Comparison of F-18 FET-PET with F-18 FDG-PET for biopsy planning of non-contrast-enhancing gliomas

Objective:

The management of non-contrast-enhancing brain tumours largely depends on biopsy, which allows a differentiation of low-grade gliomas (LGG) from high-grade gliomas (HGG). The aim of this study was to compare positron emission tomography using 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (FDG-PET) and O-(2-[¹⁸F]-fluoroethyl)-l-tyrosine (FET-PET) in terms of providing target regions for biopsies.

Materials and methods:

Fifteen consecutive patients with newly diagnosed brain tumours (n?=?11) or suspected recurrence of a known LGG (n?=?4), in whom MRI demonstrated no contrast enhancement, were studied by both FET-PET and FDG-PET. FET-PET, FDG-PET and MRI data were fused, and then transferred to the neurosurgical navigation system, prior to neurosurgical interventions.

Results:

Histology showed HGG (WHO grade III) in 6/15 and LGG (WHO grade II) in 9/15 patients. FET-PET revealed an increased intratumoural tracer uptake in 8/9 LGG and in 5/6 HGG. FDG-PET depicted hypermetabolic spots in 2/9 LGG and in 4/6 HGG. In 6 patients we observed an increased intratumoural uptake of both tracers. In 4 of them, the area of highest FET accumulation in the tumour corresponded to the focus of increased FDG uptake.

Conclusions:

FET-PET appears to be superior to FDG-PET for biopsy planning in non-contrast-enhancing brain tumours. FDG-PET does not provide any additional information in this issue.     

Rapid Quantitative Analysis of Individual (18)FDG-PET Scans

To evaluate an objective, quantitative, semi-automatic method of single (18)FDG-PET scan analysis. Scans of 60 normal controls was compared to scans from individuals with known pathology using two methods of visual analysis and Statistical Parametric Mapping with two different smoothing filters. We analyzed the sensitivity, specificity, and accuracy of each technique and evaluated the agreement between the four methods using a kappa statistic. When corrected for false positives, which were due to anatomical distortions, all techniques had a sensitivity and accuracy of 0.5 to 0.6. Specificity was highest, 1.0, using SPM with a 16 mm smoothing filter, followed by visual analyses. Good agreement between all techniques was found. A computerized expert which makes use of a normal data base and SPM to analyze single (18)FDG-PET scans can aid in the routine interpretation of scans and provide rapid, quantification of abnormalities for research or clinical purposes.     

Usefulness of F-18 FDG-PET in detection of multiple endocrine tumors with duodenal carcinoid.

In a 76-year-old woman in whom hypercalcemia had been followed, whole body fluorodeoxyglucose positron emission tomography (FDG-PET) scan detected hypermetabolic areas in the left lower region of the thyroid gland, pancreas tail, and duodenum. CT, MR, biopsy, and surgery were performed and parathyroid adenoma, pancreatic gastrinoma, and duodenal carcinoid were diagnosed. Fluorine-18 (F-18) FDG-PET may be useful for diagnosis of multiple endocrine tumors with duodenal carcinoid.     

Anatomo-metabolic characteristics of atelectasis in F-18 FDG-PET/CT imaging

PURPOSE: To evaluate the structural and metabolic characteristics of atelectasis in FDG-PET/CT. METHODS: Twenty one consecutive patients (13 males, 8 females, median age 67 years) with CT features of atelectasis, undergoing PET/CT imaging for preoperative staging of histologically proven malignancies (20 lung cancer and 1 ovarian cancer metastasis to lung), were included in the study. RESULTS: Hounsfield units of atelectasis (-383.58+/-189, range -631 to 82) were significantly higher than in normal lung (-756+/-67.46, range -839 to -555; P=0.0001), and lower than in malignant tissue (35+/-19, range 4-77; P=0.0001). The main patterns of FDG uptake observed in atelectasis were diffuse and homogenous. The standard uptake value (SUV) in atelectasis was low to moderate (SUV(avg): 1.13+/-0.50; SUV(max): 1.44+/-0.54), and generally lower than in tumor tissue (SUV(avg): 6.25+/-3.58, range 2.0-16.5), but always higher than in normal lung (0.56+/-0.18 and 0.70+/-0.23, respectively) (P=0.0001). There was a positive correlation between the density of atelectatic lesions and the degree of uptake, with no relationship to size. CONCLUSION: There is a positive relationship between the density of collapsed lung and the intensity of FDG uptake. FDG uptake in atelectasis is higher than in normal lung, and generally lower than in tumor tissue.     

