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Biomedical subjects

G Marchal

Publications and source records attributed to G Marchal.

At least 37 records · Page 2Linked to original sources
PubMed2001

Lymph node metastases from head and neck squamous cell carcinoma: MR imaging with ultrasmall superparamagnetic iron oxide particles (Sinerem MR) -- results of a phase-III multicenter clinical trial.

The aim of this study was to compare the clinical usefulness of ultrasmall superparamagnetic iron oxide (USPIO) MR contrast media (Sinerem, Guerbet Laboratories, Aulnay-sous-Bois, France) with precontrast MRI in the diagnosis of metastatic lymph nodes in patients with head and neck squamous cell carcinoma, using histology as gold standard. Eighty-one previously untreated patients were enrolled in a multicenter phase-III clinical trial. All patients had a noncontrast MR, a Sinerem MR, and surgery within a period of 15 days. The MR exams were analyzed both on site and by two independent radiologists (centralized readers). Correlation between histology and imaging was done per lymph node groups, and per individual lymph nodes when the short axis was > or = 10 mm. For individual lymph nodes, Sinerem MR showed a high sensitivity (> or = 88%) and specificity (> or = 77%). For lymph node groups, the sensitivity was > or = 59% and specificity > or = 81%. False-positive results were partially due to inflammatory nodes; false-negative results from the presence of undetected micrometastases. Errors of interpretation were also related to motion and/or susceptibility artifacts and problems of zone assignment. Sinerem MR had a negative predictive value (NPV) > or = 90% and a positive predictive value (PPV) > or = 51%. The specificity and PPV of Sinerem MR were better than those of precontrast MR. Precontrast MR showed an unexpectedly high sensitivity and NPV which were not increased with Sinerem MR. The potential contribution of Sinerem MR still remains limited by technical problems regarding motion and susceptibility artifacts and spatial resolution. It is also noteworthy that logistical problems, which could reduce the practical value of Sinerem MR, will be minimized in the future since Sinerem MR alone performed as good as the combination of precontrast and Sinerem MR.

Adult↗
PubMed2001

Laryngeal squamous cell carcinoma presenting as a prelaryngeal neck abscess: report of two cases.

Head and neck tumours presenting as a neck abscess are extremely rare. Two patients with laryngeal squamous cell carcinoma, presenting with a prelaryngeal abscess, are described. Although clinically and on the CT studies these cases were suspect for underlying malignancy, the initial biopsies were negative for cancer. Because of persistent suspicion, repeat biopsies finally confirmed the presence of a squamous cell carcinoma. Pathological examination after total laryngectomy showed cancer localised in one of the true vocal cords, invading the anterior commissure and thyroid cartilage. However, the prelaryngeal soft tissues were free of tumour, showing only inflammatory changes and collections of pus. These cases emphasize the importance of repeat targeted biopsies and follow-up CT-studies in patients with a prelaryngeal abscess of obscure aetiology, in order to exclude or confirm a possible underlying malignancy.

Airway Obstruction↗
PubMed2001

Mixed immune response induced in rodents by two naked DNA genes coding for mycobacterial glycosylated proteins.

Two genes of Mycobacterium tuberculosis, apa (Rv1860) and pro (Rv1796), coding for two glycosylated excreted proteins have been injected to mice and guinea pigs. They produce an extended immunological response of Th1 and Th2 types. Despite the fact that mycobacterial glycosylation is necessary for a high level of delayed-type hypersensitivity (DTH) reaction, plasmids bearing each of the two genes induced an elevated level of DTH sensitization. An inverse relation between the CpG-N hexamer cluster frequency and the protective effect of injected genes is described. A comparison of the strength of several eukaryotic promoters based on the diameter of the DTH reaction shows that CMVIE followed by the ubiquitin promoter are the most efficient among those tested. A significant protective effect (0.7 log unit CFU) in mice was found for the apa gene while the pro gene had no effect.

