Value of Diffusion-Weighted Imaging in Grading Tumours Localized in the Fourth Ventricle Region by Visual and Quantitative Assessments

Abstract

This study investigated visual and quantitative assessment of diffusion-weighted imaging (DWI) for grading tumours localized in the fourth ventricle region. Patients were diagnosed histopathologically and classified into two groups: those with high-grade (World Health Organization [WHO] grades III and IV) and those with low-grade tumours (benign, WHO grades I and II). DWI signal intensity was described using a five-point scale. Minimum apparent diffusion coefficient (ADC) values were obtained from areas with the lowest signal. The mean signal intensity was significantly higher in high-grade than in low-grade tumours. The mean minimum ADC value was significantly lower in high-grade than low-grade tumours. Marked hyperintensity had sensitivity, specificity, positive predictive value and negative predictive value of 89.7%, 100%, 100% and 94.2%, respectively, when used as a diagnostic tool for high-grade tumours compared with 96.6%, 97.9%, 96.6% and 97.9%, respectively, when using a minimum ADC of 0.9 × 10(-3) mm(2)/s as a diagnostic marker. It was concluded that DWI is helpful in predicting the grades of tumours in the fourth ventricle region.

Evaluation of Apparent Diffusion Coefficient Thresholds for Diagnosis of Medulloblastoma Using Diffusion-Weighted Imaging

“…This feature is most likely due to the fact that medulloblastomas are characterized by a high degree of cellularity and often contain cells with a high nuclear:cytoplasmic ratio, which provides an increased number of membrane barriers to microscopic water diffusion 14,15 . While not conclusive, recent work has suggested that ADC maps may be useful to noninvasively diagnose medulloblastoma using this characteristic [8][9][10]12,13,[16][17][18][19][20][21][22] . A number of methods exist for measuring water diffusivity in tumors.…”

“…A number of methods exist for measuring water diffusivity in tumors. These methods include measuring the minimum ADC value (hereafter termed ADC min ) within the entire tumor 15,18,19 , measuring the average ADC value within the entire tumor or within contrastenhancing portions of tumor 20,23,24 , normalizing ADC values within the tumor to those in normal tissue (hereafter referred to as nADC) 8,14,24 and using ADC histograms 12 . Most studies of nADC values are performed in a quantitative manner but some studies have measured nADC values by qualitative visual inspection 17,19 .…”

“…These methods include measuring the minimum ADC value (hereafter termed ADC min ) within the entire tumor 15,18,19 , measuring the average ADC value within the entire tumor or within contrastenhancing portions of tumor 20,23,24 , normalizing ADC values within the tumor to those in normal tissue (hereafter referred to as nADC) 8,14,24 and using ADC histograms 12 . Most studies of nADC values are performed in a quantitative manner but some studies have measured nADC values by qualitative visual inspection 17,19 . Each method has shown promise for distinguishing the major pediatric posterior fossa tumors from one another, but these studies have produced conflicting results [8][9][10]12,13,[16][17][18][19][20][21][22] .…”

“…Most studies of nADC values are performed in a quantitative manner but some studies have measured nADC values by qualitative visual inspection 17,19 . Each method has shown promise for distinguishing the major pediatric posterior fossa tumors from one another, but these studies have produced conflicting results [8][9][10]12,13,[16][17][18][19][20][21][22] . Furthermore, a number are limited by small sample sizes.…”

“…Not surprisingly, in some studies, use of the mean ADC value resulted in substantial overlap between ADC values of various tumor types and a relative inability to discriminate tumor types 18 . ADC min values for analysis of tumors have been employed by other investigators 15,19 . For instance, in one small study, the authors found significant differences between ADC min of medulloblastoma (0.54 × 10 -3 mm 2 /s) and that of ependymoma (0.91 × 10 -3 mm 2 /s) 15 .…”