Tomographic 3D Ultrasound for Thyroid Volumetry-A Comparison Between Multiplanar 2D and 3D Imaging Methods

Area of Science:

• Medical Imaging
• Radiology
• Endocrinology

Background:

• Accurate thyroid volume measurement is crucial for diagnosing and managing thyroid conditions and radioiodine therapy.
• Two-dimensional B-mode ultrasound (Bmode-2D-US) is standard but has observer dependence and accuracy issues.
• Tracked three-dimensional ultrasound (3D-US) is a potential radiation-free alternative, but comparative studies are limited.

Purpose of the Study:

• To compare the accuracy and reproducibility of tracked 3D-US modalities against conventional Bmode-2D-US and other imaging techniques.
• To evaluate the impact of observer experience on thyroid volume measurements across different ultrasound methods.

Main Methods:

• A multi-modality phantom with realistic thyroid lobes was used for ground truth volume verification.
• Six observers performed measurements using Bmode-2D-US, electromagnetically tracked 3D-US (EM-3D-US), inertial-measurement-unit-tracked 3D-US (IMU-3D-US), and optically tracked 3D-US (Opt-3D-US).
• Computed tomography (CT) and magnetic resonance imaging (MRI) were included for comparison; inter- and intraobserver variability were assessed.

Main Results:

• All 3D-US methods demonstrated reduced inter- and intraobserver variability compared to Bmode-2D-US.
• 3D-US achieved variability comparable to CT and superior to MRI, with similar mean accuracy.
• Bmode-2D-US exhibited high observer dependence, influenced by operator experience; EM-3D-US and Opt-3D-US were less sensitive to movement quality than IMU-3D-US.

Conclusions:

• Tracked 3D-US offers a promising, radiation-free approach for thyroid volumetry, outperforming conventional Bmode-2D-US.
• This technology enhances reproducibility and accuracy, particularly for operators with varying experience levels.
• Phantom-based evaluation supports 3D-US as a valuable tool for thyroid imaging and management.