Illustrations cliniques en neurologie

The examples and clinical cases presented in this section are not intended to be considered as absolute models in terms of image quality or device parameter settings. They must initiate an individual analysis according to CT parameters and image quality. Nevertheless, they present practically different CT levels, which can be used according to the clinical context and the type of device.     

Indications et performances de la TEP/TDM au fluorure de sodium (FNA)

18F-NAF PET/CT is a relatively uncommon imaging procedure in France, for which indications are similar to those for bone scan and that shows substantial advantages when compared to it. In this review article, we propose to introduce this poorly known radiotracer, its validated indications, performances and some tips for interpretation that will be illustrated by 6 case reports.     

Quantification and monitoring of PET/CT data in multicentre trials: The Swiss SAKK 56/07 trial experience

AimTo outline the importance of continuous monitoring of quantitative positron emission tomography (PET) data in multicentre trials to minimize quantitative bias in longitudinal intra-patient PET studies in light of the multicentre SAKK 56/07 experience in quantification and monitoring ¹⁸F-FDG PET/CT data.Patients and methodsWe collected 64 uniform phantom ¹⁸F-FDG PET acquisitions periodically at the enrolling centres (12 European institutions). A core-laboratory analysed them for standard uptake value (SUV) accuracy (desired 1.00 ± 10%) and acceptable image noise was defined by a coefficient of variation (COV) less than 15%. In total, 151 patients ¹⁸F-FDG PET acquisitions (baseline and follow-up) were also collected and analysed to verify longitudinal coherence of main acquisition/reconstruction parameters (DICOM tags verification) and patient preparation, in particular the uptake time (desired uptake time [UT] = 60 ± 10 min).ResultsUniform phantom PET acquisition satisfied the inclusion criteria in 58/64 (89%) examinations. All PET scanner exhibited comparable SUV quantification, but we found large dispersion in terms of noise, with COV ranging 3–15%. Only 1 phantom PET acquisition was out of range with COV = 21.5%. Patient data exhibited important variation in uptake time with UT = 65 ± 10 min (mean ± SD), with only 111/151 (74%) patients’ examinations satisfying inclusion criteria while 26% were out of range.ConclusionsRegular monitoring of PET data in multicentre trials is capital to ensure longitudinal intra-patient PET data consistence and minimize quantitative bias while it helps to spread the culture of quality in participating centre. Recent EARL (EANM Research Ltd) standardization and unification of procedures is a welcome step in this direction.     

Production of transparent exopolymer particles (TEP) by benthic suspension feeders in coastal systems

In the marine environment, transparent exopolymer particles (TEP) are ubiquitous and abundant, playing a significant role in carbon cycling and the structuring of food webs. Previous studies have shown that phytoplankton, bacteria, and oysters contribute to the production of TEP through the release of exopolymers. However, little is known about other potential sources of TEP and TEP precursors, especially in coastal systems. It was hypothesized that suspension feeders contribute to the TEP pool in near-shore environments through the release of exopolymers in both the dissolved and particulate form, and tested these hypotheses in both laboratory and field experiments. In the laboratory, the production of TEP by several species of benthic suspension feeders (the blue mussel, Mytilus edulis; the bay scallop, Argopecten irradians; the slipper snail, Crepidula fornicata; and the solitary ascidians, Ciona intestinalis and Styela clava) was investigated from October to November 2002 and June 2003. Concentrations of TEP and DOC were determined by spectrophotometry after alcian blue staining and high-temperature, catalytic oxidation, respectively. Similar analyses were conducted on water samples from the field in July 2003, collected in close proximity to dense beds of mussels in the Poquonnock River, Connecticut, USA (41°19′ N, − 72°02′ W). Laboratory results indicated that actively-pumping blue mussels, bay scallops, slipper snails, and both species of solitary ascidians significantly enhanced TEP concentrations above background levels over a five-hour period. However, only the solitary tunicate S. clava significantly enhanced DOC concentrations above background levels over the same period of time. Field samples indicated that TEP and DOC concentrations were high in close proximity to dense beds of mussels. These results imply that a variety of benthic suspension feeders produce TEP during feeding activities which could lead to enhanced flocculation of organic matter and carbon deposition in near-shore waters.     

