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Biomedical subjects

P Croisille

Publications and source records attributed to P Croisille.

At least 19 recordsLinked to original sources
PubMed2004

[Ischemic heart disease (myocardial perfusion and viability): techniques and results].

Over the last two decades, the understanding, diagnosis and treatment of patients with suspected or known coronary artery disease have made tremendous progress, in particular with the help of the development of non-invasive methodologies for assessing myocardial perfusion and viability. Clinically, nuclear medicine techniques (particularly SPECT imaging) have predominated. With the recent technical developments allowing for a combined assessment of perfusion and irreversible damage with late enhancement imaging, MRI will now play a major role in the assessment of ischemic heart disease.

Coronary Circulation↗
PubMed2000

MR imaging of the heart: functional imaging.

To date, most applications of cardiovascular MRI relate to the evaluation of major vessels rather than the heart itself. However, MRI plays a major role in the evaluation of specific types of cardiovascular pathology, namely intracardiac and paracardiac masses, pericardial disease, and congenital heart disease. In addition, because the visualization of cardiovascular anatomy with MR is non-invasive and permits three-dimensional analysis but also allows functional assessment of the cardiac pump, it is clear that MRI will have a growing and significant impact over the next years. We review some of the technical aspect of cardiac MRI and describe the current and potential clinical and investigative applications of this new methodology.

Cardiotonic Agents↗
PubMed2000

Two-dimensional spatial and temporal displacement and deformation field fitting from cardiac magnetic resonance tagging.

Tagged magnetic resonance imaging is a specially developed technique to noninvasively assess contractile function of the heart. Several methods have been developed to estimate myocardial deformation from tagged image data. Most of these methods do not explicitly impose a continuity constraint through time although myocardial motion is a continuous physical phenomenon. In this paper, we propose to model the spatio-temporal myocardial displacement field by a cosine series model fitted to the entire tagged dataset. The method has been implemented in two dimensions (2D)+time. Its accuracy was successively evaluated on actual tagged data and on a simulated two-dimensional (2D) moving heart model. The simulations show that an overall theoretical mean accuracy of 0.1 mm can be attained with adequate model orders. The influence of the tagging pattern was evaluated and computing time is provided as a function of the model complexity and data size. This method provides an analytical and hierarchical model of the 2D+time deformation inside the myocardium. It was applied to actual tagged data from a healthy subject and from a patient with ischemia. The results demonstrate the adequacy of the proposed model for this evaluation.

Computer Simulation↗
PubMed2000

Airway narrowing in healthy humans inhaling methacholine without deep inspirations demonstrated by HRCT.

Normal subjects prevented from taking a deep breath show changes in airflow similar to those of asthmatics when challenged with methacholine (MCh). To confirm airway narrowing by MCh in this setting and to determine its location, we concurrently measured changes in airway lumenal area using high resolution computed tomography (HRCT) and airflow using partial spirometry in five normal subjects challenged with increasing doses of MCh under prohibition of deep breaths. In an attempt to improve imaging accuracy, we corrected for the changes in lung volume during bronchoprovocation. At every step of the provocation, scanning was performed at approximately the same lung volume. On the HRCT images, airway area decreased in response to the increasing doses of MCh to 91 +/- 2%, 88 +/- 2%, and 80 +/- 2% of baseline at the doses of MCh 0.25, 0.75, and 2.5 mg/ml, respectively (p < 0.001). Airway narrowing showed no predilection for particular airway sizes and occurred in a heterogeneous pattern. The changes in the mean airway lumenal area as measured by HRCT and the mean partial spirometric outcomes were highly correlated: FEV(1)p (r(2) = 0.46, p = 0.001), FVCp (r(2) = 0.20, p = 0.05), FEV(1)/FVCp (r(2) = 0.55, p = 0.002), MMEFp (r(2) = 0.31, p = 0.01), and taup (r(2) = 0.51, p = 0.0004). We conclude that in normal subjects who are prevented from taking a deep breath, the spirometric changes occurring with aerosol MCh challenge are associated with conducting airway narrowing.

Adult↗
PubMed2000

[Right atrial angiosarcoma and MRI: a case report].

The authors report a case of right atrial angiosarcoma in a 29 year old man presenting with massive pericardial effusion. This case illustrates the value of MRI in the preoperative evaluation, providing accurate information about the site and extension of the tumor, and even about the malignant nature of the lesion. Multiplanar transesophageal echocardiography did not provide any additional information in this case.

Adult↗
PubMed2000

Dobutamine magnetic resonance imaging predicts contractile reserve of chronically dysfunctional myocardium: comparison with was fluorine-18 fluorodeoxyglucose positron emission tomography.

