Intensity Of FDG Uptake Research Articles

Intensity of18Fluorodeoxyglucose Uptake in Positron Emission Tomography Distinguishes Between Indolent and Aggressive Non-Hodgkin’s Lymphoma

(18)Fluorodeoxyglucose positron emission tomography (FDG PET) is widely used for the staging of lymphoma. We investigated whether the intensity of tumor FDG uptake could differentiate between indolent and aggressive disease. PET studies of 97 patients with non-Hodgkin's lymphoma who were untreated or had relapsed and/or persistent disease and had not received treatment within the last 6 months were analyzed, and the highest standardized uptake value (SUV) per study was recorded. Correlations were made with histopathology. FDG uptake was lower in indolent than in aggressive lymphoma for patients with new (SUV, 7.0 +/- 3.1 v 19.6 +/- 9.3; P < .01) and relapsed (SUV, 6.3 +/- 2.7 v 18.1 +/- 10.9; P = .04) disease. Despite overlap between indolent and aggressive disease in the low SUV range (indolent, 2.3 to 13.0; aggressive, 3.2 to 43.0), all cases of indolent lymphoma had an SUV <or= 13. A receiver operating characteristic (ROC) analysis demonstrated that the SUV distinguished reasonably well between aggressive and indolent disease (area under ROC curve, 84.7%), and an SUV > 10 excluded indolent lymphoma with a specificity of 81%. With a higher cutoff for the SUV, the specificity would have been higher. FDG uptake is lower in indolent than in aggressive lymphoma. Patients with NHL and SUV > 10 have a high likelihood for aggressive disease. This information may be helpful if there is discordance between biopsy and clinical behavior.

FDG-PET and Beyond: Molecular Breast Cancer Imaging

Positron emission tomography (PET) scanning has gained widespread acceptance for the diagnosis, staging, and management of a variety of malignancies, including breast cancer. This has heralded an exciting new era of molecular imaging research of which using FDG as the primary PET tracer is only the beginning. The fundamental strength of PET over conventional imaging is the ability to convey functional information that even the most exquisitely detailed anatomic image cannot provide. As the standard PET radiotracer in current clinical use, FDG is a glucose analog that is taken up by cells in proportion to their rate of glucose metabolism. The increased glycolytic rate and glucose avidity of malignant cells in comparison to normal tissue is the basis of the ability of FDG-PET imaging to accurately differentiate cancer from benign tissue irregardless of morphology. The level or intensity of FDG uptake on PET is semiquantified and reported as the standardized uptake value (SUV). A multitude of new PET tracers are under development, many of which are aimed at targeting cellular processes that are more specific than glucose metabolism. In relation to breast cancer, these tracers include thymidine analogs such as [F-18]fluoro-L-thymidine (FLT) that target DNA replication as a measure of cell proliferation, annexin V derivatives that evaluate apoptosis, estrogen receptor (ER) tracers such as 16 -[F-18]fluoroestradiol-17 (FES), and engineered antibody fragments that directly target HER-2/neu receptors. In addition to new tracers, scanner technology is also rapidly evolving. Chief among these is the advent of the dual modality PET/CT scanner, which at the very least increases patient convenience by permitting PET and computed tomography (CT) imaging in a single appointment. But perhaps more importantly, initial studies indicate that the sum of the two modalities is better than either used separately and also may be an extremely useful tool in preradiation therapy planning. Other new scanning devices are also being developed, including small gantry PET scanners designed specifically for breast imaging, and handheld PET probes for direct intraoperative localization of tracer-avid tumor foci.

Positron Emission Tomography Helps in Excluding Distant Lesions in a Case of Mesothelioma

Malignant pleural mesothelioma (MPM) is an uncommon neoplasm (2500 cases per year in the United States) of the pleura. Computed tomography (CT) is the primary modality for diagnosis and staging of MPM. Positron emission tomography (PET) is useful for staging of malignant mesothelioma, because it can provide information regarding extrathoracic spread and lymph node metastasis. PET imaging is helpful in selecting the most appropriate site for biopsy based on the metabolic activity. The intensity of FDG uptake can predict the prognosis of MPM. A case of malignant mesothelioma encasing the entire tight lung is presented here.

