Automatic one-click planning for hippocampal-avoidance whole-brain irradiation in RayStation

Abstract

This study aimed to verify the accuracy of auto-contouring and auto-dose optimization for hippocampal-avoidance whole-brain radiation therapy (HA-WBRT). Head computed tomography (CT) images of 15 patients were selected. The regions of interest, containing the brain, hippocampus, eyes, and lacrimal glands, were contoured manually and automatically on CT images. They were compared and evaluated for concordance rates using the Simpson coefficient. To verify the performance of dose optimization, auto-dose planning was compared with manual planning for 15 cases. All optimization plans were performed using the volumetric modulated arc therapy technique. The automatically contoured brain showed a very high concordance rate with the manually contoured brain; the Simpson coefficient was 0.990 ± 0.01. Contrastingly, the concordance rate of the hippocampal contour was low at 0.642 ± 0.15 (right) and 0.500 ± 0.16 (left); however, the rate improved to 0.871 ± 0.09 (right) and 0.852 ± 0.11 (left) with an additional 3-mm margin. For 2% of each planning target volume with the prescribed dose (D2%) and Dmean, there was no significant difference between the automatic and manual plans (35.50 Gy vs 35.23 Gy; p = 0.233 and 33.09 Gy vs 32.84 Gy; p = 0.073, respectively). The D98% was significantly better for the manual plan than for the automatic plan (25.49 Gy vs 26.11 Gy; p < 0.01). Dmax and D100% for the hippocampus did not show any significant difference between the automatic and manual plans (15.65, 16.09 Gy (right, left) vs 15.51, 15.80 Gy; p = 0.804, 0.233 and 8.08, 8.03 Gy vs 8.13, 8.01 Gy; p = 0.495, 1 respectively). The accuracy of auto-contouring for HA-WBRT can be guaranteed by providing an appropriate margin, and the precision of the auto-dose optimization was comparable to that of the manual plan.

Keywords: Automatic planning; Brain metastasis; Hippocampal dose; Hippocampal-avoidance whole-brain radiation therapy; Lacrimal gland dose; Volumetric modulated arc therapy.