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Biomedical subjects

A de Roos

Publications and source records attributed to A de Roos.

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

Magnetic resonance microscopy at 17.6-Tesla on chicken embryos in vitro.

The non-destructive nature and the rapid acquisition of a three-dimensional image makes magnetic resonance microscopy (MRM) very attractive and suitable for functional imaging investigations. We explored the use of an ultra high magnetic field for MRM to increase image quality per image acquisition time. Improved image quality was characterized by a better signal-to-noise ratio (SNR), better image contrast, and higher resolution compared to images obtained at lower magnetic field strengths. Fixed chicken embryos at several stages of development were imaged at 7.0-T (300 MHz) and at 17.6-T (750 MHz). Maximum intensity projection resulted in three-dimensional vascular images with ample detail of the embryonic vasculature. We showed that at 750 MHz frequency, an image with approximately three times better SNR can be obtained by T1-weighting using a standard gadolinium contrast agent, compared to the same measurement at 300 MHz. The image contrast improved by around 20 percent and the contrast-to-noise ratio improved by almost a factor of 3.5. Smaller blood vessels of the vascular system were identified at the high field, which indicates a better image resolution. Thus, ultra high field is beneficial for MRM and opens new areas for functional imaging research, in particular when SNR, resolution, and contrast are limited by acquisition time.

Animals↗
PubMed2001

Barium enema and endoscopy for the detection of colorectal neoplasia: sensitivity, specificity, complications and its determinants.

AIM: To analyse sensitivity, specificity and complication rate of endoscopy, and barium enema for the detection of colorectal neoplasia. MATERIALS AND METHODS: A MEDLINE search was performed (1980-2000) directed at the endoscopic and radiologic literature on barium enema. Articles were selected based on the type of study, availability of sensitivity and specificity values in sizeable patient groups, and reports on complications. Sixty articles were included in the analysis. RESULTS: Endoscopy proved to have superior sensitivity for polyps in patients at high-risk for colorectal neoplasia. The role of endoscopy and radiology in average-risk screening populations is not known. Sensitivity and specificity rates ranged widely, probably due to bias. For the detection of small polyps endoscopy has superior performance, whereas sensitivity is similar for endoscopy and barium enema for the detection of larger (>1 cm) polyps and tumours. Overall, endoscopy is associated with a higher complication rate. CONCLUSION: Endoscopy is the preferred detection method in high-risk patients. The role of endoscopy and radiology in a screening setting requires evaluation. This review provides the test characteristics of endoscopy and radiology which are relevant for a cost-effectiveness analysis. Double-contrast barium enema may play an important role for screening purposes, owing to its good sensitivity for detecting larger (>1 cm) polyps and its lack of major complications. de Zwart, I. M.et al. (2001). Clinical Radiology56, 401-409.

Barium Sulfate↗
PubMed2001

Improved MR flow mapping in coronary artery bypass grafts during adenosine-induced stress.

PURPOSE: To validate a recently developed fast high-temporal-resolution magnetic resonance (MR) flow sequence and use it to assess coronary artery bypass graft function during pharmacologic stress. MATERIALS AND METHODS: Aortic and internal mammary artery flow was measured in 11 healthy volunteers by using conventional cine gradient-echo imaging as a reference standard method and turbo-field echo-planar imaging (TFEPI). By using TFEPI, breath-hold flow mapping with a spatial and temporal resolution of 0.8 mm(2) and 23 msec, respectively, can be performed. This sequence was applied in 20 angiographically normal grafts, and total blood flow at rest and during adenosine infusion (140 microgram/kg/min) was measured. RESULTS: Good agreement in aortic and internal mammary artery flow values between conventional fast-field echo and TFEPI techniques was found. The mean bypass graft total flow (+/- SD), as assessed with TFEPI, increased from 30.8 mL/min +/- 13.5 to 76.7 mL/min +/- 36.5 (P <.05) to yield a flow reserve of 2.7. Furthermore, this sequence revealed a difference in total flow between single and sequential grafts at rest (25.4 mL/min vs 40.9 mL/min; P <.05) and during stress (65.2 mL/min vs 98.3 mL/min; P <.05). CONCLUSION: Breath-hold TFEPI provides fast accurate flow measurements with high temporal resolution and allows motion-compensated flow quantification in multiple coronary artery bypass grafts during one 6-minute adenosine infusion.

