PubMed Health⌕ Search

Biomedical subjects

Steven Dymarkowski

Publications and source records attributed to Steven Dymarkowski.

33 records · Page 2Linked to original sources
PubMed2003

Respiration-induced movement of the upper abdominal organs: a pitfall for the three-dimensional conformal radiation treatment of pancreatic cancer.

Respiration-induced movement of the upper abdominal organs (pancreas, liver and kidneys) was assessed in 12 subjects using dynamic magnetic resonance imaging. The movement of each organ in the cranio-caudal, the lateral and the anterior-posterior direction was deduced from the movement of the center of gravity on two-dimensional images. This center of gravity was computed from the volume delineated on sequential 8-mm slices of both sagittal and coronal dynamic series. The largest movements were noticed in the cranio-caudal direction for pancreas and liver (23.7+/-15.9 mm and 24.4+/-16.4 mm). The kidneys showed smaller movements in the cranio-caudal direction (left kidney 16.9+/-6.7 mm and right kidney 16.1+/-7.9 mm). The movements of the different organs in the anterior-posterior and lateral directions were less pronounced. It is of the greatest importance to be aware of these movements in the planning of a conformal radiation treatment for pancreatic cancer.

Humans↗
PubMed2003

Implications of SENSE MR in routine clinical practice.

Sensitivity encoding (SENSE) uses multiple MRI receive coil elements to encode spatial information in addition to traditional gradient encoding. Requiring less gradient encodings translates into shorter scan times, which is extremely beneficial in many clinical applications. SENSE is available to routine diagnostic imaging for the past 2 years. This paper highlights the use of SENSE with scan time reduction factors up to 6 in contrast-enhanced MRA, routine abdominal imaging, mammography, cardiac and neuro imaging. It is shown that SENSE has opened new horizons in both routine and advanced MR imaging.

Contrast Media↗
PubMed2003

The ratio of flow in the superior and inferior caval veins after construction of a bidirectional cavopulmonary anastomosis in children.

In patients who have undergone a superior cavopulmonary anastomosis, the superior caval venous flow provides the only, or the most important, pulmonary blood supply, while the inferior caval venous blood is not oxygenated, being mixed with the pulmonary venous blood before entering the systemic circulation. In healthy children, the contribution of superior caval venous flow to total cardiac output has been shown to decrease during growth. Patients who have undergone a superior cavopulmonary anastomosis, however, often have a higher oxygen saturation than predicted by the age-matched ratio of superior to inferior caval venous flows. This study was designed, therefore, to assess the ratio of flows in the superior and inferior caval veins subsequent to a superior cavopulmonary anastomosis. We carried out 18 magnetic resonance imaging studies with velocity-mapping and heart catheterisations so as to assess the contribution of superior caval venous flow to total cardiac output. Patients were divided into 3 groups according to their age. There were five aged from 8 to 24 months, eight aged from 24 to 48 months, and five older than 48 months. No significant difference could be found in the ratios of superior-to-inferior caval venous flow, nor of superior caval venous-to-systemic flow, between the 3 groups. The ratio of venous flows was 0.89 +/- 0.34 in those aged from 8 to 24 months, 1.09 +/- 0.42 in those from 24 to 48 months, and 1.25 +/- 0.27 in the older patients (F analysis of variance 1.06, p 0.37). The ratio of superior caval venous-to-systemic flow was 0.46 +/- 0.08 in the youngest patients, 0.50 +/- 0.09 in those aged from 24 to 48 months, and 0.55 +/- 0.05 in the older patients (F analysis of variance 0.76, p 0.49). These findings suggest that the hemodynamics of a cavopulmonary anastomosis may affect the normal decrease of superior caval venous flow with age. This could be related to a redistribution of flow, with a proportionally higher flow to the head and upper body after construction of a superior cavopulmonary anastomosis. Since increasing cyanosis and progressive exercise intolerance are the main indications for creation of a total cavopulmonary connection, these findings should be taken into account when determining the timing for completion of the Fontan circulation.

Cardiac Catheterization↗
PubMed2003

Original report. Late myocardial enhancement in hypertrophic cardiomyopathy with contrast-enhanced MR imaging.

OBJECTIVE: Contrast-enhanced MR imaging has great clinical value as a means of characterizing myocardial tissue in patients with ischemic heart disease. The purpose of our study was to evaluate use of this technique in the assessment of patients with hypertrophic cardiomyopathy. CONCLUSION: On late-enhancement MR imaging, the various types or patterns of enhancement found in patients with hypertrophic cardiomyopathy are related to differences in morphology and regional function. Enhancement in hypertrophied areas likely reflects the presence of abundant connective tissue, foci of myocardial necrosis, or a combination of both.

