Imaging Modalities
MRI
MRI has superior soft tissue contrast resolution with better assessment
of soft tissue spatiality and extension and bone marrow involvement
compared to CT27,28.
MRI with post contrast T1WI with fat saturation is the imaging modality
of choice for evaluation of perineural tumor spread although gross
perineural spread may be seen with contrast-enhanced CT30,31.
MRI sequences for skull base protocol should include T1WI and T2WI with
FS and contrast-enhanced T1WI with FS in axial and coronal planes.
Precontrast T1WI without FS allows for assessment of bone marrow
replacement and abnormalities of adipose tissue within the extracranial
spaces adjacent to skull base tumors as well as detection of intrinsic
T1 hyperintensity if present. Intrinsic T1 hyperintensity within tumors
may be secondary to intratumoral hemorrhage, fat, mineralization or
melanin 32. Images
should be obtained with thin slices (slice thickness <3 mm). Sagittal images provide additional information regarding
craniocaudal extension of the lesions. Detailed evaluation of cranial
nerves is required for skull base and temporal bone tumors; dedicated MR
sequences including high-resolution 3D T2WI, pre- and post-contrast 3D
T1WI with multiplanar reformations of cranial nerves are recommended at
the temporal bone and skull base33,34.
Entire brain imaging is necessary to assess the integrity of the
subjacent brain and dura. The role of advanced MRI techniques such as
DWI, MR perfusion, or MR spectroscopy remains under investigation in
research 35. MRA and
MRV (or CTA/CTV) are adjunctive radiological exams that can be used to
assess vascular anatomy (compression, displacement, invasion)23.