Place de la tomographie par émission de positons (TEP) au [18F]FDG dans l’exploration des vascularites

[¹⁸F]fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) is a noninvasive metabolic imaging modality that is well suited to the assessment of activity and extent of large vessel vasculitis, such as giant cell arteritis and Takayasu arteritis. PET could be more effective than magnetic resonance imaging in detecting the earliest stages of vascular wall inflammation. The visual grading of vascular [¹⁸F]FDG uptake makes it possible to discriminate arteritis from atherosclerosis, providing therefore high specificity. High sensitivity can be achieved provided scanning is performed during active inflammatory phase, preferably before starting corticosteroid treatment. Large scale prospective studies are needed to determine the exact value of PET imaging in assessing the large vessel vasculitis outcome and response to immunosuppressive treatment.     

Intérêt de la tomographie par émission de positons (TEP) au 18FDG dans le suivi des patients traités pour carcinome épidermoïde des voies aérodigestives supérieures (VADS) en rémission clinique

IntroductionPosttreatment follow-up of head and neck squamous cell carcinoma (HNSCC) recurrence is a diagnostic challenge. Tissue distortions from radiation and surgery can obscure early detection of recurrence by conventional follow-up approaches such as physical examination (PE), computed tomography, and magnetic resonance imaging. A number of studies have shown that ¹⁸Fluoro-fluorodeoxyglucose (¹⁸FDG) Positron emission tomography (PET) may be an effective technique for the detection of persistent, recurrent, and distant metastatic HNSCC after treatment. The aim of this prospective study was to determine the benefits (sensitivity, specificity, predictive values, and accuracy) of ¹⁸FDG PET using hybrid PET–Computed tomography system (PET/CT) in the detection of HNSCC subclinical locoregional recurrence and distant metastases, in patients 12 months after curative treatment with a negative conventional follow up.Materials and MethodsNinety-one patients cured from head and neck squamous cell carcinoma (HNSCC) without any clinical element for recurrence were included. Whole-body ¹⁸FDG PET/CT examination was performed 11.6 ± 4.4 months after the end of the treatment. The gold standard was histopathology or 6 months imaging follow-up.ResultsThe whole-body ¹⁸FDG PET/CT of the 91 patients in this study consisted of 52 negative and 39 positive results. Nine of these patients who exhibited abnormal ¹⁸FDG uptake in head and neck area did not have subsequently proven recurrent HNSCC (false positive). Thirty had proven recurrence (true positive). All 52 patients with negative readings of ¹⁸FDG PET/CT remained free of disease at 6 months (true negative). The sensitivity and specificity of ¹⁸FDG PET/CT in this study for the diagnosis of HNSCC recurrence were 100% (30/30) and 85% (52/61) respectively. The positive predictive value was 77% (30/39). The negative predictive value was 100% (52/52). The overall accuracy was 90% (82/91).ConclusionThe results of our study confirm the high effectiveness of ¹⁸FDG PET/CT in assessment of HNSCC recurrence. It suggests that this modality is more accurate than conventional follow-up PE alone in the assessment of patient recurrence after previous curative treatment for HNSCC. Therefore, a PET study could be systematically proposed at 12 months after the end of the treatment.     

Bilan initial d’imagerie de l’adénocarcinome pancréatique : données de la littérature sur la place actuelle de la tomographie par émission de positons au 18F-fluorodéoxyglucose (TEP FDG)

In pancreatic adenocarcinoma, initial imaging is essential to better select patients for surgery. Recent literature analysis of F18-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET) in pancreatic adenocarcinoma is summarized in the present article. Performances of FDG PET in the fields of lymph node involvement, metastatic involvement and therapeutic efficacy assessment are described for its correct use in pancreatic adenocarcinoma.     

La tomographie par émission de positons en cardiologie

Cardiovascular PET imaging is progressively emerging, owing to wider availability of cameras for non-oncology indications, as well as to the development of dedicated imaging agents. This article briefly reviews main indications of cardiovascular PET.     

