• Mario Giordano, Amir Samii, Madjid Samii, and Arya Nabavi.
• Department of Neurosurgery, International Neuroscience Institute, Hannover, Germany. Electronic address: giordano.nch@gmail.com.
• World Neurosurg. 2019 May 1; 125: e820-e823.

ObjectiveTo investigate the validity of various approaches to extract quantitative measurements of diffusion imaging (i.e., apparent diffusion coefficient [ADC]) to investigate tumors of the central nervous system. In current studies, the region of interest (ROI) for the quantitative measurements are placed arbitrarily according to morphology. Our aim is to investigate how placement patterns influence the ADC estimation in intracranial tumors.MethodsTwenty consecutive patients affected by vestibular schwannoma were studied using diffusion imaging. ADC values were obtained using different ROI placement methods: segmentation ADC values of the entire volume (vADC), random ADC values were obtained in 10 different ROI points, and a single ROI in the ADC of the internal auditory canal portion of the tumor.ResultsADC of the internal auditory canal portion of the tumor and vADC differed significantly (P < 0.01). vADC was different between cystic and microcystic schwannomas (P = 0.009) and between cystic and solid schwannomas (P = 0.006).ConclusionsThe positioning of ROI in these measurements is pivotal. Although "whole tumor volume" measurements represent the largest amount of information, multiple seed points can be used as well. However, there must be multiple seeds and their placement must be reported. ADC can be used as a versatile tool for tumor assessment but must be used judiciously and structured to yield comparable results.Copyright © 2019 Elsevier Inc. All rights reserved.

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