Biomedical subjects

Joost Doornbos

Publications and source records attributed to Joost Doornbos.

11 recordsLinked to original sources

PubMed2006

Aortic root dysfunctioning and its effect on left ventricular function in Ross procedure patients assessed with magnetic resonance imaging.

BACKGROUND: This study evaluated the diameters and distensibility of the aortic root as well as the degree of aortic regurgitation (AR) and its effect on left ventricular (LV) function in patients 8.2 +/- 3.1 years after they underwent the Ross procedure, with a comparison of these parameters between patients and matched healthy subjects. METHODS: Eighteen Ross procedure patients (16 male patients, age [mean +/- SD] 19.2 +/- 3.8 years) and 18 matched healthy subjects (16 male patients, age [mean +/- SD] 19.7 +/- 4.2 years) underwent magnetic resonance imaging. Measurements for diameters (at 4 levels) and the distensibility of the aortic root were performed using a steady-state free precession sequence. Aortic flow was assessed with a velocity-encoded phase-contrast sequence. Left ventricular systolic function was assessed with a gradient-echo sequence in the short-axis plane. Comparison of parameters was performed using the Mann-Whitney U test. Correlations between diameters, distensibility, AR fraction, and LV systolic function were expressed with Spearman rank correlation coefficients. Linear regression analysis was used to identify predictors of LV systolic dysfunction. RESULTS: Aortic root diameters were increased in Ross procedure patients as compared with healthy subjects (mean difference 6.3-11.6 mm, P < or = .02 at all 4 levels). Distensibility of the aortic root was lower in patients (1.9 +/- 1.1 vs 7.8 +/- 3.3 mm Hg(-1), P < .01). An AR fraction > 5% was present in 14 of the 18 patients (mean AR fraction 8% +/- 5% vs 1% +/- 1%, P < .01). Left ventricular ejection fraction was lower in patients (50% +/- 6% vs 57% +/- 6%, P < .01). Dilatation, decreased distensibility, and AR fraction were correlated with impaired LV systolic function (P < .05 for all). The AR fraction predicted impaired LV systolic function (P < .01). CONCLUSIONS: Magnetic resonance imaging shows dilatation and decreased distensibility of the aortic root, AR, and consequent impaired LV systolic function in patients after the Ross procedure.

Adolescent↗

PubMed2006

MDCT assessment of right ventricular systolic function.

OBJECTIVE: The objective of our study was to validate using MDCT for the assessment of right ventricular (RV) function. MDCT with retrospective ECG gating was performed in 15 patients being evaluated for suspected cardiovascular disease. Echocardiography was performed for comparison. The MDCT images were reconstructed at 20 phase points over the cardiac cycle. The end-diastolic and end-systolic volumes of both ventricles were measured. Stroke volumes and ejection fractions were calculated from these data. CONCLUSION: RV volumes can be accurately assessed using MDCT.

Electrocardiography↗

PubMed2005

MRI to evaluate left atrial and ventricular reverse remodeling after restrictive mitral annuloplasty in dilated cardiomyopathy.

BACKGROUND: Data on reverse remodeling of the left atrium (LA) and left ventricle (LV) after restrictive annuloplasty in patients with dilated cardiomyopathy are scarce, and follow-up studies are performed with echocardiography. METHODS AND RESULTS: Twenty patients with dilated cardiomyopathy and severe mitral regurgitation selected for restrictive mitral annuloplasty underwent serial MRI studies (within 1 week before surgery, and 2 months [n =18] and 1 year [n =13] after surgery). Early mortality was 10%; all patients were free from endocarditis and thromboembolism. New York Heart Association class improved from 3.2+/-0.4 to 1.2+/-0.9. Only 1 patient developed recurrent severe mitral regurgitation during follow-up and it was re-repaired. LA end-systolic volumes decreased significantly over time (from 165+/-48 mL to 109+/-23 mL to 111+/-28 mL; P < 0.01), as did LA end-diastolic volumes (from 92+/-32 mL to 71+/-22 mL to 75+/-17 mL; P = 0.01). LV end-diastolic volumes decreased significantly (from 244+/-56 mL to 184+/-54 mL to 195+/-67 mL; P < 0.01), whereas end-systolic volumes did not change significantly. LV ejection fraction increased significantly (from 35+/-8% to 46+/-13% to 46+/-15%; P < 0.01) and LV mass decreased significantly (from 150+/-43 grams to 132+/-39 grams to 136+/-33 grams; P = 0.02). CONCLUSIONS: Restrictive annuloplasty in patients with dilated cardiomyopathy yielded excellent clinical results associated with significant LA and LV reverse remodeling over time as demonstrated by MRI.

Adult↗

PubMed2004

Accurate quantitation of regurgitant volume with MRI in patients selected for mitral valve repair.