OBJECTIVE: This study sought to investigate whether low-dose dobutamine-MRI can detect residual myocardial viability in patients with chronic myocardial infarction and, left ventricular dysfunction. METHODS: Eleven patients with chronic myocardial infarction and left ventricular dysfunction were employed for identification of viable myocardium by cine-MRI during dobutamine infusion. All patients underwent coronary angiography and left ventriculography, 18FDG-PET, MRI at rest and stress. The systolic wall thickening measured at rest and during stress was compared with the results of 18FDG-PET, respectively. RESULTS: A significant difference of either dobutamine-induced systolic wall thickening (SWthstress) or dobutamine-induced contractile reserve (deltaSWth = SWthstress - SWthrest) was present between viable and scar regions (1.0 +/- 0.3 versus -0.3 +/- 0.1, P < 0.01; 1.0 +/- 0.3 versus -0.2 +/- 0.2, P < 0.01). CONCLUSIONS: obutamine-induced contractile reserve can be predicted in the regions of akinesia or dyskinesia at rest when systolic wall thickening was > or = 1.0 mm during dobutamine stimulation.

Adult↗
PubMed1999

Differentiation of viable and nonviable myocardium by the use of three-dimensional tagged MRI in 2-day-old reperfused canine infarcts.

BACKGROUND: To limit ischemic myocardial injury, it is important to differentiate viable from infarcted myocardium. Three dimensional (3D) tagged MRI has the ability to quantify myocardial 3D deformation and strain (noninvasively and precisely), and can achieve a true comparison of contraction not only from region to region, but also at different levels of function. In this study, we investigated whether regional strain mapping obtained by 3D-tagged MRI can differentiate between viable but stunned myocardium and nonviable myocardium. METHODS AND RESULTS: We examined 7 dogs 2 days after a 90-minute closed-chest left anterior descending coronary artery occlusion followed by 48 hours of reperfusion. 3D-tagged MR images spanning the entire left ventricle were acquired both at rest and during dobutamine infusion (5 microg. kg-1. min-1 IV). Regional blood flow was measured with radioactive microspheres and used to define risk regions. Infarcted regions were defined as 2,3,5 triphenyltetrazolium chloride negative regions. Strains in infarcted regions were greatly impaired compared with remote regions (P<0.001) and remained unchanged during dobutamine stress. Risk regions showed a dysfunction at rest, with improved function during dobutamine infusion. Receiver operating characteristics analysis showed that radial strain was more accurate for identifying viable regions. CONCLUSIONS: When coupled with a stress test, 3D strain mapping by the use of tagged MRI is a sensitive and noninvasive method for characterizing ischemic injury. Regional strain can be used to differentiate between viable but stunned and nonviable myocardium within the postischemic injured myocardium.

Animals↗
PubMed1999

Prospective comparison of MR lung perfusion and lung scintigraphy.

This study attempted to assess the accuracy and potential of lung magnetic resonance (MR) perfusion imaging compared with perfusion scintigraphy in the evaluation of patients with suspected lung perfusion defects. The technique, which uses an inversion recovery turbo-FLASH sequence with ultra-short TE (1.4 msec), was tested in 24 patients suspected clinically of having acute pulmonary embolism (n = 19) and in patients with severe pulmonary emphysema (n = 5). Perfusion lung scintigraphy was performed within 48 hours prior to the MRI examination in both groups of patients. The dynamic study was acquired in the coronal plane and consisted of 10 images of 6 slices (a total of 60 images per series). Gadopentetate dimeglumine (0.1 mmol/kg) was manually injected as a compact bolus during the acquisition of the first image. Three senior radiologists reviewed all unprocessed two-dimensional coronal sections. They were blinded to clinical data and other imaging modalities. For the three observers, the average sensitivity and specificity of MR were 69% and 91%, respectively. The overall agreement between MR and scintigraphy appears to be good, with a good correlation between the two modalities (kappa = 0.63). However, the data showed variability depending on the location of the perfusion defect, with higher accuracy in the upper lobes. The agreement between MR perfusion and scintigraphy appears to be moderate in the left inferior lobe (kappa = 0.48). The data showed an overall good interobserver agreement (kappa = 0.66). MR perfusion of the lung is a promising technique in detecting lung perfusion defects.

Adult↗
PubMed1999

[Cardiac MRI in adults: principles, current and future clinical applications].