La tomographie par émission de positons (TEP) hors oncologie : l’exploration du cerveau

Positron emission tomography (PET) allows evaluation of the central nervous system function. Imaging of regional cerebral blood flow and metabolism, and of several neurotransmission systems may be obtained using PET. PET quantification is accurate and has good test–retest reliability. For research purposes, PET has been used to study brain physiology, to explore neurological and psychiatric diseases patophysiology and for the new drugs research and development. FDG is the only PET radioligand with clinical application. Following criteria of evidence-based medicine, the clinical indications of FDG-PET are: evaluation of treated gliomas, presurgical study of partial refractory epilepsy and diagnosis of Alzheimer's disease when it is impossible to differentiate clinically from frontotemporal dementia.     

Apport de la tomographie à émission de positons au 18F-fluorodéoxyglucose dans la prise en charge des lymphomes folliculaires

PurposeTo assess the usefulness of positron emission tomography/computed tomography in staging, prognosis evaluation and restaging of patients with follicular lymphoma.Patients and methodsa retrospective study was performed on 45 patients with untreated biopsy-proven follicular lymphoma who underwent FDG-PET/CT and CT before and after chemo-immunotherapy induction treatment (rituximab combined with cyclophosphamide, doxorubicin, vincristine and prednisone).ResultsPET/CT detected more nodal (+51%) and extranodal (+89%) lesions than CT. PET/CT changed Ann Arbor stage in eight patients (18%). Five patients (11%) initially considered with early stage (I/II) were finally managed as advanced stage (III/IV). In this study, initial PET/CT was significantly more accurate to identify patients with poor prognosis than FLIPI. Poor prognosis was defined as incomplete therapeutic response or early relapse. Accuracy of PET/CT for therapeutic response assessment was significantly higher than that of CT (0.97 vs 0.64), especially because of its ability to identify inactive residual masses. Beside, post-treatment PET/CT was able to predict patients’ outcome. The median progression free survival (PFS) was 48 months in the PET/CT negative group as compared to 17.2 months for the group with residual uptake (P < 10^?4).ConclusionFDG-PET/CT is a very useful tool for staging, assessing prognosis and therapeutic response of patients with follicular lymphoma.     

Les examens cardiaques en tomographie par émission de positons

Cardiac positron emission tomography (PET) is yet considered as a reference imaging technique but remains poorly used in clinical practice. At the present time, the advantages of cardiac PET investigations are far to be evident, when compared with conventional tomoscintigraphy (SPECT), except for perfusion imaging in the obese and for viability assessment in case of very severe cardiac dysfunction. However, this situation might quickly move because of an enhanced availability of PET imaging, dramatic technical progresses and promising new tracers. In particular, the last-generation PET-cameras allow reaching spatial resolutions and detection sensitivities, which are now spectacularly higher than those from conventional SPECT imaging. In addition, the list mode recording allows the subsequent images reconstruction to be synchronized to cardiac cycle but also to respiratory cycle; and the quantifications of myocardial perfusion flow and of coronary flow reserve are now available in clinical routine. Furthermore, new tracers labelled with fluorine-18 are under development, especially for perfusion investigations, and kinetics properties of these new tracers are dramatically enhanced when compared with current perfusion SPECT tracers.     

Apport de la tomographie par émission de positons dans les tumeurs endocrines digestives : choix du traceur

Digestive endocrine tumors represent a heterogeneous group of neoplasm sharing common characteristics such as their high density of peptide receptors, their ability to take up amino acids and decarboxylate them into biogenic amines and their low glycolytic activity. These features are used for nuclear imaging targeting. To date, somatostatin receptor scintigraphy is considered the “gold standard” imaging procedure of well-differentiated tumors. Despite the significant contribution of SPECT/CT, the use of positron emission tomography imaging (PET) is growing rapidly. Three PET imaging modalities are currently available: 68Ga-labeled somatostatin analogs PET, 18F-dihydroxyphenylalanine PET (¹⁸F-DOPA) and 18F-deoxyglucose PET (¹⁸F-FDG). This article focuses on the current targets of molecular imaging and highlights the potential clinical applications of new targets.     

