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Biomedical subjects

Guy Marchal

Publications and source records attributed to Guy Marchal.

46 records · Page 3Linked to original sources
PubMed2002

Percutaneous injection of human thrombin to treat iatrogenic femoral pseudoaneurysms: short- and midterm ultrasound follow-up.

Our objective was to determine the efficacy of ultrasound-guided direct injection of human thrombin to close postcatheterization pseudoaneurysms and to evaluate the midterm results of this new percutaneous technique by ultrasound follow-up. One hundred one postcatheterization pseudoaneurysms in 100 patients were treated by direct injection of human thrombin (mean dose 200 IU, range 50-750 IU) under ultrasound guidance. Patient demographics, clinical data and ultrasonographic morphology of the pseudoaneurysms were analyzed. Midterm (mean 99 days, range 25-210 days) ultrasonographic follow-up was performed in 57 of 82 called patients (69.5%). Ninety-six of 101 pseudoaneurysms thrombosed completely after the first procedure. Of the remaining 5 pseudoaneurysms, 3 were treated successfully after the second attempt, and 2 patients underwent surgical repair; thus, the primary success rate was 95% (96 of 101), and the overall success rate was 98% (99 of 101). No changes in distal pulses or other adverse events were noted immediately or 1 day after the procedure. Ultrasound follow-up revealed complete disappearance of the pseudoaneurysm in 70% (40 of 57), presence of small, residual groin hematoma in 26% (15 of 57), and partial reperfusion of the pseudoaneurysm in 3.5% (2 of 57). Human thrombin injection under ultrasound guidance is a very effective and safe method of therapy. Failure (immediate and late) of the technique as well as procedure-related complications are very rare. In our institution, sonographically guided human thrombin injection has become the treatment of choice for postcatheterization pseudoaneurysms.

Adult↗
PubMed2002

In vivo animal functional MRI: improved image quality with a body-adapted mold.

PURPOSE: To reduce functional magnetic resonance imaging (fMRI) susceptibility distortion at the air/tissue interphase in animal experiments. MATERIALS AND METHODS: We investigated the applicability of a body-adaptable flexible mold consisting of a fast-setting alginate. This technique was implemented for subcutaneous growing tumors in rats and for the brains of monkeys. RESULTS: The T(2)*-weighted gradient-echo, echo-planar imaging (GE-EPI) data obtained with the body-adapted mold showed a reduction of susceptibility artifacts and improved image quality. With both rat tumor and monkey brain, an optimized match with the anatomical T(1) images was possible. CONCLUSION: The present mold methodology is a rapid, easy, and inexpensive way to reduce magnetic susceptibility during animal GE-EPI.

Animals↗
PubMed2002

Evaluation of radiofrequency ablation as an alternative for the treatment of brain tumor in rabbits.

Radiofrequency ablation (RFA) has emerged recently as a promising therapy for extracranial malignancies. This experiment was conducted to explore the potential of RFA for the treatment of brain tumor in a rabbit model with imaging-histological assessment. Eighteen rabbits with intracranially implanted VX2 tumors of 0.9+/-0.2 cm in diameter were divided into two groups. Group A (n = 12) was treated with a cooled-tip RFA technique at 30 watts for 30-60 s. Group B (n = 6) received sham operation. The therapeutic efficacy was evaluated by comparing survival rate, magnetic resonance imaging (MRI) and histological findings. All animals in Group B died within one month after tumor implantation (19+/-2.6 days). Tumor eradication was achieved in 6/12 rabbits (50.0%) in Group A, of which three rabbits survived longer than three months, another three rabbits were found free of viable tumor when sacrificed. Five rabbits suffered from local tumor relapse. One rabbit developed intracranial metastasis to the brain stem despite a complete ablation of the original tumor. Three-month survival rate of RFA treated rabbits was significantly higher (p < 0.05) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of three characteristic concentric zones, which corresponded to central coagulative tissues (Zone A), peripheral hemorrhagic rim (Zone B) and interstitial edema (Zone C) on histology. This study suggests that RFA may become a promising alternative therapy for the treatment of brain tumor. The recognized characters of thermal lesion on MRI and histology may prove valuable in delimitating the ablation range and understanding the biological response of the RFA.

Animals↗
PubMed2002

Value of t2-weighted magnetic resonance imaging early after myocardial infarction in dogs: comparison with bis-gadolinium-mesoporphyrin enhanced T1-weighted magnetic resonance imaging and functional data from cine magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Magnetic Resonance Imaging (MRI) has proved to provide noninvasive methods to investigate the functional repercussion of myocardial infarction and to measure infarct size with specific contrast agents. In this study, we evaluate whether the combination of T2-weighted and contrast-enhanced T1-weighted MRI could detect and discern necrotic and ischemic, but salvageable, myocardium. METHODS: Reperfused myocardial infarction was surgically induced in 14 dogs. T1- and T2-weighted MRI was performed 6 hours after administration of the necrosis avid contrast agent Gadophrin-2 at 0.05 mmol/kg. Gradient-echo cine MRI series were performed at baseline and at 6 hours. Quantification of myocardial infarction was performed with triphenyltetrazolium chloride staining. RESULTS: There was a strong correlation between of postcontrast T1-weighted MRI and histomorphometry (r2 = 0.98, P < 0.01). T2-weighted MRI overestimated the infarct size by 10.5% +/- 4.3% of left ventricular area. A good correlation was found between hyperintense areas on T2-weighted images and the percentage of dysfunctional areas on cine MRI (r2 = 0.84, P < 0.01). In regions with increased signal intensity on T2-weighted MRI, a decreased maximal systolic thickening (11.8% +/- 4.9%, P = 0.043) was found. CONCLUSION: In this study, the difference between the hyperintense areas on T2-weighted and enhanced T1-weighted images after myocardial infarction likely represents viable myocardium.

