Nasopharynx

Imaging of nasopharyngeal tumor requires the greatest expenditure of techniques to confirm the status of bone as well as perineural involvement.38 Confirming that disease is limited to the mucosal compartment allows treatment of nasopharyngeal lesions with a standard radiation portal while sparing the cranial nerves (particularly cranial nerve II) and the temporal lobes is the main goal of imaging. While one modality may be adequate and efficient for follow-up surveillance, it is the combination of CT and MRI that is crucial at the baseline for this disease. MRI is more sensitive than CT for invasion of the cancellous bone of the central skull base. CT is more sensitive to early involvement of the overlying cortical bone of the sphenoid and basi occiput. The minor change in the bone cortex that is not well shown with MRI may have prognostic implications, but will not likely change the treatment portal. MRI may be the single best staging exam (Figure 3-16) given the greater sensitivity to perineural exten-sion,39 cavernous sinus extension4 and the more accurate estimation of cancellous bone involvement. MRI is adequate for nodal staging. Treatment planning is widely performed with CT although MRI-based planning continues to develop.

Imaging follow-up is best performed with the modality that is most compatible with the patients' condition. CT remains an efficient method for fol-

Figure 3-9. Coronal coincidence FDG image of the upper body.

(1) Clinically symptomatic metastatic lower left cervical lymph node.

(2) Primary base of tongue lesion, occult on cross-sectional imaging.

(3) Normal intensity brain activity.

Figure 3-9. Coronal coincidence FDG image of the upper body.

(1) Clinically symptomatic metastatic lower left cervical lymph node.

(2) Primary base of tongue lesion, occult on cross-sectional imaging.

(3) Normal intensity brain activity.

Figure 3-10. MRI images of sinus tumor. Sagittal upper and coronal lower images with T1 and T2 weighting. (1) Penetration through fovea ethmoidalis into extradural space. No brain invasion. (2) Displaced lamina papyracea without invasion of orbital fat or muscle cone. (3) Obstructed sphenoid sinus secretions, not tumor extension.

Figure 3-10. MRI images of sinus tumor. Sagittal upper and coronal lower images with T1 and T2 weighting. (1) Penetration through fovea ethmoidalis into extradural space. No brain invasion. (2) Displaced lamina papyracea without invasion of orbital fat or muscle cone. (3) Obstructed sphenoid sinus secretions, not tumor extension.

low-up surveillance imaging of the primary site and the neck. It is very reproducible between patients' visits and among different institutions. CT

does require intravenous contrast for detailed restaging, however. Patients receiving nephrotoxic chemotherapeutic agents should be followed with

Figure 3-11. Enhanced coronal T1-weighted MR image through mid-orbits. (1) Thickened first division of left trigeminal nerve due to neurotropic skin tumor at forehead. (2) Normal appearing first division of left trigeminal nerve.

Figure 3-12. Coronal T2-weighted MR image through cavernous sinuses. (1) Tumor extension into left cavernous sinus. (2) Intact dura stretched by expanding tumor. (3) Normal heterogeneous appearance of non-contrast MR of cavernous sinus.

MRI if their mucositis doesn't produce too much swallowing motion artifact. Scanning of both the primary site and comprehensive evaluation of the neck does result in a lengthy exam, however. A bonus for the MRI cohort is evaluation of the CNS white matter injury of the spinal cord, brainstem and optic nerves.

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