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Biomedical subjects

C Grandin

Publications and source records attributed to C Grandin.

At least 19 recordsLinked to original sources
PubMed2006

Ischemic cerebral lesions after carotid surgery and carotid stenting.

OBJECTIVES: To evaluate the risk of new ischemic cerebral lesions after carotid endarterectomy and carotid stenting and their clinical significance. METHODS: Prospective and non-randomized single-center study including 121 patients with symptomatic and asymptomatic significant carotid stenosis. 60 patients were treated by surgery and 61 treated by carotid stenting. Stenting was restricted to patients at high risk for surgery. Neurological examination and Diffusion-Weighted Cerebral Magnetic Resonance (DW-MRI) were performed before and after each procedure. The presence, location and volume of new cerebral lesions were determined. RESULTS: In the surgical group, 2 minor strokes were registered. DW-MRI showed new lesions in 7 patients (11.6%). All except one were located in the ipsilateral anterior circulation. In the stenting group, 1 minor stroke and 1 occurrence of quadranopsia were registered. DW-MRI showed new lesions in 26 patients (42.6%). 10 of these patients (38.4%) had lesions in the contralateral hemisphere and 7 patients (26.9%) in the posterior circulation. Deficits are found in patients with higher lesion volumes. CONCLUSIONS: Cerebral ischemic lesions are significantly (p<0.0001) more frequent after carotid stenting than after endarterectomy. The majority of these lesions have no immediate clinical implication, but more specific tests are needed to evaluate their exact significance.

Aged↗
PubMed2003

[MRI of closed head injury].

The superiority of MR imaging to demonstrate the presence of intra- or extra-axial hemorrhage or edematous lesions, including axonal injuries, following closed head trauma has been proven over the last 15 years. CT remains the initial imaging modality in the evaluation of these patients because it is easier to obtain and allows detection of lesions requiring immediate surgical management. However, MRI should replace CT in patients with moderate to mild trauma in order to better precise the extent and degree of injuries, especially in a context of litigation. MRI could also be used following CT to further assess patients following severe trauma for prognosis purposes and better classification of traumatic injuries as well as therapeutic management.

Head Injuries, Closed↗
PubMed2002

Apparent diffusion coefficient measurements within intracranial epidermoid cysts in six patients.

The purpose was to determine whether a strong decrease in apparent diffusion coefficient (ADC) within epidermoid cysts (ECs) is actually responsible for their bright signal intensity on diffusion-weighted (DW) trace images. We studied six patients with surgically proven ECs in whom ADC calculation from T2-weighted DW-EPI-SE data were performed within the ECs and within the deep white matter and cerebrospinal fluid (CSF) as references. All ECs displayed highest signal intensity on the DW trace images. ADC values ranged from 1,280 to 807 x 10(-6) mm(2)/s within cysts (with a mean value of 1,070), from 849 to 698 x 10(-6) mm(2)/s within white matter (with a mean value of 764) and from 3,370 to 2,980 x 10(-6) mm(2)/s within CSF (with a mean value of 3,185). ECs exhibited slightly higher ADC values than white matter, and not the strongly decreased ones which would have been expected if diffusion-weighting were the prominent mechanism for bright signal intensity of the ECs on DW images. However, the EC ADC values are much lower than those of the CSF. Other mechanisms must therefore be involved, i.e. the T2 shine-through effect. Reduced ADC is not the only explanation of the EC bright signal intensity on the DW trace images.

Brain Diseases↗
PubMed2001

Is there an apparent diffusion coefficient threshold in predicting tissue viability in hyperacute stroke?

