La tomographie par émission de positons (TEP) est dorénavant un outil de référence en routine clinique en oncologie, notamment dans le cadre du diagnostic. Des applications plus récentes, telles la prise en charge et le suivi thérapeutique, ou la définition de cibles en radiothérapie nécessitent une détermination rapide, précise et robuste des volumes métaboliquement actifs sur les images d’émission, ce qui ne peut être obtenu par contours manuels. Ce besoin clinique a motivé de nombreux développements ces dernières années pour la mise au point de méthodes automatiques. Cette revue propose une vue d’ensemble de ces méthodologies, et discute leur mise en œuvre et leur validation méthodologique et/ou cliniques. Des perspectives sur les travaux encore à accomplir sont également suggérées.

PET imaging is now considered a gold standard tool in clinical oncology, especially for diagnosis purposes. More recent applications such as therapy follow-up or tumor targeting in radiotherapy require a fast, accurate and robust metabolically active tumor volumes delineation on emission images, which cannot be obtained through manual contouring. This clinical need has sprung a large number of methodological developments regarding automatic methods to define tumor volumes on PET images. This paper reviews most of the methodologies that have been recently proposed and discusses their framework and methodological and/or clinical validation. Perspectives regarding the future work to be done are also suggested. (C) 2011 Societe francaise de radiotherapie oncologique (SFRO). Published by Elsevier Masson SAS. All rights reserved.

Purpose: We have previously demonstrated that functional tumor volume (TV) and Total Lesion Glycolysis (TLG=TV×SUVmean) measured on pretreatment 18F‐FDG PET scans were significant predictors of response and prognostic factors of survival, whereas SUV measurements were not. The objective of this study was to investigate the impact of partial volume effects (PVE) correction (PVC) on this clinical value. Methods: 50 patients with esophageal cancer treated with concomitant radiochemotherapy were retrospectively analyzed. 18F‐FDG PET baseline scans were corrected for PVE with iterative deconvolution with wavelet‐based denoising. Tumors were subsequently delineated using the Fuzzy Locally Adaptive Bayesian (FLAB) algorithm on both original and corrected images. Maximum and peak SUV, TV, mean SUV, and TLG were extracted and compared. The value of each parameter (with or without PVC) was investigated using Kruskal‐Wallis tests regarding response and Kaplan‐Meier curves regarding survival. Results: Whereas PVC had a significant quantitative impact on the absolute values of each parameter (up to more than 100% for SUVmax), the respective clinical value was not significantly modified whether for overall survival or response to therapy. No significant improvement was observed after PVC for the already established significant predictive and prognostic value of TV and TLG. Similarly, the non significant predictive and prognostic value of the various SUV measurements was not improved by PVC and was even lowered in some cases. Conclusions: PVC did not modify significantly the previously established clinical value of tumor volume or TLG. In addition, the limited value of SUV measurements in this context may therefore not be explained by the lack of PVC since PVC did not improve their clinical value and in most cases it even lowered it.

Purpose: The objective of this study was to investigate the impact of tumor size and tracer uptake heterogeneity on the automatic delineation of 18F‐FDG PET and CT tumor volumes (TV) in NSCLC. Methods: 26 NSCLC patients with FDG PET/CT were considered. For 18 cases, the tumor maximum diameter was measured by macroscopic examination. Two observers performed manual delineation of the tumors on the CT images and of the PET uptakes using a fixed threshold (50% of the max), an adaptive threshold and the Fuzzy Locally Adaptive Bayesian (FLAB). Diameters of the delineated volumes were compared to the histopathology reference when available. Uptake heterogeneity was assessed using the coefficient of variation (std.dev/mean) within TV. Results: High consensus was reached regarding manual delineation of the CT TV (<10% variability). All diameters measured on the delineated images correlated with histopathology (r>0.84, p<0.0001). However, various levels of accuracy were reached depending on the method: manual delineation on CT resulted in large overevaluation (+30±40%), whereas all delineations on PET images resulted in underevaluation (from −16±17% for T50, to −5±10% for FLAB). CT‐based TV were significantly (p<0.05) larger than PET‐based ones. No correlation was found between CT TV and differences between CT‐based and PET‐based TV. On the other hand, a significant correlation (r=0.5, p<0.01) was found between CT TV and the PET uptake heterogeneity, as well as between this heterogeneity and differences between FLAB and threshold‐based delineations (r>0.7, p<0.0002). Conclusions: 18F‐FDG PET has the potential to provide specific tumor targeting for dose boosting/painting in NSCLC. However, threshold‐based techniques that have been suggested for the auto contouring of the PET uptake should not be used for tumors above 2–3cm in size, as they fail to address heterogeneous uptakes that tend to occur in these larger volumes. More advanced automatic delineation tools are required in such cases.

