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Abstract
Objective To determine the utility of quantitative metrics obtained from fMRI using diffusion-weighted imaging (DWI)/apparent diffusion coefficient (ADC) mapping compared with metabolic (18F-fluorodeoxyglucose [FDG]-PET/CT) imaging in patients with neurofibromatosis type 1 (NF1) for the characterization of peripheral nerve sheath tumors (PNSTs) as benign or malignant.
Methods This Institutional Review Board–approved, Health Insurance Portability and Accountability Act–compliant study retrospectively reviewed imaging of 55 PNSTs in 21 patients with NF1. Imaging included anatomic (unenhanced T1, fluid-sensitive, contrast-enhanced T1-weighted), functional DWI (b = 50, 400, 800 s/mm2) and ADC mapping, magnetic resonance sequences, and FDG-PET/CT imaging. Anatomic (size), functional (minimum ADC values), and metabolic (maximum standardized uptake values [SUVmax]) imaging characteristics were recorded. ADC values were correlated with SUVmax. With histologic correlation for all malignant PNSTs (MPNSTs) or clinical or imaging stability (>12 months) for benign lesions used as reference standards, diagnostic accuracy was calculated.
Results Of 55 PNSTs, there were 19 (35%) malignant and 36 (65%) benign PNSTs. Benign PNSTs were overall smaller than MPNSTs (largest diameter 4.3 ± 1.3 vs 8.2 ± 3.3 cm, respectively, p = 0.014). Benign PNSTs had higher ADCmin (×10−3 mm2/s) than MPNSTs (1.6 ± 0.4 vs 0.6 ± 0.2, respectively, p < 0.0001) and lower SUVmax than MPNSTs (3.2 ± 1.8 vs 8 ± 3.9, p < 0.0001, respectively). ADCmin correlated inversely with SUVmax (correlation coefficient r = −0.0.58, p < 0.0001). Maintaining a sensitivity of 100% with threshold values of ADCmin ≤1 or SUVmax >3.2, DWI yielded a specificity of 94% while FDG-PET/CT offered a specificity of 83%.
Conclusions Both quantitative metabolic imaging and functional imaging offer high sensitivity for the characterization of PNSTs in NF1; however, DWI/ADC mapping offers increased specificity and may be a more useful modality.
Classification of evidence This study provides Class II evidence that for patients with NF1, MRI using DWI/ADC mapping accurately distinguishes malignant and benign PNSTs.
Glossary
- ADC=
- apparent diffusion coefficient;
- ADCmin=
- minimum ADC value;
- ANNUBP=
- atypical neurofibromatous neoplasm of uncertain biologic potential;
- DWI=
- diffusion-weighted imaging;
- FDG=
- 18F-fluorodeoxyglucose;
- MPNST=
- malignant PNST;
- MR=
- magnetic resonance;
- NF1=
- neurofibromatosis type 1;
- PNST=
- peripheral nerve sheath tumors;
- ROC=
- receiver operating curve;
- SUVmax=
- maximum standardized uptake value
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Class of Evidence: NPub.org/coe
- Received October 15, 2018.
- Accepted in final form April 16, 2019.
- © 2019 American Academy of Neurology
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