Animals↗
PubMed2002

Gadobenate dimeglumine-enhanced MR angiography of the abdominal aorta and renal arteries.

OBJECTIVE: This study was conducted to determine the efficacy and safety of four different doses of gadobenate dimeglumine for contrast-enhanced three-dimensional MR angiography of the abdominal aorta and renal arteries. SUBJECTS AND METHODS: Ninety-four patients with suspected abnormality of the abdominal aorta or renal arteries underwent unenhanced three-dimensional gradient-recalled echo time-of-flight MR angiography and contrast-enhanced MR angiography after the IV injection of one of four doses of gadobenate dimeglumine (0.025, 0.05, 0.1, and 0.2 mmol/kg of body weight). Efficacy was assessed on-site and by two blinded off-site reviewers in terms of change in total diagnostic quality score and diagnostic quality score per vessel segment from baseline unenhanced time-of-flight MR angiography to contrast-enhanced MR angiography. Secondary efficacy end points included lesion count and level of confidence in lesion characterization. Safety assessments comprised adverse event monitoring, physical evaluation, vital signs, ECG, and laboratory investigations. RESULTS: A significant change in the total diagnostic quality score from unenhanced to contrast-enhanced MR angiography was observed at all doses. The change increased with increased dose, plateauing at the 0.1 mmol/kg dose level. More patients with lesions detected and increased reviewer confidence for lesion characterization were noted on contrast-enhanced MR angiography compared with unenhanced MR angiography, although no dose-related trends were observed. All doses were well tolerated, and no significant changes in safety parameters were observed. CONCLUSION: Gadobenate dimeglumine is an effective and safe agent for contrast-enhanced MR angiography of the abdominal aorta and renal arteries. A dose of 0.1 mmol/kg of body weight appears to be the most suitable.

Adult↗
PubMed2001

Computer-aided diagnosis in virtual colonography via combination of surface normal and sphere fitting methods.

The success of CT colonography (CTC) depends on appropriate tools for quick and accurate diagnostic reading. Current advancements in computer technology have the potential to bring such tools even to personal computer level. In this paper a technique for computed-aided diagnosis (CAD) using CT colonography is described. The method uses a combination of surface normal and sphere fitting methods to label positions in the volume data, which have a strong likelihood of being polyps, and presents them in a user-friendly way. The method was tested on a study group of 18 patients and the detection rate for polyps of 10 mm or larger was 100%, comparable to that of human readers. The price paid for a high detection rate was a large number of approximately eight false-positive findings per case. Our results show that CAD is feasible, and if the number of false positives is further reduced, then this method can be useful for clinical screenings.

Algorithms↗
PubMedDate not supplied

Magnetic resonance imaging of acute reperfused myocardial infarction: intraindividual comparison of ECIII-60 and Gd-DTPA in a swine model.

PURPOSE: To compare a necrosis-avid contrast agent (NACA) bis-Gd-DTPA-pamoic acid derivative (ECIII-60) after intracoronary delivery with an extracellular agent Gd-DTPA after intravenous injection on magnetic resonance imaging (MRI) in a swine model of acute reperfused myocardial infarction (MI). METHODS: Eight pigs underwent 90 min of transcatheter coronary balloon occlusion and 60 min of reperfusion. After intravenous injection of Gd-DTPA at a dose of 0.2 mmol/kg, all pigs were scanned with T1-weighted MRI until the delayed enhancement of MI disappeared. Then they were intracoronarily infused with ECIII-60 at 0.0025 mmol/kg and imaged for 5 hr. Signal intensity, infarct-over-normal contrast ratio and relative infarct size were quantified, compared, and correlated with the results of postmortem MRI and triphenyltetrazolium chloride (TTC) histochemical staining. RESULTS: A contrast ratio over 3.0 was induced by both Gd-DTPA and ECIII-60. However, while the delayed enhancement with Gd-DTPA virtually vanished in 1 hr, ECIII-60 at an 80x smaller dose depicted the MI accurately over 5 hr as proven by ex vivo MRI and TTC staining. CONCLUSION: Both Gd-DTPA and ECIII-60 strongly enhanced acute MI. Comparing with fading contrast in a narrow time window with intravenous Gd-DTPA, intracoronary ECIII-60 persistently demarcated the acute MI, indicating a potential method for postprocedural assessment of myocardial viability after coronary interventions.

Animals↗
PubMedDate not supplied

Stool tagging applied in thin-slice multidetector computed tomography colonography.

OBJECTIVE: To compare thin-slice multidetector computed tomography colonography (CTC) that uses stool tagging with colonoscopy. METHOD: One hundred fifty patients scheduled for colonoscopy underwent high-resolution CTC. An iodinated contrast agent was added to the preparation to tag the residual colonic fluid and stool. The effect of fluid tagging was assessed first. Sensitivity and specificity were calculated for two independent readers. In addition, values were recalculated separately for the first and last 75 patients. RESULTS: Tagging was optimal in 95.3% of the cases, and reader confidence was high. Sensitivities were 64.1%-66.7% (for the 2 readers) for 5- to 9-mm polyps and 91.7% for larger polyps. The overall specificity was 94.2% and 95%. Sensitivity improved during the study for both 5- to 9-mm polyps (from 54.2%-58.3% to 80%) and polyps larger than 9 mm (from 50% to 100%). Specificity changed nonuniformly. CONCLUSION: The combination of fluid tagging and high-resolution scanning in CTC showed high sensitivity and specificity, especially concerning sensitivity for polyps of 10 mm and larger.

Colon↗