Intravoxel incoherent motion magnetic resonance imaging in head and neck cancer: A systematic review of the diagnostic and prognostic value

Intravoxel incoherent motion (IVIM) imaging is increasingly applied in the assessment of head and neck cancer (HNC). Our purpose was to determine the diagnostic and prognostic performance of IVIM in HNC by performing a critical review of the literature. Pubmed and EMBASE were searched until May 2016. Study and patients characteristics, imaging protocol and diagnostic or prognostic outcomes were extracted by 2 independent reviewers. The studied IVIM parameters were diffusion coefficient (D), pseudodiffusion coefficient (D∗), and perfusion fraction (f). We included 10 diagnostic studies, 5 prognostic studies and 2 studies assessing both. Studies were very heterogeneous in terms of applied b-values, imaging protocols, outcome measurements and reference standards; therefore we did not perform a meta-analysis. The most commonly used sequence was “spin-echo planar imaging”. A median of 10.5 b-values (range, 3-17) were used. All but three studies included at least 4 b-values below b = 200 s/mm2. By combining IVIM-parameters squamous cell carcinomas, lymphomas, malignant salivary gland tumors, Warthin's tumors and pleomorphic adenomas could be differentiated with a sensitivity of 85-87% and specificity of 80-100%. Low pre-treatment D or f and an increase in D during treatment were associated with a favorable response to treatment. D∗ appeared to be the parameter with the lowest prognostic value. Future research should focus on finding the optimal IVIM protocol, using uniformly accepted study methods and larger patient populations.