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Matthijs Oudkerk

Publications and source records attributed to Matthijs Oudkerk.

At least 19 recordsLinked to original sources
PubMed2006

Nodule management protocol of the NELSON randomised lung cancer screening trial.

In December 2003, the Dutch-Belgian NELSON trial, a Dutch acronym for "Nederlands-Leuvens Longkanker Screenings ONderzoek", has been launched. Primary objective of the NELSON trial is to investigate whether screening for lung cancer by 16-detector multi-slice CT with 16 mm x 0.75 mm collimation and 15 mm table feed per rotation (pitch=1.5) in year 1, 2 and 4 will lead to a decrease in lung cancer mortality in high risk subjects of at least 25% compared to a control group which receives no screening. In this paper, the screening regimen and the classification and management of the screen-detected nodules at baseline and incidence screening is presented. This is the first large lung cancer screening trial in which the nodule management protocol is based on volumetric nodule assessment and the presence or absence of growth. Furthermore, the quality assurance measures and the NELSON management system (NMS) are presented.

Clinical Protocols↗
PubMed2006

Multiple voxel 1H MR spectroscopy of phosphorylase-b kinase deficient patients (GSD IXa) showing an accumulation of fat in the liver that resolves with aging.

BACKGROUND/AIMS: Phosphorylase-b deficient patients suffer from glycogen storage disease (GSD IXa) leading to liver enlargement which usually resolves during puberty and adolescence. This pathology has not yet been documented by (1)H MR spectroscopy (MRS) investigation. METHODS: MRS of eight GSD IXa patients was performed in this study to assess whether or not liver fat content is elevated in GSD IXa and decreases with aging. An improvement in our MRS method compared with previous liver fat MRS studies is that we measured a plane of liver voxels at once rather than a single MRS voxel, yielding a reliable determination of liver fat content. RESULTS: Fat contents of 3.4-10% were observed in young GSD IXa patients, as compared with 0.5-0.9% in controls, these dropped to control levels in patients past age 40 (r = -0.82; P < 0.01). CONCLUSIONS: Liver fat content is increased in glycogen storage disease (GSD IXa) and normalizes with ageing. Assessing liver fat levels in this population is a novel and interesting concept. This could potentially enhance the understanding of liver function in that 20% of the population who has increased liver fat.

Adipose Tissue↗
PubMed2006

Pulmonary nodules detected at lung cancer screening: interobserver variability of semiautomated volume measurements.

PURPOSE: To retrospectively determine interobserver variability of semiautomated volume measurements of pulmonary nodules and the potential reasons for variability. MATERIALS AND METHODS: The Dutch-Belgian lung cancer screening trial (NELSON) is a lung cancer screening study that includes men between the ages of 50 and 75 years who are current or former heavy smokers. The NELSON project was approved by the Dutch Ministry of Health and the ethics committee of each participating hospital. Informed consent was obtained from all participants. For this study, the authors evaluated 1200 consecutive low-dose computed tomographic (CT) scans of the chest obtained during the NELSON project and identified subjects who had at least one 50-500-mm(3) nodule. One local and one central observer independently evaluated the scans and measured the volume of any detected nodule by using semiautomated software. Noncalcified solid nodules with volumes of 15-500 mm(3) were included in this study if they were fully surrounded by air (intraparenchymal) and were detected by both observers. The mean volume and the difference between both measurements were calculated for all nodules. Intermeasurement agreement was assessed with the Spearman correlation coefficient. Potential reasons for discrepancies were assessed. RESULTS: There were 232 men (mean age, 60 years; age range, 52-73 years) with 430 eligible nodules (mean volume, 77.8 mm(3); range, 15.3-499.5 mm(3)). Interobserver correlation was high (r = 0.99). No difference in volume was seen for 383 nodules (89.1%). Discrepant results were obtained for 47 nodules (10.9%); in 16 cases (3.7%), the discrepancy was larger than 10%. The most frequent cause of variability was incomplete segmentation due to an irregular shape or irregular margins. CONCLUSION: In a minority (approximately 11%) of small solid intraparenchymal nodules, semiautomated measurements are not completely reproducible and, thus, may cause errors in the assessment of nodule growth. For small or irregularly shaped nodules, an observer should check the segmentation shown by the program.

