DTI could assess tumor microstructure in pediatric patients with brainstem glioma

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CHICAGO—Cellularity assessed with diffusion tensor imaging (DTI) at initial presentation is potentially an important parameter to further characterize tumor microstructure and predict clinical course in the pediatric population, according a study presented Monday in the Pediatric Radiology Series at the 94th annual meeting of the Radiological Society of North America (RSNA).

Hui Chen, MD, of the University of California, Los Angeles, presented the results of the study, which sought to determine regional variations of mean diffusivity (ADC) and fractional anisotropy in diffuse intrinsic brainstem glioma (DIBSG). The study also sought to compare ADC and FA with other tumors with different cellularity; as well as to compare ADC and FA with survival outcomes.

Chen noted that few studies have focused on the DTI qualities on these tumors, despite the high mortality rates.

Chen and colleagues collected a total of 454 DTI values from December 2004 to November 2008, and reviewed serial ADC and FA maps in 13 patients DIBSG (mean age of 7.2 years old). The researchers also measured the ADC and FA values of the tumors at the five standard axial levels of the brainstem: caudal midbrain; rostral pons; mid pons; caudal pons; and rostral medulla.

The researchers found that there was no statistically significant regional variation in initial ADC and initial FA values. When compared with cellular tumors, such as medulloblastoma, edendymoma and anaplastic astrocytoma, Chen reported that DIBSG had a higher mean ADC (1.047 x 10(-3) mm2/sec). However, the researchers also found no significant variation for FA values of DIBSG. Chen also reported that they found a linear inverse correlation between FA and ADC values for DIBSG, normal brain and pilocytic astrocytoma.

Importantly, the investigators found a statistically significant positive correlation between initial ADC values and survival time. Chen said that the findings suggest low ADC values correlate with poorer prognosis.

However, ADC and FA yielded different results with the age of the patient. While the researchers found significant positive correlation between initial ADC values and age of presentation, they did not find any significant correlations between FA values or age at presentations and survival time.  
Chen concluded that there is a significant regional variation in ADC values, which suggests the necessity of standardized analysis at multiple anatomic levels. However, she also stressed the needed for longer, much more long-term studies to validate these findings.