Search PubMed⌕ Search

Biomedical subjects

Charles B Higgins

Publications and source records attributed to Charles B Higgins.

61 records · Page 4Linked to original sources
PubMed2002

Influence of blood-pool contrast media on MR imaging and flow measurements in the presence of pulmonary arterial stents in swine.

PURPOSE: To compare the effects of various stents on magnetic resonance (MR) imaging flow volume measurements and to determine the value of a blood-pool MR imaging contrast medium in assessment of vascular stents. MATERIALS AND METHODS: In 11 pigs, six nitinol stents (Memotherm), four platinum stents (NuMed), and one elgiloy stent (Wallstent) were placed in the main pulmonary artery under x-ray fluoroscopic guidance. MR imaging was performed 3 months after stent placement before and after injection of NC100150 contrast medium. Blood flow volumes were assessed with velocity-encoded cine MR imaging through and next to the stent. The signal-to-noise ratio and width of susceptibility artifacts of the stents also were determined. Measurements were analyzed with the paired Student t test and Bland-Altman test, where appropriate. RESULTS: Blood flow volumes measured through the nitinol and platinum stents disclosed no significant difference between velocity-encoded cine MR imaging measurements through and next to the stent. On cine MR images, small susceptibility artifacts were observed around the nitinol and platinum stents. Signal-to-noise ratio in the stent lumen was reduced in nitinol and platinum stents when compared with that next to the stent. The elgiloy stent produced severe susceptibility artifacts, making measurement of flow volumes impossible. NC100150 injection caused no significant effect on flow volume measurements. It improved the signal-to-noise ratio of the pulmonary arterial lumen outside and, to a lesser extent, inside the stent. CONCLUSION: Assessment of morphology and flow volumes through nitinol and platinum stents is feasible with MR imaging. Blood-pool contrast media provide persistent signal enhancement in the pulmonary artery and, to a lesser extent, in the lumina of nitinol and platinum stents.

Alloys↗
PubMed2002

Left ventricular remodeling after infarction: sequential MR imaging with oral nicorandil therapy in rat model.

PURPOSE: To use magnetic resonance (MR) imaging in quantification of the short- and long-term effects of therapy with orally administered nicorandil on left ventricular (LV) geometry and function independent of infarction size. MATERIALS AND METHODS: Forty-six rats were subjected to reperfused infarction and randomly divided into two groups. Group 1 rats (n = 21) were treated with nicorandil (3 mg/kg/day in drinking water) for 4 days before infarction and 8 weeks after infarction (hereafter, the nicorandil group). Group 2 rats (n = 25) received tap water for the same period and served as the control group. Mesoporphyrin- (as a necrosis-specific agent) enhanced MR imaging was used to define necrotic myocardium on day 2 after infarction in all 46 animals. Contrast material-enhanced MR images showed large but identical infarction size in 11 control and 11 nicorandil rats. Only these 22 rats underwent repeat MR imaging at 8 weeks after infarction. The following variables were measured: LV volumes, ejection fraction, mass, wall thickness, and infarction size. Student t test and analysis of variance for repeated measurements were used for statistical analysis. RESULTS: The size of the necrotic region on mesoporphyrin-enhanced MR images was 39% +/- 3 of the size of the left ventricle in the control group and 41% +/- 2 in the nicorandil group (difference not significant, unpaired Student t test). Pretreatment with nicorandil for 6 days before imaging did not reduce LV dilation or improve function compared with those in control animals with identical infarction size. Eight weeks after infarction, control animals showed deterioration in LV function, wall thinning, and gradient in regional dysfunction (analysis of variance test). Nicorandil produced significant salutary effects on LV ejection fraction (37% +/- 3 in the nicorandil group vs 24% +/- 3 in the control group), end-diastolic volume (0.53 mL +/- 0.03 vs 0.65 mL +/- 0.04), end-systolic volume (0.36 mL +/- 0.03 vs 0.49 mL +/- 0.05), LV wall thickening in remote noninfarcted myocardium (28% +/- 2 vs 19% +/- 1), and a rim of infarction (16% +/- 2 vs 8% +/- 1) (P <.05 for all parameters). The increase in LV mass was reduced in the nicorandil group (0.73 g +/- 0.03) compared with that in the control group (0.89 g +/- 0.04) (P <.05). CONCLUSION: In animals studied longitudinally, MR imaging demonstrated the deleterious changes in LV geometry and function in the period after infarction and the salutary effects of medical therapy.

