Part 2:

TECHNIQUES

FUNCTIONAL IMAGING OF CNS NEOPLASMS

Limitations of Structural MR/CT Imaging:

1) Limited prognostic value

2) Poor indicator of true extent of tumor, especially in high grade lesions

3) Post-treatment changes (surgical, radiation) limit capability to detect tumor recurrence

4) Overlap in imaging appearance among tumor types and between tumors and non-neoplastic lesions, with potential implications for treatment approach

MAGNETIC RESONANCE SPECTROSCOPY (MRS)

Measures: Relative chemical composition of metabolically relevant compounds

Diagnostic Uses:

Very useful in distinguishing destructive lesions from neoplastic processes. "Classic" spectra occur in cerebral infarctions (including large lactate peak).

Advantages:

In certain specific situations, biopsy may be avoided (e.g. tumefactive lesion of demyelination mimics neoplasm => spectra suggests destructive demyelination).

Disadvantages:

Voxel size may be larger than lesion. Irregularly shaped lesions may not conform to voxel margins.