New techniques of thyroid medical imaging. Progress and limits in the exploration of isolated thyroid nodules

The exploration of thyroid nodules deals mainly with the problem of detection of malignancy. Except in the cases of characteristic clinical situations which suggest at once malignancy, classical investigations offer mostly an insufficient approach including erroneous conclusions. Scintigraphy, whose morphological definition remains limited, can miss non - or hypofixing lesions. Pharmacological tests of nodule reduction by suppression of thyreostimulin do not provide specific informations. Fine needle- biopsy cannot absolutely exclude malignancy, depending too much of the sites of punction and of the difficulties of cytological analysis. Echography brings an important progress in the precision of thyroid volume, nodules counting and gross connections. The liquid or solid characterization is an important echographic information as well. Tomodensitometry provides useful data in the retrosternal and retrotracheal areas. The connections with aerodigestive tract are more clearly pointed out and the presence of metastatic nodes as well. Magnetic resonance imaging gives further information because of the ability of multiple longitudinal slices, and of the trial of a tissular characterization from signal analysis and ultrastructural macroanatomic study. Additive precisions will be likely in the future by a more accurate determination of criteria of malignancy. The complementarity of magnetic resonance imaging and fine needle-biopsy should lead to a more frequent use of these investigations before the decision of surgical removal