A Study of Dose Painting Guided by Three-Dimensional Arterial Spin Labeling for Non-Enhancing Low-Grade Gliomas During Radiotherapy

Background: The purpose of this study was to investigate the feasibility and dosimetric characteristics of dose painting for non-enhancing low-grade gliomas (NE-LGGs) guided by three - dimensional arterial spin labeling (3D-ASL) . Methods: : Eighteen patients with NE-LGGs were enrolled. 3D-ASL, T2 fluid-attenuated inversion recovery (T2 Flair) and contrast-enhanced T1-weighted magnetic resonance images were obtained. The gross tumor volume (GTV) was delineated on the T2 Flair . The hyper-perfusion region of the GTV (GTV-ASL) was determined by 3D-ASL, and the GTV-SUB was obtained by subtracting the GTV-ASL from the GTV. The clinical target volume (CTV) was created by isotropically expanding the GTV by 1cm. The planning target volume (PTV), PTV-ASL were obtained by expanding the external margins of the CTV, GTV-ASL, respectively. PTV-SUB was generated by subtracting PTV-ASL from PTV. Three plans were generated for each patient: a conventional plan (plan1) without dose escalation delivering 95%-110% of 45-60Gy in 1.8–2Gy fractions to the PTV and two dose-painted plans (plan2 and plan3) with dose escalating by 10%-20% (range, 50-72Gy) to the PTV-ASL based on plan1. The plan3 was obtained from plan2 without the maximum dose constraint. The dosimetric differences among the three plans were compared. Results: : The volume ratio of the PTV-ASL to the PTV was (23.49±11.94) % ( Z =-3.724, P =0.000). Compared with plan 1, D 2% , D 98% and D mean of PTV-ASL increased by 14.67%,16.17% and 14.31% in plan2 and 19.84%,15.52% and14.27% in plan3, respectively ( P <0.05); the D 2% of the PTV, PTV-SUB increased by 11.89% and 8.34% in plan2, 15.89% and 8.49% in plan3, respectively (P0.05). In plan2 and plan3, the conformity indexes decreased by 18.60% and 12.79%; while the homogeneity index increased by 1.43 and 2 times ( P <0.05). Compared with plan1, the D 0.1cc of brain stem and D max of optic chiasma were slightly increased in plan 2 and plan 3, and the absolute doses met the dose constraint. The doses of the other organs at risk (OARs) were similar among the three plans ( P >0.05). Conclusions: : The dose delivered to hyper-perfusion region derived from 3D-ASL can increased by 10-20% while respecting the constraints to the OAR, which provides a basis for future individualized and precise radiotherapy for NE-LGGs.