Aged↗
PubMed2006

Commonly used imaging techniques for diagnosis and staging.

Imaging plays a vital role in the management of patients with cancer. Not only is it important for diagnosis, indicating sites of abnormality, and guiding biopsies, but it is also crucial in assessing disease extent and thereby determining treatment. In this review, conventional imaging techniques such as ultrasound, computed tomography, magnetic resonance imaging, and [18F]fluorodeoxyglucose-positron emission tomography are described, with attention to their mechanisms of action, and their strengths and weaknesses in diagnosis and staging of tumors. New developments are addressed and radiation safety issues are highlighted. In addition, we describe current and expected future uses of imaging techniques in oncology. Given that each technique has its inherent strengths and weaknesses, the combination of the methods will result in improved diagnosis, staging, and treatment prediction and monitoring.

Contrast Media↗
PubMed2006

Lipoprotein-associated phospholipase A2 and coronary calcification. The Rotterdam Coronary Calcification Study.

OBJECTIVES: Although several studies have recently suggested that lipoprotein-associated phospholipase A2 (Lp-PLA2) is an independent predictor of coronary events, only one study has examined the association between Lp-PLA2 and coronary calcification, using young adults. We investigated the association between Lp-PLA2 activity and coronary calcification assessed by electron-beam computed tomography (EBT) in a population of older participants. METHODS AND RESULTS: The Rotterdam Coronary Calcification Study is a population-based study in men and women aged >/=55 years. Coronary calcification assessed by EBT was quantified in a calcium score according to Agatston's method. Lp-PLA2 activity measured in samples collected 7 years before scanning (n=520) was associated with coronary calcification in men after adjustment for age. The odds ratio per standard deviation of Lp-PLA2 activity of having a total calcium score >1000 was 1.6 (95% confidence interval: 1.1-2.4), as compared to a total calcium score </=100. After adjustment for non-HDL and HDL-cholesterol, this association disappeared. In women, the association was less consistent. For Lp-PLA2 measured concurrently to scanning (n=703), no association was found with coronary calcification. CONCLUSIONS: Lp-PLA2 activity is moderately associated with coronary calcification after adjustment for age. The effect of Lp-PLA2 on coronary calcification may be exerted through its effect on LDL-cholesterol.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2006

Fluoxetine increases cerebral white matter NAA/Cr ratio in patients with multiple sclerosis.

Axonal degeneration in multiple sclerosis (MS) may be caused by mitochondrial dysfunction and is associated with decreased levels of N-acetylaspartate (NAA) as measured with 1H-magnetic resonance spectroscopy (MRS). Fluoxetine stimulates astrocytic glycogenolysis, which serves as an energy source for axons. Eleven patients with MS received fluoxetine orally 20 mg a day during the first week, and 40 mg a day during the second week. The mean NAA/Creatine ratio in cerebral white matter of the MS patients increased from 1.77 at baseline to 1.84 at the end of the second week (p=0.007). These findings show evidence for a reversible axonal dysfunction in patients with MS and provide a rationale for investigating whether fluoxetine has neuroprotective effects in MS.

Administration, Oral↗
PubMed2006

Assessment of metastatic liver disease in patients with primary extrahepatic tumors by contrast-enhanced sonography versus CT and MRI.