OBJECTIVE: Echocardiography, the currently preferred diagnostic approach for mitral valve regurgitation, cannot accurately quantify the amount of regurgitation. Flow quantification with MRI is possible, but the conventional method (1-directional velocity-encoding) acquires the flow at a fixed location during the cardiac cycle, which is not necessarily the location of the mitral valve during the whole cycle. In this study, the exact flow through the mitral valve was quantified with a 3-directional velocity-encoded MRI approach. METHODS: Ten patients with severe mitral valve regurgitation (class 3-4+with echocardiography) resulting from systolic restrictive motion of both leaflets (Carpentier IIIb) which were selected for valve repair and 10 healthy volunteers without cardiac valvular disease confirmed with echocardiography were included in this study. The intra-ventricular flow was sampled with a radial stack of six acquisition planes parallel to the long-axis of the left ventricle. Three-directional velocity-encoded MRI was performed resulting in the intra-ventricular flow velocity vector field for 30 phases during the cardiac cycle. The position of the mitral valvular plane in this vector field was indicated manually for each phase. Velocity values perpendicular to this plane determined the flow through the mitral valve. Both the 3-directional encoded mitral valve flow and the 1-directional encoded mitral valve flow were compared with the flow determined with MRI at the ascending aorta. RESULTS: One-directional velocity-encoded MRI showed a mean overestimation (P<0.01) of 25 ml/cycle compared to the aortic flow. Correlation was very poor (r(P)=0.15, P=0.68). The 3-directional velocity-encoded MRI on the other hand, showed no over/underestimation and a good correlation (r(P)=0.91, P<0.01 for volunteers, r(P)=0.90, P<0.01 for patients). The regurgitant flow fractions were between 3 and 30%. CONCLUSION: With 3-directional velocity-encoded MRI, measurement of the flow through the mitral valve is accurate and reproducible. This is a valuable tool for diagnosing and absolute quantification of regurgitant volume.

Adult↗

PubMed2004

Magnetic resonance imaging of knee cartilage using a water selective balanced steady-state free precession sequence.

PURPOSE: To compare an optimized water selective balanced steady-state free precession sequence (WS-bSSFP) with conventional magnetic resonance (MR) sequences in imaging cartilage of osteoarthritic knees. MATERIALS AND METHODS: Flip angles of sagittal and axial WS-bSSFP sequences were optimized in three volunteers. Subsequently, the knees of 10 patients with generalized osteoarthritis were imaged using sagittal and axial WS-bSSFP and conventional MR imaging techniques. We calculated contrast-to-noise ratios (CNR) between cartilage and its surrounding tissues to quantitatively analyze the various sequences. Using dedicated software we compared, in two other patients, the accuracy of cartilage volume measurements with anatomic sections of the tibial plateau. RESULTS: CNRtotal eff (CNR efficiency between cartilage and its surrounding tissue) using WS-bSSFP was maximal with a 20-25 degrees flip angle. CNRtotal eff was higher in WS-bSSFP than in conventional images: 6.1 times higher compared to T1-weighted gradient echo (GE) images, 5.1 compared to proton-density (PD) fast spin echo (FSE) images, and 4.8 compared to T2-weighted FSE images. The mean difference of cartilage volume measurement on WS-bSSFP and anatomic sections was 0.06 mL compared to 0.24 mL for T1-GE and anatomic sections. CONCLUSION: A WS-bSSFP sequence is superior to conventional MR imaging sequences in imaging cartilage of the knee in patients with osteoarthritis.

Aged↗

PubMed2004

Accurate and reproducible mitral valvular blood flow measurement with three-directional velocity-encoded magnetic resonance imaging.

A new method for quantifying the transvalvular flow through the mitral valve (MV) based on three-directional velocity-encoded magnetic resonance imaging (MRI) is presented. For thirty time phases during one cardiac cycle, the three-dimensional (3D) velocity vector field of the blood flow is reconstructed from the MRI measurement. Retrospectively, for each time phase, the MV-plane is indicated manually in the velocity data and the flow through this plane is determined, representing the MV flow. Measurements are performed in 10 healthy volunteers. The new method is compared to the conventional, one-directional velocity-encoded MRI method for which an acquisition plane is positioned at the mitral valve at end-systole and remains fixed during the acquisition. The flow measurements with the new method correlate very well with the flow measured in the aorta (r(p)=0.92, p<0.01), whereas the conventional method shows no statistically significant correlation (r(p)=0.15, p=0.68). The low differences between the flow measured at the MV and the flow in the aorta proves high accuracy of the new method. Also, the new method shows very low intra- and interobserver variation, proving the high reproducibility. Three-directional velocity-encoded MRI is a patient-friendly and easy-to-use method suitable for quantifying accurately and reproducibly the transvalvular MV flow.

Adult↗

PubMed2004

Quantitative analysis of focal masses at MR imaging: a plea for standardization.

