In-vivo optical imaging in head and neck oncology: basic principles, clinical applications and future directions

Abstract

Head and neck cancers become a severe threat to human's health nowadays and represent the sixth most common cancer worldwide. Surgery remains the first-line choice for head and neck cancer patients. Limited resectable tissue mass and complicated anatomy structures in the head and neck region put the surgeons in a dilemma between the extensive resection and a better quality of life for the patients. Early diagnosis and treatment of the pre-malignancies, as well as real-time in vivo detection of surgical margins during en bloc resection, could be leveraged to minimize the resection of normal tissues. With the understanding of the head and neck oncology, recent advances in optical hardware and reagents have provided unique opportunities for real-time pre-malignancies and cancer imaging in the clinic or operating room. Optical imaging in the head and neck has been reported using autofluorescence imaging, targeted fluorescence imaging, high-resolution microendoscopy, narrow band imaging and the Raman spectroscopy. In this study, we reviewed the basic theories and clinical applications of optical imaging for the diagnosis and treatment in the field of head and neck oncology with the goal of identifying limitations and facilitating future advancements in the field.

Fig. 1

Optical properties of tissue and the different wavelength range of each fluorescent imaging devices. Image resolution improves with shorter wavelengths, and tissue penetration increases with longer wavelengths. Hemoglobin (Hb) dominates absorption of light in the visible (400–700 nm). Water absorption plays a small role in the infrared (>900 nm). The extinction coefficients for Hb (blue), oxyhaemoglobin (HbO₂; red) and water (black) are shown. AFI, autofluorescence imaging; NBI, narrow band imaging; WLE, white-light endoscopy. Reprinted with permission from ref. by BMJ Publishing Group Ltd. and Copyright Clearance Center

Fig. 2

Current AFI devices to identify the neoplastic transformation and their representative images showing the tumor detections. Neoplastic tissues appear darker (due to autofluorescence loss) compared with the healthy surroundings when illuminated by AFI devices. The appearances of each instrument, diagnosis of lesions, brightfield images, and autofluorescence images are displayed. AFI, autofluorescence imaging; Dx, diagnosis; SCC, squamous cell carcinoma. Original figures can be found in refs. –

Fig. 3

Representative TFI image and overlapping wavelength region of IRDye800CW and ICG. a NIR Device detecting SCC of oral cavity in Panitumumab-IRDye800CW clinical trial patient. b Wavelength region of IRDye800CW and ICG are overlapped, thus NIR camera system designed for ICG imaging could be utilized for TFI guided surgery. TFI, targeted fluorescence imaging; ICG, Indocyanine green; NIR: Near-infrared; SCC, squamous cell carcinoma