Biomedical subjects
Publications and source records attributed to J P Laissy.
The recent developments of synchronized cardiac MRI are a unique opportunity for the radiology community to integrate cardiac imaging. This educational aticle aims to help radiologists and technicians to obtain cardiac planes comparable to those of cardiac ultrasound and gated SPECT. Of course, cardiac planes described herein for MRI also apply to multi-detector CT.
Explore the source record for details and available documents.
Cardiac output relies on an appropriate contractile function. It is mandatory to recognize kinetic alterations of the myocardium and to precise their extent (i.e. segmental, regional or global), to quantify their consequences on the function of the cardiac pump, and to assess if the underlying disease is reversible or fixed.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A case of aortic dissection extending to an aberrant right subclavian artery seen at CT and MRI is reported. The clinical and imaging patterns of this rare disease are described and compared with those of the literature. Multiplanar views are, in this particular case, very useful for a precise assessment of the involved aberrant artery.
Explore the source record for details and available documents.
The aim of this study was to investigate the effect of gadolinium chelate dilution on vascular enhancement in contrast-enhanced two-dimensional (2D) MR subtraction angiography of aorta and renal arteries. Twenty patients were prospectively included. 2D subtraction MR angiography consisted of successive multisection breathhold GRE acquisitions of 16 s (2D FLASH, TR/TE 72/4, flip angle 60 degrees) obtained in the coronal plane before and after intravenous bolus administration of 0.1 mmol/kg BW gadolinium chelate. Patients underwent both diluted and undiluted gadolinium chelate administration in a random order. The data were studied both qualitatively and quantitatively on source and maximum intensity projection images. The length of renal arteries opacified was found not to differ significantly according to contrast dilution. The contrast enhancement percentage was not significantly modified according to the dilution used, but the time to peak enhancement was observed to be longer with the diluted contrast. Qualitatively, the best MR images were those obtained when undiluted contrast was injected first (chi2, P = 0.01). At a dosage of gadolinium chelate 0.1 mmol/kg BW, undiluted contrast 2D MR subtraction angiography seems to be more appropriate for studying diseases of the aorta and renal arteries than a similar diluted dose.
Intravenous injection of complete Freund's adjuvant (CFA) in rats has been proposed as an experimental model for pulmonary sarcoidosis, but only some animals develop granulomas. Because the detection of the presence of granulomas and evaluation of the extent of the reaction has required histological evaluation, this model has been of limited use in following the evolution of the granulomatous process. The present study evaluated the ability of lung computed tomography (CT) scanning to identify in vivo pulmonary granulomas induced by CFA in rats. Wistar rats were injected with CFA to induce pulmonary sarcoid-like granulomas, and the presence and extent of pulmonary abnormalities, as detected by spiral CT and histopathological analysis, were compared. Spiral CT had a high sensitivity and specificity for the detection of sarcoid-like granulomas in rats injected with CFA. The extent of the pulmonary granulomatous reaction as assessed by the two techniques strongly correlated (r=0.93, p<0.01). In contrast, the mean density of lungs containing granulomas was not significantly different from that of lungs with no granulomatous reaction. Thus, lung computed tomography appears to be a valuable tool for the in vivo evaluation of the pulmonary granulomatous reaction induced by complete Freund's adjuvant in rats. With the help of computed tomography, this experimental model should be suitable for the sequential study of pulmonary sarcoid-like granulomas, particularly in response to various therapeutic strategies.
Endocrine tumours of the pancreas (ETPs) are rare neoplasms that are frequently malignant. Despite their usual slow growth, metastases do occur and have a major impact on prognosis. Metastases may be the first manifestation of disease, and recognition of particular radiological features of these hypervascular metastases should suggest their possible neuroendocrine origin. Although somatostatin receptor scintigraphy has changed the imaging strategy for these tumours and has become their principal imaging modality, radiological techniques are still required for precise localization of scintigraphic hot spots and monitoring of response to therapy. This pictorial review shows the typical radiological features of ETP metastases and emphasizes the role of different imaging modalities.
Explore the source record for details and available documents.
