Frédéric Lefèvre

Advances in ultrasound

Abstract. Significant advances have been recently introduced into various fields of technology, taking advantage of the use of new piezoelectric materials and the large diffusion of broadband transducers. Various types of modulation may be applied to the pulse characteristics, using single pulse, multipulse or multiline techniques, and resulting in improved spatial resolution and better penetration. Non-linear imaging uses the harmonics component, which is generated by tissues or by contrast agents. Different modalities can be used to separate harmonics from fundamental bands from the received signal. New Doppler modes have been developed, whereas grey-scale flow imaging allows the simultaneous imaging of blood flow and tissues. Compounding techniques improve the contrast resolution of tissues and reduce artefacts. If 3D techniques are now currently available, real-time 4D imaging has been recently introduced. Elastographic imaging is still under evaluation, but promising clinical results have been shown. Recent release of the DICOM specification has made the full integration of ultrasound to the PACS systems easier. All these advances indicate that the contribution and potential of ultrasound in patient management is still growing.

Contrast-enhanced sonography of the renal transplant using triggered pulse-inversion imaging: preliminary results

The purpose of our study was to quantify renal transplant parenchymal sonographic enhancement using pulse-inversion imaging (PII) and intermittent emission after contrast administration by means of bolus and infusion techniques, and to evaluate renal perfusion functional indices. A total of 34 patients, presenting with minor abnormalities (n = 14) and cortical perfusion changes due to parenchymal disorders (n = 12) or renal artery stenosis (n = 8) were included. Cardiac-triggered contrast-enhanced PII ultrasound (US) was performed after administration of SHU 508 A (Schering AG, Berlin, Germany), using a high mechanical index, a frame rate of one image every four cardiac cycles for bolus study, and a decreasing frame rate for infusion study. Compared to baseline values, peak enhancement ratio ranged from 5.6 to 14.7 using a bolus administration, and reached a value of 2.1 to 4.0 using infusion technique. Qualitative analysis showed heterogeneous enhancement in most allografts presenting with acute parenchymal disease (p = 0.03). In bolus studies, time to peak, wash-in and wash-out slopes increased in renal transplants with parenchymal disease and renal artery stenosis (p = 0.0001). Infusion administration exhibited no plateau in signal level, and no significant difference in enhancement ratio was found between groups of patients. Triggered PII after contrast agent administration provides morphologic and quantitative information about cortical vascularity in renal transplants.

Lymphoproliferative disorders after renal transplantation: role of medical imaging.

Abstract. Post-transplantation lymphoproliferative disorders (PTLD) are a complication of immunosuppressed transplant recipients, and their incidence is reported to be 20–120 times greater than the rate in the general population. After kidney transplantation, PTLD more likely arise within the renal transplant fossa. Radiological patterns of these forms are presented and discussed, according to a review of the literature, and illustrated by cases from our institution. Ultrasound plays an essential role in the early diagnosis of PTLD by detecting a urinary obstruction associated with adenopathy or an ill-defined mass not previously seen. However, in the case of an inconclusive US examination, CT or MRI should be performed to confirm the presence of a mass. Both techniques are useful in evaluating the extension of the process within the transplantation fossa; MRI seems more accurate and can be used for the follow-up, especially after reduction in immunosuppressive therapy without transplant removal.

Du stockage à l’archivage des images : expériences et perspectives

Objectifs pedagogiques A partir d’experiences industrielles et radiologiques, prendre la mesure du chemin qui separe le stockage simple des donnees d’imagerie de l’archivage. Le stockage des images se generalise progressivement dans les structures radiologiques hospitalieres mais aussi liberales. Chacun etablit des regles pour organiser au mieux son propre stockage en tenant compte de son environnement (environnement de travail, contraintes reglementaires et economiques). Cette premiere etape est indispensable avant de pouvoir envisager un archivage qui figera les donnees pour les conserver sur une duree longue tout en garantissant leur integrite. Cette session a donc pour but d’eclairer et de nourrir nos reflexions afin de se preparer au mieux a cette nouvelle etape. Une premiere presentation nous apportera l’experience d’un industriel et dans le cas particulier d’une banque. Puis dans une deuxieme partie, plusieurs experiences en imagerie seront explicitees dans differents perimetres (regional, hospitalier et liberal). La derniere partie sera consacree a un expose de l’environnement legal de l’archivage des donnees medicales. Une discussion finale permettra de partager les reflexions et les experiences de chacun.

Imagerie et informatique

Objectifs pedagogiques Dossier medical : informatisation du dossier, epidemiologie, evaluation, echanges d’informations. Presenter des outils permettant d’ameliorer les conditions de la pratique quotidienne.