The value of F-18-fluorodeoxyglucose PET for the 3-D radiation treatment planning of malignant gliomas

Purpose: The aim of the study was to determine the impact of positron emission tomography using the glucose analogue fluorine-18-fluorodeoxyglucose (FDG-PET) on the delineation of the target volume in three-dimensional radiation treatment planning of primary brain tumors. Methods and Materials: In 18 patients with histologically proven (8× biopsy, 10× subtotal resection) primary brain tumors (8 astrocytomas °III, one mixed glioma °III, and 9 glioblastomas), magnetic resonance imaging (MRI) with gadolinium-DTPA and FDG-PET were performed in radiation treatment position within the same week. A computer program was developed for fusion of the PET and MR images. On corresponding axial slices, FDG uptake was compared to contrast enhancement in T1-weighted and to signal hyperintensity in T2-weighted MR images. Based on PET and MRI data, three-dimensional treatment planning was performed. All patients underwent linear accelerator (LINAC) radiotherapy. Results: In MRI, all tumors and the surrounding edema were visible as hyperintense lesions in the T2-weighted images. 17/18 tumors showed contrast enhancement. In FDG-PET, 16 tumors showed hypermetabolism compared to normal white matter, whereas only 8/18 tumors showed hypermetabolism compared to normal gray matter. White matter edema was associated with decreased FDG uptake in all patients. The area of increased FDG uptake correlated closely with contrast enhancement, only in one case the volume of increased FDG uptake was larger than the area of contrast enhancement. Mean tumor volumes obtained by MRI T1 + Gd, T2, and PET were 30, 106, and 10 ml, respectively. Survival was comparable to data in the literature with a 1-year survival of 39% and a median survival of 310 days. Conclusion: Only in a minority of patients did FDG-PET provide additional information for radiation treatment planning. This is mainly caused by the high intensity of FDG uptake in normal brain tissue. PET may be of greater value in the definition of regions that should obtain a radiation dose boost.

Prospective evaluation of 2-[18F]-2-deoxy-D-glucose positron emission tomography in staging of regional lymph nodes in patients with cutaneous malignant melanoma.

To assess prospectively the accuracy of 2-[l8F]-2-deoxy-D-glucose positron emission tomography (FDG-PET) for predicting regional node involvement in cutaneous malignant melanoma (CMM). Twenty-three patients with CMM (primary lesions > 1.5 mm thick) scheduled for lymph node dissection (LND) were preoperatively studied with FDG-PET. Thirteen patients underwent therapeutic LND of 14 node basins, while nine patients had elective LND of 10 node basins. Medical problems precluded surgery in one patient. Two observers unaware of the clinical node status-apart from whether a recent surgical scar was present-read attenuation-corrected reconstructed transverse images acquired between 50 and 60 minutes after injection. Intensity of FDG uptake was scored as 0 to 3 + on a semiquantitative four-point scale: 0, no uptake; 1 +, faint; 2 +, moderate; and 3 +, intense uptake. A node group was considered positive on FDG-PET if it contained at least one focus of FDG uptake of > or = 2+ intensity. Histopathologic examination of the 24 dissected node groups served as a reference. Considering regional node basins, PET imaging demonstrated 11 true-positive (TP), 10 true-negative (TN), two false-negative (FN), and one false-positive (FP) result, for an overall accuracy of 88%. Histopathologic from one FN case showed seven malignant cells in a marginal node sinus. The FP was due to reactive changes postbiopsy. In one patient, clinically involved lymph nodes were correctly categorized TN by PET. At least four additional 2 + foci seen outside the dissected regions on PET may represent metastases and are being monitored. FDG-PET accurately predicted regional node status in 88% of CMM cases. The failure to detect micrometastatic disease may be due to the limitations of the imaging equipment and technique used here.

