Search PubMed⌕ Search

Biomedical subjects

N de Jong

Publications and source records attributed to N de Jong.

At least 19 recordsLinked to original sources
PubMed2006

[Folic acid fortification: prevention as well as promotion of cancer].

In many countries foods are fortified with folic acid to prevent neural-tube defects. Beneficial effects on cancer, cardiovascular diseases and dementia are also assumed. Fortification with folic acid is not allowed in The Netherlands, although exemption can be granted. As well as beneficial effects, harmful effects may also occur. In addition to masking vitamin-B12 deficiency, there is some evidence that folic acid may promote progression of established tumours in laboratory animals and humans. In addition, it has been hypothesized that fortification with folic acid may have further negative effects on cancer through genetic selection. Given the high prevalence of cancer, these potentially harmful effects should also be taken into account in the Dutch debate on the advantages and disadvantages of folic acid fortification.

Animals↗
PubMed2006

High frequency attenuation measurements of lipid encapsulated contrast agents.

A number of recent studies have indicated the potential of ultrasound contrast agent imaging at high ultrasound frequencies. However, the acoustic properties of microbubbles at frequencies above 10 MHz remain poorly understood at present. In this study we characterize the high frequency attenuation properties of (1) BR14, (2) BR14 that has been mechanically filtered (1 and 2 microm pore sizes) to exclude larger bubbles, and (3) the micron to submicron agent BG2423. A narrowband pulse-echo substitution method is employed with a series of four transducers covering the frequency range from 2 to 50 MHz. For BR14, attenuation decreases rapidly from 2 to 10 MHz and then more gradually from 10 to 50 MHz. For 2 microm filtration, the attenuation peaks between 10 and 15 MHz. For 1 microm filtration, attenuation continues to rise until 50 MHz. The agent BG2423 exhibits a diffuse attenuation peak in the range of 15-25 MHz and remains high until 50 MHz. These results demonstrate a strong influence of bubble size on high frequency attenuation curves, with bubble diameters of 1-2 microm and below having more pronounced acoustic activity at frequencies above 10 MHz.

Capsules↗
PubMed2006

A KLM-circuit model of a multi-layer transducer for acoustic bladder volume measurements.

In a preceding study a new technique to non-invasively measure the bladder volume on the basis of non-linear wave propagation was validated. It was shown that the harmonic level generated at the posterior bladder wall increases for larger bladder volumes. A dedicated transducer is needed to further verify and implement this approach. This transducer must be capable of both transmission of high-pressure waves at fundamental frequency and reception of up to the third harmonic. For this purpose, a multi-layer transducer was constructed using a single element PZT transducer for transmission and a PVDF top-layer for reception. To determine feasibility of the multi-layer concept for bladder volume measurements, and to ensure optimal performance, an equivalent mathematical model on the basis of KLM-circuit modeling was generated. This model was obtained in two subsequent steps. Firstly, the PZT transducer was modeled without PVDF-layer attached by means of matching the model with the measured electrical input impedance. It was validated using pulse-echo measurements. Secondly, the model was extended with the PVDF-layer. The total model was validated by considering the PVDF-layer as a hydrophone on the PZT transducer surface and comparing the measured and simulated PVDF responses on a wave transmitted by the PZT transducer. The obtained results indicated that a valid model for the multi-layer transducer was constructed. The model showed feasibility of the multi-layer concept for bladder volume measurements. It also allowed for further optimization with respect to electrical matching and transmit waveform. Additionally, the model demonstrated the effect of mechanical loading of the PVDF-layer on the PZT transducer.

Animals↗
PubMed2006

Detecting broken struts of a Björk-Shiley heart valve using ultrasound: a feasibility study.

