Comparaison de l’IRM de diffusion et de la TEP/TDM au FDG dans le bilan des lymphomes

PurposeDiffusion weighted MRI (DW-MRI) sequences appear as a promising functional technique supplementary to morphologic MRI for oncology purposes. We evaluated the results of DW-MRI for the staging of lymphomas, compared to FDG PET/CT.MethodsTwenty-seven patients with lymphoma referred for FDG PET/CT (initial staging, relapse or treatment evaluation) were prospectively included. They underwent MRI including free breathing DW and T2 weighted imaging. Lymph node areas and organs involvement were listed for each modality and compared using Cohen's kappa (κ) test. MRI performances were evaluated using FDG PET as the gold standard. The results of PET and MRI were compared (with respect to the final staging by the haematologist).ResultsRegarding the lymph nodes, 154 involved areas were detected by MRI out of the 184 detected by PET, that is an excellent concordance (κ = 0.87), sensitivity of 0.84 and specificity of 1. Concordance and sensitivity were inferior for extranodal disease (notably bone lesions) with 27 lesions detected by MRI out of the 40 viewed with PET. Regarding pre-treatment evaluation, two patients were understaged both with PET and MRI (bone marrow involvement); assessment of stage was concordant for both modalities in 18 patients out of 21.ConclusionsPerformance of MRI including DW images was close to that of FDG PET/CT for lymph node areas involvement. Further studies are needed to assess its sensitivity for extranodal lesions, and its accuracy for determining the stage of the disease.     

Valeur pronostique de la TEP au FDG dans le bilan initial du cancer de l’œsophage

Esophageal cancer outcome greatly depends on pathological stage. Our objectives were to assess prognosis based on the initial FDG PET scan, focusing on correlation between overall survival and FDG uptake in the primary, as well as the presence of FDG positive lymph nodes or metastases. Fifty-two esophageal cancer patients undergoing FDG PET as part of initial routine staging procedure before treatment were included. The maximum standardized uptake value (SUV_max) was determined in each primary lesion and the number of abnormalities including primary, lymph nodes or distant metastases was recorded. Correlation with overall survival was performed using the Kaplan-Meier method and Cox regression analysis was used to assess the prognostic value of PET parameters. Half of the patients were planned for initial curative surgery (52%). Using univariate survival analysis, either surgery, SUV_max superior than 9, two or more PET abnormalities, or the presence of FDG positive nodes were significant overall survival prognostic predictors. After multivariate analysis, only SUV_max superior than 9 and FDG positive lymph nodes were found as independent predictors of poor outcome. In this prospective study FDG PET was found to provide prognostic information supporting a new indication for initial FDG PET examination in esophageal cancer.     

Intérêt de l’imagerie hybride TEMP/TDM pour la scintigraphie des récepteurs de la somatostatine dans le bilan des tumeurs endocrines gastro-entéro-pancréatiques

In this work, we have evaluated the potential of image fusion and attenuation correction (AC) of SPECT-CT imaging for the assessment of gastro-entero-pancreatic endocrine tumors by somatostatin receptor scintigraphy (SRS).MethodAfter optimisation of acquisition and reconstruction parameters, we have evaluated, in a prospective study, SRS performed over a period of one year. We have compared visual interpretations of planar and tomographic images versus SPECT/CT images to determine if anatomical localisation and diagnostic contributions are improved. In a semi-quantitative analysis of pathological foci, we have measured maximal intensity values (T_max), tumour to background ratios (T/B) and tumour contrasts (Ct) with and without AC.ResultsIn 25 SRS, visual analysis has shown anatomical localisation improvements in 60% of cases (CI95%, 39–79) and diagnostic improvements in 64% of cases (CI95%, 43–82). Doubtful foci proportion changed from 44 to 11%. In the semi-quantitative analysis of 41 pathological foci, Wilcoxon matched-pairs tests showed significantly higher T_max, T/B and Ct values after AC.ConclusionSPECT/CT imaging improves diagnostic quality of SRS thanks to a better foci localisation and a better lesional contrast in the image.     

