A dedicated extremity cone-beam CT scanner capable of imaging upper and lower extremities (including weight-bearing examinations) provides sufficient image quality and favorable dose characteristics to warrant further evaluation for clinical use.

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SUMMARY:High-resolution MR imaging of peripheral nerves is becoming more common and practical with the increasing availability of 3T magnets. There are multiple reports of MR imaging of peripheral nerves in compression and entrapment neuropathies. However, there is a relative paucity of literature on MRN appearance of diffuse peripheral nerve lesions. We attempted to highlight the salient imaging features of myriad diffuse peripheral nerve disorders and imaging techniques for MRN. Using clinical and pathologically proved relevant examples, we present the MRN appearance of various types of diffuse peripheral nerve lesions, such as traumatic, inflammatory, infectious, hereditary, radiationinduced, neoplastic, and tumor variants.ABBREVIATIONS: CIDP ϭ chronic inflammatory demyelinating polyneuropathy; CMT ϭ CharcotMarie-Tooth; fat sat ϭ fat saturated; FLAIR ϭ fluid-attenuated inversion recovery; FLH ϭ fibrolipomatous hamartoma; GBS ϭ Guillain Barré syndrome; CMT/HSMN ϭ Charcot-Marie-Tooth/hereditary motor and sensory neuropathy; MMN ϭ multifocal motor neuropathy; MPNST ϭ malignant peripheral nerve sheath tumor; MRN ϭ MR neurography; NF1 ϭ neurofibromatosis type 1; NL ϭ neurolymphomatosis; SE ϭ spin-echo; SNR ϭ signal-to-noise ratio; SPACE ϭ sampling perfection with application-optimized contrasts by using different flip angle evolutions; SPAIR ϭ spectralattenuated inversion recovery; STIR ϭ short-tau inversion recovery; T1WI ϭ T1-weighted imaging; T1WIFS ϭ T1-weighted fat-saturated imaging; T2WI ϭ T2-weighted imaging; T2WIFS ϭ T2-weighted fat-saturated imaging H igh-resolution MR imaging of peripheral nerves is becoming more common and practical with increasing availability of 3T magnets. These magnets provide high SNR, which can be used for a quicker acquisition time as well as higher image contrast and resolution. There have been multiple reports of MR imaging of peripheral nerves in compression and entrapment neuropathies.1-3 However, there is a relative paucity of literature on the MRN appearance of diffuse peripheral nerve lesions. 4 These lesions seen on MR imaging present a diagnostic dilemma because a long list of pathologies could be causing them. We attempt to highlight the salient imaging features of myriad diffuse peripheral nerve disorders and to describe a diagnostic approach to these lesions on the basis of the available literature and our experience in this area. Various clinical and pathologically proved relevant examples of these pathologies are illustrated. . T1WI demonstrates fat planes delineating the normal nerve (perineural fat). C, Axial STIR SPACE at the level of the thighs shows an abnormal sciatic nerve. Notice the enlarged size and T2 hyperintensity of the fascicles. The dark rim of perineural fat is also disrupted. Also note posterior compartment denervation muscle edema (arrows).

BACKGROUND AND PURPOSE A number of benign and malignant peripheral nerve tumor and tumorlike conditions produce similar imaging features on conventional anatomic MR imaging. Functional MR imaging using DTI can increment the diagnostic performance in differentiation of these lesions. Our aim was to evaluate the role of 3T anatomic MR imaging and DTI in the characterization of peripheral nerve tumor and tumorlike conditions. MATERIALS AND METHODS Twenty-nine patients (13 men, 16 women; mean age, 41 ± 18 years; range, 11–83 years) with a nerve tumor or tumorlike condition (25 benign, 5 malignant) underwent 3T MR imaging by using anatomic (n = 29), functional diffusion, DWI (n = 21), and DTI (n = 24) techniques. Images were evaluated for image quality (3-point scale), ADC of the lesion, tractography, and fractional anisotropy of nerves with interobserver reliability in ADC and FA measurements. RESULTS No significant differences were observed in age (benign, 40 ± 18 versus malignant, 45 ± 19 years) and sex (benign, male/female = 12:12 versus malignant, male/female = 3:2) (P > .05). All anatomic (29/29, 100%) MR imaging studies received “good” quality; 20/21 (95%) DWI and 21/24 (79%) DTI studies received “good” quality. ADC of benign lesions (1.848 ± 0.40 × 10−3 mm2/s) differed from that of malignant lesions (0.900 ± 0.25 × 10−3 mm2/s, P < .001) with excellent interobserver reliability (ICC = 0.988 [95% CI, 0.976–0.994]). There were no FA or ADC differences between men and women (P > .05). FA of involved nerves was lower than that in contralateral healthy nerves (P < .001) with excellent interobserver reliability (ICC = 0.970 [95% CI, 0.946–0.991]). ADC on DTI and DWI was not statistically different (P > .05), with excellent intermethod reliability (ICC = 0.943 [95% CI, 0.836–0.980]). Tractography differences were observed in benign and malignant lesions. CONCLUSIONS 3T MR imaging and DTI are valuable methods for anatomic and functional evaluation of peripheral nerve lesions with excellent interobserver reliability. While tractography and low FA provide insight into neural integrity, low diffusivity values indicate malignancy in neural masses.

SUMMARY:With advancement in 3D imaging, better fat-suppression techniques, and superior coil designs for MR imaging and the increasing availability and use of 3T magnets, the visualization of the complexity of the brachial plexus has become facile. The relevant imaging findings are described for normal and pathologic conditions of the brachial plexus. These radiologic findings are supported by clinical and/or EMG/surgical data, and corresponding high-resolution MR neurography images are illustrated. Because the brachial plexus can be affected by a plethora of pathologies, resulting in often serious and disabling complications, a better radiologic insight has great potential in aiding physicians in rendering superior services to patients. ABBREVIATIONS:EMG ϭ electromyography; MIP ϭ maximum intensity projection; MRN ϭ MR neurography; SPACE ϭ sampling perfection with application-