Three-Dimensional Pseudo-Continuous Arterial Spin Labeling Parameters Distinguish Pediatric Medulloblastoma and Pilocytic Astrocytoma

Abstract

Introduction: Arterial Spin Labeling (ASL), a perfusion assessment without using gadolinium-based contrast agents, is outstandingly advantageous for pediatric patients. The differentiation of medulloblastomas from pilocytic astrocytomas in children plays a significant role in determining treatment strategies and prognosis. This study aimed to assess the use of ASL parameters during the differentiation between pediatric medulloblastoma and pilocytic astrocytoma.Methods: The institutional review board of Children's Hospital 2 approved this prospective study. The brain magnetic resonance imaging (MRI) protocol, including axial three-dimensional (3D) pseudo-continuous ASL, was evaluated in 33 patients, who were divided into a medulloblastoma group (n = 25) and a pilocytic astrocytoma group (n = 8). The quantified region of interest (ROI) values for the tumors and the tumor to parenchyma ratios were collected and compared between the two groups. Receiver operating characteristic (ROC) curve analysis and the Youden index were utilized to identify the best cut-off, sensitivity, specificity, and area under the curve (AUC) values for significant ASL parameters.Results: The cerebral blood flow (CBF) and the ratio between the CBF of the tumor relative to that of the parenchyma (rCBF) values for medulloblastomas were significantly higher than those for pilocytic astrocytomas (p < 0.05). A cut-off value of 0.51 for rCBF was able to discriminate between medulloblastoma and pilocytic astrocytoma, generating a sensitivity of 88%, a specificity of 75%, and an AUC of 83.5%.Conclusion: The rCBF measurement, obtained during MRI with 3D pseudo-continuous ASL, plays a supplemental role in the differentiation of medulloblastoma from pilocytic astrocytoma.

Dynamic susceptibility contrast and diffusion‐weighted MRI in posterior fossa pilocytic astrocytoma and medulloblastoma

“…Duc demonstrated that the rCBF derived from ASL was significantly higher in MB than in PA with a sensitivity of 0.88, specificity of 0.75, and an AUC of 0.835 using a cutoff value of 0.51. 19 Interestingly, these diagnostic values were similar to the results found in this study (sensitivity 0.85, specificity 0.76, and AUC, 0.81). The lower blood flow/volume in PA than in highergrade tumors is also in line with studies comparing perfusion parameters between PA and high-grade gliomas.…”

“…Our current understanding of the diagnostic performance of perfusion MRI techniques in PA and MB is limited. Duc demonstrated that the rCBF derived from ASL was significantly higher in MB than in PA with a sensitivity of 0.88, specificity of 0.75, and an AUC of 0.835 using a cutoff value of 0.51 19 . Interestingly, these diagnostic values were similar to the results found in this study (sensitivity 0.85, specificity 0.76, and AUC, 0.81).…”

“…23 Moreover, the different rules in the ROI placement may have affected the results in each study. How ROIs were placed and how cysts, necrosis, hemorrhagic areas, and vasculature were handled were not detailed in the study by Duc; 19 vasculature was avoided but ROIs were placed on the region of the tumor with the highest value of each perfusion metric in the study by Gupta et al 20 Although the results of subgroup analyses for the molecular subtypes in patients with MB did not reach significance, there were tendencies that MRI parameters were different between the molecular subtypes (Table 3). Given the small number of the patients with each subtype, future studies are warranted to evaluate the MRI features of each molecular subtypes.…”

“…However, reports on the diagnostic performance of perfusion MRI are scarce, with heterogeneous results. Duc demonstrated that relative cerebral blood flow (rCBF) derived from arterial spin labeling (ASL) was significantly higher in MB than in PA, 19 while Gupta et al reported that dynamic contrast-enhanced (DCE)-MRI-derived rCBF and relative cerebral blood volume (rCBV) were significantly higher in PA than in MB. 20 Studies on dynamic susceptibility contrast (DSC)-MRI are limited; 21,22 thus, the diagnostic performance in distinguishing PA and MB has not been established.…”

Advanced Neuroimaging Approaches to Pediatric Brain Tumors

“…Yeom et al found that the maximal relative tumor blood flow of high-grade tumors (grades III and IV) was significantly higher than that of low-grade tumors (grades I and II), with a wider relative tumor blood flow range among high-grade tumors (2.14 ± 1.78) compared with low-grade tumors (0.60 ± 0.29) ( p < 0.001). Although the relative tumor blood flow did not distinguish individual histology among posterior fossa tumors, relative tumor blood flow was significantly higher for medulloblastoma compared with pilocytic astrocytoma, with a cut-off value of the ratio of tumoral CBF to the brain parenchyma of 0.51, offering a sensitivity of 88% and specificity of 75% [ 103 ]. In a cohort of 24 patients, ASL was found to be highly accurate in distinguishing pilomyxoid astrocytoma, a WHO grade II tumor, from pilocytic astrocytoma, a WHO grade I tumor, with 77% sensitivity and 100% specificity using a threshold ratio value of 0.91 [ 104 ].…”