Adenosine↗
PubMed2001

Biophysical properties of the normal-sized aorta in patients with Marfan syndrome: evaluation with MR flow mapping.

PURPOSE: To investigate the feasibility of magnetic resonance (MR) flow mapping in the assessment of aortic biophysical properties in patients with Marfan syndrome and to detect differences in biophysical properties in the normal-sized aorta distal to the aortic root between these patients and matched control subjects. MATERIALS AND METHODS: Seventy-eight patients with Marfan syndrome with aortic root dilatation and 23 matched control subjects underwent MR flow mapping in four locations in the normal-sized aorta (1, ascending aorta; 2, thoracic descending aorta; 3, descending aorta at the level of the diaphragm; and 4, abdominal descending aorta). Distensibility at each location and flow wave velocity between locations were calculated. RESULTS: Compared with the control subjects, patients with Marfan syndrome had decreased aortic distensibility at three of the four locations (levels 1, 2, and 4; P <.05) and increased flow wave velocity between all locations (P <.05) in the aorta. In patients with Marfan syndrome, flow wave velocity was also significantly increased along the entire aortic tract beyond the aortic root (from level 1 to level 4). CONCLUSION: MR imaging reveals abnormal biophysical properties of the normal-sized aorta in patients with Marfan syndrome. Monitoring of these properties is relevant for evaluating disease progression and treatment options.

Adolescent↗
PubMed2001

Aortic valve replacement in patients with aortic valve stenosis improves myocardial metabolism and diastolic function.

PURPOSE: To evaluate whether functional and metabolic changes recover after aortic valve replacement (AVR). MATERIALS AND METHODS: Eighteen men with aortic valve stenosis (mean pressure gradient +/- SD, 79.9 mm Hg +/- 15.1) underwent magnetic resonance (MR) imaging and phosphorus 31 MR spectroscopy. In nine patients who underwent AVR, MR imaging and spectroscopy were repeated 40 weeks +/- 12 after AVR. Ten age-matched healthy men were control subjects. RESULTS: Before AVR, the myocardial phosphocreatine (PCr)-to-adenosine triphosphate (ATP) ratio in the 18 patients was 1.24 +/- 0.17 and 1.43 +/- 0.14 in the control group (P <.01). In nine patients who underwent follow-up MR spectroscopy, the ratio increased from 1.28 +/- 0.17 to 1.47 +/- 0.14 (P <.05) following AVR. Before AVR, early acceleration peak corrected for cardiac output was (0.043 +/- 0.008) x 10(-3) sec(-1) in patients and (0.081 +/- 0.033) x 10(-3) sec(-1) in the control group (P <.05). After 40 weeks +/- 12, the mean early acceleration peak corrected for cardiac output in the nine patients increased significantly to (0.055 +/- 0.006) x 10(-3) sec(-1) (P <.05), although it was still significantly lower than that of the control group (P <.05). Before AVR, a significant correlation was found between the myocardial PCr-ATP ratio and left ventricular diastolic function (n = 18; P <.05). CONCLUSION: Severe aortic valve stenosis leads to a decreased myocardial PCr-ATP ratio and impairment of left ventricular diastolic function; following AVR, the ratio normalizes completely, whereas function improves significantly. There is an association between altered myocardial high-energy phosphate metabolism and impaired left ventricular diastolic function.

Adenosine Triphosphate↗
PubMed2001

Six months of recombinant human GH therapy in patients with ischemic cardiac failure does not influence left ventricular function and mass.