Respiratory motion in emission tomography leads to reduced image quality. Proposed correction methodology has been concentrating on the use of respiratory synchronised acquisitions leading to gated frames. Such frames however are of low signal to noise ratio as a result of containing reduced statistics. Therefore a method accounting for respiratory motion effects without affecting the statistical quality of the reconstructed images is necessary. In this work we describe the implementation of an elastic transformation within a list-mode based reconstruction for the correction of respiratory motion over the thorax. The developed algorithm was evaluated using datasets of the NCAT phantom generated at different points throughout the respiratory cycle. List mode data based PET simulated frames were subsequently produced by combining the NCAT datasets with a Monte Carlo simulation. Transformation parameters accounting for respiratory motion were estimated according to an elastic registration of the NCAT dynamic CT images and were subsequently applied during the image reconstruction of the original emission list mode data. The One-pass list mode EM (OPL-EM) algorithm was modified to integrate the elastic transformation in the sensitivity matrix. Three different implementations have been investigated (no interpolation, trilinear interpolation, b-spline functions incorporation). The corrected images were compared with uncorrected respiratory motion average images. Results demonstrate that the use of elastic transformations in the reconstruction system matrix lead to uniform improvement across the lung field for different lesion sizes. The use of a trilinear interpolation or the incorporation of the b-spline functions lead to times of execution equivalent to standard image reconstruction. However, trilinear interpolation leads to artefacts in areas such as the diaphragm where the largest elastic deformations are occurring.

OBJECTIVE:To compare oral anticoagulant treatment (fluindione) started on either the 1st or the 10th day of a low-molecular-weight heparin (enoxaparin) treatment for deep vein thrombosis confirmed by venography.DESIGN:An open, multicenter, randomized study in two parallel treatment groups.INTERVENTIONS:All patients received enoxaparin, 1 mg/kg s.c. twice daily, and oral fluindione, 20 mg once daily, either beginning on day 1 or on day 10 of the enoxaparin treatment. Enoxaparin was discontinued once the international normalized ratio under fluindione was stable between 2.0 and 3.0 over 2 days. Fluindione treatment was maintained during a 3-month follow-up period.OUTCOME MEASUREMENTS:Specific examinations (venography and/or V/Q lung scanning and/or angiography) were performed only in the event of a clinically suspected recurrence of venous thromboembolism during the 3-month follow-up period. All cases were blindly assessed by an independent Reading Committee.RESULTS:A clinically suspected venous thromboembolism was confirmed by objective tests in 1 of 223 patients (group of delayed introduction of fluindione; n = 111). Equivalence was demonstrated between the two treatment schedules (p < 0.0001) for a maximal difference of 10% (90% confidence interval: -2.42 to 0.58). The mean duration of hospitalization was significantly reduced (p = 0.0001) in the group with early introduction of fluindione. The incidence of hemorrhage was comparable between the two treatment groups.CONCLUSION:Early and delayed introduction of oral anticoagulant treatment in association with subcutaneous enoxaparin in patients with deep vein thrombosis was shown to be equivalent in preventing the recurrence of venous thromboembolism. In patients with early introduction of oral anticoagulant, hospitalization was significantly reduced.