S Zhang¹*, R Yang² , C Shi³ , J Li⁴ , H Zhuang⁵ , S Tian⁶ , J Wang⁷ , (1) Peking University Third Hospital, Beijing, ,(2) Peking University Third Hospital, Beijing, ,(3) Memorial Sloan Kettering Cancer Center, Marlboro, NJ, (4) Peking University Third Hospital, Beijing, ,(5) Peking University Third Hospital, Beijing, ,(6) Peking University Third Hospital, Beijing, ,(7) Peking University Third Hospital, Beijing,

• 
  S Zhang

(Tuesday, 7/16/2019) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 7

Purpose: To compare plan quality and delivery efficiency of non-coplanar VMAT (NC-VMAT) with coplanar VMAT (C-VMAT), IMRT and CyberKnife (CK) plans for multiple brain metastases.

Methods: For 15 brain metastases patients, NC-VMAT, C-VMAT, IMRT and CK plans with a prescription dose of 30 Gy in 3 fractions were generated. NC-VMAT and C-VMAT plans consisted of 4 non-coplanar arcs and 2 full coplanar arcs, respectively. IMRT plans were designed with 7 coplanar fields. All plans were generated to cover 95% volume of the planning target volume with the prescription dose. Gradient index (GI), conformity index (CI), normal brain tissue volume (V3 Gy-V24 Gy), monitor units (MUs) and beam on time (BT) were evaluated.

Results: GI was the lowest for CK (3.49±0.65), followed by NC-VMAT (4.21±1.38), C-VMAT (4.87±1.35) and IMRT (5.36±1.98). CI was the largest for NC-VMAT (0.87±0.03), followed by C-VMAT (0.86±0.04), CK (0.86±0.07) and IMRT (0.85±0.05). Normal brain tissue volume at high-to-moderate dose spreads (V24 Gy-V9 Gy) was significantly reduced in NC-VMAT over that of IMRT and C-VMAT. Normal brain tissue volume for NC-VMAT was comparable with CK at high dose level (V24 Gy-V15 Gy) and larger than CK at moderate-to-low dose level (V12 Gy-V3 Gy). MUs was highest for CK (28733.59±7197.85), followed by IMRT (4128.40±1185.38), NC-VMAT (3105.20±371.23) and C-VMAT (2997.27±446.84). BT was longest for CK (30.25±7.32 min), followed by IMRT (2.95±0.85 min), NC-VMAT (2.61±0.07 min) and C-VMAT (2.30±0.23 min).

Conclusion: NC-VMAT plans generated rapid dose falloff and high conformity compared with IMRT and C-VMAT plans. NC-VMAT plans provided a comparable dose falloff with CK plans at high dose level and a slower dose falloff than CK plans at moderate-to-low dose level. NC-VMAT plans had less MUs and shorter BT than CK plans.

Funding Support, Disclosures, and Conflict of Interest: This study was supported by National natural Science Foundation of China (81071237) and Interdisciplinary Medicine Seed Fund of Peking University (BMU20160585)

Keywords

Brain, Dosimetry

Taxonomy

TH- External beam- photons: cyberknife

Contact Email