Beneficial effects of recombinant human GH on cardiac function have been reported in humans with GH deficiency and in patients with idiopathic dilated cardiomyopathy. No randomized controlled trial has been performed on the effects of recombinant human GH on cardiac function in patients with ischemic cardiac failure. We therefore randomly assigned 22 patients with ischemic cardiac failure (left ventricular ejection fraction, <40%; 19 men and 3 women; mean age, 64 yr) to receive 6 months of unblinded therapy with recombinant human GH (2.0 IU/d) or no treatment. Primary end points were left ventricular ejection fraction and left ventricular mass. Left ventricular end-diastolic volume, left ventricular end-systolic volume, and myocardial perfusion, both at rest and during exercise, were assessed as well. Cardiac imaging techniques were electrocardiographically gated single photon emission computer tomography and magnetic resonance imaging. In addition, biochemical and biometric measurements were performed. Nineteen patients completed the study (10 controls and 9 GH-treated subjects). IGF-I and IGF-binding protein-3 increased significantly after recombinant human GH treatment (+24% and +58%, respectively) compared with control values (-14% and +5%; P < 0.05). Left ventricular ejection fraction, left ventricular end-diastolic volume, left ventricular end-systolic volume, left ventricular mass, and myocardial perfusion were not influenced by recombinant human GH therapy. We conclude that 6 months of recombinant human GH treatment in patients with ischemic cardiac failure had no beneficial effect on left ventricular function and mass.

Aged↗
PubMed2000

Comparison of gated single-photon emission computed tomography with magnetic resonance imaging for evaluation of left ventricular function in ischemic cardiomyopathy.

To perform a head-to-head comparison between magnetic resonance imaging (MRI) and gated single-photon emission computed tomography (SPECT) for the evaluation of left ventricular (LV) function (LV ejection fraction [LVEF], LV volumes, and regional wall motion) in patients with ischemic cardiomyopathy, we studied 22 patients with chronic coronary artery disease and LV dysfunction. Multislice, multiphase echoplanar MRI was performed with Philips Gyroscan ACS-NT15. Image analysis was performed using the MASS software package to determine LV end-systolic volume, LV end-diastolic volume, and LVEF. The same parameters were calculated using quantitative gated SPECT software (QGS, Cedars-Sinai Medical Center). The different parameters were compared using linear regression, and correlation coefficients were calculated. Regional wall motion was also determined from both techniques, according to a 13-segment model and a 3-point scoring system (from 1 = normokinesia to 3 = akinesia or dyskinesia). A summed wall motion score was also calculated for MRI and gated SPECT. Good correlations were found between MRI and gated SPECT for all parameters: (1) summed wall motion scoreMRI versus summed wall motion scoreSPECT: y = 0.74x + 8.0, r = 0.88, p <0.01; (2) LV end-systolic volumeMRI versus LV end-systolic volumeSPECT: y = 0.94x - 12.3, r = 0.87, p <0.01; (3) LV end-diastolic volumeMRI versus LV end-diastolic volumeSPECT: y = 0.93x - 18.4, r = 0.84, p <0.01; and (4) LVEFMRI versus LVEFSPECT: y = 0.97x + 0.68, r = 0.90, p <0.01. For regional wall motion, an exact agreement of 83% was found, with a kappa statistic of 0.77 (95% confidence intervals 0.71 to 0.83, SE 0.03), indicating essentially excellent agreement. Thus, close and significant correlations were observed for assessment of LVEF, LV volumes, and regional wall motion by MRI and gated SPECT in patients with ischemic cardiomyopathy.

Aged↗
PubMed2000

Right ventricular function in patients after acute myocardial infarction assessed with phase contrast MR velocity mapping encoded in three directions.

The purpose of the study was to assess global and regional myocardial function of the right ventricle (RV) with the use of phase contrast (PC) velocity mapping in patients after acute myocardial infarction. We examined 8 patients after acute myocardial wall infarction and 10 healthy volunteers for comparison. PC velocity mapping was performed in a single midventricular short-axis slice with velocity encoding in three different directions. RV displacement during systole in the through-plane direction differed significantly between patients and volunteers (P = 0.009). RV myocardial velocity in the through-plane and radial directions, evaluated at time of peak ejection rate, was significantly lower in patients than in healthy volunteers (P<0.05). RV abnormalities may be detected in patients after acute myocardial infarction using PC velocity mapping with velocity encoding in three different directions. Owing to their short acquisition times and relatively easy postprocessing, PC techniques are time-efficient and promising tools for the evaluation of RV function.

