Weakly supervised segmentation of intracranial aneurysms using a 3D focal modulation UNet

Accurate identification and quantification of unruptured intracranial aneurysms (UIAs) are essential for the risk assessment and treatment decisions of this cerebrovascular disorder. Current assessment based on 2D manual measures of aneurysms on 3D magnetic resonance angiography (MRA) is sub-optimal and time-consuming. Automatic 3D measures can significantly benefit the clinical workflow and treatment outcomes. However, one major issue in medical image segmentation is the need for large well-annotated data, which can be expensive to obtain. Techniques that mitigate the requirement, such as weakly supervised learning with coarse labels are highly desirable. In this paper, we leverage coarse labels of UIAs from time-of-flight MRAs to obtain refined UIAs segmentation using a novel 3D focal modulation UNet, called FocalSegNet and conditional random field (CRF) postprocessing, with a Dice score of 0.68 and 95% Hausdorff distance of 0.95 mm. We evaluated the performance of the proposed algorithms against the state-of-the-art 3D UNet and Swin-UNETR, and demonstrated the superiority of the proposed FocalSegNet and the benefit of focal modulation for the task.