unenhanced T1-weighted images to detect skull base involvement and fat planes (in at least an axial and sagittal plane)
A T2-weighted fast spin-echo sequence in axial plane is used for the additional assessment of early parapharyngeal tumor spread, paranasal sinus invasion, middle ear effusions, and detection of cervical lymph nodes.
Axial and coronal contrast-enhanced T1-weighted images (with and without fat suppression) are used to detect tumor extent, including perineural spread and intracranial extension of the tumor. The slice thickness is 3–5 mm
T1：肿瘤局限于鼻咽部，或累及口咽或鼻腔但无咽旁间隙侵犯
49-year-old woman with nasopharyngeal carcinoma (NPC) localized to nasopharynx (T1). Axial contrast-enhanced T1-weighted image shows small NPC (short arrows) centered in left Rosenmüller fossa (long arrow), which is the most common site for this cancer, and involving posterior wall. Tumor is confined to nasopharynx, and there is small metastatic left retropharyngeal node (curved arrow)
T2：肿瘤侵犯咽旁间隙或翼内/外肌、椎前肌肉
50-year-old man with nasopharyngeal carcinoma (NPC) with parapharyngeal extension (T2). Axial contrast T1-weighted image shows NPC (white arrows) with left parapharyngeal extension and involvement of parapharyngeal fat space. Note normal levator palatini muscle (red arrow), tensor palatini muscle (blue arrow), pharyngobasilar fascia (black arrow), and fat space (yellow arrow) on normal right side
T3：肿瘤侵犯颅底骨质、颈椎翼状结构或鼻旁窦
58-year-old man with nasopharyngeal carcinoma with prevertebral extension (T2). Axial T1-weighted contrast-enhanced image shows nasopharyngeal carcinoma (straight arrows) with extensive spread predominantly posteriorly into longus muscles (arrowheads) and clivus (curved arrows). Patient with nasopharyngeal carcinoma (NPC) with skull base invasion and pterygoid sclerosis (T3). Axial CT bone window shows large NPC filling nasopharynx and nasal cavity with bony destruction of sphenoid bone, including right pterygoid base, which also shows sclerosis (arrow). Right middle ear effusion is present.
T4：肿瘤有颅内侵犯、或颅神经、下咽（C3）、眼眶、腮腺或超出翼外肌外侧
Coronal T1-weighted contrast-enhanced MRI shows NPC (straight arrows) with skull base invasion at foramen ovale (arrowhead) with invasion into cavernous sinus (curved arrow). Coronal T1-weighted contrast-enhanced MRI shows invasion of NPC (straight arrows) into foramen lacerum (arrowheads), where it encases carotid artery and extends into cavernous sinus (curved arrow). Axial T1-weighted contrast-enhanced MRI shows NPC invading pterygopalatine fossa (circle), pterygomaxillary fissure (arrow), and vidian canal (arrowhead).
references：
American Journal of Roentgenology. 2012;198: 11-18. 10.2214/AJR.11.6954（https://www.ajronline.org/doi/full/10.2214/AJR.11.6954）
