Avneesh Chhabra MD, Presenter: Research Grant, Siemens AG Research Consultant, Siemens AG Research Grant, Integra LifeSciences Holdings Corporation Research Grant, General Electric Company

Rashmi Savyasachi Thakkar MD, Abstract Co-Author: Nothing to Disclose

Majid Chalian MD, Abstract Co-Author: Nothing to Disclose

Vibhor Wadhwa, Abstract Co-Author: Nothing to Disclose

Alan Belzberg, Abstract Co-Author: Nothing to Disclose

John Eng MD, Abstract Co-Author: Nothing to Disclose

John A. Carrino MD, MPH, Abstract Co-Author: Research Grant, Siemens AG Research Grant, Carestream Health, Inc Research Consultant, General Electric Company

Diffusion tensor imaging (DTI) and Diffusion weighted imaging (DWI) allow interrogation of the internal architecture of the peripheral nerves and the associated mass lesions. Benign peripheral nerve sheath tumors (PNST) are the most commonly encountered such lesions. Most commonly used quantitative measures in diffusion imaging include fractional anisotropy (FA) and mean apparent diffusion coefficient (ADC) values. Data is limited about their interobserver reliability and if differences exist among the ADC measurements on DWI and DTI imaging.

In this IRB approved retrospective study,16 subjects (6 males, 10 females; mean age 41 years, SD± 19) with benign PNST were studied using 3.0 T MR scanner (Verio, Trio, Siemens, Erlangen, Germany). 16 cases were imaged with DTI (single shot EPI, 12 encoding directions; b-values-0, 800 and 1000 s/mm2) and 10 /16 were also evaluated with DWI (b-50,400,800 s/mm2). 3D STIR SPACE anatomic MR Neurography images were matched to DTI and DWI performed as part of the nerve tumor protocol. FA of the involved and contralateral uninvolved nerves, and ADC of the mass lesions were determined by 2 trained observers with free hand drawn ROIs (at least 2mm2 area on the nerve and 8mm2 area on the lesion). The Kolmogorov-Smirnov test was used to evaluate the normality of distribution of the continuous variables. Quantitative variables were compared between groups using Wilcoxon rank-sum test. Intra-class correlation coefficient (ICC) was used to measure inter-observer reliability.

There was excellent inter-observer agreement regarding FA value on the normal side [ICC=0.970 (0.915-0.990)], FA value on the abnormal side [ICC=0.98 (0.941-0.993)], and also ADC value in the lesion [ICC=0.987 (0.969-0.994)]. There was no statistically significant difference in ADC value between DTI (1.73 ± 0.46 x 10-3) and DWI (1.77 ± 0.41 x 10-3) sequences (p>0.05).

There is excellent inter-observer reliability in the DTI measurements. DTI not only provides insight into anisotropy and allows tractography, ADC measurements are also equally well evaluated on DTI similar to DWI in the realm of PNSTs.

The study provides evidence that DTI provides a single solution for functional diffusion imaging with excellent interobserver reliability in the quantitative measurements.

Chhabra, A, Thakkar, R, Chalian, M, Wadhwa, V, Belzberg, A, Eng, J, Carrino, J, Peripheral Nerve Sheath Tumors: Reliability in Quantitative Measurements on Diffusion Tensor Imaging and Comparison with Diffusion-weighted Imaging.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043518.html