Automated Deep Learning-Based Finger Joint Segmentation in 3-D Ultrasound Images With Limited Dataset

Ultrasound imaging has shown promise in assessing synovium inflammation associated early stages of rheumatoid arthritis (RA). The precise identification of the synovium and the quantification of inflammation-specific imaging biomarkers is a crucial aspect of accurately quantifying and grading RA. In this study, a deep learning-based approach is presented that automates the segmentation of the synovium in ultrasound images of finger joints affected by RA. Two convolutional neural network architectures for image segmentation were trained and validated in a limited number of 2-D images, extracted from <i>N</i> = 18 3-D ultrasound volumes acquired from <i>N</i> = 9 RA patients, with sparse ground truth annotations of the synovium. Various augmentation strategies were employed to enhance the diversity and size of the training dataset. The utilization of geometric and noise augmentation transforms resulted in the highest dice score (0.768 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>±</mml:mo><mml:mspace></mml:mspace><mml:mn>0</mml:mn><mml:mo>.</mml:mo><mml:mn>031</mml:mn><mml:mo>,</mml:mo><mml:mspace></mml:mspace><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>6</mml:mn><mml:mo>)</mml:mo><mml:mo>,</mml:mo><mml:mspace></mml:mspace><mml:mi>and</mml:mi><mml:mspace></mml:mspace><mml:mi>intersection</mml:mi><mml:mspace></mml:mspace><mml:mi>over</mml:mi><mml:mspace></mml:mspace><mml:mi>union</mml:mi><mml:mspace></mml:mspace><mml:mo>(</mml:mo><mml:mn>0</mml:mn><mml:mo>.</mml:mo><mml:mn>624</mml:mn><mml:mspace></mml:mspace><mml:mo>±</mml:mo></mml:mrow></mml:math>0.040, <i>N</i> = 6), as determined via six-fold cross-validation. In addition, the segmentation model is used to generate dense 3-D segmentation maps in the ultrasound volumes, based on the available sparse annotations. The developed technique shows promise in facilitating more efficient and standardized workflow for RA screening using ultrasound imaging.