Adolescent↗
PubMed2003

MRI and CT revealing carcinoid heart disease.

Carcinoid heart disease is a frequent complication of the carcinoid syndrome, usually presenting as right-sided valvular heart disease. Although the diagnosis is most often made with cardiac ultrasound, MRI and CT are valuable techniques for diagnosing carcinoid heart disease.

Aged↗
PubMed2002

Visualization of ventricular thrombi with contrast-enhanced magnetic resonance imaging in patients with ischemic heart disease.

BACKGROUND: Ventricular thrombus formation is a frequent and potentially dangerous complication in patients with ischemic heart disease. Although transthoracic echocardiography (TTE) is generally used as diagnostic technique, we explored the role of contrast-enhanced (CE)-MRI to detect ventricular thrombi. METHODS AND RESULTS: In 57 patients with acute myocardial infarction, chronic myocardial infarction, or ischemic cardiomyopathy, MRI was performed to evaluate ventricular function (CINE-MRI) and to depict presence of myocardial necrosis and/or scarring and no-reflow areas (CE-MRI). All studies were analyzed for concomitant ventricular thrombi. CE-MRI depicted 12 mural thrombi (3.1+/-2.9 cm3), located in left ventricular (LV) apex or adherent to anteroseptum, presenting as black, well-defined structures surrounded by bright contrast-enhanced blood. Thrombus formation on CE-MRI was related to larger end-diastolic volumes; lower ejection fractions; the region of delayed enhancement and lowest wall motion score, especially in left anterior descending coronary artery territory; and LV aneurysm formation. On CINE-MRI, thrombi were found in 6 patients. Nonvisualized thrombi were usually small (mean size 1.2+/-0.7 cm3). TTE depicted thrombi in 5. Nonvisualized lesions were most frequently located in LV apex and had a larger size than nonvisualized lesions on CINE-MRI (3.0+/-3.2 cm3). In 3 patients with suspected apical thrombus on TTE, MRI was normal. CONCLUSIONS: CE-MRI is not only an excellent technique to depict myocardial necrosis and scar tissue in patients with ischemic heart disease, but this study also suggests a better identification of LV thrombi than with presently used clinical imaging modalities, such as TTE.

Acute Disease↗
PubMed2002

Hypercholesterolemia in minipigs impairs left ventricular response to stress: association with decreased coronary flow reserve and reduced capillary density.

BACKGROUND: Hypercholesterolemia induces functional and structural changes of the microvasculature and reduces coronary flow reserve in humans and experimental animals. The effect of hypercholesterolemia on left ventricular (LV) function in the absence of coronary stenosis is, however, unknown. Our objective was therefore to assess the effect of hypercholesterolemia and cholesterol withdrawal on LV function in the presence of advanced coronary plaques that do not cause stenosis. METHODS AND RESULTS: Twenty-eight minipigs on cholesterol diet for 34 weeks and 16 control pigs were studied. Seven hypercholesterolemic pigs were withdrawn from the diet for 26 weeks. LV function was assessed with cine-MRI, myocardial blood flow with colored microspheres, and capillary density with immunohistochemistry, and microvascular endothelial cell apoptosis with terminal dUTP nick-end labeling staining. Hypercholesterolemia (17+/-8 versus 268+/-150 versus 12+/-10 mg/dL LDL cholesterol, control versus hypercholesterolemic versus cholesterol withdrawal; P<0.001) induced atherosclerosis but not stenosis in the left coronary artery. Baseline cardiac output, ejection fraction, and stroke volume were similar in control and hypercholesterolemic pigs. In dobutamine stress test, cardiac output (P<0.05) and stroke volume (P<0.01) were lower in hypercholesterolemic pigs compared with controls. The impaired response to dobutamine was reversible by dietary cholesterol withdrawal. Hypercholesterolemia reduced endomyocardial coronary flow reserve (P<0.01) and capillary density (P<0.05) and induced capillary endothelial cell apoptosis. Hypercholesterolemic pigs failed to reduce vascular resistance in response to increased LV workload and pharmacological vasodilation. CONCLUSION: LDL hypercholesterolemia in minipigs impaired LV response to dobutamine stress in the absence of coronary stenosis.