PURPOSE: To assess the effects of changing analytic method variables on the signal intensity (SI) difference-to-noise ratios (SDNRs) for the contrast between lesions and background organs depicted on magnetic resonance (MR) images and to propose a standardized analytic method for the quantitative analysis of focal masses seen at MR imaging. MATERIALS AND METHODS: The SIs of 48 liver metastases (originating from colorectal cancer) in 20 patients, the surrounding liver parenchyma, and the background noise were measured on T2-weighted MR images. All 2000 and 2001 issues of the American Journal of Roentgenology, the Journal of Magnetic Resonance Imaging, Magnetic Resonance Imaging, and Radiology were searched for articles describing quantitative analyses. SDNRs were calculated by using formulas from these articles and various region-of-interest (ROI) locations to measure metastasis and background noise SIs. The Wilcoxon signed rank test was used to compare the various SDNR calculations. RESULTS: In 34 articles in which quantitative analyses of focal masses are described, the reported SDNRs were calculated with four different formulas. The SDNRs for our study material calculated with the four formulas reported in the literature differed grossly in both number and unit. The SDNRs for ROIs encompassing the entire metastasis differed significantly (P =.034) from the SDNRs for ROIs in a homogeneous area of the metastasis margin. Differences in SDNRs between various noise ROI locations were significant (P <.022). CONCLUSION: Slight changes in the variables of quantitative analysis of focal masses had marked effects on reported SDNRs. To overcome these effects, the use of a standardized method involving one formula, a lesion ROI in a homogeneous area at the metastasis margin, and a background noise ROI along the phase-encoding axis in the air (including systematic noise) is proposed for the quantitative analysis of findings on magnitude MR images.

Adult↗

PubMed2003

Coronary magnetic resonance angiography: technical developments and clinical applications.

Magnetic resonance angiography (MRA) is a promising method for noninvasive coronary artery imaging. The interesting features of coronary MRA are its non-invasive nature, the absence of ionizing radiation, and the possibility of imaging the coronary arteries without exogenous contrast. Moreover, three-dimensional volume information and tomographic image planes in any direction can be obtained. The current review presents an overview of the recent technical developments of coronary MRA and the potential clinical applications. New MR techniques, such as parallel image acquisition, spiral imaging, steady-state free precession and the introduction of blood pool contrast agents may result in more efficient data acquisition. After implementation of these fast techniques, coronary MRA may be integrated in a comprehensive cardiac exam.

Coronary Artery Disease↗

PubMed2003

Tetralogy of Fallot: postoperative delayed recovery of left ventricular stroke volume after physical exercise assessment with fast MR imaging.

In six asymptomatic patients with corrected tetralogy of Fallot and nine healthy control subjects, the authors assessed left ventricular (LV) function during recovery from supine bicycle exercise by performing fast magnetic resonance (MR) flow mapping in the ascending aorta. Abnormal recovery of LV function after exercise was observed in the patients. MR flow mapping allows assessment of cardiac recovery after exercise.

Adolescent↗

PubMed2002

Diffusion-weighted MRI in the characterization of soft-tissue tumors.

PURPOSE: To explore the potential of perfusion-corrected diffusion-weighted magnetic resonance imaging (MRI) in characterizing soft-tissue tumors. METHODS AND MATERIALS: Diffusion-weighted MRI was performed in 23 histologically proven soft-tissue masses using a diffusion-weighted spin-echo sequence with diffusion gradient strengths yielding five b-values (0-701 seconds/mm(2)). True diffusion coefficients and perfusion fractions were estimated and compared with apparent diffusion coefficients (ADCs). RESULTS: ADC values of all tumors, subcutaneous fat, and muscle were significantly higher than true diffusion coefficients, indicating a contribution of perfusion to the ADC. True diffusion coefficients of malignant tumors (1.08 x 10(-3) mm(2)/second) were significantly lower than those of benign masses (1.71 x 10(-3) mm(2)/second), whereas ADC values between these groups were not significantly different. CONCLUSION: Perfusion-corrected diffusion-weighted MRI has potential in differentiating benign from malignant soft-tissue masses.

Adolescent↗

PubMedDate not supplied

The effect of corticosteroid medication on quantitative MR parameters of the brain.

BACKGROUND AND PURPOSE: Quantitative MR imaging techniques such as magnetization transfer imaging (MTI), diffusion-weighted imaging (DWI), and MR spectroscopy are promising diagnostic tools for use with patients with diffuse brain diseases such as neuropsychiatric systemic lupus erythematosus (NPSLE). Such patients are often on corticosteroid (CS) treatment. Presently, it is unknown whether CSs per se influence quantitative MR imaging measurements. The aim of this study was to evaluate the effect of low-dose oral CSs on MTI, DWI, and MR spectroscopy parameters of the brain. METHODS: Twenty-seven rheumatoid arthritis (RA) patients with and without CS medication and 15 healthy controls were subjected to conventional MR imaging, whole-brain MTI and DWI, and single-voxel MR spectroscopy. Oral CSs were used by 13 of the RA patients. Univariate analyses with age as a covariate were performed on MTI, DWI, and MR spectroscopy parameters between RA patients with and without CSs and healthy controls. Pearson correlations were calculated between all imaging parameters and duration of disease, duration of CS use, and CS dosage. RESULTS: No significant differences between the groups of subjects or significant correlations with clinical parameters were found for MTI, DWI and MR spectroscopy parameters. CONCLUSION: In this study, we found no evidence for an effect of low-dose oral CSs on whole-brain MTI and DWI histogram parameters and single-voxel MR spectroscopy measurements of the brain. The results of this study demonstrate that it is unlikely that MTI, DWI, and MR spectroscopy parameters reported in NPSLE studies are confounded by low-dose oral CS.

Administration, Oral↗