If cardiac MRI have been used for a long time to study cardiac morphology only, more recent developments allow the assessment of flow, perfusion and contractile function. Breath-hold segmented and MR tagging sequences offer new capabilities to explore regional functional consequences, of particular interest to characterize post-ischemic injury after myocardial infarction, representing an alternative technique to echocardiography or nuclear medicine. Combined with pharmacologic stress test, MR cardiac imaging offer a more precise characterization of myocardial perfusion and contractile function. If MR coronary angiography requires further developments, cardiac MRI have the potential to represent in the future the only imaging modality allowing combined assessment of coronary vessels, myocardial perfusion and contractile function.

Adult↗
PubMed1999

[Characterization of arterial stenosis using 3D imaging. Comparison of 3 imaging techniques (MRI, spiral CT and 3D DSA) and 4 display methods (MIP, SR, MPVR, VA) by using physical phantoms)].

INTRODUCTION: Accurate assessment of arterial stenosis is a major public health issue for the diagnosis and treatment of cardiovascular diseases. The number of imaging techniques and types of software for display of imaging data is increasing. Few studies that compare these different techniques are available in the literature. MATERIALS AND METHODS: Using phantoms to reproduce the main types of arterial stenosis, the authors compared three 3D acquisition techniques (MRA, CTA, and 3D DSA) and four types of display methods (MIP, SR, MPVR, and VA). The degree, the shape, and the location of different types of stenoses were analyzed by three experienced observers during two successive readings. Intra- and inter-observer reproducibility were assessed. The results of the various acquisition techniques and display methods also were compared to the digital reference data (CFAO) of the physical phantoms. RESULTS: The degree of intra- and inter-observer reproducibility for the assessment of shape and location of the stenoses was good. Visual assessment of the degree of stenosis showed significant differences between two observers as well as in two readings by one observer. The 3D DSA was the most accurate technique for assessing the degree of stenosis. CTA provided better results than MRA. MPVR provided an accurate assessment of the degree of the stenosis. 3D DSA and CTA assessed stenosis form and localization adequately, with no significant difference; both methods appeared to be more accurate than MRA. SR provided the best information on the eccentric nature of the stenosis. The shape was very well assessed by VA and MPVR. CONCLUSIONS: Even though 3D DSA is the most accurate acquisition technique for visualization, the combined use of SR and MPVR appears to be the best compromise to describe the morphology and degree of stenosis. Further improvements in automatic 3D image processing could offer a better understanding and increased possibilities for assessing arterial stenosis.

Angiography, Digital Subtraction↗
PubMed1998

Precision of myocardial contour estimation from tagged MR images with a "black-blood" technique.

RATIONALE AND OBJECTIVES: The authors determined whether blood presaturation of tagged magnetic resonance (MR) images affects identification of left ventricular endocardial borders. MATERIALS AND METHODS: Three healthy volunteers underwent MR imaging performed with a breath-hold segmented spoiled gradient-recalled-echo sequence with tissue tagging. Two saturation pulses (in the basal and apical regions) were used to generate black-blood images. Manual segmentation of endocardial contours on black-blood and white-blood images was performed independently by five observers. RESULTS: Endocardial borders were better identified on black-blood images compared with white-blood images, especially in the early systolic phases. Interobserver variability in contour estimation was significantly higher for white-blood images (P < .001) and was twice that for corresponding black-blood images during early systole. Contour variability appeared to be affected mainly by tag-to-myocardium contrast (P = .009) and myocardium-to-chamber contrast (P = .05). CONCLUSION: Blood presaturation of tagged MR images improves reliability of contour segmentation.

Adult↗
PubMed1997

Comparison between qualitative and quantitative wall motion analyses using dipyridamole stress breath-hold cine magnetic resonance imaging in patients with severe coronary artery stenosis.

Breath-hold cine magnetic resonance imaging (MRI) at rest and during dipyridamole infusion was used to study wall motion abnormalities in patients with severe coronary artery stenosis proven by coronary angiography. Sixteen patients without myocardial infarction but at least one major coronary artery with > or = 70% diameter narrowing were included. Qualitative "visual" assessment of wall motion, as well as quantitative measurement "wall thickening changes (%)" were compared using receiver operating characteristic curve analysis. 201Tl-single-photon emission computed tomography (SPECT) was also studied for comparison. Using qualitative analysis, coronary artery disease detection rate was comparable when assessing wall motion abnormalities with dipyridamole-MRI (79%) and with dipyridamole-induced perfusion defects with 201-thallium-SPECT (75%). Furthermore, sensitivity and specificity for identification of all diseased coronary territories were comparable for both imaging modalities (sensitivity of dipyridamole-MRI and 201thallium-SPECT, 80% vs. 69%; specificity, 75% vs. 80%). The quantitative method has a substantially higher sensitivity than the qualitative method in identifying all diseased territories (Az = 0.81, p < 0.01 vs. Az = 0.55 and 0.59). In addition, we demonstrated that the quantitative method had higher performance than the qualitative one in identifying the diseased vessels territories related to 1-vessel, 2-vessel, and each of individual coronary artery stenoses.

