MLRecon: Robust Markerless Freehand 3D Ultrasound Reconstruction via Coarse-to-Fine Pose Estimation

TL;DR

MLRecon introduces a markerless 3D ultrasound reconstruction method using a single RGB-D camera, achieving high accuracy and robustness without intrusive sensors, suitable for resource-limited clinical environments.

Contribution

The paper presents a novel markerless 3D US reconstruction framework with drift-resilient pose tracking, divergence detection, and pose refinement, surpassing existing sensorless and sensor-aided methods.

Findings

Achieves average position error as low as 0.88 mm on complex trajectories.

Provides high-quality 3D reconstructions with sub-millimeter surface accuracy.

Outperforms competing methods in accuracy and robustness.

Abstract

Freehand 3D ultrasound (US) reconstruction promises volumetric imaging with the flexibility of standard 2D probes, yet existing tracking paradigms face a restrictive trilemma: marker-based systems demand prohibitive costs, inside-out methods require intrusive sensor attachment, and sensorless approaches suffer from severe cumulative drift. To overcome these limitations, we present MLRecon, a robust markerless 3D US reconstruction framework delivering drift-resilient 6D probe pose tracking using a single commodity RGB-D camera. Leveraging the generalization power of vision foundation models, our pipeline enables continuous markerless tracking of the probe, augmented by a vision-guided divergence detector that autonomously monitors tracking integrity and triggers failure recovery to ensure uninterrupted scanning. Crucially, we further propose a dual-stage pose refinement network that explicitly disentangles high-frequency jitter from low-frequency bias, effectively denoising the trajectory while maintaining the kinematic fidelity of operator maneuvers. Experiments demonstrate that MLRecon significantly outperforms competing sensorless and sensor-aided methods, achieving average position errors as low as 0.88 mm on complex trajectories and yielding high-quality 3D reconstructions with sub-millimeter mean surface accuracy. This establishes a new benchmark for low-cost, accessible volumetric US imaging in resource-limited clinical settings.