Silvia Taralli

Dynamic O-(2-[18F]fluoroethyl)-L-tyrosine (F-18 FET) PET for glioma grading: assessment of individual probability of malignancy.

Purpose: (1) To investigate the diagnostic value of some O-(2-[18F]fluoroethyl)-L-tyrosine (F-18 FET) indices derived from the dynamic acquisition to differentiate low-grade gliomas from high-grade; (2) to analyze the course of tumor time-activity curves (TACs); and (3) to calculate the individual probability of a high-grade glioma using the logistic regression. Methods: Seventeen low-grade (WHO I–II) and 15 high-grade (WHO III–IV) gliomas were studied with dynamic F-18 FET PET. Regions of interests were drawn over the tumor and contralateral brain, and TACs were analyzed. We considered early standardized uptake value (SUV), middle SUV, late SUV, early-to-middle SUV tumor ratio, early-to-late SUV tumor ratio; time to peak (Tpeak), in minutes, from the beginning of the dynamic acquisition up to the maximum SUV of the tumor; and SoD (sum of the frame-to-frame differences). To assess the individual probability of high-grade, logistic regression was also used. Results: High-grade gliomas showed significantly (P < 0.0001) higher values when compared with low-grade gliomas in early SUV, early-to-middle ratio, early-to-late ratio, Tpeak, and SoD. For the grading of gliomas, the best indices were early-to-middle ratio and Tpeak providing a diagnostic accuracy of 94%. TACs analysis provided an 87% diagnostic accuracy. For individual high-grade diagnosis, the logistic regression provided 93% sensitivity, 100% specificity, and 97% accuracy. Conclusion: Early-to-middle SUV tumor ratio and Tpeak were the best indices for assessing the grading of gliomas. Since early-to-middle ratio derives from the first 35 minutes of the dynamic acquisition, the PET study could last half an hour instead of 1 hour. By logistic regression, it is possible to assess the individual probability of high-grade, useful for prognosis and treatment.

Prevalence and malignancy risk of focal colorectal incidental uptake detected by 18F-FDG-PET or PET/CT: a meta-analysis

Abstract Background. The aim of the study was to meta-analyze published data about prevalence and malignancy risk of focal colorectal incidentalomas (FCIs) detected by Fluorine-18-Fluorodeoxyglucose positron emission tomography or positron emission tomography/computed tomography (18F-FDG-PET or PET/CT). Methods. A comprehensive computer literature search of studies published through July 31st 2012 regarding FCIs detected by 18F-FDG-PET or PET/CT was performed. Pooled prevalence of patients with FCIs and risk of malignant or premalignant FCIs after colonoscopy or histopathology verification were calculated. Furthermore, separate calculations for geographic areas were performed. Finally, average standardized uptake values (SUV) in malignant, premalignant and benign FCIs were reported. Results. Thirty-two studies comprising 89,061 patients evaluated by 18F-FDG-PET or PET/CT were included. The pooled prevalence of FCIs detected by 18F-FDG-PET or PET/CT was 3.6% (95% confidence interval [95% CI]: 2.6-4.7%). Overall, 1,044 FCIs detected by 18F-FDG-PET or PET/CT underwent colonoscopy or histopathology evaluation. Pooled risk of malignant or premalignant lesions was 68% (95% CI: 60-75%). Risk of malignant and premalignant FCIs in Asia-Oceania was lower compared to that of Europe and America. A significant overlap in average SUV was found between malignant, premalignant and benign FCIs. Conclusions. FCIs are observed in a not negligible number of patients who undergo 18F-FDG-PET or PET/CT studies with a high risk of malignant or premalignant lesions. SUV is not reliable as a tool to differentiate between malignant, premalignant and benign FCIs. Further investigation is warranted whenever FCIs are detected by 18F-FDG-PET or PET/CT

Usefulness of Whole-Body Fluorine-18-Fluorodeoxyglucose Positron Emission Tomography in Patients with Neurofibromatosis Type 1: A Systematic Review

Aim. To systematically review the role of positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (FDG) in patients with neurofibromatosis type 1 (NF1). Methods. A comprehensive literature search of published studies regarding FDG-PET and PET/CT in patients with NF1 was performed. No beginning date limit and language restriction were used; the search was updated until December 2011. Only those studies or subsets in studies including whole-body FDG-PET or PET/CT scans performed in patients with NF1 were included. Results. We identified 12 studies including 352 NF1 patients. Qualitative evaluation was performed in about half of the studies and semiquantitative analysis, mainly based on different values of SUV cutoff, in the others. Most of the studies evaluated the role of FDG-PET for differentiating benign from malignant peripheral nerve sheath tumors (MPNSTs). Malignant lesions were detected with a sensitivity ranging between 100% and 89%, but with lower specificity, ranging between 100% and 72%. Moreover, FDG-PET seems to be an important imaging modality for predicting the progression to MPNST and the outcome in patients with MPNST. Two studies evaluated the role of FDG-PET in pediatric patients with NF1. Conclusions. FDG-PET and PET/CT are useful methods to identify malignant change in neurogenic tumors in NF1 and to discriminate malignant from benign neurogenic lesions.

