High b-value diffusion (b = 3000 s/mm2) MR imaging in cerebral gliomas at 3T: visual and quantitative comparisons with b = 1000 s/mm2

Abstract

Background and purpose: High b-value diffusion-weighted imaging (DWI) provides different features not appreciated at lower b-value and have been recently studied in several clinical issues. The purpose of this study was to assess whether DWI at b = 3000 s/mm(2) is more useful in discriminating high-grade and low-grade gliomas than DWI at b = 1000 s/mm(2) at 3T.

Materials and methods: DWIs at both b = 1000 and 3000 s/mm(2) were performed at 3T in 62 patients, 49 high-grade gliomas (20 World Health Organization [WHO] grade III and 29 grade IV) and 13 low-grade gliomas (13 grade II). Visual assessments based on 5-point scaled evaluations, receiver operating characteristic (ROC) curve analysis, and quantitative assessment based on DWI signal intensity (SI) ratio (tumor SI/normal SI) and apparent diffusion coefficient (ADC) values were compared between DWIs at b = 1000 and 3000 s/mm(2).

Results: By visual assessment, DWI at b = 3000 s/mm(2) showed more conspicuous hyperintensity in high-grade gliomas and hypointensity in low-grade gliomas than DWI at b = 1000 s/mm(2). Sensitivity and specificity at b = 3000 s/mm(2) were higher than at b = 1000 s/mm(2) (83.7%, 84.6% vs 69.4%, 76.9%, respectively). Quantitative assessments showed that mean SI ratio of high-grade gliomas was significantly higher than that of low-grade gliomas at both b-values. The mean ADC value of high-grade gliomas was significantly lower than that of low-grade gliomas at both b-values. The difference between the SI ratios of high-grade and low-grade gliomas was significantly larger at b = 3000 s/mm(2) than at b = 1000 s/mm(2).

Conclusion: DWI at b = 3000 s/mm(2) is more useful than DWI at b = 1000 s/mm(2) in terms of discriminating high-grade and low-grade gliomas at 3T.

Fig 1.

Grade IV glioblastoma in a 27-year-old man. A, Transverse T2-weighted image shows a slightly hyperintense main mass (arrow) in the right medial temporal lobe. B, Sagittal contrast-enhanced T1-weighted image shows diffuse tumor enhancement (arrow). C, Transverse DWI at b = 1000 s/mm² shows slight tumor hyperintensity with some hypointense foci. D, Transverse DWI at b = 3000 s/mm² shows more conspicuous main mass hyperintensity. E, Transverse ADC map at b = 1000 s/mm² shows subtle or slight tumor hypointensity. F, Transverse ADC map at b = 3000 s/mm² shows more conspicuous tumor hypointensity.

Fig 2.

Grade II diffuse astrocytoma in a 66-year-old man. A, Transverse T2-weighted image shows a hyperintense mass (arrow) in the left medial temporal lobe. B, Coronal contrast-enhanced T1-weighted image shows slight tumor hypointensity without enhancement (arrow). C, Transverse DWI at b = 1000 s/mm² shows tumor isointensity. D, Transverse DWI at b = 3000 s/mm² shows marked tumor hypointensity. Transverse ADC maps at b = 1000 s/mm² (E) and b = 3000 s/mm² (F) show tumor hyperintensity.

Fig 3.

ROC curves derived from 5-point scale visual assessment scores at b = 1000 and 3000 s/mm². The Az value of DWI at b = 3000 s/mm² was higher than at b = 1000 s/mm² but this was not statistically significant (0.864 vs 0.790; P =.08).

Fig 4.

Box plots of DWI SI ratios (A) in high-grade and low-grade gliomas, and ADC values (B) of high-grade and low-grade gliomas and normal subcortical white matter at b = 1000 and 3000 s/mm². The horizontal line is the median, and the upper and lower ends of the boxes are the upper and lower quartiles, respectively. The vertical lines represent data ranges. A, The mean SI ratio of high-grade gliomas was significantly higher than that of low-grade gliomas at both b-values (P < .01). Note that the difference between the mean SI ratios of high-grade and low-grade gliomas at b = 3000 s/mm² was significantly greater than at b = 1000 s/mm² (P < .05). B, The mean ADC value of high-grade gliomas was significantly lower than that of low-grade gliomas at both b-values (P < .01). The mean ADC values of high-grade and low-grade gliomas and normal subcortical white matter at b = 3000 s/mm² were significantly lower than at b = 1000 s/mm², respectively (P < .01).