F-18 FDG-PET/CT in evaluation of patients with fever of unknown origin

Objectives

This study was carried out to evaluate the diagnostic utility of FDG-PET/CT in patients with fever of unknown origin (FUO).

Methods

Medical records of 103 patients who underwent FDG-PET/CT and anatomic imaging as a part of FUO workup were analyzed. Final diagnosis of the cause of FUO was reached based on serologic assays, cultures, biopsy, surgery or 6 months of clinical follow-up.

Results

The definite cause of fever was established in 69/103 patients. Abnormal FDG uptake was found in 63/103 patients and contributed to the final diagnosis (TP) in 62 patients (98.48 %). Of the remaining 40 patients with negative PET/CT, the final definite cause of fever (FN) could be determined only in seven patients (17.5 %). PET/CT had a sensitivity, specificity, positive predictive value and negative predictive value of 90, 97, 98.4 and 82.5 % compared to 43.5, 67.6, 73.2 and 37.1 %, respectively, for anatomic imaging. FDG-PET/CT had a higher accuracy (92.2 vs. 51.5 %; p = 0.003) compared to anatomic imaging for suggesting a cause of FUO.

Conclusions

PET/CT showed high sensitivity and specificity in suggesting a definite diagnosis in the evaluation of FUO.     

Unusual Soft Tissue Uptake of F-18 Sodium Fluoride in Three Patients Undergoing F-18 NaF PET/CT Bone Scans for Prostate Cancer

Three males aged 71 to 80 years with known stage IV metastatic prostate cancer underwent F-18 sodium fluoride (NaF) PET/CT to assess osseous metastatic disease burden and stability. In addition to F-18 NaF avid known osseous metastases, each patient also exhibited increased F-18 NaF activity in soft tissues. The first patient exhibited multiple F-18 NaF avid enlarged retroperitoneal and pelvic lymph nodes on consecutive PET/CT scans. The second patient demonstrated an F-18 NaF avid thyroid nodule on consecutive PET/CT scans. The third patient exhibited increased F-18 NaF activity in a hepatic metastasis.     

Diagnosis of Cardiac Metastasis from Endometrial Cancer by F-18 FDG-PET/CT

We report a case of a 59-year-old woman with right ventricular metastasis of undifferentiated endometrial cancer. Cardiac metastasis from endometrial cancer is a very rare finding. The case demonstrates that undifferentiated endometrial cancer is capable of metastasizing, presumably through a hematogenous route, to unexpected distant organs. These unexpected sites should not be undermined in the restaging and surveillance of these patients.     

Usefulness of F-18 FDG-PET in a long-term hemodialysis patient with renal cell carcinoma and pheochromocytoma

A patient who had been on long-term hemodialysis (HD) was diagnosed as having renal cell carcinoma (RCC) and pheochromocytoma. Abdominal computed tomography scanning demonstrated a right renal mass and a right adrenal mass, whereas positron emission tomography (PET) using F-18 fluorodeoxyglucose (FDG) revealed increased accumulation in both the renal and adrenal masses. FDG-PET is useful for detecting RCC in HD patients because FDG is not excreted in the urine, but it is difficult to distinguish pheochromocytoma from an adrenal metastasis by this imaging method.     

Peritoneal tuberculosis with elevated serum CA125 mimicking peritoneal carcinomatosis on F-18 FDG-PET/CT

18F-fluorodeoxyglucose positron emission tomography (F-18 FDG-PET) plays an important role in differentiating benign from malignant tumors. However, some false-positive findings, such as tuberculosis, may occur. We report a case referred for F-18 FDG whole-body PET computed tomography (PET/CT) scan owing to an elevated serum cancer antigen 125 (CA125). An FDG-PET/CT scan showed multiple hypermetabolic foci in the mesentery and peritoneum with further increase of FDG uptake on the delayed scan, mimicking peritoneal carcinomatosis. Subsequent laparoscopic biopsy showed granulomatous inflammation, and tuberculosis polymerase chain reaction showed a positive result. Serum CA125 returned to normal following treatment with anti-tuberculosis drugs. Peritoneal tuberculosis should be considered as a differential diagnosis in a tuberculosis endemic region.     