Intérêt de la TEP/TDM au 18FDG dans les sous-types histologiques agressifs de cancers thyroïdiens (oncocytaire et peu différencié)

IntroductionThe objective of our study was to evaluate the performance of ¹⁸FDG PET/CT in aggressive histological subtypes of differentiated cancer of the thyroid and its therapeutic impact.MethodThirty-three patients (22 Hürthle cell carcinoma and 11 poorly differentiated carcinoma) who underwent FDG PET/CT were retrospectively included. Nine scans have been performed for initial staging, 16 for suspicion of recurrence (with 11 having a rising Tg), 3 for the reassessment of metastatic disease under systemic treatment and 30 systematically during follow-up. The results of PET/CT were confronted with histological data and follow-up results.ResultsThirteen out of 18 positive scans were confirmed (8 locoregional recurrences and 5 distant metastases). The majority of them were performed for a suspicion of recurrence (8) or for initial staging (2). The sensitivity, specificity, PPV, and NPV were respectively 81.2%, 88.1%, 72.2% and 92.5%. For Hürthle cell carcinoma and poorly differentiated carcinoma, the sensitivity and specificity were respectively 100% vs. 57% and 86% vs. 93%. Systematic PET scans were most of the time negative (26/30) and in accordance with histological and follow-up results. It was the same in case of scans performed for undetectable initial Tg (16/22). PET/CT modified patient management in 14% of the cases.ConclusionThis study confirms the good performances of ¹⁸FDG PET/CT for initial staging and in case of elevated Tg during the follow-up of aggressive histological subtypes of thyroid cancer. It does not seem relevant in the absence of a suspicion of recurrence or in the case of undetectable initial Tg.     

Comparaison IRM de diffusion corps entier et TEP/TDM au 18FDG dans le diagnostic de myélome symptomatique

IntroductionOur work aims to compare whole-body diffusion MRI (DWMRI) and ¹⁸FDG PET/CT in the diagnosis of symptomatic myeloma.Patients and methodFrom November 2008 till May 2010, 19 patients were investigated by DWMRI and by ¹⁸FDG PET/CT. The patients were classified according to the criteria of the International Myeloma Working Group in eight non-symptomatic myelomas and 11 symptomatic myelomas. The sensitivity and the specificity of two methods of imaging were studied by retaining the presence or the absence of a diffuse infiltration (ID), focal lesions (FL), or both parameters (FL + ID), in both modalities of imaging. We compared the concordance between two techniques for every patient by using these signs using a weighted kappa test.ResultsThe performances of both modalities seem comparable, with superior diagnostic performances for the FL (Se = 100% and Sp = 75% in DWMRI and Se = 91% and Sp = 75% for ¹⁸FDG PET/CT). By combining both parameters, the ¹⁸FDG PET/CT seems more specific, but the sensitivity is comparable in both modalities (Se = 100% in MRI and Se = 100% in ¹⁸FDG PET/CT; Sp = 37% in DWMRI and Sp = 62% for ¹⁸FDG PET/CT). The concordance between both techniques is better by taking into account the FL than the other parameters (weighted kappa = 0.61 for FL, 0.5 for the FL + ID and 0.16 for ID alone).ConclusionDiagnostic performances of whole-body diffusion MRI and ¹⁸FDG PET/CT seem equivalent, but concordance between both techniques is imperfect. Further studies are necessary to understand this discrepancy.     

