Joël Daouk

Publications (12) View all

• Article: Improved imaging of intrahepatic colorectal metastases with 18F-fluorodeoxyglucose respiratory-gated positron emission tomography.

  Loïc Fin, Joël Daouk, Pascal Bailly, Jérôme Slama, Julie Morvan, Isabelle El Esper, Jean-Marc Régimbeau, Denis Chatelain, Momar Diouf, Marc-Etienne Meyer
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  ABSTRACT: In 18F-fluorodeoxyglucose PET/CT, respiratory motion induces bias in image interpretations (i.e. organ misregistration or lesion omission/underestimation). The present study applied our custom gating method (referred to as 'CT-based gated PET' and that has already been validated by our research group) to PET imaging of the liver and compared its per lesion sensitivity with that of standard clinical (i.e. ungated) PET. A total of 13 patients scheduled for liver surgery were referred to our department for PET/CT imaging. Each patient underwent both ungated and CT-based gated PET imaging protocols. Two independent, blinded observers interpreted the two sets of PET images and reached a consensus when necessary. Image interpretations were combined with histological analysis and/or intraoperative ultrasound examination to compute each method's per lesion sensitivity and true positive fraction. Analyses were also performed by considering lesions according to their size (longest axis over 10 mm or over 15 mm). Forty-eight lesions were confirmed by pathology reports. When considering all the uptakes, the ungated and the CT-based gated PET methods had sensitivities of 54.2 and 64.6% (P=0.025) and true positive fractions of 83.9 and 86.1%, respectively. When considering uptakes greater than 10 mm in size, ungated and CT-based gated PET had sensitivities of 74.3 and 88.6% (P=0.025), respectively. For lesions greater than 15 mm in size, the corresponding sensitivities were 85.2 and 100% (P=0.046). CT-based gated PET yielded a higher lesion-based sensitivity than routine, ungated PET did. Hence, this method improves the detection of intrahepatic colorectal metastases--especially for lesions that are close in size to the detection limit of the PET gantry.
  Nuclear Medicine Communications 02/2012; 33(6):656-62. · 1.40 Impact Factor
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  Available from: jean-marc Bugnicourt

  Article: Attenuation of brain white matter lesions after lacunar stroke.

  Julia Durand-Birchenall, Claire Leclercq, Joël Daouk, Pauline Monet, Olivier Godefroy, Jean-Marc Bugnicourt
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  ABSTRACT: White matter lesions (WMLs) are commonly observed in stroke patients with small vessel disease (SVD) and are thought to result from a progressive, irreversible disease process following arteriolosclerosis. In this study, we report a case of partial disappearance of WMLs 1 year after a lacunar stroke in a 69-year-old man with evidence of SVD. We also discuss possible mechanisms associated with this observation.
  International journal of preventive medicine 02/2012; 3(2):134-8.
• Article: Respiratory-gated 18F-FDG PET imaging in lung cancer: effects on sensitivity and specificity.

  Joël Daouk, Marie Leloire, Loïc Fin, Pascal Bailly, Julie Morvan, Isabelle El Esper, Lazhar Saidi, Véronique Moullart, Géraldine François, Vincent Jounieaux, Marc-Etienne Meyer
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  ABSTRACT: Respiratory motion is known to deteriorate positron emission tomography (PET) images and may lead to potential diagnostic errors when a standardized uptake value (SUV) cut-off threshold is used to discriminate between benign and malignant lesions. To evaluate and compare ungated and respiratory-gated 18F-fluorodeoxyglucose PET/computed tomography (CT) methods for the characterization of pulmonary nodules. The list-mode acquisition during respiratory-gated PET was combined with a short breath-hold CT scan to form the CT-based images. We studied 48 lesions in 43 patients. PET images were analyzed in terms of the maximum SUV (SUV(max)) and the lesion location. Using receiver-operating characteristic (ROC) curves, the optimal SUV cut-off thresholds for the ungated and CT-based methods were calculated to be 2.0 and 2.2, respectively. The corresponding sensitivity values were 83% and 92%, respectively, with a specificity of 67% for both methods. The two methods gave equivalent performance levels for the upper and middle lobes (sensitivity 93%, specificity 62%). They differed for the lower lobes, where the CT-based method outperformed the ungated method (sensitivity values of 90% and 70%, respectively, and a specificity of 73% with both methods) - especially for lesions smaller than 15 mm. The CT-based method increased sensitivity and did not diminish specificity, compared with the ungated method. It was more efficient than the ungated method for imaging the lower lobes and smallest lesions, which are most affected by respiratory motion.
  Acta Radiologica 04/2011; 52(6):651-7. · 1.37 Impact Factor
• Article: Preliminary clinical applications of a device-dedicated whole-body positron emission tomography reconstruction method: impact on standardized uptake values.