Animals↗
PubMed2001

Radiofrequency ablation for eradication of pulmonary tumor in rabbits.

BACKGROUND: Radiofrequency ablation (RFA) has emerged as an alternative for surgery in clinical oncology. This animal experiment was conducted to evaluate the feasibility of RFA in the treatment of pulmonary tumor. METHODS: Eighteen rabbits with pulmonary implantation of VX2 tumors were divided into two groups. Group A (n = 12) was treated with RFA by using a cooled-tip electrode technique. Group B (n = 6) received sham operation. The therapeutic efficacy was evaluated by survival rate, magnetic resonance imaging (MRI), postmortem microangiography, and histology. RESULTS: All animals in group B died within 3 months after tumor implantation. Tumor eradication was achieved in 9 of 12 rabbits (75.0%) in group A, of which 4 rabbits survived longer than 3 months free of disease and another 5 rabbits were found free of viable tumor when sacrificed. One rabbit was subjected to incomplete tumor ablation and two rabbits suffered from local tumor relapse and/or lung metastasis. The 3-month survival rate of RFA-treated rabbits was significantly higher (P < 0.01) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of five characteristic concentric zones, which corresponded to central needle track (zone A), tumor coagulation (zone B), pulmonary parenchyma coagulation (zone C), peripheral hemorrhage (zone D), and inflammatory layer (zone E) on histology. CONCLUSIONS: Eradication of pulmonary tumor could be achieved with current RFA technique in rabbits. MRI is a useful modality for assessment of lung tumor ablation.

Angiography↗
PubMed2001

Sinochoanal polyp and its variant, the angiomatous polyp: MRI findings.

The angiomatous polyp corresponds to the vascular compromised nasochoanal part of a sinochoanal polyp. We describe the MRI characteristics of such lesions in four patients. All patients had an angiomatous polyp, in three cases as part of an antrochoanal polyp, and in one case as part of a sphenochoanal polyp. The unenhanced MR images depicted the typical appearance of a sinochoanal polyp, hypointense on T1-weighted and hyperintense on T2-weighted images. On gadolinium-enhanced MR images, the sinusal part showed little or no peripheral enhancement; however, the nasochoanal part, corresponding to the angiomatous polyp, showed strong enhancement. An angiomatous polyp mimics a hypervascular mass lesion on enhanced MR studies. The anatomic location and association with a sinusal polyp allows the correct diagnosis.

Adolescent↗
PubMed2001

Intracoronary delivery of Gd-DTPA and Gadophrin-2 for determination of myocardial viability with MR imaging.

The aim of this study was to compare intracoronary (i.c.) administration of Gadophrin-2, a necrosis-avid contrast agent (NACA), and nonspecific agent Gd-DTPA for determination of myocardial viability (MV) in acute myocardial infarction (AMI) with MRI. Reperfused AMI was induced in 12 dogs by transcatheter balloon occlusion of coronary artery. In 6 dogs each, Gd-DTPA at 0.1 mmol/kg or Gadophrin-2 at 0.005 mmol/kg was administered into coronary artery by fast bolus (n = 3) or slow infusion (n = 3). Serial ECG-triggered cardiac MRI of T1-weighted segmented turbo fast low-angle shot (FLASH) sequence was conducted and compared with triphenyltetrazolium chloride (TTC) histochemical staining. The contrast ratio and infarct size were quantified and analysed statistically. No cardiovascular side effects were found with local delivery of both agents. After i.c. administration, Gadophrin-2 induced a strong (CR > or = 1.78) and persistent (> or = 10 h) contrast enhancement of infarcted region. The infarct size defined with Gadophrin-2 was almost identical to that with TTC staining throughout the postcontrast period. With a dose 20 times higher, Gd-DTPA also strongly enhanced infarct-to-normal contrast; however, the enhancement diminished with time, i.e. from early strong to later faint enhancement and eventual loss of contrast. The delineated infarct size was also unstable, i.e. from early overestimation to later underestimation and eventual disappearance of the enhanced infarct. In combination with PTCA procedure, i.c. administration of MRI contrast agents may prove useful for post-procedure verification of diagnosis. The NACA-enhanced MRI may serve as an in vivo surrogate of postmortem histochemical staining for determination of MV. Although applicable in clinical setting, cardiac MRI with nonspecific Gd-DTPA is less reliable and should be performed within less than 1 h after contrast.