161 The assistance of PET and MRI in 3-D radiation treatment planning for primary brain tumors

MR imaging has been shown to be superior to CT in the treatment planning for malignant brain tumors. However, even with MR after administration of Gd-DTPA it remains often difficult to differentiate between tumor tissue and surrounding normal tissue and edema. Therefore, we evaluated whether the functional metabolic information provided by F-l8-FDG-PET would allow for a better delineation of the target volume. In 10 patients with primary brain tumors (2 oligodendrogliomas, 3 anaplastic astrocytomas and 5 glioblastomas) MR imaging with gadolinium contrast and F-18-FDG-PET were performed in radiation treatment position within the same week. Tumors were histologically proven by biopsy in 2 patients and by subtotal resection in 8 cases. A computer program based on an external Z-shaped marker was developed for fusion of the PET and MR images. On corresponding axial slices FDGuptake was compared to contrast enhancement in T 1 weighted images and to signal hyperintensity in T2 weighted MR-images. Based on the combined PET and MRI data three-dimensional treatment planning was performed. Afterwards all patients underwent LINAC radiotherapy. In all cases tumor and surrounding edema were visible as hyperintense lesions in the T2 weighted images, 8/10 tumors showed Gd-contrast enhancement. Nine out of 10 tumors showed hypometabolism compared to normal gray matter, 6/10 tumors hypermetabolism compared to normal white matter. The area of increased uptake correlated in 5/6 cases with Gd-contrast enhancement, only in 1/6 cases the area of increased FDG-uptake was larger than the area of Gd-contrast enhancement. White matter edema was associated with decreased FDG-uptake in all patients. The authors conclude that only in a minority of patients F-18-FDG-PET provides additional information for radiation treatment planning. This is mainly caused by the high intensity of FDG uptake in normal brain tissue. PET may be of greater value in the definition of viable tumor tissue using different tracers, especially amino acids or thymidine. MR imaging has been shown to be superior to CT in the treatment planning for malignant brain tumors. However, even with MR after administration of Gd-DTPA it remains often difficult to differentiate between tumor tissue and surrounding normal tissue and edema. Therefore, we evaluated whether the functional metabolic information provided by F-l8-FDG-PET would allow for a better delineation of the target volume. In 10 patients with primary brain tumors (2 oligodendrogliomas, 3 anaplastic astrocytomas and 5 glioblastomas) MR imaging with gadolinium contrast and F-18-FDG-PET were performed in radiation treatment position within the same week. Tumors were histologically proven by biopsy in 2 patients and by subtotal resection in 8 cases. A computer program based on an external Z-shaped marker was developed for fusion of the PET and MR images. On corresponding axial slices FDGuptake was compared to contrast enhancement in T 1 weighted images and to signal hyperintensity in T2 weighted MR-images. Based on the combined PET and MRI data three-dimensional treatment planning was performed. Afterwards all patients underwent LINAC radiotherapy. In all cases tumor and surrounding edema were visible as hyperintense lesions in the T2 weighted images, 8/10 tumors showed Gd-contrast enhancement. Nine out of 10 tumors showed hypometabolism compared to normal gray matter, 6/10 tumors hypermetabolism compared to normal white matter. The area of increased uptake correlated in 5/6 cases with Gd-contrast enhancement, only in 1/6 cases the area of increased FDG-uptake was larger than the area of Gd-contrast enhancement. White matter edema was associated with decreased FDG-uptake in all patients. The authors conclude that only in a minority of patients F-18-FDG-PET provides additional information for radiation treatment planning. This is mainly caused by the high intensity of FDG uptake in normal brain tissue. PET may be of greater value in the definition of viable tumor tissue using different tracers, especially amino acids or thymidine.