The Björk-Shiley (BScc) mechanical heart valve has extensively been used in surgery from 1979 to 1986. There is, compared with equivalent valve types, increased occurrence of unexpected mechanical failure of the outlet strut of the valve, with a high incidence of mortality, when it occurs. Many approaches have been attempted to noninvasively determine BScc valve integrity. None of the approaches resulted in adequate assessment, mostly due to a lack of either sensitivity or specificity demonstrated in in vitro and/or in vivo studies. In our study we analyze leg movement of the BScc valves outlet strut during the cardiac cycle with ultrasound. For a broken strut, the movement of both legs will be significantly different, whereas the difference will be negligible for an intact strut. BScc valves were mounted in the mitral position in an in vitro pulse duplicator system. A focused single-element transducer was used to direct ultrasound on a leg of the outlet strut. Correlation-based time delay estimation was used to estimate differences in time of flight of the outlet strut echoes to determine outlet strut leg movement. The movement of an intact valve and a valve with a single-leg fracture with both ends grating against each other (SLF), the most difficult fracture to diagnose, has been studied. The results showed no significant difference in movement between both legs of the outlet strut of the intact BScc valve (amplitude of movement 9.2 microm +/- 0.1 microm). Whereas for the defective valve, the amplitude of movement of the broken leg of the SLF valve was 12 microm +/- 1.6 microm vs. 8.6 microm +/- 0.1 microm for the intact leg. In conclusion, the proposed method has shown to be feasible in vitro and has potentials for in vivo detection of BScc valve outlet strut fracture.

Echocardiography↗
PubMed2006

Does fluoride rinsing have an effect on teeth status? Evaluation of preventive dental health activities for the youth of Woudenberg, The Netherlands.

Surveys among primary school children of group 8 (mainly 12-year olds) in 1988/1989 and 1995/1996 revealed that the dental status in Woudenberg was worse than in other municipalities in the Eemland region. Therefore, several dental preventive activities were started in Woudenberg for children aged 0-12 years. This included fluoride rinsing and teeth brushing lessons at primary schools. So as to evaluate the effect of these school activities, a new survey was carried out in Woudenberg in 2004. The teeth status (DMF-S value, percentage sound teeth, percentage erosion) was investigated by examination. Information regarding dental hygiene behaviour and participation in teeth brushing lessons was obtained by questionnaire. Teeth status (measured by DMF-S value as well as percentage sound teeth) at rinsing schools in 2004 was significantly better than at the same schools in 1995/1996. Multivariate analyses revealed that fluoride rinsing for at least 3 years (besides educational level of parents) is the most determining factor for teeth status independent of other variables. Pupils who never rinsed with fluoride were almost four times more likely to have caries lesions than pupils who rinsed for at least 3 years. This study strongly indicates that long-term rinsing with fluoride has a positive effect on teeth status.

Adolescent↗
PubMed2005

Course of mental fatigue and motivation in breast cancer patients receiving adjuvant chemotherapy.

BACKGROUND: The purpose of this study is to determine the course of fatigue referring to cognitive symptoms (scale 'mental fatigue') as well as the motivation to start any activity (scale 'reduced motivation'), as a function of chemotherapy, in breast cancer patients undergoing adjuvant chemotherapy. PATIENTS AND METHODS: In a prospective cohort study a sample of 157 patients with breast cancer was interviewed at the first, third and fifth cycle of adjuvant chemotherapy as well as 4 and 12 weeks after completion of adjuvant chemotherapy. Patients were treated with standard adjuvant chemotherapy, either a doxorubicin containing schedule or CMF (cyclophosphamide, methotrexate and fluorouracil). The psychological dimensions of fatigue were measured by the Multidimensional Fatigue Inventory. A linear multilevel model was used for analysing the courses. RESULTS: The course of mental fatigue and motivation were not affected by the type of chemotherapy. The course of mental fatigue and motivation varied, but seemed to be stable during the treatment of chemotherapy. After the completion of chemotherapy, a weak improvement was seen. Relatively many patients experienced depressive symptoms during the study. These symptoms were correlated with both dimensions of fatigue. At all measurements mental fatigue was influenced by type of operation where women with a mastectomy were significantly more mentally fatigued than women that had undergone a lumpectomy, but nevertheless they were significantly more motivated to start any activity. Age, marital status, number of treatments and the interval between the operation and the first treatment of chemotherapy also seemed to be important determinants. CONCLUSIONS: An unequivocal pattern of mental fatigue and reduced motivation during as well as after adjuvant chemotherapy was not found. Depressive symptoms were definitely related to these variables. Type of operation had a significant impact on mental fatigue and motivation to start any activity. Health care providers should be aware of the high rate of patients who experience depressive symptoms during and after the treatment of chemotherapy. Further research should include the trajectory preceding adjuvant chemotherapy and a longer study period afterwards. Moreover, the exact influence of the variables 'age', 'marital status', 'number of treatments' and 'the interval between the operation and the first treatment of chemotherapy' on fatigue is unclear and needs further study.

Adult↗
PubMed2004

Microbubbles and ultrasound: from diagnosis to therapy.