Animals↗
PubMed2001

An ex vivo study on radiofrequency tissue ablation: increased lesion size by using an "expandable-wet" electrode.

The present comparative study was conducted to validate a newly developed "expandable-wet" electrode for an increased lesion size of radiofrequency ablation (RFA) on excised beef liver. The expandable-wet electrode, which allows interstitial hypertonic saline infusion through retractable curved needles, was compared with "expanded-dry" and "unexpanded-wet" electrodes for RFA lesion size and other parameters. A total of 120 lesions were created under 50 W (groups A-C) and 90 W (groups A'-C') power control mode for 10 min at each ablation site with the following groups: group A and A' of expanded-dry electrode (needles deployed but saline uninfused); group B and B' of unexpanded-wet electrode (saline infused but needle undeployed); and group C and C' of expanded-wet electrode (needles deployed and saline infused). Together with lower impedance and higher power output, the lesion size in group C (5.3+/-0.4 cm) and C' (6.0+/-1.0 cm) were significantly larger (P<0.01) than that in group A (3.3+/-0.3 cm) and A' (2.0+/-0.2 cm), and group B (3.8+/-1.0 cm) and B' (2.6+/-0.4 cm). The RFA lesion size can be significantly enlarged when the expandable electrode is complemented with interstitial hypertonic saline infusion. This design may improve the efficacy of RF tumor ablation.

Animals↗
PubMed2001

BOLD contrast fMRI of whole rodent tumour during air or carbogen breathing using echo-planar imaging at 1.5 T.

The aim of this study was to evaluate the feasibility of functional MR imaging (fMRI) at 1.5 T, exploiting blood oxygenation level-dependent (BOLD) contrast, for detecting changes in whole-tumour oxygenation induced by carbogen (5% CO2+95% O2) inhalation of the host. Adult WAG/Rij rats with rhabdomyosarcomas growing subcutaneously in the lower flank were imaged when tumours reached sizes between 1 and 11 cm3 (n=12). Air and carbogen were alternatively supplied at 2 l/min using a snout mask. Imaging was done on a 1.5-T MR scanner using a T2*-weighted gradient-echo, echo-planar imaging (GE-EPI) sequence. Analysis of the whole-tumour EPI images was based on statistical parametric maps. Voxels with and without signal intensity changes (SIC) were recorded. Significance thresholds were set at p<0.05, corrected for multiple comparisons. In continuous air breathing condition, 3 of 12 tumours showed significant negative SIC and 1 tumour had a clear-cut positive SIC. The remaining tumours showed very little or no change. When switching to carbogen breathing, the SIC were significantly positive in 10 of 12 tumours. Negative SIC were present in 4 tumours, of which three were simultaneously characterised by positive SIC. The overall analysis indicated that 6 of the 12 tumours could be considered as strong positive responders to carbogen. Our research demonstrates the applicability of fMRI GE-EPI at 1.5 T to study whole-tumour oxygenation non-invasively. The observed negative SIC during air condition may reflect the presence of transient hypoxia during these measurements. Selection of tumours on the basis of their individual response to carbogen is possible, indicating a role of such non-invasive measurements for using tailor-made treatments.

Animals↗
PubMed2001

Radiofrequency ablation for eradication of renal tumor in a rabbit model by using a cooled-tip electrode technique.

