No abstract

Positron emission tomography (PET) using 2-(18)F-fluoro-2-deoxy-D-glucose (FDG), a radioactive derivative of glucose, is an advanced imaging tool, based on the increased glucose consumption of cancer cells. FDG-PET provides information that is not obtainable with other imaging modalities, and is very effective in the diagnosis and management of patients with various types of cancers. However, there are some limitations, such as low FDG uptake in some cancers, substantial FDG uptake in inflammatory cells, and the lack of anatomical information and poor imaging quality of PET. A recently developed integrated PET/computed tomography (CT) system, which combines a PET camera and CT scanner in a single session, has overcome these drawbacks by providing both anatomical and functional imaging at the same position. PET and/or PET/CT using FDG is clinically useful in the detection of cancer, the differentiation of malignant and benign lesions, the staging of cancer before therapy, and the assessment of cancer therapy, as well as for determining the recurrence after therapy of most cancers, including lung cancer, gastrointestinal cancer, breast cancer, and malignant lymphoma. PET/CT has become the new standard approach to imaging in the diagnosis and management of many cancer patients.

P ositron emission tomography (PET) is a non-invasive imaging technique that uses various radiolabeled compounds.PET was developed almost three decades ago and was used initially for evaluating cerebral blood flow and metabolism under physiological conditions and also for assessing pharmacological or neuropsychological intervention.In the past decade, the clinical applications of PET have expanded with the improvement of PET detectors used for whole-body imaging, and the development of PET in combination with computed tomography (PET-CT). PET-CT offers advantages in accurate diagnosis based on both morphological and metabolic images.Use of PET has spread particularly in clinical oncology using 18 F-fluorodeoxyglucose ( 18

The aim of this study was to evaluate the role of positron emission tomography (PET) with 18 F-fluoro-2deoxy-D-glucose (18 F-FDG) in the restaging of hepatocellular carcinoma (HCC) treated with radiofrequency ablation (RFA). This study was performed on 33 lesions in 24 patients with HCC. 18 F-FDG PET and computed tomography (CT) studies were performed in all patients before treatment. PET acquisition was started 50-60 min after injection of 18 F-FDG (5-6 MBq/kg). Semi-quantitative analysis using Standardized Uptake Value (SUV) was measured for the evaluation of tumour 18 F-FDG uptake. All patients underwent RFA treatment and were followed up at least 2 years with 18 F-FDG PET, CT and clinical evaluation in the interval of every 3 months in the first year and every 6 months in the second year. 18 F-FDG PET detected recurrence earlier than CT between 4-6 months in 2 patients and between 7-9 months in 6 patients whereas CT was positive in 4 patients. Overall detection rate of recurrence with 18 F-FDG PET was 92% which was higher than that of CT (75%). Statistically significant difference in the SUV was observed between well and moderately differentiated HCC (p=0.033) and also between well and poorly differentiated HCC (p=0.037). The size of tumours showed a significant correlation with the time of recurrence (p<0.00033, r=0.8601, n=12). The results of this study indicate that 18 F-FDG PET could detect recurrence earlier in patients with HCC treated with RFA, as compared with CT and could diagnose extrahepatic lesions. SUV showed a significant correlation with time of recurrence after RFA. 18 F-FDG PET may be a dominant imaging modality as a follow-up procedure of HCC after RFA, in terms of early detection of recurrence.

L‐[3‐18F]‐α‐methyltyrosine (18F‐FMT) is an aminoacid tracer for positron emission tomography (PET). The aim of this study was to determine whether PET‐CT with 18F‐FMT provides additional information for the preoperative diagnostic workup as compared with 18F‐FDG PET. PET‐CT studies with 18F‐FMT and 18F‐FDG were performed as a part of the preoperative workup in 36 patients with histologically confirmed bronchial carcinoma, 6 patients with benign lesions and a patient with atypical carcinoid. Expression of L‐type amino acid transporter 1 (LAT1), CD98, Ki‐67 labeling index, VEGF, CD31 and CD34 of the resected tumors were analyzed by immunohistochemical staining, and correlated with the uptake of PET tracers. For the detection of pulmonary malignant tumors, 18F‐FMT PET exhibited a sensitivity of 84% whereas the sensitivity for 18F‐FDG PET was 89% (p = 0.736). 18F‐FMT PET‐CT and 18F‐FDG PET‐CT agreed with pathological staging in 85 and 68%, respectively (p = 0.151). 18F‐FMT uptake was closely correlated with LAT1, CD98, cell proliferation and angiogenesis. The specificity of 18F‐FMT PET for diagnosing thoracic tumors was higher than that of 18F‐FDG PET. Our results suggest that coexpression of LAT1 and CD98 in addition to cell proliferation and angiogenesis is relavant for the progression and metastasis of lung cancer. © 2008 Wiley‐Liss, Inc.