AIM: To evaluate contrast-enhanced ultrasonography (CEUS) using SonoVue in the detection of liver metastases in patients with known extrahepatic primary tumors versus the combined gold standard comprising CT, MRI and clinical/histological data. METHODS: It is an international multicenter study, and there were 12 centres and 125 patients (64 males, 61 females, aged 59+/-11 years) involved, with 102 patients per protocol. Primary tumors were colorectal in 35%, breast in 27%, pancreatic in 17% and others in 21%. CEUS using SonoVue was employed with a low-mechanical-index technique and contrast-specific software using Siemens Elegra, Philips HDI 5000 and Acuson Sequoia; continuous scanning for at least five minutes. RESULTS: CEUS with SonoVue increased significantly the number of focal liver lesions detected versus unenhanced sonography. In 31.4% of the patients, more lesions were found after contrast enhancement. The total numbers of lesions detected were comparable with CEUS (55), triple-phase spiral CT (61) and MRI with a liver-specific contrast agent (53). Accuracy of detection of metastatic disease (i.e. at least one metastatic lesion) was significantly higher for CEUS (91.2%) than for unenhanced sonography (81.4%) and was similar to that of triple-phase spiral CT (89.2%). In 53 patients whose CEUS examination was negative, a follow-up examination 3-6 mo later confirmed the absence of metastatic lesions in 50 patients (94.4%). CONCLUSION: CEUS is proved to be reliable in the detection of liver metastases in patients with known extrahepatic primary tumors and suspected liver lesions.

Adult↗
PubMed2006

User questionnaire to evaluate the radiological workspace.

Over the past few years, an increase in digitalization of radiology departments can be seen, which has a large impact on the work of the radiologists. This impact is not only demonstrated by the increased use of digital images but also by changing demands on the whole reading environment. In this study, we evaluated the satisfaction of our radiologists with our digital Picture Archival and Communication System environment and their workspace. This evaluation was performed by distribution of a questionnaire consisting of a score sheet and some open questions to all radiologists and residents. Out of 25 questionnaires, 12 were adequately answered and returned. Results clearly showed that most problems were present in the area of reading room design and layout and comfort and ergonomics. Based on the results from this study, adaptations were made and the results were also used in the planning of the redesign of the entire department of radiology.

Analog-Digital Conversion↗
PubMed2006

Aortic stiffness is associated with atherosclerosis of the coronary arteries in older adults: the Rotterdam Study.

OBJECTIVE: Aortic stiffness can lead to low diastolic blood pressure, thereby possibly limiting coronary perfusion. Therefore, the simultaneous occurrence of both aortic stiffness and coronary atherosclerosis can lead to an increased risk of subendocardial ischaemia. The aim of the present study was to investigate the association between aortic stiffness and coronary atherosclerosis. METHODS: The study was performed in 1757 subjects of the Rotterdam Study, a population-based study of elderly individuals. Aortic stiffness was assessed by measuring carotid-femoral pulse wave velocity (PWV). Coronary atherosclerosis was assessed by measuring coronary calcification using electron beam tomography and expressed as a total calcium score. The total calcium score was log-transformed because of its skewed distribution. The association between PWV and coronary calcification was first evaluated after adjustment for age, sex, mean arterial blood pressure and heart rate. RESULTS: Linear regression analyses showed that increased PWV was associated with a higher log total coronary calcium score [beta-regression coefficient 0.11, 95% confidence interval (CI) 0.07-0.15]. Compared with the lowest quartile of PWV, multivariate odds ratios and corresponding 95% CI for advanced coronary calcification in the second, third and fourth highest quartiles were 1.17 (0.79-1.74), 1.58 (1.07-2.34) and 2.12 (1.40-3.20), respectively. CONCLUSIONS: In this large population-based study performed in elderly subjects aortic stiffness was strongly and independently associated with coronary atherosclerosis.

Aged↗
PubMed2005

Relationships between brain water content and diffusion tensor imaging parameters (apparent diffusion coefficient and fractional anisotropy) in multiple sclerosis.