BACKGROUND: Radiofrequency ablation (RFA) has emerged as a potential alternative for surgery in clinical oncology. This animal experiment was conducted to evaluate the feasibility of RFA in the treatment of renal tumor. METHODS: Eighteen rabbits with renal implantation of VX2 tumors were divided into two groups. Group A (n = 12) was treated with RFA by using a cooled-tip RF system at 30 W for 80 to 180 seconds. Group B (n = 6) received a sham operation. The therapeutic efficacy was evaluated by survival rate, magnetic resonance imaging (MRI), and histology. RESULTS: All animals in group B died within 3 months after tumor implantation. Total tumor eradication was achieved in 10 of 12 rabbits (83.3%) in group A, of which 5 rabbits survived longer than 6 months (absolute eradication) and another 5 rabbits were found free of viable tumor when killed (relative eradication). Two rabbits experienced local tumor relapse, lung metastasis, or both. Six-month survival rate of RFA-treated rabbits was significantly higher (P < .01) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of five characteristic concentric zones, which corresponded to central needle track (zone A), tumor coagulation (zone B), renal tissue coagulation (zone C), peripheral hemorrhage (zone D), and inflammatory layer (zone E) on histology. CONCLUSIONS: RFA may become a promising therapy for the treatment of renal tumor. MRI is a useful modality for assessment of renal tumor ablation.

Animals↗
PubMed2001

Basic principles of MRA.

Two types of MR angiography techniques are used in the radiological practice for neurovascular applications: flow based techniques and ultrafast contrast enhanced acquisitions. Both techniques have their specific advantages and limitations. Whereas flow based techniques can be run on most MR scanners, high quality contrast enhanced studies require a state-of-the-art system with high slew rates and dedicated tools to match bolus passage and MR scanning. In this text, we focus on the physical acquisition principles and we illustrate the different phenomena in clinical examples. Numerous studies have proven the clinical applications for the 2 acquisition strategies. So far, an understanding of the basic physics remains necessary to explain occasional artefacts: MR angiography techniques are not yet fully robust. Further optimizations of the current approaches can be expected as there is still a need to improve image quality.

Humans↗
PubMed2001

Magnetic resonance angiography of the intracranial vessels.

In this overview the results and indications of Magnetic Resonance Angiography of the intracranial vasculature will be discussed. The value of MRA will be studied in the visualisation of normal variants of the cerebral anatomy, the imaging of cerebrovascular disease, the diagnosis of aneurysms and cerebral arteriovenous malformations, the preoperative setup of cerebral tumors and the demonstration of vascular compression.

Cerebral Arteries↗
PubMed2001

The assessment of dose and image quality of storage phosphor systems: an overview of the different tasks.

The assessment of the dose-image quality relation using storage phosphor systems requires a series of tasks. In the text, the main aspects are summarized and the differences with the measurements for X ray equipment using film-screen cassettes are indicated. Standards of testing are becoming available for quality control measurements of the equipment. The global analysis is, however, less standardised. Large scale trials concerning dose and image quality are missing. In particular, guidelines about the appropriate use of post processing parameters and image visualisation are scarce. In this regard, a newly proposed method to evaluate image quality as a function of post-processing parameters for particular types of clinical images is mentioned. It is concluded that a thorough analysis may be very time consuming, but if the properties of the digital detectors are exploited, many tasks can be automated.

European Union↗
PubMed2001

MRI contrast enhancement of necrosis by MP-2269 and gadophrin-2 in a rat model of liver infarction.

