F-18 fluorodeoxyglucose positron emission tomography in malignant lymphoma

Abstract

Non-invasive imaging methods are important diagnostic tools for initial staging and re-staging after radiochemotherapy in patients with malignant lymphomas. Conventional imaging is mainly based on CT although MRI and sonography also gain more and more importance in these indications. The F-18-Fluorodeoxyglucose-positron emission tomography (F-18-FDG-PET) imaging is based upon increased glucose metabolism in tumor tissue, a phenomenon also seen in lymphomas with the exeption of MALT type lymphomas. Comparative studies between conventional imaging methods and F-18-FDG-PET showed that F-18-FDG-PET is capable of visualizing the extent of lymphomas with high sensitivity and specificity at initial staging and at re-staging after therapy. Results of F-18-FDG-PET were better than those of conventional imaging. One of the major limitations of conventional imaging with CT is the lack of distinguishing residual lymphoma tissue and fibrotic scar tissue after therapy. However, F-18-FDG-PET is capable to resolve this problem as it is based on metabolism and it can distinguish with high sensitivity and specificity between residual lymphoma tissue and fibrotic scar tissue after therapy. Thus, in particular, in those patients with residual lymphoma bulks after therapy, the use of F-18-FDG-PET can give essential informations with regard to the planning of further therapeutic interventions. In conclusion, F-18-FDG-PET seems to open new dimensions in imaging of lymphoma both for initial staging and for restaging after therapy. Moreover, studies have shown that the use of F-18-FDG-PET in lymphoma patients is cost effective. Due to this background and the fact that the availability of F-18-FDG will be further facilitated, the F-18-FDG-PET will probably gain increasing importance in the management of patients with lymphomas in the close future.