Intégration des critères métaboliques de la TEP au 18FDG pour le choix des lésions cibles en imagerie onco-hématologique

IntroductionMalignant lymphoma is a heterogeneous and widespread disease. The morphological response assessment is currently based on the choice of target lesions at baseline, defined by size criteria on enhanced CT (eCT). FDG PET/CT is now commonly used at staging and the aim of this study was to evaluate the relevance of using metabolic criteria rather than size criteria to define the target lesions.Patients and methodsFifty-nine patients with aggressive lymphoma were retrospectively included. Target lesions were chosen by two radiologists on eCT and by two nuclear physicians on PET/CT. Response assessment, based on the sum of the products of the greatest diameters of up to six target lesions chosen either by size or metabolic criteria, was computed and compared to a clinical gold standard (GS) for each patient. Interobserver agreement and comparison to the GS were assessed with kappa (κ) and intraclass correlation (ICC) statistics.ResultsThe spatial distribution of target nodal areas was equivalent among eCT and PET/CT readers with a maximum of target lesions in cervical and mediastinal areas. Choosing with PET/CT led to significant heterogeneity in the size of target lesions when compared with eCT alone (P = 0.03). Interobserver agreement for quantifying the response rate was equivalent in both groups. However, there was a greater correlation to the response of the GS when using PET/CT to target the patient (κ = 0.64 vs. 0.47) and an increased rate of complete responses.ConclusionsMetabolic criteria can replace current size criteria to define target lesions on FDG PET/CT. The morphological response rate appears accurate with an increased rate of complete responses after therapy and a better correlation to the haematological standard of reference.     

Apport de la TEP/TDM au FDG en cancérologie de l’intestin grêle

This article focuses on the indication for FDG PET/CT in case of tumours of the small intestine, neuro-endocrine tumours excluded. The adenocarcinomas, lymphomas and sarcomas (including stromal tumours or GIST) are studied. There is no specific recommendation for FDG PET/CT in adenocarcinomas, extremely rare in comparison with colorectal adenocarcinomas. However, the utility of FDG PET/CT has been reported in clinical cases for detection and staging, especially in patients with high risk of developing the disease (Crohn's disease being the most important risk factor). The primary lymphomas of the small gut are also very rare, corresponding in all cases to non-Hodgkin lymphomas, for which the role of FDG PET/CT is recognised in follicular lymphoma, large B-cell lymphoma and Burkitt lymphoma. The stromal tumours correspond to the most frequent sarcomas. Stromal tumours in the small intestine are less frequent in the small intestine than in the stomach. The role of FDG PET/CT is well established in stromal tumours for the staging of the disease and for determining the efficacy of therapy with tyrosine kinase inhibitor. FDG PET is especially effective to evaluate the response since the radiologic criteria are difficult to assess, based not on the decrease of size of the lesions but on the decrease of density and of contrast enhance.     

Intérêt de l’imagerie hybride TEMP-TDM dans l’exploration des infections

Single-Photon Emission Computed Tomography-Computerized Tomography (SPECT-CT) is a new hybrid technique which offers new diagnostical capabilities in daily nuclear medicine practice. This technique not only allows to acquire fusioned anatomic and functional images in the same time, but also, it increases sensitivity and accuracy of SPECT thanks to attenuation and scattering corrections got from transmission data. Until now, SPECT-CT data have been mainly obtained in oncology and cardiology, but now, many authors use it in many scan studies and particularly for infectious diseases. In inflammatory bowel diseases, SPECT-CT seems to increase diagnostical performances and to modify management of many patients. In suspected vascular sepsis, SPECT-CT could increase sensitivity of white blood cell scintigraphy but also its specificity thanks to spatial resolution of CT. In osteoarticular sepsis, SPECT-CT has the advantage to distinguish osteomyelitis from soft tissue infection and to guide biopsies. Nevertheless, in the light of PET-CT works, SPECT-CT development will probably modify nuclear medicine practice and many studies have to be conducted to highlight consensual procedure guidelines.     

