The Initial Application Of Diffusion-Weighted MR Neurography In Wrist And Palm

ObjectiveTo demonstrate the feasibility of diffusion-weighted (DW) magnetic resonance (MR) neurography of nerves in wrist and palm and evaluate the potential clinical applicationsMaterials and MethodsThis study was approved by local institutional review board, and informed consent was obtained. Total forty-two healthy volunteers and twenty patients were recruited. The exclusion criteria were general contraindications to MRI. The volunteers (mean age,30.6±9.2 years [SD]; age range,20-61 years) had no history of or findings related to nerve abnormalities at the time of the study and no history of diabetes and rheumatic disease.20 patients (mean age,32.1 years; age range,6-56 years) were suspected peripheral nerve disorders. All the volunteers and patient underwent imaging of nerves in wrist and palm at a 3.0-T magnetic resonance system (Achieva TX, Philips Healthcare), including T1-weighted imaging, (T1WI) T2-weighted spectrally adiabatic inversion recovery imaging, (T2WI-SPAIR)、 PD-weighted spectrally adiabatic inversion recovery imaging (PDWI-SPAIR) and diffusion-weighted MR neurography(DW-MRN). A eight-channel wrist coil was used for the wrist and palm(head-first position, prone position). The MPGs were implemented in anterior-posterior direction. DW MR neurography images were displayed using a three-dimensional (3D) maximum intensity projection.In volunteers, DW-MRN images were blindly evaluated by two radiologists in consensus using a four-point grading scale:4=excellent (the nerve was visible and of excellent signal intensity);3=good (the entire nerve was visible and of moderate signal intensity); 2=poor(the nerve was partially visible); 1=not visualized (the nerve was not visible). Interobserver agreement for visualization scores was calculated using the kappa statistic. The number of the trunk of median nerve and ulnar nerve, palm digital nerve, deep and superficial branch of ulnar nerve which can be visualized in DW-MRN and FS-PDWI of 42 volunteers was compared.In patients, the same two radiologists blindly and collectively evaluated the DW-MRN and PDWI-SPAIR images. The extent of the lesions and the relationship with adjacent nerves was assed using a three-point grading scale:1= The extent of the lesions and the relationship with adjacent nerves identified with certainty; 2= Probably identified or not all lesions were identified; 3= Not identified. The statistical analysis was performed with SPSS software. Paired Mann-whitney U-test was used to assess differences in conspicuity scores between DW-MRN and PDWI-SPAIR images of the same patient. The statistically significant difference level was set at P< 0.05.ResultsIn volunteers, the trajectory of median and ulnar nerve in wrist, the branches of median nerve including the lateral and medial portion and three proper volar digital nerves, superficial and deep branches of ulnar nerve could be visualized on DW MR neurography images. The mean scores of the median nerve were 4.0±0.0 and 4.0± 0.0 for observers 1 and 2, respectively. Interobserver agreement was good(κ=1). The mean scores of ulnar nerve were 3.45±0.74 and 3.43±0.67 for observers 1 and 2, respectively. Interobserver agreement was good(κ=0.793). The numbers of visualized trunk of median nerve and ulnar nerve, palm digital nerve, deep and superficial branch of ulnar nerve were 42、42、42、42、42、38、37 on DW-MRN and 42、39、27、28、25、17、21 on FS-PDWI sequence. The percentage of visualized palm digital nerve, deep and superficial branch of ulnar nerve on DW-MRN were higher than those on FS-PDWI sequence (x2 value were 18.26,16.80,21.31,23.23,14.26, P<0.05).In patients, The extent of lesions and the relationship with adjacent nerves were clearly and easily depicted on DW-MRN images in all patients with a comprehensive overview. Except in 2 patients with injury of ulna nerve (score= 2) and in 1 patient with inflammation nerve (score=2),scores of all patients were 3 on DW-MRN images. On T2WI-SPAIR images, the scores were 3 in only 10 patients. The DW-MRN images provided improved identification of the extent of the lesions and the relationship with adjacent nerves compared with the T2WI-SPAIR images (P<0.05).ConclusionCompared with the FS-PDWI sequence, the DW-MRN can provide a three dimensional visualization of the median nerve and ulnar nerve at the wrist and palm and can display clearly the extent of lesions and the relationship with nerves in patients.