Intra-operative resection margin model of tongue carcinoma using 3D reconstructed ultrasound

Abstract

Background: Although an oncological surgeon aims to remove tongue cancer with a margin of no less than 5 mm, 85% of margins are reported as close or positive (<5 mm). Currently, the only feedback on the status of margins is provided by frozen sections and standard post-operative histopathological assessment. Objectives: To introduce a novel method for assessing intra-operative margins that includes intra-operative visual feedback by means of 3D ultrasound and to assess its feasibility. Methods: Electromagnetically tracked ultrasound imaging was used to scan tongue cancer (n = 8) directly after excision. Each specimen was fully submerged in saline during acquisition and scanned without contact between tissue and transducer. This imaging technique enables rapid generation of 3D margin models. A radiologist manually segmented the specimen and tumour intra-operatively in the 3D ultrasound volumes. The margins were computed in 3D by calculating the closest Euclidean distances between the segmented specimen and tumour boundary. Results: Using a colourmap, our proposed 3D ultrasound generated a 3D model representing the margins of the entire specimen. This model was easy to interpret and provided the surgeon with feedback on the margins intra-operatively. Conclusions: Electromagnetically tracked ultrasound imaging enables assessment of the margins of tongue cancer of the entire specimen. Future research will have to focus on improving the image reconstruction quality, the development of fully automated segmentation of tumours in 3D ultrasound and the correlation between the margins assessed by 3D ultrasound and histopathology.

Keywords

• Electromagnetically-tracking
• Ultrasonography
• Resection margin assessment
• Tongue cancer
• Three-dimensional imaging