Évaluation des thérapeutiques ciblées en tomographie par émission de positons

Thanks to breakthroughs in drug design, new kinds of treatment in oncology have been developed. These new molecules target usually a precise molecular pathway proved to be involved in the development of a malignant disease. This led to the concept of targeted therapy. Therefore, the accurate selection of patients who may experience a clinical benefit of such treatments and the way to assess the response are still challenging issues. Molecular imaging with radiolabeled compounds seemed to be a very promising tool, as for example PET with ¹⁸F FluoroDeoxyGlucose (FDG), which allows to assess and to predict the response to a tyrosine kinase inhibitors more efficiently than conventional imaging tools. FDG is only a surrogate marker of cell proliferation. The common tools (clinical and radiological assessment) are no longer sufficient to predict the clinical efficacy of these new drugs. Molecular imaging should be added in the design of clinical trials in order to detect earlier pharmacodynamic effects, to select responding patients and to provide proofs of efficacy of these non-cytotoxic compounds. Molecular imaging databases have to be created and cross-matched to tumor sample collections, providing consequently new “dynamic” pathological resources.     

Récidive biologique de cancer de la prostate : intérêt de la TEP/TDM à la fluorocholine (18F) du corps entier

Case reportA patient was referred to fluorocholine (18F) PET/CT to restage a biological recurrence of his prostate cancer. There was a doubt on local and lymph node recurrence on MRI.ResultPET/CT showed several pelvic foci evocative of local and lymph node recurrence, more extensive than the MRI anomaly without bone lesion; this recurrence was treated by hormone therapy. But FCH PET/CT also revealed a left cerebral focus. Cerebral MRI was therefore performed which confirmed an anomaly evocative of a grade II brain lesion.ConclusionThis observation illustrates the fact that, in case of prostate cancer, a whole-body imaging, including the skull, is useful, even when foci are detected in the pelvis. Several types of cancer take-up fluorocholine (18F): in case of a visceral distant focus in a patient with prostate cancer, the hypothesis of a second primary cancer should be considered.     

Place de la TEP au FDG (18F) dans l’exploration des syndromes neurologiques paranéoplasiques

Paraneoplastic neurological syndromes (PNS) are rare non-metastatic manifestations of cancer. However, in this family of diseases, to recognize the underlying malignancy is an emergency. The ultimate aim is to treat the patient and try to stabilize or improve the neurological dysfunction, which is frequently the cause of the patient's death. The yield of FDG PET seems to be poor in unselected PNS. In the last decade, neurologists have attempted to provide more rigorous diagnostic criteria for PNS. Thus, “classical” PNS and a panel of “well-characterized” onconeural antibodies have been defined in order to facilitate triage of patients for whom FDG PET would be more sensitive. Currently, given the limited availability of PET cameras in France, this examination should be performed in the presence of either a “classical” PNS with or without onconeuralantibodies positivity or other PNS with onconeural antibodies positivity. The FDG PET should be triggered after a negative conventional imaging work up.     

La tomographie par émission de positons couplée à la tomodensitométrie (TEP–TDM) au 18F-fluoro-désoxy-glucose ([18F]-FDG), avec dilution vésicale dans l’imagerie des tumeurs urothéliales. À propos de quatre cas

This article illustrates, by means of four demonstrative case reports of urothelial carcinomas, the potential role of PET–CT using ¹⁸F-fluoro-desoxy-glucose ([¹⁸F]-FDG) with delayed images after diuretic. These patients were referred to the TEP centre of the University Hospital in Bordeaux for the initial staging of a known bladder cancer or for the characterization of residual mass after radical treatment by surgery and radiotherapy. Analysing recent published results this preliminary study underlines the good performances of forced diuresis for the interpretation of bladder wall and thus enables to assess the potential clinical impact of [¹⁸F]-FDG PET–CT in the staging of urothelial carcinoma.     

Détection fortuite d’une synovite villonodulaire extra-articulaire du muscle psoas en tomographie par émission de positons au 18F-fluorodésoxyglucose

Pigmented villonodular synovitis (PVNS) is a benign but locally aggressive disorder, which commonly involves large joints. This article reports a rare case of an extra-articular PVNS located within the left psoas muscle. This lesion has been accidentally discovered during a follow-up FDG PET/CT. The patient was asymptomatic and did not undergo any surgery. This article reports that FDG PET/CT could be helpful for monitoring PVNS.