Myocardial viability assessment with gated SPECT Tc-99m tetrofosmin % wall thickening: Comparison with F-18 FDG-PET

OBJECT: This study was designed to assess the value of gated SPECT Tc-99m-tetrofosmin (TF) wall thickening (WT) in addition to TF exercise (Ex)/rest myocardial SPECT, in comparison with F-18 fluorodeoxyglucose (FDG)-PET. METHODS: The study population consisted of 33 patients with old myocardial infarction (27 men and 6 women; mean age, 62 +/- 8 years old). All patients underwent Ex/rest TF SPECT and glucose loading FDG-PET. Polar map images of Ex/rest TF were generated and divided into 24 segments for further analysis. We classified LV segments according to the exercise-rest perfusion scintigraphy. LV segments with less than 70% of the maximum TF activity on the exercise image were defined as stress-induced defects. Among these, the segments whose TF activity increased by 10% from exercise to rest images or exceeded 70% of the maximum uptake were defined as reversible (viable) defects. The remaining defects on the rest image were irreversible (non-viable) defect segments, and were considered for viability study on the basis of %WT. %WT was calculated according to the standard method: [(counts ES - counts ED)/counts ED] x 100. A viable segment on gated SPECT was defined as a segment whose %WT exceeded the lower limit of the normal value (mean - SD). PET viability was defined as FDG uptake exceeding 50% of the maximum count. RESULTS: Among the 792 segments evaluated in the 33 patients studied, there were 689 PET viable segments. Of the 689 segments analyzed, 198 (29%) were identified as having defects on Ex images. Among these defects, 55 (8%) were reversible or partially reversible, as evidenced by rest images, and 143 (21%) were irreversible. Of the irreversible segments on Ex/rest images, 106 (15%) demonstrated no apparent WT by gated TF SPECT, whereas 37 (6%) segments with irreversible defects did have apparent WT. Overall, the sensitivity of Ex/rest TF perfusion imaging was 79%. Sensitivity was improved from 79% to 85% by combining %WT and perfusion data, but specificity was reduced from 70% to 56%. CONCLUSION: %WT evaluated from gated TF imaging enhanced myocardial viability assessment in comparison with FDG-PET.     

Method to correlate 1H MRSI and 18FDG-PET.

The in vivo neuronal contribution to human cerebral metabolic rate of glucose (CMRglc), measured by 18FDG-PET, is unknown. Examining the effect of 1H MRSI-derived N-acetyl aspartate (NAA) concentration on positron emission tomography (PET) measures of metabolic activity might indicate the relationship of CMRglc to neuron density. In a population of 19 demented, cognitively impaired, and control subjects, the Miller-Gartner algorithm was applied to whole-brain PET data to isolate the PET signal originating in cortical gray matter alone (GMPET). An analogous procedure applied to multislice proton MRSI data yielded the N-acetyl aspartate concentration in cortical gray matter (GMNAA). In 18 of 19 subjects, a significant linear regression (P < 0.05) resulted when GMPET was plotted against GMNAA, whereby GMPET was higher for higher GMNAA. This suggests that CMRglc rises linearly with increasing neuron density in gray matter. This method may be used to investigate the relationship of CMRglc to neurons in various conditions.     

