title: Assessment of tissue heterogeneity using diffusion tensor and diffusion kurtosis imaging for grading gliomas.
abstract: BACKGROUND
  In this work, we aim to assess the significance of diffusion tensor imaging (DTI) and diffusion kurtosis imaging (DKI) parameters in grading gliomas.
  
  
  METHODS
  Retrospective studies were performed on 53 subjects with gliomas belonging to WHO grade II (n = 19), grade III (n = 20) and grade IV (n = 14). Expert marked regions of interest (ROIs) covering the tumour on T2-weighted images. Statistical texture measures such as entropy and busyness calculated over ROIs on diffusion parametric maps were used to assess the tumour heterogeneity. Additionally, we propose a volume heterogeneity index derived from cross correlation (CC) analysis as a tool for grading gliomas. The texture measures were compared between grades by performing the Mann-Whitney test followed by receiver operating characteristic (ROC) analysis for evaluating diagnostic accuracy.
  
  
  RESULTS
  Entropy, busyness and volume heterogeneity index for all diffusion parameters except fractional anisotropy and anisotropy of kurtosis showed significant differences between grades. The Mann-Whitney test on mean diffusivity (MD), among DTI parameters, resulted in the highest discriminability with values of P = 0.029 (0.0421) for grade II vs. III and P = 0.0312 (0.0415) for III vs. IV for entropy (busyness). In DKI, mean kurtosis (MK) showed the highest discriminability, P = 0.018 (0.038) for grade II vs. III and P = 0.022 (0.04) for III vs. IV for entropy (busyness). Results of CC analysis illustrate the existence of homogeneity in volume (uniformity across slices) for lower grades, as compared to higher grades. Hypothesis testing performed on volume heterogeneity index showed P values of 0.0002 (0.0001) and 0.0003 (0.0003) between grades II vs. III and III vs. IV, respectively, for MD (MK).
  
  
  CONCLUSIONS
  In summary, the studies demonstrated great potential towards automating grading gliomas by employing tumour heterogeneity measures on DTI and DKI parameters.
authors: International Institute of Information Technology-Bangalore, 26/C, Electronics City, Hosur Road, Bangalore, India. r.rajika@gmail.com.
authors: Rajikha
authors: R
authors: Raja
authors: International Institute of Information Technology-Bangalore, 26/C, Electronics City, Hosur Road, Bangalore, India. neel.iam@gmail.com.
authors: Neelam
authors: N
authors: Sinha
authors: National Institute of Mental Health and Neurosciences, Bangalore, India.
authors: Jitender
authors: J
authors: Saini
authors: National Institute of Mental Health and Neurosciences, Bangalore, India.
authors: Anita
authors: A
authors: Mahadevan
authors: National Institute of Mental Health and Neurosciences, Bangalore, India.
authors: Kvl Narasinga
authors: KN
authors: Rao
authors: National Institute of Mental Health and Neurosciences, Bangalore, India.
authors: Aarthi
authors: A
authors: Swaminathan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D005910:Glioma / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D010363:Pattern Recognition, Automated / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: Diffusion kurtosis imaging; Diffusion tensor imaging; Glioma grading; Textural features