Adult↗
PubMed2000

Arrhythmogenic right ventricular dysplasia: MRI findings.

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart muscle disorder of unknown cause that is characterized pathologically by fibrofatty replacement of the right ventricular myocardium. Clinical manifestations include structural and functional malformations of the right ventricle, electrocardiographic abnormalities, and presentation with ventricular tachycardias with left bundle branch pattern or sudden death. The disease is often familial with an autosomal inheritance. In addition to right ventricular dilatation, right ventricular aneurysms are typical deformities of ARVD and they are distributed in the so-called "triangle of dysplasia", i.e., right ventricular outflow tract, apex, and infundibulum. Ventricular aneurysms at these sites can be considered pathognomonic of ARVD. Another typical hallmark of ARVD is fibrofatty infiltration of the right ventricular free wall. These functional and morphologic characteristics are relevant to clinical imaging investigations such as contrast angiography, echocardiography, radionuclide angiography, ultrafast computed tomography, and magnetic resonance imaging (MRI). Among these techniques, MRI allows the clearest visualization of the heart, in particular because the right ventricle is involved, which is usually more difficult to explore with the other imaging modalities. Furthermore, MRI offers the specific advantage of visualizing adipose infiltration as a bright signal of the right ventricular myocardium. MRI provides the most important anatomic, functional, and morphologic criteria for diagnosis of ARVD within one single study. As a result, MRI appears to be the optimal imaging technique for detecting and following patients with clinical suspicion of ARVD.

Adult↗
PubMed2000

Congenital heart disease. Evaluation of anatomy and function by MRI.

With the increasing number of patients surviving after therapeutic intervention for congenital heart disease (CHD), accurate and frequent follow-up of their morphologic and functional cardiovascular status is required, preferably with a noninvasive imaging technique. Echocardiography, either transthoracic or transesophageal, has been the first choice for this purpose, and will probably keep that status, at least in a large segment of the CHD spectrum. Magnetic resonance imaging (MRI) is an established method for high-resolution visualization of cardiovascular morphology. In the past decade, newer MRI techniques have been developed that allow functional evaluation of CHD patients. Particularly the introduction of breath-hold imaging, contrast-enhanced MRA and user-friendly computer software for image analysis may move functional MRI of CHD from the science laboratory to clinical use. It is already evident that MRI is superior to echocardiography in certain areas of limited echocardiographic access, such as the pulmonary artery branches and the aortic arch in adult patients. But MRI has also a unique potential for accurate volumetric analysis of ventricular function and cardiovascular blood flow, without any geometric assumptions. If supported by increased cooperation between cardiologists and radiologists, MRI will grow into a useful noninvasive imaging tool that, together with echocardiography, will obviate the need for invasive catheter studies for diagnostic purposes.

Adult↗
PubMed2000

Evaluation of congenital heart disease by magnetic resonance imaging.

Magnetic resonance imaging has proven to be useful in the assessment of patients with complex congenital heart disease and in the post-surgical follow-up of patients with corrected congenital heart disease. A thorough understanding of the congenital cardiac malformations that can be encountered is needed and the use of the sequential segmental analysis helps to standardize the evaluation and diagnosis of (complex) congenital heart disease. After surgical correction of congenital heart defects, patients must be followed over extended periods of time, because morphological and functional abnormalities may still be present or may develop. The use of echocardiography may be hampered in these patients as scar tissue and thorax deformities limit the acoustic window. Magnetic resonance imaging has proven to be advantageous in the follow-up of these post-surgical patients and with the use of several different techniques the morphological as well as functional abnormalities can be evaluated and followed over time.

Aortic Coarctation↗
PubMed2000

Vessel diameter measurements in gadolinium contrast-enhanced three-dimensional MRA of peripheral arteries.

