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Biomedical subjects

M Moonen

Publications and source records attributed to M Moonen.

At least 19 recordsLinked to original sources
PubMed2003

[Comparison of a nurse-directed weight-based heparin nomogram with standard empirical doctor-based heparin dosage].

OBJECTIVE: To assess efficiency of a nurse directed weight-based nomogram (NWN) for heparin dosage without training. STUDY DESIGN: Prospective, comparative, before/after intervention study. PATIENTS AND METHODS: In a university medical intensive care unit, 19 patients receiving unfractionned intravenous heparin, following standard medical prescriptions (SHT), were compared to 19 patients submitted to NWN (80 U kg(-1) bolus, starting infusion at 18 U kg(-1) h(-1) and secondary dosage adaptations following a specific nomogram). RESULTS: Dose of heparin bolus and starting dose infusion were significantly greater in NWN group than in the SHT group. The delay in achieving a predetermined therapeutic APTT level of at least 60 s was 6 (1-76) hours in the SHT group and 4 (3- 32) hours in the NWN group. The target APTT (60-85 s) was obtained after 13.5 (1-76) hours and 9.5 (3-32) hours in the two groups, respectively. Although reduction in delay seemed to favour anticoagulation dictated by the NWN protocol, the difference failed to reach statistical significance. Percentage of target APTT over total number of APTT values per patient was significantly higher in the NWN group (41 [0-87] vs. 31% [0-54]) in the SHT group. Strict observance of anticoagulation by using NWN tended to be better than that in SHT group. CONCLUSIONS: NWN protocol was easy to use without previous training. NWN was associated with the best anticoagulation state although its superiority was less evident than expected.

Aged↗
PubMed2003

Recessive POLG mutations presenting with sensory and ataxic neuropathy in compound heterozygote patients with progressive external ophthalmoplegia.

Autosomal recessive progressive external ophthalmoplegia is a mitochondrial disease characterized by accumulation of multiple large-scale deletions of mitochondrial DNA. We previously reported missense mutations in POLG, the gene encoding the mitochondrial DNA polymerase gamma in two nuclear families compatible with autosomal recessive progressive external ophthalmoplegia. Here, we report a novel POLG missense mutation (R627W) in a sporadic patient and we provide genetic support that all these POLG mutations are actually causal and recessive. The novel patient presented with sensory ataxic neuropathy and has the clinical triad of sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO). This is the first finding of a genetic cause of Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoparesis and it implies that this disorder may actually be a variant of autosomal recessive progressive external ophthalmoplegia. Sensory neuropathy is the initial feature in Belgian compound heterozygote autosomal recessive progressive external ophthalmoplegia patients, all carrying the POLG A467T mutation, which occurs at a frequency of 0.6% in the Belgian population.

Adolescent↗
PubMed2003

Evaluation of various attenuation corrections in lung SPECT in healthy subjects.

The effect of increasingly more sophisticated attenuation correction methods on image homogeneity has been studied in seven healthy subjects. The subjects underwent computed tomography (CT), single photon emission computed tomography (SPECT) and transmission computed tomography (TCT) of the thorax region in the supine position. Density maps were obtained from the CT and TCT studies. Attenuation corrections were performed using five different methods: (1) uniform correction using only the body contour; (2) TCT based corrections using the average lung density; (3) TCT based corrections using the pixel density; (4) CT based corrections using average lung density; and (5) CT based corrections using the pixel density. The isolated attenuation effects were assessed on quotient images generated by the division of images obtained using various attenuation correction methods divided by the non-uniform attenuation correction based on CT pixel density (reference method). The homogeneity was calculated as the coefficient of variation of the quotient images (CV(att)), showing the isolated attenuation effects. Values of CV(att) were on average 12.8% without attenuation correction, 10.7% with the uniform correction, 8.1% using TCT map using the average lung density value and 4.8% using CT and average lung density corrections. There are considerable inhomogeneities in lung SPECT slices due to the attenuation effect. After attenuation correction the remaining inhomogeneity is considerable and cannot be explained by statistical noise and camera non-uniformity alone.

Adult↗
PubMed2003

Effect of hemodiafiltration on pulmonary hemodynamics in endotoxic shock.

