Abstract
BackgroundWhole brain radiotherapy (WBRT) can impair patients’ cognitive function. Hippocampal avoidance during WBRT can potentially prevent this side effect. However, manually delineating the target area is time-consuming and difficult. Here, we proposed a credible approach of automatic hippocampal delineation based on convolutional neural networks.MethodsReferring to the hippocampus contouring atlas proposed by RTOG 0933, we manually delineated (MD) the hippocampus on the MRI data sets (3-dimensional T1-weighted with slice thickness of 1 mm, n = 175), which were used to construct a three-dimensional convolutional neural network aiming for the hippocampus automatic delineation (AD). The performance of this AD tool was tested on three cohorts: (a) 3D T1 MRI with 1-mm slice thickness (n = 30); (b) non-3D T1-weighted MRI with 3-mm slice thickness (n = 19); (c) non-3D T1-weighted MRI with 1-mm slice thickness (n = 11). All MRIs confirmed with normal hippocampus has not been violated by any disease. Virtual radiation plans were created for AD and MD hippocampi in cohort c to evaluate the clinical feasibility of the artificial intelligence approach. Statistical analyses were performed using SPSS version 23. P < 0.05 was considered significant.ResultsThe Dice similarity coefficient (DSC) and Average Hausdorff Distance (AVD) between the AD and MD hippocampi are 0.86 ± 0.028 and 0.18 ± 0.050 cm in cohort a, 0.76 ± 0.035 and 0.31 ± 0.064 cm in cohort b, 0.80 ± 0.015 and 0.24 ± 0.021 cm in cohort c, respectively. The DSC and AVD in cohort a were better than those in cohorts b and c (P < 0.01). There is no significant difference between the radiotherapy plans generated using the AD and MD hippocampi.ConclusionThe AD of the hippocampus based on a deep learning algorithm showed satisfying results, which could have a positive impact on improving delineation accuracy and reducing work load.
Highlights
Brain metastases are an increasingly common complication of systemic cancers [1, 2]
Eric L Chang reported that patients treated with stereotactic radiosurgery (SRS) combined with Whole brain radiotherapy (WBRT) were at a greater risk of a significant decline in cognitive function compared with patients that received SRS alone [6]
The Radiation Therapy Oncology Group (RTOG) 0212 [7] and 0214 [8] trials have demonstrated that WBRT without avoidance of the hippocampus increased cognitive impairment by 3 times at 6 and 12 months after WBRT, which is significantly higher than the placebo group
Summary
20–40% of the patients with primary extra-cranial cancer develop brain metastases during the course of their disease [3], which is usually associated with poor prognosis requiring urgent treatment [4]. Patients receiving brain RT, especially WBRT, often experience radiation-related side effects. Eric L Chang reported that patients treated with SRS combined with WBRT were at a greater risk of a significant decline in cognitive function compared with patients that received SRS alone [6]. The Radiation Therapy Oncology Group (RTOG) 0212 [7] and 0214 [8] trials have demonstrated that WBRT without avoidance of the hippocampus increased cognitive impairment by 3 times at 6 and 12 months after WBRT, which is significantly higher than the placebo group. Whole brain radiotherapy (WBRT) can impair patients’ cognitive function. Hippocampal avoidance during WBRT can potentially prevent this side effect. We proposed a credible approach of automatic hippocampal delineation based on convolutional neural networks
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