Struijk, P.C.

Re: Three-dimensional power Doppler: Validity and reliability (Article)

2011-05-01T00:00:00Z

Estimating the effect of gestational age on test performance of combined first-trimester screening for down syndrome: A preliminary study (Article)

2010-05-01T00:00:00Z

Objective: To establish how different methods of estimating gestational age (GA) affect reliability of first-trimester screening for Down syndrome. Methods: Retrospective single-center study of 100 women with a viable singleton pregnancy, who had first-trimester screening. We calculated multiples of the median (MoM) for maternal-serum free beta human chorionic gonadotropin (free b-hCG) and pregnancy associated plasma protein-A (PAPP-A), derived from either last menstrual period (LMP) or ultrasound-dating scans. Results: In women with a regular cycle, LMP-derived estimates of GA were two days longer (range -11 to 18), than crown-rump length (CRL)-derived estimates of GA whereas this discrepancy was more pronounced in women who reported to have an irregular cycle, i.e., six days (range -7 to 32). Except for PAPP-A in the regular-cycle group, all differences were significant. Consequently, risk estimates are affected by the mode of estimating GA. In fact, LMP-based estimates revealed ten "screen-positive" cases compared to five "screen-positive" cases where GA was derived from dating-scans. Conclusion: Provided fixed values for nuchal translucency are applied, dating-scans reduce the number of screen-positive findings on the basis of biochemical screening. We recommend implementation of guidelines for Down syndrome creening based on CRL-dependent rather than LMPdependent parameters of GA.

Jugular lymphatic sacs in the first trimester of pregnancy: The prevalence and the potential value in screening for chromosomal abnormalities (Article)

2008-11-01T00:00:00Z

Objective: To investigate the prevalence of detectable jugular lymphatic sacs in a setting for first trimester screening for Down syndrome, and to evaluate the influence of jugular lymphatic sacs on the screening performance for chromosomal abnormalities. Methods: A prospective single center study (Erasmus University Medical Center, Rotterdam, The Netherlands) over a period of one year (January 2003-February 2004). First trimester nuchal translucency measurement was performed in a study population of 415 fetuses. Additionally, the transversal plane with the spine and mandible was visualized to verify the presence of jugular lymphatic sacs. The jugular lymphatic sacs were measured anterior-posterior. The association between nuchal translucency and jugular lymphatic sacs was tested. Results: Follow-up was complete in 406 cases (97.8%). Jugular lymphatic sacs could be visualized in 98 out of 415 (23.5%). The nuchal translucency thickness and the mean of the left and right jugular lymphatic sac were significantly correlated. Conclusion: The sonographic visualization of jugular lymphatic sacs significantly predicts chromosomal abnormalities, although nuchal translucency is a better predictor. Nuchal translucency and jugular lymphatic sacs are strongly correlated and therefore not applicable in a combination test.

Blood pressure estimation in the human fetal descending aorta (Article)

2008-10-01T00:00:00Z

Objectives: The objectives of this study were to estimate fetal blood pressure non-invasively from two-dimensional color Doppler-derived aortic blood flow and diameter waveforms, and to compare the results with invasively derived human fetal blood pressures available from the literature. Methods: Aortic pressures were calculated from digitally recorded color Doppler cineloops of the fetal descending aorta by applying the Womersley model in combination with the two-element Windkessel model, assuming constant pulse wave velocity during the second half of pregnancy. The results were compared with invasively derived human fetal blood pressures obtained from the literature. Results: In 21 normal pregnancies the estimated mean aortic pressure regression line increased linearly from 28 mmHg at 20 weeks of gestation to 45 mmHg at 40 weeks of gestation. The pulse pressure based on the regression line increased linearly from 21 mmHg at 20 weeks of gestation to 29 mmHg at 40 weeks of gestation. The aortic compliance exhibited a log linear relationship with the gestational age and a statistically significant eightfold increase was observed between 20 and 40 weeks. The aortic downstream peripheral resistance exhibited an exponentially decaying relationship across the same gestational age range. Non-invasively derived aortic systolic and diastolic aortic pressures were comparable with previously reported invasively derived systolic and diastolic umbilical arterial pressures; however, the mean pressures differed significantly from those reported in the umbilical artery in a separate study. The aortic systolic pressures calculated in this study were significantly higher than invasively derived left ventricular systolic pressures that have been previously reported in the literature. Conclusions: This study demonstrates the feasibility of estimating arterial blood pressure in the human fetus. The method described is of potential use in assessing fetal blood pressure non-invasively, particularly for studying relative changes with time. Copyright

