The feasibility of endoscopy-CT image registration in the head and neck without prospective endoscope tracking

• Published in: PloS one Vol. 12; no. 5; p. e0177886
• Main Authors: Ingram, W. Scott, Yang, Jinzhong, Beadle, Beth M., Wendt, Richard, Rao, Arvind, Wang, Xin A., Court, Laurence E.
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.05.2017; Public Library of Science (PLoS)
• Subjects: 3-D graphics; Accuracy; Adult; Algorithms; Biocompatibility; Bioinformatics; Biology and Life Sciences; Biopsy; Cancer; Cancer therapies; Care and treatment; CAT scans; Computation; Computed tomography; Computer applications; Computer programs; Computer vision; Condensation; Data acquisition; Data collection; Data processing; Delineation; Diagnosis; Edema; Endoscopes; Endoscopy; Engineering and Technology; Feasibility Studies; Female; Fluorescence; Frames; Ground truth; Head; Head & neck cancer; Head and neck cancer; Head and Neck Neoplasms - diagnostic imaging; Humans; I.R. radiation; Image processing; Image Processing, Computer-Assisted - methods; Imaging techniques; Inspection; Magnetic resonance imaging; Male; Medical imaging; Medical instruments; Medicine and Health Sciences; Mucosa; NMR; Nodules; Nuclear magnetic resonance; Oncology; Optimization; Patients; Phantoms, Imaging; Physics; Position (location); Projection; Radiation; Radiation dosage; Radiation therapy; Radiotherapy; Registration; Research and Analysis Methods; Resonance; Sinus; Skull; Studies; Surgery; Tomography, X-Ray Computed; Toxicity; Tracking; United States > US; Texas
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0177886

Endoscopic examinations are frequently-used procedures for patients with head and neck cancer undergoing radiotherapy, but radiation treatment plans are created on computed tomography (CT) scans. Image registration between endoscopic video and CT could be used to improve treatment planning and analysis of radiation-related normal tissue toxicity. The purpose of this study was to explore the feasibility of endoscopy-CT image registration without prospective physical tracking of the endoscope during the examination. A novel registration technique called Location Search was developed. This technique uses physical constraints on the endoscope's view direction to search for the virtual endoscope coordinates that maximize the similarity between the endoscopic video frame and the virtual endoscopic image. Its performance was tested on phantom and patient images and compared to an established registration technique, Frame-To-Frame Tracking. In phantoms, Location Search had average registration errors of 0.55 ± 0.60 cm for point measurements and 0.29 ± 0.15 cm for object surface measurements. Frame-To-Frame Tracking achieved similar results on some frames, but it failed on others due to the virtual endoscope becoming lost. This weakness was more pronounced in patients, where Frame-To-Frame tracking could not make it through the nasal cavity. On successful patient video frames, Location Search was able to find endoscope positions with an average distance of 0.98 ± 0.53 cm away from the ground truth positions. However, it failed on many frames due to false similarity matches caused by anatomical structural differences between the endoscopic video and the virtual endoscopic images. Endoscopy-CT image registration without prospective physical tracking of the endoscope is possible, but more development is required to achieve an accuracy suitable for clinical translation.