Clinical applications of quantitative T2 determination: a complementary MRI tool for routine diagnosis of suspected myelination disorders.

BACKGROUND AND AIMS: Though magnetic resonance imaging (MRI) plays an important role in studying pathological changes in central nervous system, a quantitative measure of contrast variance on MRI, allowing the detection of subtle signal variances in pathological processes, is not readily available for routine imaging. We report on the first experiences with evaluation of routine T2 relaxation time measurement as a diagnostic tool in routine imaging of suspected myelination disorders. METHODS: Twenty patients suffering from defined or suspected myelination disorders were examined by MRI. T2 relaxation time maps of the brain were derived from a triple spin echo sequence. T2 values were measured for each patient by regions of interest (ROI) analysis. As references age-dependent T2 prediction values in normal maturating brains were calculated by using a biexponentional function reported earlier. Deviations from these prediction values were used as an assisting tool both for detection of pathology and for monitoring of changes over time. These quantitative results were compared to conventional visual inspections by two independent neuroradiologists. RESULTS: In 18 patients with single diagnostic MRI, the T2 measurements were more graduated or definite in 9/18 cases, confirmatory in 9/18 cases. In two patients with MRI follow up, the dynamic clinical course of the disease had no correlate in visual inspection of the images but was associated with the quantitative T2 values. CONCLUSIONS: Quantitative T2 measurement is a promising tool for routine imaging as a complementary method in detecting and monitoring of suspected myelination disorders.

Screening for cerebellopontine angle tumors: is a CISS sufficient?

This study attempted to evaluate the reliability of ultra-thin T2-weighted imaging with a constructive interference in steady state (CISS) sequence as a screening method for tumors in the cerebellopontine angle. A retrospective study of 200 CISS examinations was made by five investigators. The examinations were inspected on plain film supported by clinical information. The interobserver agreement in the detection of lesions was analyzed. Fourteen cases (50% of the contrast-enhancing lesions) were rated pathological by all five readers. One case of subarachnoid lymphoma infiltration was overlooked by all five readers. Overall, six pathological lesions (median = 6, range 1-9) were not identified. The interobserver agreement for all pathological lesions was moderate (kappa=0.53; 95% CI, 0.43-0.62). The mean sensitivity was 77.8% (range 72.0-96.3%), and the mean specificity was 97.6% (range 94.8-100%). The median sensitivity for pathological lesions concerning only patients with acute sensorineural hearing loss (n=148, patients with 20 contrast-enhancing cases) was 86.6% (range 80-100%), and median specificity was 95.2% (range 84.4-96.9%) with a moderate interobserver agreement (kappa=0.55; 95% CI, 0.44-0.66). In our opinion the CISS sequence is a valuable addition to the examination of the cerebellopontine angle but lacks sufficient reliability for the detection of tumors of small size or of tumors adjacent to brain parenchyma or the temporal bone.