Non-Gaussian Analysis of Diffusion Weighted Imaging in Head and Neck at 3T: A Pilot Study in Patients with Nasopharyngeal Carcinoma

Jing Yuan,Kunwar S Bhatia,Greta S P Mok,Yi-Xiang J Wang,David Ka Wai Yeung,Anil T Ahuja,Ann D King,Xiaoliang Zhang

doi:10.1371/journal.pone.0087024

Abstract

PurposeTo technically investigate the non-Gaussian diffusion of head and neck diffusion weighted imaging (DWI) at 3 Tesla and compare advanced non-Gaussian diffusion models, including diffusion kurtosis imaging (DKI), stretched-exponential model (SEM), intravoxel incoherent motion (IVIM) and statistical model in the patients with nasopharyngeal carcinoma (NPC).Materials and MethodsAfter ethics approval was granted, 16 patients with NPC were examined using DWI performed at 3T employing an extended b-value range from 0 to 1500 s/mm2. DWI signals were fitted to the mono-exponential and non-Gaussian diffusion models on primary tumor, metastatic node, spinal cord and muscle. Non-Gaussian parameter maps were generated and compared to apparent diffusion coefficient (ADC) maps in NPC.ResultsDiffusion in NPC exhibited non-Gaussian behavior at the extended b-value range. Non-Gaussian models achieved significantly better fitting of DWI signal than the mono-exponential model. Non-Gaussian diffusion coefficients were substantially different from mono-exponential ADC both in magnitude and histogram distribution.ConclusionNon-Gaussian diffusivity in head and neck tissues and NPC lesions could be assessed by using non-Gaussian diffusion models. Non-Gaussian DWI analysis may reveal additional tissue properties beyond ADC and holds potentials to be used as a complementary tool for NPC characterization.

Highlights

Diffusion-weighted imaging (DWI) is capable of noninvasively measuring water diffusivity in living tissues [1]
Non-Gaussian diffusion coefficients were substantially different from mono-exponential apparent diffusion coefficient (ADC) both in magnitude and histogram distribution
Non-Gaussian DWI analysis may reveal additional tissue properties beyond ADC and holds potentials to be used as a complementary tool for nasopharyngeal carcinoma (NPC) characterization

Summary

Introduction

Diffusion-weighted imaging (DWI) is capable of noninvasively measuring water diffusivity in living tissues [1]. In the traditional diffusion theory, the displacement of freely mobile water molecules diffusing from one location to another in a certain time is considered to have a Gaussian distribution. Based on this Gaussian diffusion behavior, a mono-exponential decay function of DWI signal intensity with regard to the increase of b-value has been adopted for diffusion analysis in most clinical studies [2]. Because microstructural changes at the cellular level in tissues due to pathology may hinder the motion of water molecules and affect ADC, DWI is growing rapidly in scope and importance for various clinical applications. Several advanced diffusion models (referred to as non-Gaussian diffusion models here) have been proposed to account for the non-Gaussian diffusion behavior of biological tissues to allow a more comprehensive analysis of DWI data [3,4,5,6,7,8]

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