In this study, the possibilities for quantification of vessel diameters of peripheral arteries in gadolinium contrast-enhanced magnetic resonance angiography (Gd CE MRA) were evaluated. Absolute vessel diameter measurements were assessed objectively and semi-automatically in maximum intensity projections (MIPs) of contrast-enhanced T1-weighted 3D spoiled gradient-echo datasets, studied with digital subtraction techniques. In vivo, the complete peripheral arterial bed of six patients was studied, from the aorto-iliac bifurcation down to the distal run-off. By measuring the signal intensity (SI) over the lumen of a vessel in the MIP, an SI-plot was obtained. Next, the vessel boundaries were determined using a threshold algorithm; from these boundary points individual diameter values could be obtained along the trajectory of the vessel. In an in vitro study, an optimal threshold value of 30% of the range of SI-values between the background and the maximal SI in the vessel was obtained for accurate diameter measurement in Gd CE MRA (i.e., full-width 30%-maximum). Furthermore, the relationship between the accuracy of these measurements and the scan resolution was investigated. Accuracy was found to be acceptable (i.e., less than 10% over/underestimation) for vessel sizes covering at least 3 pixels. In six patients, diameters were measured in MIPs of the total datasets (i.e., D(T)) as well as in selective MIPs of the clipped datasets (i.e., D(S)) (n = 209). D(T) and D(S) were statistically significantly correlated (p < 0.01) with a Pearson correlation coefficient rP = 0.98. Measurements in the total MIPs yielded statistically significant (p < 0.01) smaller diameter values compared with measurements in selective MIPs, with a mean difference of 0.15 mm. Diameter values from the selective MIPs of the aorto-iliac arteries were also compared with diameter values measured at corresponding anatomic positions in X-ray angiograms of these patients (i.e., D(x)) (n = 70). D(X) and D(S) were statistically significantly correlated (p < 0.01) with a Pearson correlation coefficient rP = 0.92. Diameters measured in the selective MIPs were smaller than those measured in the X-ray angiograms (mean difference 0.49 mm) and this difference was statistically significant (p < 0.01). In conclusion, diameter values can be evaluated accurately in MIPs of vessels with at least 3 pixels in diameter, using the full-width 30%-maximum criterion.

Adult↗
PubMed2000

Spin echo MRI in the evaluation of hearts with a double outlet right ventricle: usefulness and limitations.

The surgical approach to a double outlet right ventricle (DORV) is dependent on the spatial relationship of the semilunar valves, outflow tracts and ventricular septal defect (VSD). The purpose of the study was to assess the value of MRI for the evaluation of cardiovascular anatomy in patients before and after surgery for DORV. Spin echo MRI was performed in 12 patients with DORV (eight preoperative and four postoperative patients). Thin-section MRI was performed in three orthogonal planes and selected angulated views were obtained. Conventional imaging by color Doppler echocardiography and cine-angiocardiography and surgical findings, when present, served as the reference standards. The results found that the spatial relationship between semilunar valves and VSD was accurately assessed by MRI in eight out of eight preoperative patients. In the four postoperative cases MRI depicted the morphology of both outflow tracts and provided adequate information on their patency. Of the eight preoperative patients, five have undergone corrective surgery and the MRI findings were confirmed. MRI provided additional information to conventional imaging preoperatively in three cases in which the VSD opened into the outlet portion of the DORV, without there being a direct relation to a semilunar valve. In two preoperative cases in which the VSD was directly committed to the aorta, conventional imaging was conclusive. MRI was unable to depict aberrant chordae tendineae in four out of four cases. We conclude that MRI provides accurate additional anatomic information in patients with DORV, which is helpful in presurgical planning as well as during follow-up. Spin echo MRI does not visualize aberrant chordae tendineae.

Adolescent↗
PubMed2000

Imaging of an aneurysm of the sinus of Valsalva with transesophageal echocardiography, contrast angiography and MRI.

A sinus of Valsalva aneurysm is an uncommon congenital defect, which requires appropriate diagnosis with either echocardiography, magnetic resonance imaging or contrast angiography. Treatment consists of aortic valve repair. We describe a young woman with an aneurysm of the non-coronary sinus of Valsalva, an atrial septal defect and pulmonary insufficiency. The different imaging techniques and possibilities of surgical correction are described.