Fifteen multiple sclerosis patients were examined by diffusion tensor imaging (DTI) to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in a superventricular volume of interest of 8 x 8 x 2 cm(3) containing gray matter (GM) and white matter (WM) tissue. Point resolved spectroscopy 2D-chemical shift imaging of the same volume was performed without water suppression. The water contents and DTI parameters in 64 voxels of 2 cm(3) were compared. The water content was increased in patients compared with controls (GM: 244+/-21 vs. 194+/-10 a.u.; WM: 245+/-32 vs. 190+/-11 a.u.), FA decreased (GM: 0.226+/-0.038 vs. 0.270+/-0.020; WM: 0.337+/-0.044 vs. 0.402+/-0.011) and ADC increased [GM: 1134+/-203 vs. 899+/-28 (x10(-6) mm(2)/s); WM: 901+/-138 vs. 751+/-17 (x10(-6) mm(2)/s)]. Correlations of water content with FA and ADC in WM were strong (r=-0.68, P<0.02; r=0.75; P<0.01, respectively); those in GM were weaker (r=-0.50, P<0.05; r=0.45, P<0.1, respectively). Likewise, FA and ADC were more strongly correlated in WM (r=-0.88; P<0.00001) than in GM (r=-0.69, P<0.01). The demonstrated relationship between DTI parameters and water content in multiple sclerosis patients suggests a potential for therapy monitoring in normal-appearing brain tissue.

Anisotropy↗
PubMed2005

Correlation of proton MR spectroscopy and diffusion tensor imaging.

Proton magnetic resonance spectroscopy ((1)H-MRS) provides indices of neuronal damage. Diffusion tensor imaging (DTI) relates to water diffusivity and fiber tract orientation. A method to compare (1)H-MRS and DTI findings was developed, tested on phantom and applied on normal brain. Point-resolved spectroscopy (T(R)/T(E)=1500/135) was used for chemical shift imaging of a supraventricular volume of interest of 8 x 8 x 2 cm(3) (64 voxels). In DTI, a segmental spin-echo sequence (T(R)/T(E)=5500/91) was used and slices were stacked to reproduce the slab used in MRS. The spatial distributions of choline and N-acetylaspartate (NAA) correlated to mean fractional anisotropy and apparent diffusion coefficient (ADC) for the inner 6 x 6=36 voxels defined in MRS, most notably NAA and ADC value (r=-.70, P<.00001; correlation across four subjects, 144 data pairs). This is the first association of neuron metabolite contents in volunteers with structure as indicated by DTI.

Adult↗
PubMed2005

(1)H MR spectroscopy of the brain in multiple sclerosis subtypes with analysis of the metabolite concentrations in gray and white matter: initial findings.

Many MR spectroscopy (MRS) studies of multiple sclerosis (MS) have focussed on metabolism in normal-appearing white matter (NAWM) and in white matter lesions (WML). In this study, eight patients suffering from primary or secondary progressive MS (PPMS/SPMS) and seven patients with relapsing/remitting MS (RRMS) were examined by (1)H-MRS to assess metabolite levels in gray matter (GM) as well. (1)H-MRS chemical-shift imaging of a cerebral volume of interest of 8x8x2 cm(3) above the lateral ventricles revealed differences between the metabolite concentrations in the three groups varying from almost significant [NAWM, choline (cho); P=0.0547] to highly significant [GM, N-acetylaspartate (NAA); P=0.0003]. In PPMS/SPMS patients, the decreases in choline, creatine (Cr) and N-acetylaspartate compared with six healthy controls were significant in GM and to a lesser extent, in NAWM. No significant differences in metabolite concentrations were found between RRMS and controls. In WML, all metabolites were reduced compared with white matter in controls (Cho: P=0.0020; Cr and NAA: P<0.0001, both). In conclusion, the concentrations of Cho, Cr and NAA are reduced in PPMS/SPMS patients, especially in GM and in WML. Despite contrary observations in previous studies, increases in the concentrations of Cr and/or Cho were not observed.

Adult↗
PubMed2005

Coronary calcification improves cardiovascular risk prediction in the elderly.

