ABSTRACT. The purpose of this study is to evaluate the role of diffusion-weighted imaging (DWI) in combination with T 1 and T 2 weighted MRI for the characterisation of renal carcinoma. The institutional review board approved the study protocols and waived informed consent from all of the patients. 47 patients (32 male and 15 female; age range, 21-85 years; median age, 65 years) who had suspected renal lesions on abdominal CT underwent MRI for further evaluation and characterisation of the lesions from April 2005 to August 2007 in our university hospital. A region of interest was drawn around the tumour area on apparent diffusion coefficient (ADC) maps. Final diagnosis was confirmed by histological examination of surgical specimens from all patients. The ADC value was significantly higher in renal cell carcinoma (RCC) ; p50.0004), whereas intensity on T 1 and T 2 weighted imaging did not reach statistical significance. In conclusion, DWI has clinical value in the characterisation of renal carcinomas and could be applied in clinical practice for their management. Renal cell carcinoma (RCC) is the most common primary malignant tumour of the kidney; it accounts for 2-3% of all adult cancers and is the sixth cause of death by tumour throughout the world. More than 80% of renal cancers that arise in the renal parenchyma are RCC, whereas the majority of renal pelvis cancers are transitional cell carcinomas (TCCs) [1][2][3]. The three most common subtypes of RCC are (i) clear cell carcinoma, one of the most common types, accounting for 70-80% of cases; (ii) papillary renal cell carcinoma, accounting for about 10-15% of cases; and (iii) chromophobe renal carcinoma, which is the least common, accounting for 5% of all RCCs. The annual rate of RCC diagnosis is increasing as a result of incidental detection by crosssectional abdominal imaging of patients with suspected abdominal disorders. Increased detection rates carry a favourable prognosis; however, mortality from RCC has not decreased [2][3][4].Diffusion-weighted imaging (DWI) is frequently used in cranial MRI studies and has shown potential for the characterisation of lesions such as acute cerebral infarctions, intracranial tumours, various infectious diseases and metabolic disorders [5][6][7][8]. The role of DWI is limited outside the central nervous system, owing to its inherent extreme sensitivity to motion, such as that related to respiration, peristalsis and artefacts, thus resulting in a high signal to noise ratio. With the development of advanced MR technology and the use of faster robust sequences, better quality has been obtained in abdominal imaging [9]. DWI with high b-values has been reported to have a high sensitivity for depicting malignant disease. Apparent diffusion coefficient (ADC) values of malignant hepatic, ovarian, breast, prostatic, colonic and uterine cervical tumours were lower than those of benign lesions or normal tissue [10][11][12][13][14][15][16][17][18].Previous studies have suggested that patients with chromophobe and papillary RCC ha...

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.