Hemofiltration can improve pulmonary hemodynamics during septic shock. The main objective of the study was to determine whether hemodiafiltration (HDF) would also have beneficial effects on pulmonary hemodynamics during septic shock. In the Endo group, six anesthetized pigs received a 0.5 mg/kg endotoxin infusion over 30 min. In the HDF group (n = 6), HDF was started 30 min after the end of the endotoxin infusion, while in the Control group (n = 4) they received HDF but no endotoxin infusion. Pulmonary hemodynamics were analyzed in detail with a four-element windkessel model. Although in the Control group, HDF did not alter pulmonary hemodynamic parameters, in the HDF group, it was responsible for an amplification of the deleterious pulmonary vascular response to endotoxin insult. Our results show that HDF must be used cautiously in septic shock since it can precipitate right heart failure by increasing pulmonary vascular resistance.

Animals↗
PubMed2002

On visual determination of full inspiration on CT images.

The aim of this study was to evaluate the ability of experienced thoracic radiologists to assess full inspiration based on two CT slices, one above and one below the carina, in normal subjects. Ten healthy volunteers were studied. Total lung capacity (TLC) was measured with a body plethysmograph. High-resolution computed tomography (HRCT) was performed in two slices at TLC and at various expired volumes. Mean Hounsfield values (HU) were calculated. Unidentifiable images, stored on a web server, were analysed visually by experienced thoracic radiologists. The results show that the mean lung density at TLC varied by approximately 40 HU between individuals. Within an individual this may correspond to a decrease in lung volume of approximately 25% of TLC. On visual determination of images taken at 65-74% of TLC, more than one-third of the images were assessed as taken at full inspiration; of the images taken at 75-84% of TLC, approximately 50% were assessed as taken at full inspiration. We conclude that visual determination of full inspiration on CT images in normal subjects is highly inaccurate. If quantitative density measurements are to be used in the diagnosis or follow-up of lung disease, thorough control of full inspiration is recommended.

Adult↗
PubMed2002

Digital hearing aids and future directions for hearing aids.

In recent years many technical evolutions have been applied in hearing aids. In this paper differences between analog, programmable and fully digital hearing aids, the basic and supplementary functions of a hearing aid, and some important issues and future directions for digital hearing aids will be mentioned.

Computers↗
PubMed2001

Quantitative analysis of inhomogeneity in ventilation SPET.

The aim of this study was to evaluate a method for quantification of inhomogeneity in ventilation single-photon emission tomography (SPET). Nine emphysematous patients, nine life-long non-smokers and nine smokers were included in the study. The SPET investigation was performed after 50 MBq (99m)Tc-Technegas had been inhaled by each subject in the supine position. A single-head gamma camera, equipped with a general-purpose parallel-hole collimator using 64 projections (20 s each) over 360 degrees, was used. Data were acquired in 128x128 matrices. Attenuation correction was applied based upon computed tomography (CT) density maps. Lung regions of interest were delineated manually on CT images and then positioned on SPET images. Several attenuation-corrected transaxial SPET slices (thickness 1 cm, spacing 3.5 cm) were reconstructed. Each SPET slice was divided into several 2x2x1 cm(3) elements. Inhomogeneity was assessed by the coefficient of variation (CV) of the pixel counts within these elements (micro-level) and the CV of the total counts of the elements (macro-level). Micro-level CVs in non-smokers varied between 1% and 41%, whereas they were dispersed over a wide range (1%-600%) in emphysematous patients. In seven smokers, the frequency distribution of micro-level CVs was within the normal range, whereas in the other two smokers the values were between the normal range and the range in emphysematous patients. The pooled mean values of micro-level CVs and macro-level CVs in each subject clearly separated the patients from the others. Parametric images of micro-level CV indicated the localisation and severity of ventilation inhomogeneity. We conclude that the present method enables quantification and localisation of regional inhomogeneity in ventilation SPET images.

Adult↗
PubMed2001

Prediction of post-operative glomerular filtration rate after nephrectomy for renal malignancy.

