- POPULATION: We included the first 500 consecutive exams, 96 % with known or suspected malignant disease (479 cases). The rest of them were referred for other neurological or psychiatric diagnosis in four cases and for myocardial viability in one and another to evaluate fever of unknown origin. Sixty percent were females Their mean age was 53±12 years old, ranging from 3 to 94 (only 20 patients under 20 year old) Thirty-eight patients were known diabetics (only two insulin dependent). We have received patients from different national centers and from several countries (Argentina, Peru, Bolivia, Brazil, Ecuador and Uruguay).

- F18-FDG: It was obtained from the IBA Cyclone 18/9 cyclotron installed at the Chilean Agency of Nuclear Energy (CCHEN), distant about 15 miles away from the clinical PET facility (30 min). Mean F18-FDG injected dose was 444 MBq (12 mCi) and [range :1-19 mCi] . Mean blood glucose level was 93±16 [range 59-164] previous to injection. If glucose level was >160mg/dl a standard insulin schema was used in a few cases.

- GENERAL PROTOCOL: All patients were fasting at least 4-6 hours and Hemoglucotest was performed prior to FDG injection. A 60 min period at rest was allowed for FDG distribution in an isolated and silent room with mild light and under video control. Bladder voiding was asked before positioning the patient. No diuretics, cathartics or bladder catheterization were used. The patients were with their arms above the head, when possible. Sedation was required very occasionally.

- ACQUISITION AND PROCESSING: A PET dedicated Siemens HR+ (4mm resolution) was employed, with 6-7 min / bed acquisition (14 cm each). Data acquisition protocol consisted in 6-8 beds/study; 36% transmission, with germanium 68 rods. In most cases 2D acquisition was preferred. Only few were acquired with 3D (lower FDG dose). All oncological patients underwent whole body scan from head to proximal thighs; additionally, inferior limbs in melanoma or brain, pelvis, head and neck were also acquired in other tumors. The data were reconstructed with standard OSEM protocol.

- INTERPRETATION: The patients were carefully interviewed by a physician prior to the test with special attention to surgical or inflammatory history, chemo or radiotherapy, histological and conventional images results. PET studies were analyzed by at least 4 independent observers visually. Standardized uptake value (SUV) was calculated in some cases. Fusion of FDG images with recent anatomical (CT, MRI) studies was performed when available with e-soft Siemens software. Initially, most of referring clinicians were contacted in order to explain them the results and conclusions. Institution radiologists discussion was undertaken in the most problematic cases, in order to obtain adequate correlation and the maximal information of the FDG exam.