Manual qualitative analysis of IR imaging

Qualitative analysis was performed by two experienced head and neck radiologists who were unaware of the histological results and the contrast-enhanced CT results using Infrec Analyzer 2.6 software (NEC Corp., Japan) with manual brightness and contrast adjustment. Disagreements between two radiologists were resolved via consensus. In this study, IR criteria for the detection of metastasis were modified from those used in breast cancer^19,20. The presence of at least one of the following criteria (Fig. 2) was considered a positive indicator for cervical lymph nodal metastasis: (a) increased vascular density with a tortuous vascular morphologic pattern or aberrant vasculature in the region of interest (ROI) but not in the contralateral side; (b) unilateral dilated vasculature such as a facial artery, a submental artery or a carotid artery; (c) a surface temperature difference >1 °C in the ROI compared to the mirror image site on the contralateral neck; (d) a bulging outline contour with elevated surface temperature in and around the ROI.

Manual qualitative analysis of IR imaging. (a) An asymmetric thermographic pattern that includes an elevated surface temperature and a vascular pattern; (b) Increased vascular density with a tortuous vascular morphologic pattern; (c) A unilateral dilated vascular image; (d) A surface temperature difference of over 1 °C.