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Biomedical subjects

N Grenier

Publications and source records attributed to N Grenier.

At least 19 recordsLinked to original sources
PubMed1998

D-dimer strategy in thrombosis exclusion--a gold standard study in 100 patients suspected of deep venous thrombosis or pulmonary embolism: 8 DD methods compared.

DD are now recognized as a valuable tool to screen patients suspected of deep venous thrombosis or pulmonary embolism before carrying out a gold standard radiologic examination. The newest methods available claim to be able to ascertain the absence of thrombosis, but they have yet to prove their efficiency. We compared the performances of 3 reference ELISA methods (D-DI Asserachrom Stago, D-dimer Enzygnost Behring and Dimertest GOLD EIA Agen), 5 recent rapid methods (VIDAS D-Dimer bioMérieux, Instant IA Stago, Simplired Agen, Nycocard D-dimer Nycomed and Accuclot D-Dimer Sigma Diagnostics) and two routine latex methods (Dimertest American Diagnostica and FDP-Slidex bioMérieux) in 100 patients. One of the rapid quantitative methods was demonstrated to have a level of efficiency comparable to that of ELISA methods. Finally, the cost and efficiency of different strategies were evaluated, the association of a routine latex method with the VIDAS D-Dimer bioMérieux being proven to be the most efficient.

Adult↗
PubMed1997

[The value of transrectal MRI in the staging of localized prostate cancer].

OBJECTIVE: To determine the diagnostic value of transrectal magnetic resonance imaging (MRI) in the local staging of prostatic cancer. METHOD: 75 patients suffering from clinically localized prostatic cancer were included consecutively from December 1992 to September 1996. An MRI examination (1.5 Tesla, Siemens) with a transrectal coil was performed before radical prostatectomy. The results of this examination in terms of capsular invasion, seminal vesicle lesion and apical invasion were correlated with the results of histological examination of the operative specimen and the findings of digital rectal examination, transrectal ultrasonography, serum PSA level and biopsy mapping. RESULTS: The best performance of transrectal MRI concerned elimination of seminal vesicle lesion with a specificity of 92%. The positive predictive value of transrectal MRI was 90% for the capsular invasion. The positive predictive value of transrectal MRI was 56% for the apex, the sensitivity was 40% and the specificity was 82%. When transrectal MRI did not reveal any extraprostatic involvement the risk of positive margins on radical prostatectomy was less than 6%. CONCLUSION: In this study, transrectal MRI appeared to be satisfactory to improve the staging of localized prostate cancer, especially in terms of seminal vesicle lesion and apical invasion, but, most importantly, appeared to be very useful to predict negative resection margins.

Aged↗
PubMed1996

Diagnosis of renovascular hypertension: feasibility of captopril-sensitized dynamic MR imaging and comparison with captopril scintigraphy.

OBJECTIVE: Angiotensin-converting enzyme inhibitors may decrease glomerular filtration rate when a significant renal artery stenosis is present. The purpose of this preliminary study is to evaluate the feasibility of captopril-sensitized, dynamic MR imaging of the kidney in a series of patients with a high suspicion of renovascular hypertension and to compare the results with those of captopril scintigraphy. SUBJECTS AND METHODS: Fifteen hypertensive patients with renal artery stenosis shown by angiography were studied with sequential gadolinium-enhanced MR imaging after oral administration of 50 mg of captopril, an inhibitor of angiotensin-converting enzyme. Symmetry of onset and evolution of tubular phases between the two kidneys were analyzed, and medullary signal intensity time curves were drawn for each kidney. When asymmetry between kidneys was noted, the same dynamic study was repeated 24 hr later, without captopril sensitization. All patients also underwent renal scintigraphy after administration of captopril to compare captopril-induced changes in both techniques. Three-dimensional time-of-flight MR angiography was also performed on all patients. RESULTS: MR imaging with normal and symmetric tubular phases showed that 11 patients had no impairment of glomerular filtration after administration of captopril. MR imaging showed that four had impairment of glomerular filtration: studies without captopril were symmetric (n = 2) or slightly asymmetric (n = 2), but administration of captopril induced severe functional impairment on the side of stenosis--that is, a delayed tubular phase with late corticomedullary decrease of signal intensity in the first two patients and absence of tubular phase in the other two. The results of scintigraphy were concordant in all but one case, in which the segmental distribution of filtration impairment, shown by MR imaging, was not shown by scintigraphy. The renal artery stenosis was shown by MR angiography in 10 of 15 patients (67%). CONCLUSION: Captopril-sensitized dynamic MR imaging of the kidney is feasible in patients with renovascular hypertension. However, captopril-induced changes are not present in all patients proven to have the disease. Scintigraphy provides similar results but may ignore segmental functional involvement.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

[Paresthesia, pain, coldness of the arm and possible responsibility of the thoraco-brachial outlet syndrome].