RATIONALE AND OBJECTIVES: The mechanisms of action leading to specific localization of necrosis-avid contrast agents (NACAs) such as gadophrin-2 are not well defined. It has been suggested recently that agents with a high degree of serum albumin binding may also serve as NACAs by virtue of nonspecific hydrophobic interactions. The present MRI-histomorphology correlation study was conducted to verify the likelihood of the proposed albumin-binding mechanism by comparing an albumin-binding blood pool agent, MP-2269, with gadophrin-2 in a rat model of reperfused liver infarction. METHODS: Reperfused infarction in the right liver lobe was surgically induced in six rats. Serial T1-weighted MRI was performed before and after intravenous injection of MP-2269 at 0.05 mmol/kg and repeated in the same rats 24 hours later after intravenous injection of gadophrin-2 at the same dosage (0.05 mmol/kg). The MR images were matched with corresponding histomorphological findings. The signal intensity and contrast ratio of infarcted and normal hepatic lobes were quantified and compared between the two agents during the postcontrast course. RESULTS: Before contrast, the infarcted lobe was indiscernible from normal liver on T1-weighted MRI. Shortly after injection of both MP-2269 and gadophrin-2, a negative contrast occurred between infarcted and normal liver because of a strong liver signal intensity enhancement and an inferior uptake in the necrotic liver. On delayed phase (>60 minutes), a necrosis-specific contrast enhancement (contrast ratio 1.6) developed with gadophrin-2 but not with MP-2269. The MR images matched well with corresponding histomorphological findings. CONCLUSIONS: Although both MP-2269 and gadophrin-2 feature an albumin-binding capacity, only gadophrin-2 displayed a persistent necrosis-specific contrast enhancement in the rat model of reperfused liver infarction. Therefore, the role of albumin binding in the mechanisms of NACAs should be reevaluated.

Animals↗
PubMed2001

An iterative maximum-likelihood polychromatic algorithm for CT.

A new iterative maximum-likelihood reconstruction algorithm for X-ray computed tomography is presented. The algorithm prevents beam hardening artifacts by incorporating a polychromatic acquisition model. The continuous spectrum of the X-ray tube is modeled as a number of discrete energies. The energy dependence of the attenuation is taken into account by decomposing the linear attenuation coefficient into a photoelectric component and a Compton scatter component. The relative weight of these components is constrained based on prior material assumptions. Excellent results are obtained for simulations and for phantom measurements. Beam-hardening artifacts are effectively eliminated. The relation with existing algorithms is discussed. The results confirm that improving the acquisition model assumed by the reconstruction algorithm results in reduced artifacts. Preliminary results indicate that metal artifact reduction is a very promising application for this new algorithm.

Algorithms↗
PubMed2001

Effective combination therapy for invasive pneumococcal pneumonia with ampicillin and intravenous immunoglobulins in a mouse model.

Intranasal immunotherapy for Streptococcus pneumoniae invasive pneumonia with polyvalent immunoglobulins (IVIG) was effective in mice against pneumonia but failed to prevent bacteremia. The combination of subcurative doses of IVIG and of ampicillin was fully protective. Such an approach, successfully applied in the preantibiotic era, offers new perspectives for modern therapies.

Ampicillin↗
PubMed2001

Role of Mycobacterium tuberculosis copper-zinc superoxide dismutase.

Superoxide dismutases (SODs) play an important role in protection against oxidative stress and have been shown to contribute to the pathogenicity of many bacterial species. To determine the function of the mycobacterial copper and zinc-cofactored SOD (CuZnSOD), we constructed and characterized Mycobacterium tuberculosis and Mycobacterium bovis BCG CuZnSOD null mutants. Both strains were more sensitive to superoxides and hydrogen peroxide than were their respective parental strains. The survival of M. bovis BCG in unstimulated as well as activated mouse bone marrow-derived macrophages was not affected by the loss of CuZnSOD. The survival of CuZnSOD deficient-M. tuberculosis in guinea pig tissues was comparable to that of its parental strain. These results indicate that the mycobacterial CuZnSOD is not essential for intracellular growth within macrophages and does not detectably contribute to the pathogenicity of M. tuberculosis.

Animals↗
PubMed2001

Virtual colonoscopy: a new screening tool for colorectal cancer?

One of the new forays into the field of medical imaging is the 3-D computer imaging. Thanks to new and more performant computer processing and 3-D rendering methods it is nowadays possible to generate high resolution images of the inner surface of the colon based on CT and MR images. This article reviews the current status and research directions of virtual colonoscopy and its possible eligibility of becoming a new tool for colorectal screening.

Colonography, Computed Tomographic↗