BACKGROUND: Coronary calcification detected by electron beam tomography may improve cardiovascular risk prediction. The technique is particularly promising in the elderly because the predictive power of cardiovascular risk factors weakens with age. We investigated the prognostic value of coronary calcification for cardiovascular events and mortality in a general, asymptomatic population of elderly subjects. METHODS AND RESULTS: From 1997 to 2000, electron beam tomography scanning to assess coronary calcification was performed in subjects of the population-based Rotterdam Study. Risk factors were measured by standardized procedures. Coronary calcium scores were available for 1795 asymptomatic participants (mean age, 71 years; range, 62 to 85 years). During a mean follow-up of 3.3 years, 88 cardiovascular events, including 50 coronary events, occurred. The risk of coronary heart disease increased with increasing calcium score. The multivariate-adjusted relative risk of coronary events was 3.1 (95% CI, 1.2 to 7.9) for calcium scores of 101 to 400, 4.6 (95% CI, 1.8 to 11.8) for calcium scores of 401 to 1000, and 8.3 (95% CI, 3.3 to 21.1) for calcium scores >1000 compared with calcium scores of 0 to 100. The predictive value in subjects >70 years of age was similar. Risk prediction based on the cardiovascular risk factors improved when coronary calcification was added. CONCLUSIONS: Coronary calcification is a strong and independent predictor of coronary heart disease, also in the elderly. Coronary calcification improves prediction of coronary events based on cardiovascular risk factors. Risk stratification by assessment of coronary calcification may have an important role in the primary prevention of coronary heart disease events in the elderly.

Aged↗
PubMed2005

Analysis of the human brain in primary progressive multiple sclerosis with mapping of the spatial distributions using 1H MR spectroscopy and diffusion tensor imaging.

Primary progressive multiple sclerosis (ppMS; n=4) patients and controls (n=4) were examined by 1H magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) in order to map choline (Cho), creatine and N-acetylaspartate (NAA), the fractional anisotropy (FA) and the apparent diffusion constant (ADC). After chemical shift imaging (point-resolved spectroscopy, repetition time/echo time 1,500 ms/135 ms) of a supraventricular volume of interest of 8x8x2 cm3 (64 voxels) MRS peak areas were matched to the results of DTI for the corresponding volume elements. Mean FA and NAA values were reduced in the ppMS patients (P<0.01, both) and the ADC increased (P<0.02). The spatial distribution of NAA showed strong correlation to ADC in both ppMS patients and controls (r =-0.74 and r= -0.70; P<0.00001, both), and weaker correlations to FA (r=0.49 and r=0.41; P<0.00001, all). FA and ADC also correlated significantly with Cho in patients and controls (P<0.00001, all). The relationship of Cho and NAA to the ADC and the FA and thus to the content of neuronal structures suggests that these metabolite signals essentially originate from axons (NAA) and the myelin sheath (Cho). This is of interest in view of previous reports in which Cho increases were associated with demyelination and the subsequent breakdown of neurons.

Adult↗
PubMed2005

Comparison of 99mTc-sestamibi/18FDG DISA SPECT with PET for the detection of viability in patients with coronary artery disease and left ventricular dysfunction.

PURPOSE: Dual-isotope simultaneous acquisition (DISA) single-photon emission computed tomography (SPECT) is an attractive technique as it permits assessment of both myocardial glucose metabolism and perfusion within a single session, but few data on its accuracy for the assessment of viability are available as yet. In the present study, DISA SPECT was compared with positron emission tomography (PET) for the detection of myocardial viability in normal and dysfunctional left ventricular (LV) myocardium. METHODS: Fifty-eight patients with chronic coronary artery disease and LV dysfunction (LV ejection fraction 33+/-12%) were studied. Patients underwent a 1-day dipyridamole stress 99mTc-sestamibi/18F-fluorodeoxyglucose (18FDG) DISA SPECT and 13N-ammonia/18FDG PET protocol. Within 1 week, resting MRI was performed to assess contractile function. Comparison of PET and SPECT data was performed using both visual and quantitative analysis. RESULTS: The correlation of normalised activities of the flow tracers 99mTc-sestamibi and 13N-ammonia was good (r = 0.82; p < 0.001). The correlation between the two 18FDG studies was also good (r = 0.83; p < 0.001). The agreement for the assessment of viability for all segments between DISA SPECT and PET was 82%, with a kappa-statistic of 0.59 (95% CI 0.53-0.64), without a significant difference; in dysfunctional segments only, the agreement was 82%, with a kappa-statistic of 0.63 (95% CI 0.56-0.70), without a significant difference. When the DISA SPECT data were analysed visually, the agreement between DISA SPECT and PET was 83%, with a kappa-statistic of 0.58 (95% CI 0.52-0.63), without a significant difference. Moreover, there was no significant difference between visual and quantitative DISA SPECT analysis for the detection of viability. CONCLUSION: This study shows an overall good agreement between 99mTc-sestamibi/18FDG DISA SPECT and PET for the assessment of myocardial viability in patients with severe LV dysfunction. Quantitative or visual analysis of the SPECT data did not influence the agreement with PET, suggesting that visual assessment may be sufficient for clinical purposes.

