Advantage of High b Value Diffusion-Weighted Imaging for Differentiation of Hemangioblastoma from Brain Metastases in Posterior Fossa.

Abstract

It is sometimes difficult to make a differential diagnosis between brain metastases and hemangioblastomas in the posterior fossa. We assessed whether high b value diffusion-weighted image (DWI) at b = 4000 could differentiate these tumors. We acquired DWI at 3-T magnetic resonance imaging with b = 1000 and b = 4000 seconds/mm² in histologically confirmed 12 patients of hemangioblastoma without von Hippel-Lindau disease and 16 patients with brain metastases originating at the posterior fossa. Apparent diffusion coefficient (ADC) values were measured by manually placing regions of interest on ADC maps at the site of enhanced tumor confirmed on contrast-enhanced T1- weighed image. ADC was expressed as the minimum (ADC_MIN), mean (ADC_MEAN), and maximum (ADC_MAX) values. All the ADC values of hemangioblastomas were statistically higher than those of metastatic tumor in both b = 1000 and b = 4000 (P < 0.0001 in ADC_MIN, ADC_MEAN, and ADC_MAX; Mann-Whitney U test). With the cutoff value at 0.6 × 10^-3 mm²/second, the positive predictive value of ADC_MIN at b = 4000 was higher than that of ADC_MIN at b = 1000 (100% vs. 89.3%, logistic analysis) to differentiate hemangioblastomas from brain metastases. Moreover, we studied the pathologic subtype of hemangioblastoma and confirmed that ADCs (b = 4000_MIN) of cellular subtype were statistically lower than those of reticular subtype (P = 0.03; Mann-Whitney U test). High b value DWI reflects diffusion more accurately than does regular b value. Our results showed that ADC calculation by high b value (b = 4000) DWI at 3-T magnetic resonance imaging is clinically useful for differentiating hemangioblastomas from brain metastases.