BACKGROUND AND PURPOSE: Rapid and precise identification of the penumbra is important for decision-making in acute stroke. We sought to determine whether an early and moderate decrease in the apparent diffusion coefficient (ADC) may help to identify, within the diffusion/perfusion (DWI/PWI) mismatch, those areas that will eventually evolve toward infarction. METHODS: We reviewed 48 patients not treated by thrombolytics who had a DWI/PWI within 6 hours after onset, with infarct evolution documented by follow-up magnetic resonance on days 2 to 4. We calculated absolute values for ADC and the ADC ratio (ADCr) in (1) the initial DWI hypersignal; (2) the final volume of the infarct, ie, the follow-up fluid-attenuated inversion recovery abnormalities; (3) the infarct growth (IGR) area; and (4) the oligemic area (OLI) that remained viable despite initial hemodynamic disturbance. We tested the value of the ADC to predict tissue outcome by using discriminant analysis. RESULTS: ADC values were marginally but significantly decreased in the IGR area (ADC 782+/-82x10(-6) mm(2)/s, ADCr 0.94+/-0.08) compared with mirror values (P=0.01) and with OLI (ADC 823+/-41x10(-6) mm(2)/s, ADCr 0.99+/-0.07; P=0.001). Of all quantitative DWI and PWI parameters, the ADCr best discriminated between IGR and OLI (F(1,50)=13.6, cutoff=0.97, 64% sensitivity, 92% specificity) and between the final volume of infarct and OLI (F(1,83)=219, cutoff=0.91, 91% sensitivity, 100% specificity). CONCLUSIONS: A simple approach based on ADC alone may allow the identification of tissue at risk of infarction in acute-stroke patients.

Acute Disease↗
PubMed2000

Rapid three-dimensional MR imaging method for tracking a bolus of contrast agent through the brain.

A gradient-echo three-dimensional magnetic resonance imaging technique (principles of echo shifting with a train of observations, or PRESTO) is presented for use in tracking a bolus of paramagnetic contrast agent through the brain. The approach combines a segmented echo-planar type of acquisition with echo shifting, which leads to echo times that are longer than the repetition time. Unlike echo-planar imaging, the method maintains image resolution despite drastic T2* changes and frequency shifts.

Adult↗
PubMed2000

[Diffusion- and perfusion-weighted MR imaging during the hyperacute phase of stroke].

The sensitivity of diffusion-weighted MR imaging to detect a lesion within 6 hours of stroke onset was approximately 90%. The false negative results were usually small lesions (1 ml), were seen early, and were usually located in the brain stem. The specificity of this technique was nearly 100% when it was used correctly. The volume and the value of the apparent diffusion coefficient of the detected lesions provided prognostic information. After injection of a contrast agent (perfusion imaging), a time series of volumes were obtained using a T2* sensitive gradient echo EPI sequence. Hemodynamic perturbations of the cerebral parenchyma could be detected as well as the type of perturbation in the lesion. A map representing the mean transit time for each voxel was used to define the maximum volume of the perturbation. A hemodynamic penumbra was defined to be when this volume was larger than the volume detected on the diffusion images. The quantitative measure of cerebral blood flow could predict the irreversibility of the lesions when the value was below 18 ml/min/100g, and the extension of the ischemia in the penumbra zone when the value was below a threshold of 30 ml/min/100g.

Aged↗
PubMed1999

(15)O water positron emission tomography in language localization: a study comparing positron emission tomography visual and computerized region of interest analysis with the Wada test.

We compared (15)O water positron emission tomography (PET) auditory and visual confrontational naming activation with an intracarotid amobarbital (Amytal) injection procedure (IAP) for language lateralization in 12 patients with intractable epilepsy. PET scans were evaluated by three raters experienced in functional imaging as well as by a region of interest (ROI) approach. Compared with IAP, raters' positive predictive value for language lateralization ranged from 88 to 91%. ROI analysis had a positive predictive value of 80%. Six patients had surgery; 1 with right-sided IAP language dominance but left-sided PET activation had dysphasia for 6 months after left temporal lobectomy.

Adolescent↗
PubMed1999

Fast FLAIR sequence for detecting major vascular abnormalities during the hyperacute phase of stroke: a comparison with MR angiography.

