain radiotherapy(WBRT) with simultaneous in-field boost(SIB). Methods Six patients with multiple brain metastases (2 to 5 lesions) underwent WBRT(40 Gy/22 f ) with SIB(55 Gy/22 f ) in HT and IMRT plan respectively. Pair comparison was used to analyze maximum and mean doses of whole brain, brainstem and optic nerve, homogeneity and conformity indices of PGTV and PTVwb in HT and IMRT plan. Results In IMRT and HT plan, mean doses of whole brain, brainstem were (44.97±3.2),(42.48±4.0) and (41.56±2.1),(40.87±2.2) Gy(P=0.02，P=0.04), respectively; Brainstem Dmax was (44.95±4.4) and (42.35±3.2) Gy(P=0.02), respectively; Mean and maximum doses of left and right optic nerves were with no significant difference; Conformity indices of PGTV, PTVwb in IMRT and HT were (0.95 ± 0.023), (0.92±0.06) and (0.98±0.014), (0.96±0.03) respectively(P=0.02,P =0.02); Homogeneity indices of PGTV, PTVwb in IMRT and HT were (1.11±0.045), (1.22±0.03) and (1.06±0.048), (1.14±0.02) respectively(P=0.00，P=0.00). Conclusion Homogeneity and conformity of doses distribution in PGTV and PTVwb were better and brainstem radiation dose was lower in HT plan than those in IMRT in patients with multiple brain metastases receiving WBRT with SIB.