Administration, Oral↗
PubMed2002

MR imaging of spatial extent of microvascular injury in reperfused ischemically injured rat myocardium: value of blood pool ultrasmall superparamagnetic particles of iron oxide.

PURPOSE: To (a) assess the value of a blood pool magnetic resonance (MR) imaging contrast agent (Clariscan) for characterizing microvascular injury in ischemically injured rat myocardium and (b) compare the extent of microvascular injury at Clariscan-enhanced MR imaging with infarction and areas at risk seen with histochemical staining. MATERIALS AND METHODS: Twenty rats underwent 45 minutes of coronary artery occlusion and 3 hours of reperfusion. Sequential T1-weighted spin-echo MR images were acquired in 10 rats to assess leakage of Clariscan into myocardium over time. Ten other rats underwent the same duration of occlusion and reperfusion (3 hours) so that the extent of microvascular injury in the entire heart could be measured and correlated with infarction and area at risk at necropsy. The Student t test and Bland-Altman method were used for data analysis. RESULTS: Clariscan improved visualization of regions with transmural and nontransmural microvascular injury. Accumulation of Clariscan was best reflected by the mean ratios of signal intensity in injured myocardium to that in normal myocardium measured before (0.98 +/- 0.01 [standard error of the mean]) and after (1.34 +/- 0.04) injection. At 15 minutes after injection, the size of the enhanced region remained constant over the course of observation. The mean size of the hyperenhanced region (44% of the left ventricle +/- 2) was significantly (P <.001) larger than the mean size of true infarction at necropsy (29% +/- 3) but smaller than the mean size of the area at risk (50% +/- 2). CONCLUSION: Clariscan has potential for estimating the spatial extent of microvascular injury in ischemically injured myocardium and may be useful as a marker of microvascular injury after thrombolytic therapy.

Animals↗
PubMed2002

Contrast agents for cardiovascular magnetic resonance imaging. Current status and future directions.

Magnetic resonance imaging (MRI) can provide a non-invasive combined diagnostic examination of different modalities including visualisation of vascular and cardiac anatomy and measurements of blood flow and left ventricular mass, function, perfusion and viability. Contrast agents for cardiovascular imaging are used to enhance the capability of MRI in assessing perfusion, tissue viability, infarction and vascular stenosis. Furthermore, contrast agents may be used for guiding procedures and therapies in the evolving field of interventional MRI such as angioplasty and delivery of genes and growth factors. Targeted MR contrast agents are needed to further improve the specificity of MRI and to monitor pathophysiological processes including necrosis, inflammation or angiogenesis. The research and development of MR contrast agents will continue at the cellular and molecular levels in the next decade.

Animals↗
PubMedDate not supplied

Quantification of flow dynamics in congenital heart disease: applications of velocity-encoded cine MR imaging.

Velocity-encoded cine (VEC) magnetic resonance (MR) imaging is a valuable technique for quantitative assessment of flow dynamics in congenital heart disease (CHD). VEC MR imaging has a variety of clinical applications, including the measurement of collateral flow and pressure gradients in coarctation of the aorta, differentiation of blood flow in the left and right pulmonary arteries, quantification of shunts, and evaluation of valvular regurgitation and stenosis. After surgical repair of CHD, VEC MR imaging can be used to monitor conduit blood flow, stenosis, and flow dynamics. There are some pitfalls that can occur in VEC MR imaging. These include potential underestimation of velocity and flow, aliasing, inadequate depiction of very small vessels, and possible errors in pressure gradient measurements. Nevertheless, VEC MR imaging is a valuable tool for preoperative planning and postoperative monitoring in patients with CHD.

Blood Flow Velocity↗
PubMedDate not supplied

Malignant pleural mesothelioma: evaluation with CT, MR imaging, and PET.

Imaging plays an essential role in the evaluation of malignant pleural mesothelioma (MPM). Computed tomography is the primary imaging modality used for the diagnosis and staging of MPM. Magnetic resonance (MR) imaging and, more recently, positron emission tomography (PET) have emerged as modalities that can provide additional important diagnostic and prognostic information to help further delineate the extent of disease, especially in surgical candidates. Use of MR imaging performed with different pulse sequences and gadolinium-based contrast material can improve the detection of tumor extension, especially to the chest wall and diaphragm. PET can provide both anatomic and metabolic information, especially in cases of extrathoracic and mediastinal nodal metastasis. Each imaging modality has its advantages and limitations, but their combined use is crucial in determining the most appropriate treatment options for patients with MPM.

Aged↗