The development of ultrasound contrast agents, containing encapsulated microbubbles, has increased the possibilities for diagnostic imaging. Ultrasound contrast agents are currently used to enhance left ventricular opacification, increase Doppler signal intensity, and in myocardial perfusion imaging. Diagnostic imaging with contrast agents is performed with low acoustic pressure using non-linear reflection of ultrasound waves by microbubbles. Ultrasound causes bubble destruction, which lowers the threshold for cavitation, resulting in microstreaming and increased permeability of cell membranes. Interestingly, this mechanism can be used for delivery of drugs or genes into tissue. Microbubbles have been shown to be capable of carrying drugs and genes, and destruction of the bubbles will result in local release of their contents. Recent studies demonstrated the potential of microbubbles and ultrasound in thrombolysis. In this article, we will review the recent advances of microbubbles as a vehicle for delivery of drugs and genes, and discuss possible therapeutic applications in thrombolysis.

Contrast Media↗
PubMed2004

Feasibility of 3D harmonic contrast imaging.

Improved endocardial border delineation with the application of contrast agents should allow for less complex and faster tracing algorithms for left ventricular volume analysis. We developed a fast rotating phased array transducer for 3D imaging of the heart with harmonic capabilities making it suitable for contrast imaging. In this study the feasibility of 3D harmonic contrast imaging is evaluated in vitro. A commercially available tissue mimicking flow phantom was used in combination with Sonovue. Backscatter power spectra from a tissue and contrast region of interest were calculated from recorded radio frequency data. The spectra and the extracted contrast to tissue ratio from these spectra were used to optimize the excitation frequency, the pulse length and the receive filter settings of the transducer. Frequencies ranging from 1.66 to 2.35 MHz and pulse lengths of 1.5, 2 and 2.5 cycles were explored. An increase of more than 15 dB in the contrast to tissue ratio was found around the second harmonic compared with the fundamental level at an optimal excitation frequency of 1.74 MHz and a pulse length of 2.5 cycles. Using the optimal settings for 3D harmonic contrast recordings volume measurements of a left ventricular shaped agar phantom were performed. Without contrast the extracted volume data resulted in a volume error of 1.5%, with contrast an accuracy of 3.8% was achieved. The results show the feasibility of accurate volume measurements from 3D harmonic contrast images. Further investigations will include the clinical evaluation of the presented technique for improved assessment of the heart.

Contrast Media↗
PubMed2004

Emboli detection using a new transducer design.

We have presented, in a previous study, a new approach to detect, characterize and estimate the size of gaseous emboli, based on the nonlinear behavior of gaseous bubbles. In this study, a specific transducer design has been developed to be used for such a purpose. It is composed of two separate transmitting and receiving capabilities. The transmit part, consisting of a lead zirconate-titanate (PZT) material, emits at a frequency of 500 kHz and could generate pressures up to 410 kPa. On the top of the transmit surface, a thin polyvinylidene difluoride (PVDF) layer is glued and used for receiving frequencies from 250 kHz (f0/2) up to 2.5 MHz (5 f0). To evaluate this new design, ultrasonic measurements were carried out with gas bubbles with diameters ranging from 10 microm up to 90 microm and solid particles between 350 microm and 550 microm. The experimental results confirmed our previous findings: gaseous emboli with a diameter close to the resonance size scatter significantly at higher harmonic components (from the second harmonic up to the fifth), and bubbles with a diameter around twice the resonance size produce a subharmonic and/or an ultraharmonic component. Meanwhile, solid particles and other bubble sizes behave only linearly and their scattered spectrum appeared without any harmonics. The study demonstrates the utility of this approach in using a single transducer to detect and characterize selective gaseous emboli from other particles using their nonlinear behavior.

Acoustics↗
PubMed2004

The opinion of Dutch dietitians about functional foods.