  Joël Daouk, Pascal Bailly, Loïc Fin, Marc-Etienne Meyer
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  ABSTRACT: ¹⁸F-fluorodeoxyglucose positron emission tomography has proven relevance in oncological diagnosis, staging and follow-up. The standardized uptake value (SUV) is one of the most widely used semi-quantitative criteria in PET imaging. However, factors such as noise and image resolution affect the measurement of the SUV. We reported earlier that a device-dedicated projector [attenuation-weighted ordered-subsets expectation maximization detector response (AW-OSEM DR), based on point-source measurements] introduces less noise than a geometrical model (AW-OSEM). The aim of this study was to investigate the AW-OSEM DR method's impact on SUV measurements under clinical conditions. We first performed a bias analysis to assess the accuracy of the quantitation for the two reconstruction methods as a function of target size and the number of iterations, with 14 acquisitions of the NEMA IEC/2001 phantom. We then used each method to calculate the maximum and average SUVs, respectively for 32 lesions. For all spheres and all iterations, the bias was significantly lower with AW-OSEM DR than with AW-OSEM (P=0.012). Moreover, a paired Student's t-test showed significant intermethod differences for maximum SUV and average SUV (both P<0.001) in cancer patients. Conversely, the two methods did not differ significantly in terms of the mean SUV and signal-to-noise ratio calculated in the liver for each patient (P=0.5 and 0.08, respectively). Phantom and patient studies were performed to quantify the effects of AW-OSEM DR on PET images. The phantom study highlighted the fact that our method produces more accurate images in terms of the SUV, which is an essential quality for ensuring correct diagnosis, follow-up and treatment planning.
  Nuclear Medicine Communications 09/2010; 31(9):793-9. · 1.40 Impact Factor
• Article: Respiratory-gated positron emission tomography and breath-hold computed tomography coupling to reduce the influence of respiratory motion: methodology and feasibility.

  J Daouk, L Fin, P Bailly, M-E Meyer
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  ABSTRACT: Respiratory motion causes uptake in positron emission tomography (PET) images of chest and abdominal structures to be blurred and reduced in intensity. To compare two respiratory-gated PET binning methods (based on frequency and amplitude analyses of the respiratory signal) and to propose a "BH-based" method based on an additional breath-hold computed tomography (CT) acquisition. Respiratory-gated PET consists in list-mode (LM) acquisition with simultaneous respiratory signal recording. A phantom study featured rectilinear movement of a 0.5-ml sphere filled with (18)F-fluorodeoxyglucose ((18)F-FDG) solution, placed in a radioactive background (sphere-to-background contrast 6:1). Two patients were also examined. Three figures of merit were calculated: the target-to-background ratio profile (TBRP) in the axial direction through the uptake (i.e., the sphere or lesion), full-width-at-half-maximum (FWHM) values, and maximized standard uptake values (SUV(max)). In the phantom study, the peak TBRP was 0.9 for non-gated volume, 1.83 for BH-based volume, and varied between 1.13 and 1.73 for Freq-based volumes and between 1.34 and 1.66 for Amp-based volumes. A reference volume (REF-static) was also acquired for the phantom (in a static, "expiratory" state), with a peak TBRP at 1.88. TBRPs were computed for patient data, with higher peak values for all gated volumes than for non-gated volumes. Respiratory-gated PET acquisition reduces the blurring effect and increases image contrast. However, Freq-based and Amp-based volumes are still influenced by inappropriate attenuation correction and misregistration of mobile lesions on CT images. The proposed BH-based method both reduces motion artifacts and improves PET-CT registration.
  Acta Radiologica 01/2009; 50(2):144-55. · 1.37 Impact Factor