Prognostic Value of Volume Based Parameters of PET/CT in Malignant Lymphoma.

Abstract

18F FDG PET/CT has long been the corner stone for staging. It resulted in upstaging of up to 20 % of patients. Its main advantage is that it can detect metabolic changes in involved areas long before structural changes become visible. Furthermore, it’s the main stay for evaluating therapeutic response especially in situations where CT has very limited role as differentiating viable residual from necrotic/fibrotic lesions and detecting nature of small lesions.Of all semi quantitative parameters of 18F FDG PET/CT, SUV max has always been the leading parameter for Nuclear Medicine. However it doesn’t represent the whole tumour metabolic burden because it’s only measured from single voxel and therefore it’s sensitive to image noise which is impacted by patients characteristics and imaging parameters.Recently, researchers have been minded by Metabolic Tumour Volume (MTV), which is measurement of tumour volume with a high metabolism, and Total Lesion Glycolysis (TLG), which is the product of mean SUV and MTV. Recent studies suggest that MTV and TLG are more inclusive parameters that better present the whole Metabolic Tumour Burden than SUV max, but with a limitation point that these parameters require accurate segmentation of the tumour and standardization of tumour segmentation. These studies suggest usefulness of MTV and TLG for expectation of treatment response, prognosis of clinical outcome, tumour delineation for radiotherapy planning, however there’s no consensus on optimal way to measure MTV using 18F FDG PET/CT.