MR imaging analysis of the nasopharynx
| MR Imaging Features of NPC | Method of Analysis |
|---|---|
| Site | Walls: mucosa plus submucosa, including the lymphoid tissue layers in the mucosal space superficial to the fascia and pharyngeal muscles; wall subsites comprise the following: the pharyngeal recess, roof (above the level of the pharyngeal recess), and posterior/inferior walls (at or below the level of the pharyngeal recess) |
| Adenoid: central mucosal lymphoid tissues in the roof and upper posterior wall where lymphoid tissue within the nasopharynx is abundant | |
| Center: lateral, central, or diffuse | |
| Size | Volume (area of nasopharyngeal walls and adenoid on each slice × slice thickness) |
| Size asymmetry | Area difference between the right and left halves of the nasopharynx on the slice with the maximum difference, expressed as the %ΔA (difference in area between the 2 sides/area on smaller side × 100) |
| Signal intensity | Representative ROI is selected on the T1-weighted postcontrast image (T2-weighted signal intensity is measured at the corresponding site); signal intensity is expressed as a ratio of signal intensity/signal intensity of the belly of the lateral pterygoid muscle |
| Signal intensity asymmetry | Subjective signal intensity asymmetry between the right and left halves of the nasopharynx on T1-weighted postcontrast images |
| Homogeneity | Subjective assessment of signal intensity on T1-weighted postcontrast images, divided into homogeneous and heterogeneous |
| Deep mucosal white line | Line/band of greater contrast enhancement in the deep layer relative to the superficial layer of the nasopharyngeal wall at the site of the tumor, divided into absent, present with focal loss, and present and intact; assessment was not made at the adenoid |
| Adenoidal septa | Contrast-enhancing septa within the adenoid, divided into absent, present and distorted (displacement or partial loss excluding that caused by adenoidal cysts), and present and not distorted (intact and symmetric) |