Aged↗
PubMed1997

Assessment of complicated arterial bypass grafts: value of contrast-enhanced subtraction magnetic resonance angiography.

PURPOSE: To evaluate complicated aortoiliac and lower extremity arterial bypass grafts with contrast-enhanced subtraction magnetic resonance angiography (MRA). METHODS: Twenty-three patients with 40 vascular grafts with either clinical symptoms or abnormal duplex findings were selected. They were examined using a fast T1-weighted gradient-echo sequence. Twelve to 19 coronal sections of 5 to 8 mm were acquired before and after an intravenous bolus injection of gadolinium (0.1 mmol/kg) in 25 to 40 seconds. Final images were created by subtracting each precontrast section from its corresponding postcontrast section. The MRA was obtained after subtraction and maximum intensity projection. RESULTS: MRA detected 38 grafts (95%) with 28 abnormalities. Two stenoses were overestimated. MRA had a sensitivity of 91% and a specificity of 92% for diagnosis of graft stenoses and occlusions. MRA brought out more information in five cases by demonstrating four nonthrombotic ectasias that were unseen by duplex sonography and one thrombotic ectasia that was unseen by x-ray angiography. CONCLUSIONS: MRA seems to compare favorably with x-ray angiography for the diagnosis of arterial bypass graft complications. A multicenter trial will be necessary to validate these preliminary results and to assess the exact role of MRA compared with the other established techniques.

Arterial Occlusive Diseases↗
PubMed1997

Lung perfusion demonstrated by contrast-enhanced dynamic magnetic resonance imaging. Application to unilateral lung transplantation.

RATIONALE AND OBJECTIVES: The authors evaluate the use of magnetic resonance (MR) to image pulmonary perfusion in healthy controls and to detect pulmonary defects in patients with unilateral lung transplantation, using dynamic images after contrast administration. METHODS: Five patients with right lung transplantation and nine healthy volunteers underwent MR imaging. Twenty-five subsecond contrast-enhanced MR images (turbo-fast low-angle shot [FLASH]) were obtained at the level of the pulmonary arteries after a single injection of gadopentetate dimeglumine (0.1 mmol/kg) in an antecubital vein. Perfusion lung scintigraphy was done within 24 hours after the MR imaging examination in the transplanted patients. RESULTS: Before administration of contrast material, MR images showed both lungs to be homogeneous and of low signal intensity in healthy controls and in patients with lung transplantation. After contrast administration in controls, the mean signal intensity of the dependent lung increased markedly to 171 +/- 24% above baseline, whereas the nondependent signal intensity lung increased by only 105 +/- 17%; these changes were significantly different. In all patients with lung transplantation, a clear perfusion defect was demonstrated in the native lung. This defect was confirmed in all cases by perfusion nuclear scintigraphy, which showed that the majority of lung perfusion is directed to the transplanted allograft, compared with the native contralateral lung. CONCLUSIONS: Our results suggest that dynamic contrast-enhanced MR imaging is a potential method for detecting pulmonary perfusion defects in patients with lung transplantation.

Adult↗
PubMed1997

[MRI of the pulmonary parenchyma. Clinical value and research prospects].

MR imaging of the lung is handicapped by three negative influences. First, the low proton spin density in lung tissue results in a low signal-to-noise ratio relative to the surrounding structures. Second, cardiac and respiratory motion induce artifacts that tend to obscure fine structural detail in the lung. Third, a considerable magnetic susceptibility gradient, arising from the large surface areas of air and tissue interfaces, produces a very low value for T2*. MR imaging can be used to stage the activity of interstitial lung disease and for the diagnosis of lipoid pneumonia and pulmonary infarction. In combination with MR angiography, perfusion MR imaging might eventually become a test for pulmonary embolisms.

Forecasting↗
PubMed1997

Magnetic resonance imaging of cardiac and pericardial disease.

To date, most application of cardiovascular MRI relate to the evaluation of major vessels rather than the heart itself. However, MRI plays a major role in the evaluation of specific types of cardiovascular pathology, namely intracardiac and paracardiac masses, pericardial disease, and congenital heart disease. Because the visualization of cardiovascular anatomy with MR is non-invasive and permits three-dimensional analysis, it is clear that MRI will have a growing and significant impact over the next years. We will review some of the technical aspects of cardiac MRI and will describe the current and potential clinical and investigative applications of this new methodology.

Cardiac Volume↗