[New opportunities, MRI biomarkers in the evaluation of head and neck cancer].

Magnetic resonance imaging (MRI) has developed rapidly during the past few years and, according to the needs of therapy, has opened new perspectives in oncologic imaging with better and better realization of the latest technological advances. After the introduction of "organ preservation" protocols the role of imaging has become more important. New therapeutic methods (improvement in radiation therapy and chemotherapy) need better tumor characterization and prognostic information along with the most accurate anatomical information. Multiparametric anatomical and functional MR imaging (MM-MRI) using high magnetic field strength (3 Tesla) are useful in determining tumor-specific MRI biomarkers and in evaluating the changes in these parameters during therapy to provide early assessment of the therapeutic response. Diffusion-weighted MRI (DW-MRI) provides information at the cellular level about cell density and the integrity of the plasma membrane. DW-MRI shows potential in improving the detection of cancer due to its high specificity and high negative predictive value. Quantification is performed using an apparent diffusion coefficient (ADC), the values are independent of the magnetic field strength. In the latest publications the accuracy of DW-MRI has been reported around 90% for the differentiation between malignant versus benign tumor using an ADC cut-off mean value of 0.700-1.200 10(-3) mm(2)/s units, but no common threshold ADC value exists in clinical routine for the differentiation of malignant and benign tissues. Dynamic contrast-enhanced MRI (DCE-MRI), as a marker of angiogenesis, provides information about vascularization at the tissue level. Angiogenetic alterations cause changes in the parameters of vascular physiology (perfusion, blood volume, capillary permeability) and thus alter the contrast enhancement observed on contrast MRI. High-grade and/or advanced stage tumors are associated with increased blood volume, increased permeability and increased perfusion; the data can be evaluated using semiquantitative or quantitative methods. Magnetic resonance spectroscopic imaging (MRSI) provides biochemical analysis at the molecular level. The results are promising, although further studies are required to determine whether MRSI can be used to identify or exclude cancer within regions where the cancer is not evident on conventional MRI or with the other functional imaging methods. Some of the studies demonstrated the usefulness of these functional MRI methods also in the head and neck region to differentiate benign from malignant tumors, to quantify the response to radiation therapy and chemotherapy, to identify residual or recurrent tumor and to correlate the perfusion or diffusion data with prognosis. There are still some overlaps between benign and malignant changes, and the use of these functional MR measurements in routine diagnostics are still not fully validated today. Functional MR measurements are useful parts of the high quality multiparametric MRI, they offer important supportive biological and molecular information with the aid of high resolution morphological imaging.