In the hyperacute phase of stroke, occluded vessels can be seen as high signal on fast-FLAIR images or as absence of flow-related enhancement in maximum-intensity projection (MIP) MR angiography (MRA). To compare these techniques, we examined 53 patients within 6 h of a stroke, using a standardised MRI protocol including fast-FLAIR and 3D time-of-flight TOF MR to detect vessel occlusion or reduced flow corresponding to the suspected ischaemic territory. Brain infarcts were confirmed on MRI after 1-5 days in 41 cases (77%). The overall accuracy of 3D-TOF MRA was 68% and sensitivity, specificity, positive and negative predictive values were 67%, 71%, 87%, and 43% respectively. Values for the fast-FLAIR sequence were: 65%, 85%, 93% and 44%, with an overall accuracy of 70%. The fast-FLAIR sequence was thus able to show occluded vessels or reduced flow with about the same accuracy as 3D-TOF MRA and enabled better prediction of the ischaemic area.

Adult↗
PubMed1998

Comparison of unenhanced and gadoxetate disodium-enhanced spin-echo magnetic resonance imaging for the detection of experimental hepatocellular carcinoma in the rat.

RATIONALE AND OBJECTIVES: The authors compare the potential value of unenhanced and gadoxetate disodium-enhanced spin-echo images for the detection of hepatocellular carcinoma in a rat model. METHODS: Eleven rats with chemically induced hepatocellular carcinoma underwent unenhanced T2-weighted fast spin-echo imaging followed by T1-weighted spin-echo imaging before and at 5 minutes, 30 minutes, 3 hours, 1 day, and 3 days after intravenous administration of 60 micromol/kg gadoxetate disodium at 4.7 tesla. Tumor and liver enhancement, and tumor-to-liver contrast-to-noise (C/N) ratio were calculated. RESULTS: After gadoxetate disodium administration, the tumors showed less enhancement than the liver. Tumor-to-liver C/N ratio increased from 5.5 +/- 0.8% on unenhanced T1-weighted images to 12.9 +/- 2.4% on gadoxetate-enhanced T1-weighted images (P = 0.02). However, the C/N ratio on unenhanced T2-weighted images (23.5 +/- 3.6%) remained higher than that on gadoxetate-enhanced T1-weighted images, a difference that is statistically significant (P < 0.01). CONCLUSIONS: In the experimental setting of our study, the higher tumor-to-liver C/N ratio on unenhanced T2-weighted spin-echo images suggests that unenhanced T2-weighted spin-echo images are superior to gadoxetate disodium-enhanced T1-weighted spin-echo images for the detection of hepatocellular carcinoma.

Animals↗
PubMed1997

Brain energy metabolism in early blind subjects: neural activity in the visual cortex.

As an attempt to better understand the metabolic basis for the previously reported increases in glucose metabolism in the visual cortex of congenitally blind subjects, cerebral blood flow, oxygen consumption and glucose utilization were investigated with multitracer positron emission tomography. Measurements were carried out in three subjects who became blind early in life and in three age-matched blindfolded controls. Regional analysis of cerebral blood flow, metabolic rates for oxygen and glucose utilization revealed that these parameters were relatively higher in the visual cortex in case of early blindness (109.7 +/- 2.4%; 114.3 +/- 1.5%; 118.0 +/- 5.5%, respectively) than in controls (98.1 +/- 3.9%; 108.6 +/- 3.6%; 105.2 +/- 4.8%). There were slight differences, albeit statistically not significant, between early blind and control subjects in terms of oxygen-to-glucose metabolic ratios. The relatively preserved stoichiometry in the visual areas of blind subjects points to the lack of variation in the yield of glucose oxidation in this cortex. Those observations suggest that the high level of energy metabolism disclosed in early blind visual cortex is related to neural activity.

Adult↗
PubMed1997

Detection and segmental location of malignant hepatic tumors: comparison of ferumoxides-enhanced gradient-echo and T2-weighted spin-echo MR imaging.