OBJECTIVE: To obtain information about Dutch dietitian's attitudes, perceived knowledge, training preferences, counselling procedures, opinions about post-launch monitoring, and personal consumption of functional foods. DESIGN: A self-administered, 62-item, postal survey in 2002. SUBJECTS: Five hundred randomly selected registered dietitians. The response rate was 49% (n = 238). RESULTS: The responders (mean age +/- SD: 40 +/- 9 years) had regular contact with clients (90%), and many (71% of 90%) advised about functional food use. Sixty-nine per cent hardly consumed any functional food themselves. Eighty-seven per cent of the responders would greatly appreciate courses given by scientists. Confusion existed about usage practices, target groups, safety, efficacy, and claims: between 42 and 89% agreed with the statements about uncertainties. Nonetheless, 69% felt that functional foods could theoretically contribute to good bodily functioning. Ninety per cent thought post-launch monitoring (PLM) important, but ideas about a common dietetic contribution to PLM did not emerge. CONCLUSIONS: Although functional foods potentially contribute to a healthful diet, there is still confusion among dietitians about claims, safety, efficacy and product-handling aspects. It is time to meet dietitians' repeated requests to provide education by noncommercial experts. In the meantime, dietitians themselves should have more say in the PLM debate because they should and could play an important role.

Adult↗
PubMed2004

Prevalence and course of fatigue in breast cancer patients receiving adjuvant chemotherapy.

BACKGROUND: The purpose of this study was to determine the prevalence of fatigue and the course of fatigue as a function of chemotherapy in breast cancer patients undergoing adjuvant chemotherapy. PATIENTS AND METHODS: In a prospective cohort study, a sample of 157 patients with breast cancer were interviewed, using the Rotterdam Symptom Checklist and the Multidimensional Fatigue Inventory, at the first, third and fifth cycle of adjuvant chemotherapy, as well as 4 and 12 weeks after the last cycle of adjuvant chemotherapy. Patients were treated with either a doxorubicin-containing schedule, or cyclophosphamide, methotrexate and 5-fluorouracil (CMF). RESULTS: The courses of general and physical fatigue are to a large extent similar. After the last cycle of chemotherapy, the CMF group reported a significant increase in fatigue, which was followed by a significant reduction. In the doxorubicin group a significant increase in fatigue was only seen during the first cycles of chemotherapy. The fatigue experienced at the first and the last measurements do not differ significantly. CONCLUSIONS: The prevalence of fatigue increased significantly after the start of chemotherapy. After chemotherapy treatment the prevalence rate seemed to decline. A different impact of chemotherapy on the course of fatigue was found. In the doxorubicin group a direct increase in fatigue was found. In the CMF group a moderate direct increase occurred, followed by a delayed strong increase. An increase in fatigue was associated with a decrease in daily functioning. At all measurement occasions fatigue was affected by type of operation, such that women with a mastectomy were more fatigued than women that underwent a lumpectomy. Receiving radiotherapy also led to an increase in fatigue. With this knowledge breast cancer patients can be better informed about what they can expect. Further research should include interventions addressing how to reduce or cope with fatigue during as well as after receiving adjuvant chemotherapy.

Adult↗
PubMed2002

Mechanical index.

Explore the source record for details and available documents.

Acoustics↗
PubMed2002

Physical exercise or micronutrient supplementation for the wellbeing of the frail elderly? A randomised controlled trial.

OBJECTIVE: To examine the effects of 17 weeks of physical exercise and micronutrient supplementation on the psychological wellbeing of 139 independently living, frail, elderly subjects (inactive, body mass index < or =25 or experiencing weight loss). METHODS: Participants (mean (SD) age 78.5 (5.7)) were randomly assigned to: (a) comprehensive, moderate intensity, group exercise; (b) daily micronutrient enriched foods (25-100% recommended daily amount); (c) both; (d) neither. A social programme and identical regular foods were offered as attention control and placebo. RESULTS: At baseline, moderate to low but significant correlations were found between general wellbeing scores and physical fitness (r = 0.28), functional performance (r = 0.37), and blood concentrations of pyridoxine (r = 0.20), folate (r = 0.25), and vitamin D (r = 0.23) (all p values < or =0.02), but not with physical activity levels and other blood vitamin concentrations. General wellbeing score and self rated health were not responsive to 17 weeks of exercise or nutritional intervention. CONCLUSION: Psychological wellbeing in frail elderly people was not responsive to 17 weeks of intervention with exercise and/or micronutrient enriched foods. The moderate but significant correlations between wellbeing and physical fitness and several blood vitamin concentrations at baseline suggest that changes in wellbeing may occur after long term interventions.

Activities of Daily Living↗
PubMed2001

Usefulness of power Doppler contrast echocardiography to identify reperfusion after acute myocardial infarction.