Studies on 18F-labeled pyrimidines. II. Metabolic investigation of 18F-5-fluorouracil, 18F-5-fluoro-2'-deoxyuridine and 18F-5-fluorouridine in rats

18F-labeled 5-fluorouracil(FUra), 5-fluoro-2'-deoxyuridine(FdUrd), and 5-fluorouridine ( FUrd ) were synthesized with high radiochemical purities. The 18F-labeled pyrimidines were injected into rats. The metabolites in serum, bile, and urine were analyzed up to 2 h after administration by radio-high performance liquid chromatography (HPLC). The blood clearance of three pyrimidines was very rapid. In the serum the nucleosides and base disappeared very rapidly with a biological half-life of about 2 min and most of them had disappeared by 60 min. The metabolites in the urine were similar to those in the serum. In the bile pyrimidine nucleosides and base were not detected. 18F- was found in the metabolites. Our results explain the high uptakes in the kidney and liver in biodistribution studies of the 18F-labeled pyrimidines.     

Studies on 18F-labeled pyrimidines. Tumor uptakes of 18F-5-fluorouracil, 18F-5-fluorouridine, and 18F-5-fluorodeoxyuridine in animals

Three 18F-labeled pyrimidines, 18F-5-fluorouridine (18F-5-FUR), 18F-5-fluorouracil (18F-5-FU), and 18F-5-fluorodeoxyuridine (18F-5-FdUR), were examined regarding tissue distribution and tumor uptake in ascitic hepatoma AH109A-bearing rats. The differential absorption ratios of tumors of 18F-5-FUR, 18F-5-FU, and 18F-5-FdUR were 0.75 +/- 0.21, 0.92 +/- 0.15, and 0.96 +/- 0.24 at 30 min, and 0.37 +/- 0.09, 0.64 +/- 0.34, and 0.60 +/- 0.17 at 120 min, respectively. The tumor-to-organ ratios obtained with three radiopharmaceuticals, especially with blood, heart, lung, muscle, and brain were high and these ratios increased with time. The tumor-to-organ ratios obtained with 18F-5-FdUR were always 1.3-4 times higher than 18F-5-FU and 18F-5-FUR. We concluded that 18F-5-FdUR was a suitable radiopharmaceutical for tumor imaging. Positron emission tomography of a rabbit tumor located on the chest with 18F-5-FdUR clearly showed the tumor within 1 h.     

Diagnostic Accuracy of F-18 FDG-PET in the Assessment of Posttherapeutic Recurrence of Head and Neck Cancer

The purpose of this study was to compare whole-body fluorine-18-fluorodeoxyglucose positron emission tomography (F-18 FDG-PET) with conventional imaging modalities (CI: CT/MRI) in the detection of recurrent head and neck cancer. Whole-body F-18 FDG-PET was performed in 45 patients (recurrence = 39; no recurrence = 16) with previous head and neck cancer. We compared detectability by the period from initial cancer treatment and treatment modalities. Thirty were PET-positive and 15 were PET-negative. The sensitivity, specificity, and accuracy of PET were 97%, 88%, and 93%, respectively (corresponding figures of CI were 73%, 85%, and 77%). In 18 patients who underwent PET less than 3 months after the completion of cancer treatment, the sensitivity, specificity, and accuracy were 100%, 86%, and 94%, while for CI, the corresponding figures were 67%, 71%, and 69%. In 18 patients who had undergone surgery, PET results were 14 true positive and 4 were true negative; significantly higher detectability than CI. Among the patients who were evaluated for more than 6 months or treated by radiotherapy without surgery, diagnostic accuracy was almost the same. Whole body F-18 FDG-PET was a valuable tool in the evaluation of post-therapeutic recurrence of head and neck cancer.     

Evaluation of Rare Tumors with [F-18]Fluorodeoxyglucose Positron Emission Tomography

The purpose of this paper was to evaluate the utility of positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose (FDG) in the clinical assessment of rare tumors. We identified 6 patients over the last 18 months with rare tumors who were referred for PET imaging at the time of initial diagnosis, for tumor surveillance or for posttherapy reevaluation. The PET findings were compared with follow-up clinical data, the results of other imaging modalities and histology. FDG PET correctly detected disease in patients with anaplastic thyroid cancer, pleural mesothelioma, myxoid liposarcoma, malignant fibrous histiocytoma, synovial cell sarcoma and uterine leiomyosarcoma. These findings suggest that PET is useful in the evaluation of a variety of rare tumors both for initial preoperative staging and post-therapy assessment. Further experience with other uncommon tumors is necessary to define the precise role of FDG PET in this clinical setting.