Paresthesia, pain and coldness of the upper limb strongly suggest ischemia. The questions raised concern the etiology and treatment. 1) Treatment is based on confirmation of the unilateral nature of the disorder requiring search for the a locoregional cause (examination of the subclavian outlet) and on elimination of a cardiac or general origin. Two noninvasive examinations are indicated. An X-ray examination of the upper chest bones is performed to search for an abnormal formation, usually a cervical rib. Presence of a cervical rib indicates a possible damage to the sub-clavian artery in the thoraco-brachial outlet and, inversely, absence of a cervical rib suggests either arterial damage or a fibromuscular cause. Ischemia of the upper limb results from repeated microtrauma to the sub-clavian artery due to a bone-ligament anomaly resulting in thickening and parietal ulceration, and sometimes post-stenosis embolism or in situ thrombosis. Duplex Doppler may be able to identify the nature of the cause without dynamic manoeuvres. An arteriography is essential to confirm the level of the obstacle, its nature, the status of the downstream bed and possible relationship between a bone anomaly and the sub-clavian artery. Several incidences may be required. 2) Therapeutic modalities must take into account the ischemia and its cause. Surgery is required to remove the obstacle and repair the arterial damage, and possibly to remove an embolus. It is relatively easy to remove a cervical rib or repair a bone muscle anomaly, allowing arterial repair with or without venous bypass. Embolectomy of an earlier embolus may require major reconstruction vascular surgery.

Arm↗
PubMed1995

USPIO-enhanced MR imaging of glycerol-induced acute renal failure in the rabbit.

Enhanced-MR imaging in combination with ultrasmall superparamagnetic iron oxide (USPIO) was used in the glycerol-induced model of acute renal failure (ARF) in the rabbit to detect renal perfusion abnormalities. A control group (n = 5) and an ARF group (n = 5) were studied after intramuscular injection of glycerol (10 ml/kg) with T2-weighted spin-echo sequence at 1.5 T and a 27 mumol/kg IV dose of iron. The signal intensity (SI) was quantified in the cortex, the outer medulla (OM), and the inner medulla (IM). In control rabbits, the maximum SI decrease after USPIO injection was in the OM (76% +/- 3.6), as this is the region of maximal vascular density, then in the IM (73.4% +/- 2.9). In the glycerol group, SI loss in the OM (61% +/- 12.6) and the IM (45.2% +/- 16.24) was significant less than in the control group (p < .05). Pathology results showed fibrinous thrombus in the efferent arterioles and congestive aspect of the vasa recta in the medulla. We argue that a reduced medullary concentration of USPIO in the renal failure group is indicative of medullary hypoperfusion.

Acute Kidney Injury↗
PubMed1995

Evaluation of experimentally induced renal hypoperfusion using iron oxide particles and fast magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Renal perfusion can be evaluated with first-pass study of superparamagnetic iron oxide particles (SPIO). We applied this technique to a unilateral renal hypoperfusion model in rabbits. METHODS: Turbo fast low-angle shot sequences (acquisition time = 440 msec), after bolus injection of SPIO (100-140 mumol/kg iron), were performed in two control groups (n = 5 in each) and one group (n = 5) with a left renal blood flow reduction caused by a surgical interrenal aortic ligature (140 mumol/kg iron). Qualitative and quantitative analysis using relative blood volume (rRBV), relative blood flow (rRBF), and mean transit time (MTT) were performed. RESULTS: Signal changes were symmetric in control groups without significant differences between the kidneys. The experimental group showed a significantly delayed and less pronounced maximal reduction of signal related to a significantly decreased rRBF and increased rRBV and MTT in the left kidney (p < .05). CONCLUSION: This study shows the effectiveness of a dynamic magnetic resonance study using SPIO to detect unilateral kidney perfusion reduction.

Animals↗
PubMed1995

[Exploration of renal arteries by angio-MRI].

Major clinical challenges are involved in applications of MR-angiography for the study of renal arteries, mostly for the diagnosis of renovascular hypertension. This technique now competes with color Doppler flow sonography and spiral CT. MR angiography of the renal arteries can be performed with 2D or 3D, flight-time or phase contrast sequences. Main and co-dominant arteries are usual by visualized on all sequences, but small accessory arteries are often missed. The diagnosis of stenosis is based on the presence of an area of signal extinction. The degree of extinction depends on the degree of turbulence, the type of technique, the length of TE and spatial resolution parameters, which is why scoring of stenoses is difficult and frequently overestimated. The diagnostic performance for stenosis is between 50 and 100% for sensitivity and between 80 and 97% for specificity. Detection of distal stenoses is poor because of respiratory artifacts. Multiphase acquisitions make it possible to measure the renal blood flow on each renal artery, adding hemodynamic criteria to this diagnosis.

Humans↗
PubMed1995

[Functional study of Swanson's metacarpophalangeal arthroplasties in rheumatoid arthritis].