IVU has been gradually replaced over recent years as the "gold standard" investigation for the renal parenchyma and urinary tract by two new modalities: ultrasound and computed tomography. Some authors still advocate IVU for the assessment of renal colic, for the following reasons: the excess cost of CT (which is not true for plain CT) and the absence of functional data (there are specific CT signs for increased pressure). However, the advantages of CT are clearly established: contrast resolution allowing the detection of almost all stones except for certain complications of triple combination therapy in HIV seropositive patients, extensive cover facilitating identification of differential diagnoses, rapidity and greater efficacy, and finally the absence of risk related to the injection of iodinated contrast agents in this indication. However, the performance of CT may be more limited in certain situations: thin patients, or when the female genital tract also needs to be investigated, but IVU is not more contributive in this context. The current place of IVU in renal colic is therefore to establish a definitive diagnosis and to guide an urgent procedure (removal of an obstruction in a context of infection) when CT is either unavailable (maintenance...) or really excessively irradiating, as in pregnant women, when ultrasound, or even MRI and MR urography have not been sufficiently contributive. The essential indication remains detailed visualization of the urinary tract (assessment of haematuria, detection of an urothelial tumour), detailed visualization of the entire urinary tract (assessment of certain malformations), or even a gross assessment of renal function in a patient with multiple injuries, which cannot be investigated by CT and in whom the surgeon rightly hesitates before opening the retroperitoneum. However, in the absence of IVU, we may fail to diagnose papillary necrosis or a small caliceal diverticulum, but is that really important in the final analysis? IVU, in countries with adapted equipment, is therefore now only an expert examination. IVU is an examination of the past, without a future indeed, but with a descendant: CT urography.
The purpose of this study was to evaluate the potential reversibility of kidney lesions in an experimental model of acute renal failure using ultra-small particles of iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging. This study was conducted in 21 uninephrectomized rats using a model of iodinated contrast media-induced renal failure. Thirteen rats received selective intraarterial renal administration of diatrizoate (370 mg/ml) and were compared with two control groups, including six animals injected with saline and two noninjected animals. MR imaging was performed 28 hours, 8 days, and 22 days after the procedure. Each MR session included axial and coronal T1- and coronal T2-weighted images before and after intravenous administration of 60 micromol Fe/kg of USPIO. The rats were sacrificed immediately after the last MR session for pathologic evaluation. MR images were qualitatively and quantitatively interpreted with respect to pathologic data, and differences were statistically studied. At day 22, histology showed 4 severely diseased kidneys with focal areas of necrosis, 5 mildly diseased kidneys with tubular vacuolization, and 12 normal kidneys. On quantitative data, a high correlation between the percentage of negative enhancement and histologic data was observed (P < 0.05). Qualitative interpretation showed a sensitivity and specificity of USPIO-enhanced T2-weighted MR images of 88% and 91%, respectively. Follow-up enhancement curves showed a constant increase of intrarenal USPIO negative enhancement in normal kidneys between day 1 and day 22, whereas all severely involved kidneys displayed higher USPIO negative enhancement at day 1 without significant changes over time until day 22. USPIO may be useful for in vivo follow-up of the reversibility of experimentally induced iodinated contrast media renal impairment in animals.
The aim of this study was to evaluate the usefulness of gadolinium-enhanced time-of-flight magnetic resonance venography (MRV) in the diagnosis of bland thrombosis/tumoral invasion in the preoperative assessment of renal cell carcinoma. Preoperative precontrast and enhanced GRE fast lowangle shot (FLASH) images of 36 patients with renal adenocarcinoma were reviewed and compared with pre- and post-contrast T1-weighted images. All patients underwent surgery, and MR findings were blindly and prospectively compared with surgical and pathologic data, considered the standard. Renal vein and vena cava were involved in 17 and 9 patients, respectively; right atrial extension was present in one patient. Precontrast spin-echo (SE) and FLASH images were 88% sensitive and 100% specific in the detection of venous involvement, respectively, and enhanced FLASH images 100% sensitive and 96% specific. The nature of thrombus (neoplastic or bland) was more accurately assessed (McNemar's, p < 0.05) with FLASH-enhanced MR images (sensitivity 89%; specificity 96%) than with SE and precontrast FLASH images (sensitivity 79%; specificity 94%). Our data suggest that use of Gd-enhanced MRV might improve preoperative assessment of vascular involvement in renal carcinoma.
