Value of CT-MRI fusion in iodine-125 brachytherapy for high-grade glioma.

Purposes: To develop a fast, accurate and robust method of fusing Computed Tomography (CT) with pre-operative Magnetic Resonance Imaging (MRI) and evaluate the impact of using the fused data on the implantation of Iodine-125 (I-125) seeds for brachytherapy of high-grade gliomas (HGG). Methods: A study was performed on a cohort of 10 consecutive patients with HGG were treated by I-125 brachytherapy with CT-MRI fusion image guided (CMGB), and 10 patients treated with CT alone guided (CGB). Statistical analysis was performed to compare (1) the planning target volume, (2) the accuracy of location of catheters, (3) the target volume covered by 150% prescribe dose (V150), (4) the target volume covered by 200% prescribe dose (V200), and (5) the conformity index (CI) with or without fused data. Results: The median planning target volume was 50.1 cm(3) in CGB, and 56.25 cm(3) in CMGB with significant difference (p = 0.005). The accuracy of catheter insertion was 94.4% with CMGB and 78.9% with CGB. The median V150 and V200 was 45.32% vs 64.24% and 32.81% vs 53.17% in CGB and CMGB, respectively. There was significant difference for CI (83.5% vs. 74.5%, p < 0.05) in the two groups for the post-operative verification. Conclusions: The proposed MRI-CT fusion method enables a quantitative assessment of impact on HGG brachytherapy. The additional information obtained from the fused images can be utilized for more accurate delineation of lesion boundaries and targeting of catheters. Experimental results show that the fusion algorithm is robust and reliable in clinical practice.