Adult↗
PubMed2000

Patients with pulmonary fibrosis: cardiac function assessed with MR imaging.

PURPOSE: To detect abnormalities in cardiac function by using magnetic resonance (MR) imaging in patients with mild to moderate pulmonary fibrosis and to evaluate the relationship between pulmonary function and cardiac function. MATERIALS AND METHODS: Sixteen patients were compared with 16 sex- and age-matched healthy control subjects. Systolic function was assessed by using multisection multiphase cine MR imaging. Diastolic function was assessed with flow-sensitive MR imaging across the mitral and tricuspid valves. MR imaging results were compared with the severity of impairment in pulmonary function. RESULTS: Biventricular systolic function and left ventricular diastolic function were normal in patients, but right ventricular diastolic function was significantly impaired versus that of control subjects, with a ratio of peak flow during early diastolic (E) filling to peak flow during atrial contraction (A) of 0.85 +/- 0.40 versus 1.28 +/- 0.50 (P =.035). Biventricular E/A ratios were strongly correlated to age in patients and control subjects. The right ventricular E/A ratio in patients corresponded with values that are normally expected in people 20 years older. Diastolic left and right ventricular functions were significantly correlated with each other. There was no relationship between pulmonary function and cardiac function. CONCLUSION: Impairment of right ventricular diastolic function was found by using MR imaging in patients with mild to moderate pulmonary fibrosis, whereas left ventricular diastolic function and biventricular systolic function were preserved.

Adult↗
PubMed2000

Left ventricular function: correlation of quantitative gated SPECT and MR imaging over a wide range of values.

In 21 patients, the authors compared results with quantitative gated single photon emission computed tomography (SPECT) to results with magnetic resonance imaging in the assessment of left ventricular (LV) end-diastolic volume (LVEDV), end-systolic volume (LVESV), and ejection fraction (LVEF). Between the two methods, correlations were good for LVEF (r = 0.85), LVEDV (r = 0.94), and LVESV (r = 0.95). Quantitative gated SPECT can help determine LVEF, LVEDV, and LVESV.

Adult↗
PubMed1999

Diastolic dysfunction in hypertensive heart disease is associated with altered myocardial metabolism.

BACKGROUND: Hypertension is an important clinical problem and is often accompanied by left ventricular (LV) hypertrophy and dysfunction. Whether the myocardial high-energy phosphate (HEP) metabolism is altered in human hypertensive heart disease and whether this is associated with LV dysfunction is not known. METHODS AND RESULTS: Eleven patients with hypertension and 13 age-matched healthy subjects were studied with magnetic resonance imaging at rest and with phosphorus-31 magnetic resonance spectroscopy at rest and during high-dose atropine-dobutamine stress. Hypertensive patients showed higher LV mass (98+/-28 g/m2) than healthy control subjects (73+/-13 g/m2, P<0.01). LV filling was impaired in patients, reflected by a decreased peak rate of wall thinning (PRWThn), E/A ratio, early peak filling rate, and early deceleration peak (all P<0. 05), whereas systolic function was still normal. The myocardial phosphocreatine (PCr)/ATP ratio determined in patients at rest (1. 20+/-0.18) and during stress (0.95+/-0.25) was lower than corresponding values obtained from healthy control subjects at rest (1.39+/-0.17, P<0.05) and during stress (1.16+/-0.18, P<0.05). The PCr/ATP ratio correlated significantly with PRWThn (r=-0.55, P<0.01), early deceleration peak (r=-0.56, P<0.01), and with the rate-pressure product (r=-0.53, P<0.001). CONCLUSIONS: Myocardial HEP metabolism is altered in patients with hypertensive heart disease. In addition, there is an association between impaired LV diastolic function and altered myocardial HEP metabolism in humans. The level of myocardial PCr/ATP is most likely determined by the level of cardiac work load.

Adenosine Triphosphate↗