Elsevier

Clinical Imaging

Volume 52, November–December 2018, Pages 88-94
Clinical Imaging

Neuroradiology
Perilesional apparent diffusion coefficient in the preoperative evaluation of glioma grade

https://doi.org/10.1016/j.clinimag.2018.07.005Get rights and content

Highlights

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    Water diffusivity within normal-appearing brain surrounding gliomas in twenty-one treatment-naïve patients was assessed.

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    Apparent diffusion coefficient (ADC) values were significantly different between high- and low-grade tumors.

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    Lower ADC values were seen in normal appearing brain surrounding high grade gliomas.

Abstract

Preoperative identification of high-grade gliomas is critical to optimize treatment strategy and to predict prognosis. To determine whether perilesional apparent diffusion coefficient (ADC) values differ between high- and low-grade tumors, we assessed water diffusivity within normal-appearing brain parenchyma (NABP) surrounding gliomas in twenty-one treatment-naïve patients. This showed significantly lower mean and 25th percentile (Q1) ADC values in high- grade compared to low-grade gliomas respectively in the range of 10–25 and 10–30 mm away from combined tumor and surrounding T2 signal. Thus, perilesional ADC measurement may reflect the extent of tumor infiltration beyond the abnormality seen on conventional MRI.

Introduction

Despite advances in therapeutic options and the use of multimodality treatment approaches, the prognosis of high-grade gliomas remains poor due to their infiltrative nature and high relapse rate compared to low-grade gliomas [1]. Thus, prospective preoperative identification of aggressive neoplasms is critical to optimize treatment strategy and to predict prognosis. Histopathological assessment of glioma grading has several limitations, such as the risks of the neurosurgical procedure, sampling error due to intratumoral heterogeneity, and inter- and intra-individual disagreement in pathology interpretation, especially when the sample is obtained by means of a stereotactic biopsy. Conventional magnetic resonance (MR) imaging, including T2-weighted and gadolinium enhanced T1-weighted images, has limitations in the assessment of the grade and extent of a primary brain tumor [2, 3]; however, it has been traditionally used as a reference for planning of surgery and radiation therapy. Nevertheless, in patients with malignant glioma tumor infiltration occurs in regions that appear normal on conventional MR imaging [[3], [4], [5], [6]].

Apparent diffusion coefficient (ADC) is widely used in clinical practice and provides information on tumor microstructure derived from microscopic motion of water molecules [[7], [8], [9]]. Several studies have shown an inverse correlation between ADC values of gliomas calculated from diffusion-weighted imaging (DWI) and tumor cellularity and grading [7, [10], [11], [12], [13], [14], [15]]. In addition, previous studies have evaluated ADC measurements in areas of T2 prolongation around gliomas, metastases, and meningiomas [[15], [16], [17]].

The purpose of this study was to assess water diffusivity within the brain parenchyma beyond the area of abnormal signal identified on conventional MR imaging in patients with treatment-naïve gliomas. To accomplish this, we measured mean and 25th percentile ADC values. 25th percentile ADC was used to capture focal areas of high cellularity within the normal appearing brain tissue that would predominantly contain normal brain parenchyma. 25th percentile ADC has been shown to outperform mean and median ADCs in prostate cancer tumor differentiation where there is a large portion of interspersed normal tissue [18]. Our hypothesis was that perilesional ADC values differ between low-grade and high-grade gliomas due to greater cellularity within the normal appearing brain parenchyma surrounding high-grade gliomas.

Section snippets

Materials and methods

This retrospective study was approved by the Institutional Review Board and was compliant with Health Insurance Portability and Accountability Act regulations. A waiver of informed consent was granted by the Institutional Review Board. We retrospectively reviewed a database of 187 patients with pathology proven glioma seen at the neuro-oncology clinic at our institution over the course of four years. Inclusion criteria for the study were: 1. histopathologic diagnosis of cerebral glioma

Results

There was not a statistically significant difference between low-grade and high-grade tumors with respect to volumes of the lesion VOIs and of the dilated VOIs at each of the 5 mm incremental steps (0–5, 5–10, 10–15, 15–20, 20–25, 25–30, 30–35 and 35–40 mm) (Table 1, Table 2).

Normalized mean and Q1 ADC values of the dilated perilesional VOIs were different between the high- and low-grade groups, with lower ADC values in high-grade gliomas (Table 3, Fig. 2, Fig. 3). Specifically, there was a

Discussion

We conducted a retrospective study designed to study the hypothesis that ADC measurements of perilesional normal appearing brain parenchyma differ between low- and high-grade gliomas. We found significantly lower ADC values in the normal appearing brain parenchyma surrounding high-grade than low-grade gliomas. Specifically, differences in ADC measurements were noted 10–30 mm away from the tumor and any surrounding area of T2 prolongation.

Abnormal diffusion metrics of normal appearing white

Acknowledgments

None.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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