OBJECTIVE: The aim of our prospective study was to compare the values of ferumoxides-enhanced gradient-echo and T2-weighted spin-echo MR imaging for the detection and segmental location of malignant hepatic tumors. SUBJECTS AND METHODS: Eighteen patients underwent ferumoxides-enhanced T2 weighted spin-echo and steady-state gradient-echo imaging before surgery. Intraoperative sonography was used as the reference examination and showed 28 malignant tumors involving 39 of the 144 hepatic segments. The MR images were reviewed independently by two observers who recorded the number of tumors and their segmental location. The results of the segmental location were subjected to receiver-operating-characteristic analysis. Tumor-liver, vessel-liver, and tumor-vessel contrast-to-noise ratios were calculated. RESULTS: Detection on the gradient-echo images did not differ significantly from that on the T2-weighted spin-echo MR images (observers A and B detected 23 and 24 tumors, respectively, on the gradient-echo images; the two observers each detected 22 tumors on the T2-weighted spin-echo images). Segmental localization was significantly better on the gradient-echo images than on the T2-weighted spin-echo images (mean area under the receiver-operating-characteristic curve: 0.974 versus 0.895 for observer A and 0.962 versus 0.906 for observer B, p = .024). The highest contrast-to-noise ratios for vessel to liver and tumor to vessel were obtained on the gradient-echo images and the highest tumor-liver contrast-to-noise ratio was obtained on the T2-weighted spin-echo images. CONCLUSION: In our study, ferumoxides-enhanced gradient-echo imaging was as accurate as T2-weighted spin-echo imaging for revealing malignant hepatic tumors and was superior for showing their segmental location.

Contrast Media↗
PubMed1997

Unusual location of an intracranial chondroma.

We describe the MR findings in a case of chondroma arising from the falx. At MR imaging, the mass appeared well defined, lobulated, hypointense to isointense on T1-weighted images, and very heterogeneous with marked hyperintense areas on T2-weighted images. After contrast administration, this tumor enhanced slightly on delayed images.

Adult↗
PubMed1996

MRI of the anal canal: correlation with histologic examination.

The purpose of this study was to correlate the MRI features of the anal canal with histologic findings. T1- and T2-weighted MR images of nine anal canals were obtained after fixation in 10% formalin. In three specimens, imaging was repeated after removal of histologic layers with a dissecting microscope. Corresponding histologic slices were stained with hematoxylin-eosin, Masson trichrome, and periodic acid-Schiff. Four layers were visualized on T2-weighted images. An inner layer of high signal intensity and a second layer of low signal intensity corresponded to the mucosa as well as mucous secretions and to the submucosa. The high signal intensity layer vanished at the distal part of the anal canal in accordance with the lack of mucus-secreting epithelium below the level of the dentate line. A third layer of intermediate signal intensity corresponded to the internal sphincter. A fourth layer of low signal intensity corresponded to the longitudinal muscle and external sphincter. T2-weighted MRI is capable of showing the internal architecture of the wall of the anal canal. In particular, the internal sphincter can be differentiated from the external sphincter and longitudinal muscle.

Anal Canal↗
PubMed1996

Ferristene as intestinal MR contrast agent. Distribution and safety of a fast ingestion procedure with oral metoclopramide.

PURPOSE: To compare the small bowel distribution and safety of a fast ingestion procedure of ferristene to those of the standard ingestion procedure. MATERIAL AND METHODS: Sixty-four patients received 0.5 g/l ferristene in 800 ml water. Thirty-four patients of the fast ingestion group ingested ferristene with 20 mg of oral metoclopramide during the course of 30 min before MR imaging and received an i.v. injection of an antiperistaltic agent during the MR study. Thirty patients of the standard group ingested ferristene during the course of 2 h, without additional drugs. Ferristene distribution was assessed by 2 reviewers and adverse events were recorded. RESULTS: More than 50% of the small bowel segments analyzed were filled with ferristene in 30 patients in the fast ingestion group and in 28 patients in the standard ingestion group. One patient in each group experienced nausea and/or vomiting. Some bloating or sensation of fullness was reported by 2 patients in the fast ingestion group and by 3 patients in the standard ingestion group. CONCLUSION: The distribution of ferristene in the small bowel and the safety of the procedure were thus similar in the 2 groups using either a fast ingestion procedure with oral metoclopramide or the more time-consuming standard ingestion procedure.

Administration, Oral↗