Fascicular Ratio: A New Parameter to Evaluate Peripheral Nerve Pathology on Magnetic Resonance Imaging: A Feasibility Study on a 3T MRI System

摘要

Abstract: The objective of the study was to define and quantitatively evaluate the fascicular ratio (FR) on magnetic resonance imaging (MRI) in patients with peripheral neuropathies compared with healthy controls. Forty control subjects (20 women, 20 men; age, 44.6?±?13.4 years) and 40 patients with peripheral neuropathy (22 women, 18 men; age, 50.3?±?10.2 years) were examined with a standard 3T MRI protocol. With customized software (with semiautomatic and automatic interface), the hypointense and hyperintense areas of the peripheral nerves corresponding to fascicular and nonfascicular tissue were examined on T1-weighted sequences. The ratio of fascicular pixels to total pixels was called FR. Correlation with FR calculated on high-resolution ultrasound was performed. The statistical analysis included the Mann–Whitney U test of controls versus patients, the receiver operating characteristic (ROC) analysis, and the subgroup analysis of patients according to etiologies of neuropathy. Intraobserver and interobserver agreement was calculated based on the evaluation made by 3 readers. Finally, a complete automatic evaluation was performed. On MRI, FRs were significantly increased in patients compared with controls (FR, 76.7?±?15.1 vs 56?±?12.3; P?P?r?=?0.49; 95% confidence interval for r, 0.21–0.70; P?=?0.012). With the semiautomated evaluation, the mean intraobserver agreement was good (K?=?0.86). The interobserver agreements were also good (reader 1 vs reader 2, k?=?0.71; reader 2 vs reader 3, k?=?0.78; reader 3 vs reader 1, k?=?0.71). There were no statistically significant differences between the results obtained using the 2 methods. FR calculation on MRI is feasible, and it may be used in adjunct to standard MRI evaluation in peripheral nerve disorders.