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Dosimetric Comparison of Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Radiotherapy for the Treatment of Multiple Intracranial Metastases

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X Liu

X Liu1*, Y Yin2 , (1) Shandong Cancer Hospital Affiliated to Shandong Shandong Cancer Hospital, Jinan, Shandong, (2) Shandong Cancer Hospital Affiliated to Shandong University, Jinan, Shandong


SU-I-GPD-T-364 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To evaluate the dosimetric differences of intensity-modulated radiotherapy(IMRT) and volumetric modulated arc radiotherapy (VMAT)for multiple intracranial metastases.

Methods: Ten patients with multiple intracranial metastases were included in this analysis. Three treatment techniques were designed for each patient: intensity-modulated radiotherapy with seven fixed field(IMRT), volumetric modulated arc radiotherapy with single 358° coplanar arc(VMAT1) and volumetric modulated arc radiotherapy with double 358° coplanar arcs(VMAT2) . Dose prescription was 60Gy to PTV in 30 fractions. All plans were normalized to the mean dose to PTV.The dose distribution in the target ,the dose to the organs at risk,total MU and delivery time in three techniques were compared.

Results: The best conformity and homogeneity in PTV were observed in V-MAT2 plans,no statistically significant differences were observed between IMRT and V-MAT1.For the maximum dose in lens,eyes and brainstem,the two VMAT plans were significantly lower than IMRT plan(p<0.05). For the maximum dose in optic nerves,the VMAT2 plans were statistically lower than IMRT plan(p<0.05).For the mean dose to normal brain tissue, no statistically differences were observed in the three techniques. V-MAT2 plans showed the highest values in the normal brain tissue volume receiving 5Gy and 10 Gy doses.In the normal brain tissue volume receiving 20Gy,30Gy and 40 Gy doses,IMRT and VMAT2 plans showed the highest and lowest values respectively. Compared with IMRT plans,the average monitor units reduced 29% and 24% in VMAT1 and VMAT2 plans and the delivery time was significantly shorter in VMAT plans.

Conclusion: Comparing to IMRT plans, VMAT plans showed similar or better in the target dose distribution,reduced irradiation doses on organs in risk and moreover significantly decreased the monitor units and delivery time.

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