Temporal profile of fluorodeoxyglucose uptake in malignant lesions and normal organs over extended time periods in patients with lung carcinoma: implications for its utilization in assessing malignant lesions.

AIM: In this study, the fluorodeoxyglucose (FDG) uptake was prospectively investigated in tumors as well as the normal organs over 8 h in patients with non small cell lung carcinoma (NSCLC). The intent of this study was to collect positron emission tomography (PET) data with regard to the time course of FDG uptake in the primary and metastatic sites and the normal tissues over extended time periods (up to 8 h) after intravenous FDG injection in patients. METHODS: Three patients (2 males, 1 female; mean age: 64 years; age range: 57-76 years) with the diagnosis of NSCLC underwent a series of whole body FDG-PET at several time points, beginning at 5 min and extending up to 8 h after the intravenous administration of FDG. We calculated the standardized uptake values (SUVmax) in the malignant lesions and all organs. SUVmax was calculated over contiguous slices and the highest value was considered for the analysis. Similar locations were used for the placement of regions of interest in subsequent images. Time activity curves (TACs) were generated utilizing these SUV values for each of these sites. The ratios of the SUVmax of the malignant lesions to those of normal organs (viz. lung and liver) at specific time points were also calculated and the TACs for these ratios were generated. The blood and plasma decay curves of (18)F activity over time were generated based on the counts obtained from blood sample analysis. The ratios of 18F activity of blood to plasma were also calculated and the TACs of this ratio were generated. RESULTS: The observed mean SUVmax at different time points (5 min, 1 h, 2 h, 4 h, 6 h and 8 h) in the organs and the lesions were as follows: 1) heart: 2.9, 2, 1.9, 1.6, 1.3, 1.5; 2) kidney: 3.3, 3.5, 2.6, 2.1, 2, 2; 3) liver: 3.9, 2.2, 1.9, 1.6, 1.5, 1.8; 4) lung: 0.6, 0.5, 0.4, 0.4, 0.4, 0.4, 0.4; 5) large bowel: 2.1, 1.4, 1.8, 1.4, 2, 2.2; 6) small bowel: 2.6, 1.6, 1.4, 1.2, 1.3, 1.5; 7) lung neoplasm: 3.7, 5.1, 6.1, 6.8, 6.9, 6.8; 8) mediastinal lesion 1: 6.8, 8.8, 13, 12.7, 13.8, 12.5; 9) mediastinal lesion 2: 5.5, 8.6, 10.7, 13.2, 11.7, 12.1; 10) adrenal metastasis (starting at 1 h): 3.3, 3.7, 4.7, 4.7, 4.7; 11) right iliac metastasis: 2.6, 2.6, 3.1, 3.5, 3.4. For the right iliac metastasis, we had SUVmax up to 6 h. The SUVmax ratios of malignant lesions to those of normal lung and liver and their TACs demonstrate initial rise followed by a delayed plateau. Increasing (18)F count ratios of blood to plasma with time was observed in 2 patients where these data were available. CONCLUSIONS: The results from this preliminary study indicate that while the tumor sites show increased uptake of FDG during the course of 8 h, surrounding normal tissues demonstrate declining or stable values with time. This would indicate increasing contrast between the lesion and the background and, therefore, possibly improved sensitivity of the test. While the high SUV at 5 min can be explained by the blood pool activity in the organs and the malignant lesions, the SUVmax values at the later times decreases or remains the same in normal organs. The observation on the different slopes of the curves among the various malignant lesions can be partly explained by the well known ''seed and soil'' theory in cancer biology. The finding of continued increases in the blood to plasma count ratios of (18)F activity is also noteworthy and most likely reflects GLUT-1 mediated glucose transport into red blood cells.

Magnetic resonance imaging based bone marrow segmentation for quantitative calculation of pure red marrow metabolism using 2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography: a novel application with significant implications for combined structure-function approach.

AIMS: The aim of this study was to introduce a new concept for accurate measurement of the global metabolic activity of the red marrow by combining segmented volumetric data from structural imaging techniques such as magnetic resonance imaging (MRI) and quantitative metabolic information provided by functional modalities such as positron emission tomography (PET). MATERIALS AND METHODS: Imaging studies from five subjects who had undergone both MRI and 2-deoxy-2-[F-18]fluoro-D-glucose(FDG)-PET were selected for this analysis to test the feasibility of this approach. In none of the subjects, there were any marrow abnormalities as determined either by the MRI or by FDG-PET studies. The mean blood glucose level was 96+/-25 mg/dl. The first step was to calculate vertebral volume at L1, L3, and L5 from the available MRI studies. The red and yellow marrows were then segmented within the lumbar vertebrae using the 3DVIEWNIX software system from which the respective volumes were also calculated for each. This also allowed calculating the bone volume in each of the vertebral bodies examined. By employing the standard techniques, the mean of the maximum standardized uptake values (mean SUVmax) for the bone marrow were calculated in L1, L3 and L5 of the lumbar spine, and then global red marrow activity was calculated using the following approach: (1) Whole vertebral metabolic activity (WVMA)=vertebral volume x mean SUVmax of the entire marrow, (2) whole vertebral metabolic activity for yellow marrow (WVMAYM)=yellow marrow volume x mean SUVmax of fat (obtained from measurements of subcutaneous fat), (3) whole vertebral metabolic activity for red marrow (WVMARM)=WVMA-WVMAYM; and finally, (4) SUVmax for pure red marrow=whole vertebral metabolic activity for red marrow (WVMARM)/red marrow volume (obtained from the segmentation data). RESULTS: The mean volume of the lumbar vertebral body was 15.6+/-1.4 cm3, the bone marrow mean SUVmax was 1.5+/-0.3, and the MVP for the lumbar vertebral body was 23.4+/-5.9. The mean volume of the yellow marrow in the lumbar vertebral body was 7.7+/-1.1 cm3, the yellow marrow mean SUVmax was estimated to be 0.38+/-0.1 and the MVP for the yellow marrow in the lumbar vertebral body was 2.9+/-0.9. The mean volume of the red marrow in lumbar vertebral body was 7.9+/-1.1 cm3, the red marrow mean SUVmax was estimated to be 2.6+/-0.6, and the MVP for the red marrow in the lumbar vertebral body was 20.5+/-5.9. CONCLUSION: Estimation of the individual component of the bone marrow is plausible using medical image segmentation with combined structure-function approach. This can have potential research and clinical applications concerning the study of global metabolic activity of the individual component and diagnosis of benign and malignant bone marrow disorders.