Is there a role for fluorine 18 fluorodeoxyglucose-positron emission tomography and positron emission tomography/computed tomography in evaluating patients with mycobacteriosis? A systematic review.

Objective: This study was designed to review the emerging role of fluorine 18 fluorodeoxyglucose (18F-FDG)-positron emission tomography (PET) CT/computed tomography (PET/CT) in patients with mycobacteriosis. Methods: A comprehensive literature search of published studies through October 2010 in PubMed/MEDLINE database regarding 18F-FDG-PET and PET/CT in patients with mycobacteriosis was performed. Results: Ultimately, we identified 16 studies comprising a total of 220 patients with mycobacteriosis. Main findings of the included studies are presented. Conclusions: (1) Mycobacteriosis commonly causes increased 18F-FDG uptake; therefore, positive 18F-FDG-PET results should be interpreted with caution in differentiating benign from malignant abnormalities. (2) 18F-FDG-PET and PET/CT are potentially useful in detecting sites of Mycobacterium infection. (3) Dual-phase 18F-FDG-PET is not useful for the differential diagnosis between malignant lesions and sites of Mycobacterium infection. (4) 18F-FDG-PET and PET/CT are useful for the evaluation of disease activity and in monitoring response to therapy in patients with mycobacteriosis. (5) Dual-tracer PET and PET/CT are potentially useful for presumptive diagnosis of solitary pulmonary nodules.

Usefulness of 18F-FDG PET/CT in Disease Extent and Treatment Response Assessment in a Patient With Syphilitic Aortitis

A 40-year-old man was admitted to our hospital for surgical treatment of aortic insufficiency and coronary ostial stenosis. Histopathology and serological tests revealed a syphilitic aortitis. F-FDG PET/CT was performed to assess the extent of aortitis, showing increased radiopharmaceutical uptake along the ascending aortic wall. A repeated FDG PET/CT after antibiotic therapy showed a markedly reduced uptake in the aortic wall, suggesting resolution of the infection according to clinical and serological data. This case highlights the usefulness of FDG PET/CT for the assessment of disease extent and treatment response in patients with syphilitic aortitis.

Diagnostic Performance of 18F-Fluorodeoxyglucose in 162 Small Pulmonary Nodules Incidentally Detected in Subjects Without a History of Malignancy

BACKGROUND Solitary pulmonary nodule (SPN) still represents a diagnostic challenge. The aim of our study was to evaluate the diagnostic performance of (18)F-fluorodeoxyglucose positron emission tomography-computed tomography in one of the largest samples of small SPNs, incidentally detected in subjects without a history of malignancy (nonscreening population) and undetermined at computed tomography. METHODS One-hundred and sixty-two small (>0.8 to 1.5 cm) and, for comparison, 206 large nodules (>1.5 to 3 cm) were retrospectively evaluated. Diagnostic performance of (18)F-fluorodeoxyglucose visual analysis, receiver-operating characteristic (ROC) analysis for maximum standardized uptake value (SUVmax), and Bayesian analysis were assessed using histology or radiological follow-up as a golden standard. RESULTS In 162 small nodules, (18)F-fluorodeoxyglucose visual and ROC analyses (SUVmax = 1.3) provided 72.6% and 77.4% sensitivity and 88.0% and 82.0% specificity, respectively. The prevalence of malignancy was 38%; Bayesian analysis provided 78.8% positive and 16.0% negative posttest probabilities of malignancy. In 206 large nodules (18)F-fluorodeoxyglucose visual and ROC analyses (SUVmax = 1.9) provided 89.5% and 85.1% sensitivity and 70.8% and 79.2% specificity, respectively. The prevalence of malignancy was 65%; Bayesian analysis provided 85.0% positive and 21.6% negative posttest probabilities of malignancy. In both groups, malignant nodules had a significant higher SUVmax (p < 0.0001) than benign nodules. Only in the small group, malignant nodules were significantly larger (p = 0.0054) than benign ones. CONCLUSIONS (18)F-fluorodeoxyglucose can be clinically relevant to rule in and rule out malignancy in undetermined small SPNs, incidentally detected in nonscreening population with intermediate pretest probability of malignancy, as well as in larger ones. Visual analysis can be considered an optimal diagnostic criterion, adequately detecting a wide range of malignant nodules with different metabolic activity.