RATIONALE AND OBJECTIVES: To assess the abilities of dynamic diffusion-weighted MRI to demonstrate the effects in vivo of a high-viscosity iodinated contrast agent on medullary and cortical blood flow in the rat kidney. METHODS: Dynamic diffusion-weighted, echoplanar MR images obtained from five b-value single-shot acquisitions and their isotropic apparent diffusion coefficient maps were obtained from nine rats anesthetized by pentobarbital sedation, before and after intravenous injection of a high-viscosity, dimeric iso-osmolar iodinated contrast medium (iodixanol), and compared with those obtained from four control rats that received saline. RESULTS: The mean baseline apparent diffusion coefficient values were 1.64 +/- 0.05 x 10(-3) mm2/s for the cortex and 1.75 +/- 0.06 x 10(-3) mm2/s for the medulla. In the iodixanol group, a significant decrease in renal diffusion was observed at 12 minutes and lasted at least until 24 minutes. The decrease in diffusion occurred earlier for the cortex and lasted less than for the medulla. There was no significant modification in diffusion over time in the control group. CONCLUSIONS: This preliminary experience in rats shows that dynamic diffusion-weighted MRI can be used to study noninvasively the in vivo renal hemodynamic response after injection of iodinated contrast.
Explore the source record for details and available documents.
To evaluate the ability of ECG-gated spin-echo (SE)-MR imaging vs. cine-MR imaging to assess coarctation of the aorta, 11 patients aged 15-45 years, with known or suspected coarctation of the aorta, and five patients suspected of re-stenosis or postoperative false-aneurysms after coarctation repair were examined by multisection SE-MR imaging and single-section multiphase cine-MR imaging on a 1.0 Tesla device. Aortography was performed in 15, and surgery in 14 of these 16 patients. Qualitatively, the location, severity, and length of the coarctation were shown in all cases with MR imaging, as well as the relationship with the arteries arising from the aortic arch. The respective sensitivities and specificities in the assessment of severity of stenoses were 86% and 100% for SE MR images, and 100% and 100% for cine-MR images. Cine-MR imaging was superior to SE imaging in stenosis diameter assessment with contrast angiography as reference, as well as to identify the site of leakage in cases of postoperative pseudoaneurysm. Pre-stenotic dilation or post-stenotic aneurysm, collateral channels, and associated malformations were better identified on SE images. Quantitatively, a better stenosis diameter correlation was found between cine-MR images and angiography than between SE-MR images and angiography (r=0.99 vs. r=0.78; p=0.001 vs. p=0.004), related to overestimation of stenoses with SE-MR imaging. The use of a combination of spin-echo and cine-MR imaging correlates well with conventional angiographic findings in this small series of patients with coarctation of aorta or postoperative pseudoaneurysmal complications. Cine-MRI can provide anatomic information that is equivalent to angiography for surgical planning.
RATIONALE AND OBJECTIVES: The authors sought to evaluate prospectively magnetic resonance angiography (MRA) versus fistulography in the detection and characterization of complications associated with malfunctioning hemodialysis access fistulas (arteriovenous fistulas [AVF]). METHODS: Nineteen patients with clinical AVF dysfunction were studied by MRA and fistulography. Data from each study were collected prospectively and analyzed in a blinded manner. RESULTS: The main diagnosis was stenosis in eight patients, thrombosis in five patients (mural thrombosis with preserved flow in one), aneurysm without stenosis in two patients, and normal AVF in four patients. A hazy flow void, assumed to be related to turbulence, was observed in normal arterial anastomoses. When flow void was considered as a criterion of stenosis or thrombosis, one false-positive and one false-negative MRA study were determined, yielding a sensitivity and specificity of 92% and 86%, respectively. CONCLUSIONS: Magnetic resonance angiography is a feasible and sensitive technique with which to portray suspected malfunctioning hemodialysis access fistulas.