To validate a functional hand evaluation and to obtain an historical control group in a project of metacarpophalangeal total joint prosthesis, we reviewed our experience over a ten year period of Swanson's metacarpophalangeal joint arthroplasty in rheumatoid arthritis. Forty-nine implants in fourteen rheumatoid arthritis patients were reviewed clinically, radiologically and evaluated by the Arthritic Hand Function Test. The mean follow up was 4.5 years. All patients were ready to repeat the experience except one. The mean metacarpophalangeal joint range of motion was 37 degrees (18 degrees to 55 degrees) with a mean of 7 degrees ulnar deviation. Although their functional performance was 50% of normal, all patients completed the test. The strength was generally greater on the operated side. The low complication rate (6% fracture rate) with the successful functional outcome of Swanson's metacarpophalangeal joint arthroplasty in rheumatoid arthritis will be the gold standard for any new implant to develop.

Adult↗
PubMed1995

[Thromboembolism and ovarian hyperstimulation].

Three new cases of thromboembolic accidents involving the superior vena cave were associated with ovarian hyperstimulation and multiple pregnancy. On the basis of a review of the literature, three syndromes were individualized. First embolic arteries are infrequent and serious with an important morbidity; low doses of gonadotrophines is sufficient for causing this pathology. Second, thrombosis of the superior vena cava is late, during in vitro fertilization regimens with GnRH analogs complicated with serious hyperstimulation (degree III). Third, pregnancy is always present; pulmonary complications are very uncommon. Thrombosis of inferior vena cava is late, pregnancy is often present but women are frequently at risk of thromboembolic accident. Prevention of hyperstimulation is important. When present, HBPM is recommended for prevention of thromboembolism. Diagnostic of thrombosis is made with clinical examination and morphologic complementary exams such colour-vascular Doppler and magnetic resonance imaging. Curative treatment requires heparinization.

Adult↗
PubMed1994

Evaluation of intrarenal distribution of ultrasmall superparamagnetic iron oxide particles by magnetic resonance imaging and modification by furosemide and water restriction.

RATIONALE AND OBJECTIVES: The steady-state intrarenal distribution of ultrasmall superparamagnetic iron oxide (USPIO) particles in the cortex, the outer medulla (OM), and the inner medulla (IM) was investigated using magnetic resonance imaging in the normal rabbit kidney and in situations that modify the corticopapillary osmotic gradient. METHODS: Experiments were performed on rabbit kidneys with T2-weighed spin-echo sequence and T2-weighted gradient-recalled-echo sequence. The intravenous dose was 27 mumole/kg of iron in all rabbits. Three groups were studied: normally hydrated rabbits (n = 5), after water restriction (n = 5) to increase the osmotic gradient, and after furosemide injection (n = 5) to decrease the osmotic gradient. The signal intensity (SI) was quantified by region of interest placed on the cortex, the OM and the IM. RESULTS: In normally hydrated rabbits, a maximal decrease of the SI after USPIO was noted in the medulla, without significant difference between the OM and the IM on spin-echo sequences. The decrease of the SI was maximal in the IM on gradient-recalled echo sequences. In dehydrated animals, the maximum SI loss was in the OM. The furosemide-induced transient enhancement of the IM lasted a few minutes. CONCLUSIONS: The observed SI changes due to the distribution of the USPIO between OM and IM were not based on modifications of the osmotic gradient. The authors suggest that these SI changes were mostly dependent on the vascular density.

Animals↗
PubMed1994

[Comparison of different monitoring techniques for vascular access in chronic hemodialysis].

Aim of the study was to compare different techniques of monitoring for vascular accesses in our chronic hemodialysis patients. Twenty seven patients (14 men, 13 women) were investigated. The accesses studied consisted of 19 arteriovenous fistulas and 8 vascular protheses. Twenty-four were trouble free, venous pressure was high in two, one was difficult to puncture. Three measurements of recirculation percentage were made for each patient, as well as a color Doppler flow imaging, and a digital angiography of the access. Recirculation measurements were normal for all patients including those with functional abnormalities. A stenosis was found 9 times with the Doppler and 10 times by angiography, there being disagreement between the two techniques in one case. The location of the stenosis was the same in the 9 concordant cases. There was a very strong correlation between the degree of stenosis found using the two techniques (p < 0.0001). In conclusion, measurement of recirculation appears to us to be of no interest for verifying a vascular access. On the other hand, the color Doppler seems to be an excellent choice for detecting an abnormality. An arteriographic confirmation seems necessary before correction.

Adolescent↗
PubMed1994

[Imaging of the renal transplant. Radiological methods].

Ultrasound examination with morphological sonography and color flow imaging is now considered as the main technique for the follow-up of renal transplants. Morphology of the graft, and quality of perfusion can be assessed non invasively with this technique. Indications of IV pyelography decreased considerably in many centers. CT can help in characterizing intra-abdominal collections. MR will probably play a major role in the future allowing the graft itself, the perirenal space, and the intrarenal vessels to be studied by means of MR-angiography techniques.

Diagnostic Imaging↗