Apport de la TEP/TDM au 18FDG dans la stadification initiale et l’évaluation précoce de la réponse thérapeutique des rhabdomyosarcomes pédiatriques

PurposeThe objective of this study was to retrospectively evaluate the impact of positron emission tomography/computed tomography (PET/CT) using fluorine-18-fluorodeoxyglucose (FDG), in comparison with conventional imaging modalities (CIM), for initial staging and early therapy assessment in paediatric rhabdomyosarcoma.Patients and methodsPrior to treatment, 18 patients (age range, 9 months to 18 years) with histologically proven rhabdomyosarcoma underwent FDG PET/CT in addition to CIM (magnetic resonance imaging of primary site, whole body CT and bone scintigraphy). After three courses of chemotherapy, 12 patients underwent FDG PET/CT in addition to CIM. RECIST criteria and visual analysis of FDG uptake were used for assessment of response. The standard of reference was determined by an interdisciplinary tumor board based on imaging material, histopathology and follow-up data (median = 5 years).ResultsPET/CT sensitivity was superior to CIM's concerning lymph node involvement (100% versus 83%, respectively) and metastases detection (100% versus 50%, respectively). PET/CT results changed therapeutic management in 11% of cases. After three courses of chemotherapy, the rate of complete response was 66% with PET/CT versus 8% with CIM. Five percent of patients relapsed during follow-up (median = 5 years).ConclusionThis study confirms that PET/CT depicts important additional information in initial staging of paediatric rhabdomyosarcomas and suggests a superior prognostic value of PET/CT in early response to chemotherapy assessment.     

La TEP au 18F-FDG dans le diagnostic et le suivi évolutif des plasmocytomes solitaires

AimTo assess the role of [¹⁸F]FDG-PET in solitary plasmacytoma with regards to staging, therapeutic follow-up and monitoring.Patients and methodsTwenty consecutive patients were included in the present study when following conditions were met: (i) solitary plasmacytoma histologically confirmed (bone, n = 16; extramedullary, n = 4); (ii) [¹⁸F]FDG-PET scan from July 2004 to April 2009. The clinical follow-up was over than 2 years for 13 patients. Ten patients underwent a post-therapy PET scan. PET scans were visually analysed.ResultsPET scan enabled confirmation of all main lesions (sensitivity: 100%) and also detected infra-clinical lesions in eight cases. Follow-up for more than 2 years showed a progression disease into myeloma in five from six cases (83%) with infraclinical lesions at the baseline PET scan. Among 10 patients who underwent post-therapeutic PET scan, six experienced a complete response at the main lesion site and four experienced a partial response.ConclusionFDG-PET may play an important role in plasmacytoma staging and enables detection of smaller lesions (otherwise undetected).     

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.     

Utilité de la TEP au 18FDG dans l’épilepsie. Méthodes et indications

Positron emission tomography (PET) using ¹⁸fluorodeoxyglucose (¹⁸FDG) is currently used in presurgical work-up for drug-resistant partial epilepsies in children as in adults, in addition to MRI. Recent cameras with less than 5 mm spatial resolution allow to obtain thin slices (about 2 mm thickness) in 3D planes. ¹⁸FDG is intravenously injected at the mean dose of 3 MBq/kg of body weight in interictal and resting state, in a quiet, dimly lit environment and careful monitoring for head movements and ictal events. In children, sedation may be necessary. Image acquisition starts 30 min after injection and ended 15 to 20 min later. Semiquantitative analysis is visually assessed in clinical practice using colour scales. PET sensibility is improved by superimposition of metabolic imaging on MRI. Statistical analysis with SPM may be useful but comparison with health subjects database is required. In medial temporal lobe epilepsy associated with hippocampal sclerosis, hypometabolism ipsilateral to the epileptogenic focus is found in 70 to 90% of the cases and is predictive of surgical outcome. In other types of temporal and extratemporal epilepsy with negative MRI, focal hypometabolism can be detected, allowing identification of minor gyral abnormalities corresponding to focal cortical dysplasias. In such MRI negative cases, PET findings may improve surgical outcome.