Physiological Activity of Spinal Cord in Children: An 18F-FDG PET-CT Study

Study Design. Retrospective study. Objective. To evaluate, in a pediatric population, 18F-Fluoro-deoxy-glucose (18F-FDG) metabolic activity of normal spinal cord and to assess the correlation with demographic, clinical, and environmental variables. Summary of Background Data. 18F-FDG uptake of normal spinal cord is variable in children. The knowledge of physiological metabolism of spinal cord is essential to distinguish normal from pathological findings by positron emission tomography–computed tomography (PET-CT). Methods. We retrospectively evaluated 18F-FDG positron emission tomography–computed tomography scans from a total of 167 pediatric patients (97 males; 3.9–18.9 yr) divided into 4 age groups (0–4.9 yr, 5–9.9 yr, 10–14.9 yr, and 15–18.9 yr), excluding those submitted to previous or recent therapeutic procedures influencing spinal cord metabolism or with central nervous system diseases. Spinal cord was divided into 3 levels (C1–C7; D1–D6; and D7–L1), and maximum standardized uptake value (SUVmax) of each cord level was measured. Correlations between SUVmax and spinal cord level, age, body weight, sex, type of disease, and season were statistically assessed. Results. Median SUVmax was similar and significantly (P < 0.01) higher at C1–C7 and D7–L1 levels than at D1–D6 level and it significantly (P < 0.01) increased with age in all spinal cord levels. A positive and significant association between SUVmax and body weight, female sex, and Hodgkin lymphoma was found. No significant association with season was observed. By multivariate analysis, only weight and female sex remained significant. Conclusion. Knowledge of physiological 18F-FDG spinal cord activity in children is essential for a correct interpretation of positron emission tomography–computed tomography, especially in oncologic pediatric patients to avoid potential pitfalls. Level of Evidence: N/A

18 F-fluoro-deoxy-glucose focal uptake in very small pulmonary nodules: fact or artifact? Case reports

Background18F-fluoro-deoxy-glucose (18 F-FDG) positron emission tomography integrated/combined with computed tomography (PET-CT) provides the best diagnostic results in the metabolic characterization of undetermined solid pulmonary nodules. The diagnostic performance of 18 F-FDG is similar for nodules measuring at least 1 cm and for larger masses, but few data exist for nodules smaller than 1 cm.Case presentationWe report five cases of oncologic patients showing focal lung 18 F-FDG uptake on PET-CT in nodules smaller than 1 cm. We also discuss the most common causes of 18 F-FDG false-positive and false-negative results in the pulmonary parenchyma.In patient 1, contrast-enhanced CT performed 10 days before PET-CT did not show any abnormality in the site of uptake; in patient 2, high-resolution CT performed 1 month after PET showed a bronchiole filled with dense material interpreted as a mucoid impaction; in patient 3, contrast-enhanced CT performed 15 days before PET-CT did not identify any nodules; in patients 4 and 5, contrast-enhanced CT revealed a nodule smaller than 1 cm which could not be characterized. The 18 F-FDG uptake at follow-up confirmed the malignant nature of pulmonary nodules smaller than 1 cm which were undetectable, misinterpreted, not recognized or undetermined at contrast-enhanced CT.ConclusionIn all five oncologic patients, 18 F-FDG was able to metabolically characterize as malignant those nodules smaller than 1 cm, underlining that: 18 F-FDG uptake is not only a function of tumor size but it is strongly related to the tumor biology; functional alterations may precede morphologic abnormalities. In the oncologic population, especially in higher-risk patients, PET can be performed even when the nodules are smaller than 1 cm, because it might give an earlier characterization and, sometimes, could guide in the identification of alterations missed on CT.

Somatostatin receptor positron emission tomography/computed tomography imaging in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an uncommon aggressive primary cutaneous carcinoma with neuroendocrine differentiation. However, literature data about the use of somatostatin receptor positron emission tomography/computed tomography (PET/CT) imaging in MCC are limited and its role is not clearly stated.

A rare case of synchronous bilateral pulmonary neuroendocrine tumor detected by 68Ga-DOTANOC PET/CT

A 64-year-old man was referred to our center for metabolic characterization of 2 bilateral pulmonary lesions, incidentally detected at computed tomography (CT). F-FDG PET/CT scan showed a weak radiopharmaceutical uptake in both pulmonary lesions. A subsequent Ga-DOTANOC PET/CT showed intense radiopharmaceutical uptake in both pulmonary lesions. Subsequently, the patient underwent histopathological examinations of both lesions, which showed a synchronous well-differentiated pulmonary neuroendocrine carcinoma (typical carcinoid tumor). This case reports a rare occurrence of synchronous pulmonary carcinoid, highlighting the role of different PET tracers for metabolic characterization of pulmonary nodules.