Adult↗
PubMed2005

Study on motion artifacts in coronary arteries with an anthropomorphic moving heart phantom on an ECG-gated multidetector computed tomography unit.

Acquisition time plays a key role in the quality of cardiac multidetector computed tomography (MDCT) and is directly related to the rotation time of the scanner. The purpose of this study is to examine the influence of heart rate and a multisector reconstruction algorithm on the image quality of coronary arteries of an anthropomorphic adjustable moving heart phantom on an ECG-gated MDCT unit. The heart phantom and a coronary artery phantom were used on a MDCT unit with a rotation time of 500 ms. The movement of the heart was determined by analysis of the images taken at different phases. The results indicate that the movement of the coronary arteries on the heart phantom is comparable to that in a clinical setting. The influence of the heart rate on image quality and artifacts was determined by analysis of several heart rates between 40 and 80 bpm where the movement of the heart was synchronized using a retrospective ECG-gated acquisition protocol. The resulting reformatted volume rendering images of the moving heart and the coronary arteries were qualitatively compared as a result of the heart rate. The evaluation was performed on three independent series by two independent radiologists for the image quality of the coronary arteries and the presence of artifacts. The evaluation shows that at heart rates above 50 bpm the influence of motion artifacts in the coronary arteries becomes apparent. In addition the influence of a dedicated multisector reconstruction technique on image quality was determined. The results show that the image quality of the coronary arteries is not only related to the heart rate and that the influence of the multisector reconstruction technique becomes significant above 70 bpm. Therefore, this study proves that from the actual acquisition time per heart cycle one cannot determine an actual acquisition time, but only a mathematical acquisition time.

Algorithms↗
PubMed2005

Coronary artery calcification score by multislice computed tomography predicts the outcome of dobutamine cardiovascular magnetic resonance imaging.

The aim of this study was to determine whether a coronary artery calcium (CAC) score of less than 11 can reliably rule out myocardial ischemia detected by dobutamine cardiovascular magnetic resonance imaging (CMR) in patients suspected of having myocardial ischemia. In 114 of 136 consecutive patients clinically suspected of myocardial ischemia with an inconclusive diagnosis of myocardial ischemia, dobutamine CMR was performed and the CAC score was determined. The CAC score was obtained by 16-row multidetector compued tomography (MDCT) and was calculated according to the method of Agatston. The CAC score and the results of the dobutamine CMR were correlated and the positive predictive value (PPV) and the negative predictive value (NPV) of the CAC score for dobutamine CMR were calculated. A total of 114 (87%) of the patients were eligible for this study. There was a significant correlation between the CAC score and dobutamine CMR (p<0.001). Patients with a CAC score of less than 11 showed no signs of inducible ischemia during dobutamine CMR. For a CAC score of less than 101, the NPV and the PPV of the CAC score for the outcome of dobutamine CMR were, respectively, 0.96 and 0.29. In patients with an inconclusive diagnosis of myocardial ischemia a MDCT CAC score of less than 11 reliably rules out myocardial ischemia detected by dobutamine CMR.

Aged↗