Microvascular integrity, as seen by myocardial contrast echocardiography (MCE), assesses whether myocardium has been successfully reperfused after an acute myocardial infarction. Until now this has been demonstrated only with intracoronary injection of an ultrasound contrast agent. Power Doppler imaging is a recently developed myocardial contrast echocardiographic method that counts the contrast microbubbles destroyed by ultrasounds and displays this number in color. This study sought to evaluate whether power Doppler MCE is able to visualize myocardial reperfusion during intravenous contrast injection. Thirty patients were evaluated 2 days after their first myocardial infarction during intravenous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA). Coronary artery angiography and single-photon emission computed tomography (SPECT) were used as reference techniques. A 16-segment left ventricular model was used to relate perfusion to coronary artery territories. Sensitivity and specificity of power Doppler MCE for segments supplied by infarct-related arteries were 82% and 95%, respectively. Accuracy of power Doppler MCE and SPECT were similar (90% vs 92% on segmental basis and 98% vs 98% on coronary artery territory basis). Two-dimensional echocardiography was repeated after 6 weeks. Segments recovering wall motion after 6 weeks were defined as stunning myocardium. Dysfunctional but perfused myocardium at day 2 after the infarction showed a better late recovery of wall motion compared with dysfunctional but nonperfused myocardium (p <0.001). In conclusion, harmonic power Doppler imaging is a sensitive and specific method for the identification of myocardial reperfusion early after myocardial infarction. It yields prognostic information for late recovery of ventricular function differentiating stunning (dysfunctional but perfused) from necrotic myocardium (dysfunctional and nonperfused).

Adult↗
PubMed2001

New technique for emboli detection and discrimination based on nonlinear characteristics of gas bubbles.

Detection and characterization of emboli in the blood stream is of high clinical importance for making decisions after surgery. In this study, a new technique based on the nonlinear oscillations of gas bubbles was applied to gaseous emboli detection, characterization and sizing. To simulate gaseous emboli, an experimental system was developed to produce air bubbles of uniform diameters ranging from 19 microm up to 200 microm. The ultrasonic setup consisted of low-frequency transducers operating at 130 kHz and 250 kHz and using low acoustic pressures (30 kPa and 55 kPa). The experimental and theoretical results show that, depending on the transmitted frequency and the bubble sizes, higher harmonic components were produced in the frequency spectrum of the backscattered echo. Nonresonating bubbles scatter either linearly when their sizes are far away from the resonance size or nonlinearly at the second or third harmonic frequency when their sizes are getting close to the resonance size. Only resonant bubbles or bubbles very close to the resonance size are able to scatter at higher harmonic frequencies (fourth and fifth). This property is used to discriminate resonating bubbles from other bubble sizes. The appearance of harmonic component in the frequency spectrum seems to be an unambiguous tool to differentiate gaseous emboli from solid emboli that scatter linearly.

Acoustics↗
PubMed2001

Physical exercise and/or enriched foods for functional improvement in frail, independently living elderly: a randomized controlled trial.

OBJECTIVE: To examine the effects of an exercise program and an enriched food regimen on physical functioning of frail elderly persons. DESIGN: A 17-week randomized, placebo-controlled trial. SETTING: Community. PARTICIPANTS: One hundred fifty-seven independently living frail elderly (mean age, 78.7 +/- 5.6yr). INTERVENTION: Thirty-nine subjects participated in a twice weekly group exercise designed to improve daily functioning; 39 subjects daily ate foods enriched with vitamins and minerals (at 25%-100% of the recommended daily allowances); 42 subjects exercised and ate enriched foods; and 37 subjects served as controls. Nonexercising groups followed a social program; nonsupplement groups received the same food products without the micronutrients. MAIN OUTCOME MEASURES: Functional performance based on 6 performance tests, physical fitness based on 7 fitness tests, and disabilities based on the self-reported ability to perform 16 daily activities. RESULTS: Performance sum scores were significantly enhanced in trained (+8%) compared with nontrained subjects (-8%) (difference in change: 1.9 points, p < .001, adjusted for baseline scores). Fitness sum scores were significantly enhanced as well (+3% in trained vs -2% in nontrained) (difference in change: 0.9 points, p = .05, adjusted for baseline scores). No exercise effects on the disability score were observed. Consumption of enriched products did not affect performance, fitness, or disability scores. CONCLUSION: Our comprehensive exercise program, designed for widespread applicability, enhanced physical performance and fitness in a population of frail elderly. Daily consumption of micronutrient enriched foods showed no functional benefits within 17 weeks.

Activities of Daily Living↗