Measurement of Apparent Diffusion Coefficient (ADC) Values of Ependymoma and Medulloblastoma Tumors: a Patient-based Study

Abstract

Background: aimed to compare the apparent diffusion coefficient (ADC) of two different cerebellar pediatric tumors, including ependymoma and medulloblastoma which have shown similar clinical images in conventional magnetic resonance imaging (MRI) methods.Material and Methods: Thirty six pediatric patients who were suspected to have the mentioned tumors according to their CT image findings were included in this study. The patients were subjected to conventional MRI protocols followed by diffusion weighted imaging (DWI) and ADC values of the tumors were calculated automatically using MRI scanner software.Results: The mean (± SD) ADC value for ependymoma (1.2± 0.06 ×10-3 mm2/s) was significantly higher than medulloblastoma (0.87 ± 0.02 ×10-3 mm2/s) (p = 0.041). Moreover, the maximum ADC value of ependymoma was considerably different in comparison with medulloblastoma (1.4 ×10-3 mm2/s and 0.96×10-3 mm2/s, respectively; p = 0.035) Furthermore, the minimum ADC value of ependymoma was higher compared to medulloblastoma (1.0 ×10-3 mm2/s and 0.61×10-3 mm2/s, respectively), but it was not significant (p = 0.067).Conclusion: Evaluation of ADC values for ependymoma and medulloblastoma is a reliable method to differentiate these two malignancies. This is due to different ADC values reflected during the evaluation.

Meta‐Analysis of Apparent Diffusion Coefficient in Pediatric Medulloblastoma, Ependymoma, and Pilocytic Astrocytoma

“…30 Six of the seven studies acquired DWI echo planar imaging (EPI) acquisitions. 21,27,[29][30][31][32] Of these six studies, repetition times ranged from 2435 to 8575 msec, echo times ranged from 60 to 161 msec, slices thickness ranged from 4 to 6 mm and slice gaps ranged from 0 to 3 mm. These six studies acquired b-values of 0 and 1000, with one study also acquiring an additional b-value of 500.…”

“…27 One study in the final cohort did not report any DWI parameters. 16 Three studies acquired data solely from Philips Achieva 1.5 T scanners, 16,21,32 one study acquired data solely from a Siemens 1.5 T scanner, 27 one study acquired data solely from a GE 1.5 T scanner, and two studies combined data from multiple scanners. 29,30 Only one study included the use of 3 T MRI scanners 30 and was also the only multi-institutional study (Table 2).…”

“…Twenty four were discarded after a full-text review as they did not meet the inclusion criteria. Seven papers were ultimately identified which reported mean ADC while matching the inclusion criteria 16,21,27,[29][30][31][32] (Figure 1). Only one of these studies collected data from multiple scanners across multiple institutions.…”

“…Four of the seven included studies explicitly stated that only solid portions of the tumor were considered and necrotic, cystic, and hemorrhagic regions were excluded. 16,[29][30][31] Two further studies defined their ROIs as the enhancing portion of the tumor 21,32 and these were included as only solid tumor tissue enhances. Finally, one study 27 placed a single ROI inside the solid and nonnecrotic area of the tumor.…”

“…[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] It is broadly recognized in clinical practice that medulloblastoma typically show reduced ADC within the tumor compared to surrounding tissues, pilocytic astrocytoma typically show elevated ADC compared to surrounding tissue, and that ependymomas typically "sit in the middle," often demonstrating mixed ADC values including areas of low and high ADC. 30 Many studies in the literature consider the mean ADC within the tumor regionof-interest (ROI) and use this value to identify differences between tumor types [14][15][16][17][18][20][21][22][23][25][26][27][28][29]31,32 and to identify the optimal cut-offs for distinguishing tumor types. [18][19][20][21][22][23][24]26,28,29 In addition, histogram analyses have been performed to identify percentiles that distinguish tumor types.…”