The importance of a correct estimation of contralateral renal function in cases of renal malignancy is obvious, necessitating a conservative approach to tumour resection when function of the contralateral kidney is markedly reduced. The aim of the present study was to determine the accuracy of preoperative gamma camera renography and (51)Cr-EDTA clearance to predict the glomerular filtration rate (GFR) early and up to 6 months after nephrectomy for renal malignancy. Patients (n=40) underwent both gamma camera renography ((99m)TC-DTPA) and (51)Cr-EDTA clearance preoperatively, whereas (51)Cr-EDTA clearance was measured within 1 week and up to 6 months after nephrectomy. The single kidney GFR values of the contralateral kidneys were estimated preoperatively and then compared with the post-operative (51)Cr-EDTA clearance values. The predicted GFR values were lower compared with the measured post-operative (51)Cr-EDTA clearance values (45 +/- 2 vs. 54 +/- 3 ml min(-1) 1 week after nephrectomy and 53 +/- 3 ml min(-1) 6 months later, P<0.01, respectively). The difference between the measured and predicted GFR was larger in patients below the median age of 60 years (P<0.05) and confined to patients with a relative uptake of >30% by the tumour affected kidney. Prediction of post-operative GFR by non-invasive renal function tests performed prior to surgery for renal malignancy underestimate post-operative GFR when the function of the tumour affected kidney is preserved, indicating an adaptive GFR increase in these cases.

Aged↗
PubMed2001

Dynamics of 'Technegas' deposited in the lung.

In tomographic Technegas ventilation studies, the deposited aerosol should be stable. The aim of this study was to investigate the stability of deposited Technegas in severely obstructed patients and in healthy volunteers. Six emphysematous patients and five healthy volunteers were studied. Anterioposterior (AP) and posterioanterior (PA) dynamic images of ventilation (120 frames, 1 frame.min-1) were acquired after inhalation of 99mTc-Technegas' in the supine position. The time-activity curve of the whole lung showed two phases in the emphysematous patients as well as in the healthy volunteers. The activity decreased rapidly in the first phase, then reached almost a constant level (the second phase) after approximately 50 min. The logarithms of both the first phase and the second phase were close to straight lines. The half-time of the first phase was approximately 9 min. No systematic differences in 'Technegas' clearance rate were found between central regions and peripheral regions and between high count rate regions and normal count rate regions. Pertechnegas contamination was subsequently detected, and we conclude that the rapid first phase is probably due to clearance of Pertechnegas. When stable Technegas is required, we suggest that data acquisition should start about 50 min after inhalation.

Adult↗
PubMed2001

[Ventricular septal defect and recent myocardial infarction].

Rupture of the interventricular septum is a classical complication of acute myocardial infarction. The diagnosis should be evoked when the patient's hemodynamic condition deteriorates in the presence of a new systolic murmur. A transthoracic or, preferably, transesophageal echocardiography confirms the diagnosis. Early surgical correction constitutes the best treatment. Despite recent progresses, mortality remains high but long term results are encouraging. The risk factors conditioning prognosis, the surgical options and the question of simultaneous coronary bypass will be discussed after a thorough review of the literature.

Coronary Artery Bypass↗
PubMed2000

Distribution of ventilation-to-perfusion ratios analysed in planar scintigrams of emphysematous patients.

The aim of the present study was to develop and evaluate a method for semi-quantification of ventilation-to-perfusion ratios in small regions in planar pulmonary scintigrams using 99mTc-Technegas (Tetley Manufacturing Ltd, Sydney, Australia) and 99mTc-macro-aggregated human albumin. Eight emphysematous patients and eight healthy volunteers were investigated in the supine position. Anterio-posterior and posterio-anterior images of ventilation and ventilation-and-perfusion were acquired consecutively. Perfusion images were obtained by subtracting the corrected ventilation images from ventilation-and-perfusion images. Lung regions of interest were divided into 2.03 x 2.03 cm regions. The ratio of normalized counts of ventilation-to-perfusion (V/Q) was calculated in each square region. The log (V/Q)s of healthy volunteers were distributed symmetrically and similarly around 0, whereas the corresponding ratios in patients distributed unevenly. The standard deviations of log (V/Q)s were significantly higher in patients than in healthy volunteers. Parametric images of V/Q distribution were constructed to visualize the magnitude and location of 'waste ventilation' and 'shunt' effects. In conclusion, the present semi-quantitative method is validated by confirming the expected dispersed V/Q distribution in emphysematous patients compared to healthy volunteers.

Adult↗
PubMed1999

Administered activity of 99Tcm-MAG3 for gamma camera renography in children.

