[F-18]FDG, an analog of glucose, is a metabolic tracer which is trapped in the cell after its conversion into FDG-6-PO4 by hexoquinase. Tissues with high levels of glucose-6-phosphatase such as the liver, kidneys, intestines and muscles, accumulate FDG-6-PO4. The purpose of this study is to demonstrate the normal distribution of [F-18] FDG and its variations. Whole body images were performed after an intravenous injection of [F-18]FDG in 5 patients after fasting for 6 hours and in 1 patient after insulin clamp. Studies were analyzed visually and semi-quantitatively. Whole body, brain, heart, liver and muscle counts were obtained in the anterior projection. In the patients studied in the fasting state the following [F-18]FDG distribution was observed: muscles (54,4%), brain (11,7%), liver (9,7%) and heart (1,9%). In the patient submitted to insulin clamp there was a significant change in [F-18]FDG distribution : muscles (75,2%), liver (4,4%), heart (3,7%) and brain (2,8%). The marked change in concentration in muscles, brain, liver and to a lesser extent in the heart when fasting is compared to insulin clamp should be taken into consideration when planning these studies. For example, myocardial concentration must be minimized when one searches for lung metastases; liver concentration must be minimized when one searches for liver metastases; muscle concentration must be minimized when searching for skin metastases. Besides insulin there are other factors that interfere with [F-18]FDG uptake. In these patients, [F-18]FDG was present in other normal structures such as kidneys, bladder and intestines. There are also reports that demonstrate increased [F-18]FDG uptake in increased muscular activity, sites of inflammation, bladder diverticulum, breasts while feeding, thymus, etc.

The preferential [F-18]FDG distribution occurs in the brain, muscles, heart but other structures may eventually take up the tracer and many factors may change this. Particularly, insulin clamp increases myocardial and muscular concentration and reduces cerebral concentration. These differences have direct implication in each study to be performed in each patient.

9.2 - SUV-CORRELATION OF FDG-PET TO VOLU-/RELAXOMETRY OF THE HIPPOCAMPUS IN TEMPOROMESIAL SEIZURES.

Menzel , C; Grünwald, F; Ruhlmann, J; Elger, C; Biersack, H - University of Bonn Department of Nuclear Medicine – Bonn Germany

In addition to a qualitative evaluation, quantitative data of functional (FDG-PET) and morphologic (MRI) imaging were obtained to evaluate a potential correlation between the degree of mesial temporal sclerosis (MTS) and the temporal metabolism. In 33 patients with partial epilepsy (mean age 31.5 yrs., range 8-53 yrs., m:f = 16:17) FDG-PET imaging (Siemens/CTI, ECAT EXACT) including a SUV-analysis of the hippocampus, ncl. amygdalae, and the temporopolar, -basal and -lateral neocortical structures was done as well as a MRI study (Philips Gyroscan ACS II, 1.5 T) including a coronal T2w TSE (THK 2 mm) for volumetry and a coronal sequence for T2-relaxometry (THK 5 mm). Mean hippocampal volume was 2.12 ml +/- 0.59 for diseased hippocampi and 2.62 +/- 0.4 for the healthy side (normal range 1.9 - 3.0 ml). Mean T2-relaxometry was 117.7 ms and 107.9 ms (normal < 114 ms). In contrast, mean SUV within the hippocampus was 3.7 +/- 0.74 (side of seizure onset) and 3.79 +/- 0.79 (healthy side). Spearman's correlation of the quantitative results showed no positive or negative correlation. In conclusion, these data underline the relative independence of morphologic and functional information and furthermore the value of metabolic imaging as a measure of cortical dysfunction and anomalies which can clarify the extent of diseased cortex and also detect an epileptogenic focus / region even in morphologically normal subjects.

Nilton M. Hanaoka, Dilma M. Morita, Marcelo L. da Cunha, Whemberton M. Araújo, Roberval de Campos. - Institutions: DIMEN &-Medicina Nuclear - Campinas/SP/Brazil.

The use of F-18-FDG with positron emission tomography (PET) is a well established method in oncology investigation on clinical practice. With the development of dual-head gamma-cameras equipped with coincidence circuit and local production of that tracer, metabolic studies with this glucose analog became possible in our country. The aim of this work is show the first results obtained with that methodology. We studied 18 patients with different tumors such as colorectal , breast , ovarian , thyroid, head and neck and gastric carcinomas, melanoma and soft tissue sarcomas. All of them had clinical suspicions of tumor recurrence or residual tumor presence. Studies were performed in a gamma-camera equipped with coincidence circuit (Elscint &ndash;VariCam), 45 minutes after I.V. administration of 5 a 10 mCi (185 a 370 MBq) of F-18-FDG . Abnormal studies were found in 9 out 18 patients. F-18-FDG studies disclosed occult disease and helped the oncological evaluation in cases where conventional diagnostic images failed to show any abnormality.

Ramos CD, Santos AO, Etchebehere ECSC, Sagarra A, Pizão PE, Lima MCL, Camargo EE. Division of Nuclear Medicine, Department of Radiology, Campinas State University (UNICAMP) and Division of Oncology, Hospital Celso Pierro (PUCC), Campinas, Brazil.

Oncologic studies with [F-18] FDG have been recently further expanded with the new scintillation cameras that perform positron emission images using high energy collimators or coincidence detection. To evaluate the usefulness of [F-18] FDG images acquired on a two-detector scintillation camera equipped with high energy collimators 6 patients (pts) (6 males, 4 females, 25 to 67 years, mean 51.7 yrs) were studied: 2 with adenocarcinoma of the colon, 1 with spindle-cell lung carcinoma, 1 with renal cell carcinoma, 1 with carcinoid tumor and 1 with thymoma. Images were begun 40 to 90 minutes after an intravenous injection of 440 to 740 MBq (12 to 20 mCi) of [F-18] FDG. All pts were in the fasting state for 6 hours and had blood glucose levels below 110 mg% at the time of injection. Whole-body and tomographic images of the thorax and abdomen/pelvis were acquired in all pts. [Tc-99m] sulfur colloid images in 3 pts, [Tc-99m]MDP images in 2 pts and gallium-67 images in 1 pt were acquired simultaneously to the [F-18] FDG images. [F-18] FDG images were compared to computed tomography (CT) and surgical findings in 2 pts, to CT only in 2 pts, to CT and bone scintigraphy in 1 pt, and to octeotride scintigraphy and mammography in 1pt. [F-18]FDG images demonstrated clinically relevant findings in 4 pts and led to a change in pt management. In one pt there was no [F-18] FDG uptake and in another pt it was not possible to distinguish tumor uptake from the physiologic uptake of the radiopharmaceutical in the intestines. [F-18] FDG images acquired in a scintillation camera equipped with high energy collimators are very useful and may change clinical management in a significant number of pts. These systems also allow simultaneous acquisition of images with another radiopharmaceutical thus improving anatomical references and the level of confidence.

9.5 - FDG-PET DURING THERAPY AND FOLLOW-UP OF DIFFERENTIATED THYROID CARCINOMA

Menzel, C; Grünwald, F; Biersack, H - University of Bonn Department of Nuclear Medicine &ndash; Bonn- Germany