Value of 111In-Pentetreotide scintigraphy and 18F-FDG PET for clinical prognosis of patients with neuroendocrine neoplasms

Despite the existence of biological markers of aggressiveness, the clinical course of gastro-entero-pancreatic (GEP) neuroendocrine neoplasms (NEN) remains difficult to predict. Discrepancies between imaging data generated with ¹¹¹In-pentetreotide scintigraphy and ¹⁸F-FDG-PET could reflect the degree of cellular de-differentiation. NEN patients with both types of studies were identified retrospectively from the SwissNET database, which is collecting information on Swiss NEN patients since 2008. Progression free survival (PFS) and overall survival (OS) were assessed depending on functional imaging results. Correlation between histological grading (according to the WHO 2010 classification) and functional imaging status was also assessed. We identified 31 patients with both imaging studies, either on the primary tumor site (21/31) or for metastases (21/31), with 12/31 on both sites. Mean follow-up was 36 months (95% CI 27–45). 21 patients had a metastatic disease at diagnosis and 11 died at follow-up. 7/31 (22%) were NET G1, 16/31 (52%) were NET G2 and 8/31 (26%) were NEC G3. Only ¹⁸F-FDG PET status almost reached statistical significance (P = 0.054) with histological grading. Progression free-survival was significantly poorer in the ¹⁸F-FDG positive group (n = 21), with a median time for progression of 8 months, compared to 51 months in the negative group (n = 10) with a HR of 3.2 (97.5% CI 1.1–9.5, P = 0.04). Overall survival tended to be worse with a positive PET and a negative ¹¹¹In-pentetreotide scintigraphy status with a HR 1.63 (97.5%CI 0.11–21, P = 0.08). ¹¹¹In-pentetreotide scintigraphy status was not found to be predictive of survival nor progression.ConclusionThese data demonstrate the poorer prognostic value of a positive ¹⁸F-FDG-PET imaging in this cohort of patients.     

Évaluation de la perfusion myocardique par TEP-TDM

For the past decade, PET and PET/CT have been widely studied for myocardial perfusion imaging. Several studies demonstrated the incremental value of PET for the diagnostic and prognostic assessment of patients with coronary artery disease. Moreover, PET allows for non-invasively quantifying myocardial blood flow and myocardial flow reserve, that both are recognized as surrogate marker of cardiac event free survival. By enabling the exploration of epicardial disease and the microvasculature, PET constitutes a unique tool to study pathophysiogical mechanisms leading to atherosclerosis genesis. The recent emergence of high-tech hybrid machines may even provide further incremental information about coronary function and morphology. By taking the best of each modality, a better assessment of patients with coronary artery disease is expected.     

A K<Superscript>+</Superscript>/H<Superscript>+</Superscript> P-ATPase transport in the accessory cell membrane of the blowfly taste chemosensilla sustains the transepithelial potential

An electrogenic K(+) transport in the tormogen cell of insect chemosensilla is involved in the generation and maintenance of the transepithelial potential (TEP). To gain more information about the K(+) transport system underlying the TEP generation and the location of its components in the plasma membrane of the tormogen cell, we studied the effects of inhibitors of K(+)/H(+) P-ATPase (bafilomycin A1, omeprazole and Na-orthovanadate), of K(+)/Cl(-) co-transport (bumetanide), of Cl(-) channels (NPPB) and of a K(+) channel blocker (BaCl(2)). The relationship between TEP amplitude and spike firing activity was also studied. Experiments were performed on the labellar chemosensilla of the blowfly Protophormia terraenovae using a modified tip-recording technique. Results show that: (a) K(+)/H(+) P-ATPase inhibitors significantly decrease the TEP, when properly applied to the labellum for 20 min, so as to reach the basolateral side of the plasma membrane, while no effect was detected when applied to the apical side, (b) bumetanide, NPPB and BaCl(2) decrease the TEP value only when administered to the apical side, (c) spike activity is positively correlated with the TEP. A model is proposed of the active and passive K(+) transports sustaining the TEP associated with the blowfly chemosensilla.     

Cancer de la prostate : utilité de la TEP-TDM à la F-fluorocholine

In oncology, positron emission computed tomography (PET/CT) has become an essential tool for initial staging, response evaluation and follow-up of cancer patients. Most of the frequent tumors (lung, breast, esophagus, and lymphomas) are highly avid for ¹⁸F-fluorodeoxyglucose (¹⁸FDG), but prostate cancer has not demonstrated significant uptake of FDG. The development of new tracers labeled with ¹⁸F such as choline analogs allowed already to obtain interesting results particularly in patients with biological relapse and inconclusive conventional imaging work-up. The impact of ¹⁸F-flurocholine PET/CT on patient management needs to be validated in large studies, but many centers use already this examination in order to guide further management, including radiotherapy planning.