Dosimetric Comparison of Robotic and Linear Accelerator Multi-Leaf Collimator-Based Stereotactic Radiosurgery for Arteriovenous Malformation

摘要

Purpose: To investigate the dosimetric comparison of different collimators which are used in robotic radiosurgery (cyberknife-CK) and linear accelerator (LINAC) for stereotactic radiosurgery (SRS) in arteriovenous malformation (AVM). Materials and Methods: Twenty-five AVM patients were planned in CK using FIXED cone, IRIS collimator, and multi-leaf collimator (MLC) based in LINAC. Dosimetric comparison was performed using Paddick conformity index (CI Paddick ) and International Commission on Radiation Units and measurements (ICRU) homogeneity index (HI ICRU ), gradient score (GS), normal brain dose received by 10cc (D 10cc ) and critical structure (brain stem, optic chiasma, optic nerves) doses. Paired sample t -test was used for statistical analysis. Results: Mean treatment volume was 3.16cc (standard deviation ± 4.91cc). No significant deviation ( P =0.45, 0.237 for FIXED vs. IRIS and FIXED vs. MLC, respectively) was found in target coverage. For CI Paddick , the mean difference (MD) between FIXED- and MLC-based plans was 0.16( P = 0.001); For HI ICRU , difference between FIXED and IRIS was insignificant (0.5, P = 0.823); but, when FIXED versus MLC, the deviation was 7.99% ( P = 0.002). In FIXED- and MLC-based plans, significant difference was found in GS70 and GS40 ( P < 0.041 and 0.005, respectively). MD between FIXED- and MLC-based plans for normal brain for 5Gy, 10Gy, 12Gy, and 20Gy were 36.08cc ( P = 0.009), 7.12cc ( P = 0.000), 5.84cc ( P = 0.000) and 1.56cc ( P = 0.000), respectively. AVM volume <0.7cc should be treated with CK FIXED and >0.7cc were treated by using FIXED or IRIS collimators. AVM volume > 1.4cc can be treated by either LINAC MLC-based SRS or CK. Conclusion: Our study shows CK collimator (IRIS and FIXED) could be able to treat brain AVMs in any size. Linac MLC-based SRS has some limitations in terms of conformity and low-dose spillage, and advantages like reduced treatment time and MU.