Adrenergic beta-Agonists↗
PubMed2002

Dietary cholesterol withdrawal reduces vascular inflammation and induces coronary plaque stabilization in miniature pigs.

OBJECTIVE: To study the effect of dietary cholesterol withdrawal on size and composition of LDL-hypercholesterolemia-induced coronary plaques in miniature pigs. METHODS: Pigs were on normal chow (control group), on a cholesterol-rich diet for 37 weeks (hypercholesterolemic group) or on a cholesterol-rich diet followed by normal chow for 26 weeks (cholesterol withdrawal group). Endothelial function was assessed with quantitative angiography after intracoronary infusion of acetylcholine, plaque load with intra-coronary ultrasound and plaque composition with image analysis of cross-sections. The effect of porcine serum on coronary smooth muscle cell (SMC) function was studied in vitro. RESULTS: Cholesterol-rich diet caused LDL-hypercholesterolemia, increased plasma levels of oxidized LDL (ox-LDL) and C-reactive protein (CRP), and induced endothelial dysfunction and coronary atherosclerosis. Dietary cholesterol withdrawal lowered LDL, ox-LDL and CRP. It restored endothelial function, did not affect plaque size but decreased lipid, ox-LDL and macrophage content. Smooth muscle cells and collagen accumulated within the plaque. Increased smoothelin-to-alpha-smooth muscle actin ratio indicated a more differentiated SMC phenotype. Cholesterol lowering reduced proliferation and apoptosis. In vitro, hypercholesterolemic serum increased SMC apoptosis and decreased SMC migration compared to non-hypercholesterolemic serum. CONCLUSIONS: Cholesterol lowering induced coronary plaque stabilization as evidenced by a decrease in lipids, ox-LDL, macrophages, apoptosis and cell proliferation, and an increase in differentiated SMC and collagen. Increased migration and decreased apoptosis of SMC may contribute to the disappearance of the a-cellular core after lipid lowering.

Acetylcholine↗
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

Improved visualization of coronary arteries using a new three-dimensional submillimeter MR coronary angiography sequence with balanced gradients.

OBJECTIVE: The goal of our study was to evaluate a new three-dimensional real-time navigator MR coronary angiography sequence to noninvasively visualize the coronary arteries. SUBJECTS AND METHODS: Fifteen healthy volunteers underwent MR coronary angiography with a new balanced turbo field-echo sequence in comparison with the standard turbo field-echo sequence. Signal-to-noise, blood-to-myocardium, blood-to-fat, and blood-to-pericardial fluid contrast ratios of the left and right coronary artery systems were measured. Image quality was graded, the length and diameter of the coronary arteries were measured, and the number of visible side branches was assessed. RESULTS: The balanced turbo field-echo images yielded a higher blood-to-myocardium and blood-to-pericardial fluid contrast ratio, a similar blood-to-fat contrast ratio, and a lower signal-to-noise ratio than the turbo field-echo images. On a 5-point grading scale (1, nondiagnostic or unreadable; 2, poor; 3, moderate; 4, good; 5, excellent), image quality was rated significantly better for the balanced turbo field-echo sequence than for the turbo field-echo sequence (left coronary artery, 4.0 +/- 0.6 vs 3.6 +/- 0.5 [p = 0.015]; right coronary artery, 4.4 +/- 0.4 vs 3.6 +/- 0.4 [p < 0.0001], respectively), resulting in a significantly longer segment of the three major coronary arteries visualized (left anterior descending coronary artery, 92 +/- 21 mm vs 79 +/- 24 mm; left circumflex coronary artery, 70 +/- 7 mm vs 60 +/- 18 mm; right coronary artery, 112 +/- 28 mm vs 95 +/- 27 mm) and a significantly higher number of side branches visualized (left anterior descending coronary artery, 2.9 +/- 1.3 vs 1.5 +/- 1.3; left circumflex coronary artery, 2.1 +/- 1.7 vs 1.0 +/- 1.2; right coronary artery, 3.7 +/- 1.7 vs 2.6 +/- 1.5). Mean imaging time per coronary artery was significantly shorter for the balanced turbo field-echo sequence (5.7 +/- 1.0 min) than for the turbo field-echo sequence (8.4 +/- 1.4 min) (p < 0.0001). CONCLUSION: Compared with standard turbo field-echo MR coronary angiography, optimized balanced turbo field-echo MR coronary angiography improves the visualization of the coronary arteries and their side branches within a significantly shorter imaging time.

Adult↗