Multi-label segmentation of carpal bones in MRI using expansion transfer learning

Physics in Medicine and Biology, vol. 70, pp. 055004

Abstract

Abstract Objective. The purpose of this study was to develop a robust deep learning approach trained with a small in-vivo MRI dataset for multi-label segmentation of all eight carpal bones for therapy planning and wrist dynamic analysis. Approach. A small dataset of 15 3.0-T MRI scans from five health subjects was employed within this study. The MRI data was variable with respect to the field of view (FOV), wide range of image intensity, and joint pose. A two-stage segmentation pipeline using modified 3D U-Net was proposed. In the first stage, a novel architecture, introduced as expansion transfer learning (ETL), cascades the use of a focused region of interest (ROI) cropped around ground truth for pretraining and a subsequent transfer by an expansion to the original FOV for a primary prediction. The bounding box around the ROI generated was utilized in the second stage for high-accuracy, labeled segmentations of eight carpal bones. Different metrics including dice similarity coefficient (DSC), average surface distance (ASD) and hausdorff distance (HD) were used to evaluate performance between proposed and four state-of-the-art approaches. Main results. With an average DSC of 87.8 %, an ASD of 0.46 mm, an average HD of 2.42 mm in all datasets (96.1 %, 0.16 mm, 1.38 mm in 12 datasets after exclusion criteria, respectively), the proposed approach showed an overall strongest performance than comparisons. Significance. To our best knowledge, this is the first CNN-based multi-label segmentation approach for MRI human carpal bones. The ETL introduced in this work improved the ability to localize a small ROI in a large FOV. Overall, the interplay of a two-stage approach and ETL culminated in convincingly accurate segmentation scores despite a very small amount of image data.

Authors 7

1. Stefan Raith Aachen Department of Oral and Maxillofacial Surgery

   RWTH Aachen University · Universitätsklinikum Aachen

   Affiliation as printed

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Aachen, Germany

   Inzipio GmbH, Aachen, Germany

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30. 52074 Aachen, Aachen, 52074 , GERMANY

2. Matthias Deitermann

   University of Stuttgart

   Affiliation as printed

   Inzipio GmbH, Aachen, Germany

   University of Stuttgart, Stuttgart, Germany

   Inzipio GmbH, Krantzstraße 7 Gebäude 80 52070 Aachen, Aachen, 52070 , GERMANY

3. Tobias Pankert Aachen Department of Oral and Maxillofacial Surgery

   RWTH Aachen University · Universitätsklinikum Aachen

   Affiliation as printed

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Aachen, Germany

   Inzipio GmbH, Aachen, Germany

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30. 52074 Aachen, Aachen, 52074 , GERMANY

4. Ali Modabber Aachen Department of Oral and Maxillofacial Surgery

   RWTH Aachen University · Universitätsklinikum Aachen

   Affiliation as printed

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Aachen, Germany

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30. 52074 Aachen, Aachen, 52074 , GERMANY

5. Frank Hölzle Aachen Department of Oral and Maxillofacial Surgery

   RWTH Aachen University · Universitätsklinikum Aachen

   Affiliation as printed

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Aachen, Germany

   Department of Oral and Maxillofacial Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30. 52074 Aachen, Aachen, 52074 , GERMANY

6. Frank Hildebrand Aachen Department of Orthopaedics, Trauma and Reconstructive Surgery

   RWTH Aachen University · Universitätsklinikum Aachen

   Affiliation as printed

   Department of Orthopaedics, Trauma and Reconstructive Surgery, University Hospital RWTH Aachen, Aachen, Germany

   Universitatsklinikum Aachen, Pauwelsstraße 30. 52074 Aachen, Aachen, Nordrhein-Westfalen, 52074 , GERMANY

7. Jörg Eschweiler

   University Hospital in Halle · BG Klinikum Bergmannstrost Halle

   Affiliation as printed

   Department of Trauma and Reconstructive Surgery, BG Hospital Bergmannstrost, Halle (Saale), Germany

   Department of Trauma and Reconstructive Surgery, University Hospital, Halle (Saale), Germany

   Department of Trauma and Reconstructive Surgery, BG Hospital Bergmanntrost, Merseburger Straße 165 06112 Halle, Halle, Sachsen-Anhalt, 06112, GERMANY