Which imaging modality can be used to characterize central nervous system tumors?

• A. CT
• B. MRI
• C. PET
• D. Ultrasound

Answer: (C)

Characterizing central nervous system tumors relies on an imaging tool that best shows brain tissue detail and how a lesion interacts with surrounding structures. Magnetic resonance imaging provides superior soft-tissue contrast, multiple planes, and the ability to use contrast to reveal tumor margins, peritumoral edema, and invasion. This combination makes MRI the most informative single study for identifying the size, location, and extent of a brain tumor, which is crucial for planning treatment. Advanced MRI techniques (like diffusion, perfusion, and spectroscopy) add even more detail about cellularity, blood flow, and metabolism, helping further characterize tumor type and grade.

Other modalities have useful roles but are not as effective for initial characterization. CT is excellent for acute hemorrhage and calcifications and is faster, but its soft-tissue contrast is inferior to MRI for delineating tumor tissue from normal brain and edema. Ultrasound isn’t suitable for intraparenchymal brain imaging in adults due to the skull, and PET, while valuable for assessing metabolic activity and distinguishing tumor recurrence from treatment effect in certain contexts, does not provide the detailed anatomical information MRI offers and is typically used as an adjunct rather than the primary means of characterization.