A method of calculating the activity of 99Tcm-MAG3 to be administered to children of different ages has been developed and evaluated. The suggested administered activity schedule is only valid for estimation of split renal function. The activity required to obtain the same count rate over the kidneys for all ages was calculated as a fraction of the activity administered to an adult by using a biokinetic model and taking attenuation effects into account. The activity schedule is based on the age of the child and was tested using renograms from patients of different ages. Statistical noise was added to the smoothed renograms simulating an injected activity corresponding to 45 MBq for an adult. The precision in the determination of split renal function calculated with four different methods was determined for 500 simulated renograms. The precision was approximately the same for all ages, but varied with the method used. The activity to be administered to a very small child is 90% of the adult activity, decreases to less than 50% between 2 and 5 years of age, and then slowly increases to 100% as the child grows to adulthood.

Adolescent↗
PubMed1998

Inhomogeneity in planar ventilation scintigraphy of emphysematous patients.

The aim of this study was to develop and evaluate a method for the quantification of inhomogeneity in ventilation scintigraphy. Ten healthy volunteers and 10 emphysematous patients were investigated. Anteroposterior (AP) and Posteroanterior (PA) images of planar ventilation scintigraphy were acquired. Lung regions of interest (ROI) were obtained by manual delineation of the lung contours and then divided into several 10-pixel-high horizontal-stripe regions. By allowing for the statistical noise of the pixel count rate, the biological coefficient of variation (CVB) of the pixel counts in each stripe region was calculated. The apex-to-base distribution of the CVB in the emphysematous lungs dispersed largely and with higher values than the corresponding distribution in the healthy lungs. The mean values of the CVB (MCVB), the ranges of the CVB (RCVB) and the maximum values of the CVB (MAXCVB) in the stripe regions in emphysematous lungs were significantly higher than the corresponding ones in the healthy lungs (all P < 0.001). The intraobserver variations of the MCVB, RCVB and MAXCVB (calculated using the standard deviations of the differences) were less than 2.3% units, 5.2% units and 3.9% units respectively. The corresponding values for interobserver variation were 5.7% units, 6.1% units and 6.4% units. A systematic decrease in lung ROI size, i.e. inclusion of successively less of the lung edge, resulted in a linear decrease of 1.7% units in the MCVB and MAXCVB of both emphysematous and normal lungs. In conclusion, the stripe-region method is a reliable tool for the quantification of inhomogeneity in the planar ventilation scintigraphy.

Adult↗
PubMed1998

Evaluation of attenuation corrections using Monte Carlo simulated lung SPECT.

SPECT (single photon emission computed tomography) images are distorted by photon attenuation. The effect is complex in the thoracic region due to different tissue densities. This study compares the effect on the image homogeneity of two different methods of attenuation correction in lung SPECT; one pre-processing and one post-processing method. This study also investigates the impact of attenuation correction parameters such as lung contour, body contour, density of the lung tissue and effective attenuation coefficient. The Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing a homogeneous activity distribution in the lung. Homogeneity in reconstructed images was calculated as the coefficient of variation (CV). The isolated effect of the attenuation correction was assessed by normalizing pixel values from the attenuation corrected lung by pixel values from the lung with no attenuation effects. Results show that the CV decreased from 12.8% with no attenuation correction to 4.4% using the post-processing method and true densities in the thoracic region. The impact of variations in the definition of the body contour was found to be marginal while the corresponding effect of variations in the lung contour was substantial.

Algorithms↗
PubMed1997

Effect of administered activity on precision in the assessment of renal function using gamma camera renography.

Split and total renal function are commonly assessed from time-activity curves obtained from gamma camera renography with 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA) and 99Tcm-mercaptoacetyl-triglycine (99Tcm-MAG3). The impact of the statistical noise associated with these curves on the total precision in split and total renal function impairment was studied at different levels of administered activity by simulation. The simulation consisted of generated time-activity curves, with statistical noise corresponding to the administration of 10-400 MBq 99Tcm-DTPA or 7.5-150 MBq 99Tcm-MAG3. Our results indicate that the error induced by statistical noise in split renal function calculations is generally very low (< 3% at 100 MBq 99Tcm-DTPA or 75 MBq 99Tcm-MAG3) and only affects precision slightly in calculations at 45-50 MBq 99Tcm or more. Similar results were obtained for precision in GFR calculations, where the total error increased from 12.3% at 100 MBq 99Tcm-DTPA to 12.8% at 50 MBq, but decreased to 12.0% at 400 MBq. Consequently, statistical noise has a minor effect on the precision in split and total renal function calculations at commonly used activity levels when it is reduced to approximately 50 MBq.

Gamma Cameras↗