Evaluation of volume vascularization index and flow index: A phantom study (Article)

2008-09-01T00:00:00Z

Objectives Three-dimensional (3D) power Doppler ultrasonography provides indices to quantify moving blood within a volume of interest (e.g. ovary, endometrium, tumor or placenta). The purpose of this study was to determine the influence of ultrasound instrument settings on vascularization index (VI) and flow index (FI) at different flow velocities, using a specially built flow phantom with a small tube diameter. Methods Blood-mimicking fluid was pumped at 10-100 mL/h through a plastic tube with a diameter of 0.65 mm within a virtual spherical volume (content 137.12 cm3) of a Voluson 730 Expert 3D power Doppler ultrasound instrument. VI and FI were determined at different pulse repetition frequency (PRF) settings, with minimal and maximal wall motion filter (WMF) settings. The measured VI was compared with the actual VI. Results The ability to measure VI and FI at different flow velocities was highly dependent on the PRF and WMF settings. In our experimental set-up, using a PRF of 0.3 kHz, flow velocities of about 2 cm/s and higher could be registered. Measured VI was overestimated up to 44 times relative to actual VI. Conclusions Our main finding in a laboratory set-up was a considerable overestimation of moving blood volume using 3D power Doppler ultrasound in a single small tube. The degree of overestimation depends on the spatial resolution and on the settings of the ultrasound instrument. When small vessels are involved in a clinical setting, interpretation of VI should take this overestimation of moving blood volume into account. Copyright

Application of the Magnitude-Squared Coherence Function Between Uterine and Umbilical Flow Velocity Waveforms for Predicting Placental Dysfunction: A Preliminary Study (Article)

2007-07-01T00:00:00Z

To examine whether the magnitude-squared coherence between uterine and umbilical blood flow velocity waveforms can, in conjunction with estimated fetal weight, uterine and umbilical pulsatility indices, fetal and maternal heart rates, diastolic notching and the amniotic fluid index, create a sensitive and specific model for the prediction of placental dysfunction. Binary logistic prediction models are created for preeclampsia, pregnancy induced hypertension and intrauterine growth restriction in a study group of 284 unselected midtrimester pregnancies. In each study group, the median value of derived parameters were compared with the uncomplicated pregnancy control group. The magnitude-squared coherence function between the uterine and umbilical flow velocity waveforms was found to be a statistically significant predictor of preeclampsia during the midtrimester of pregnancy. The magnitude-squared coherence did not improve the prediction of intrauterine growth restriction or pregnancy induced hypertension. The inclusion of magnitude-squared coherence as one of the prediction parameters may improve the early identification of pregnancies subsequently complicated by preeclampsia. (E-mail: p.struijk@erasmusmc.nl).

Assessment of Hemodynamic Parameters in the Fetal and Utero-placental Circulation using Doppler Ultrasound (Doctoral Thesis)

2006-12-13T00:00:00Z

A short history of ultrasound in obstetrics and gynecology is given. So far there is no evidence that diagnostic ultrasound is harmful to the human fetus. However, it is known that ultrasound energy is partly absorbed by tissue and bony structures. As a result, temperature warming can be expected if during a considerable time the ultrasound beam is aimed at one particular spot. Modern ultrasound scanners are equipped with temperature index monitoring upon which the user may decide to use lower machine output settings or limit examination time to minimize any possible risk. The combination of the Doppler principle and two-dimensional ultrasound imaging enables blood flow velocity measurement in fetal blood vessels. This modality of ultrasound contributed to a better understanding of the physiology and pathophysiology of the fetal cardiovascular system. The aim of this Ph.D. study was to further improve our knowledge of the fetal and utero-placental circulation. To this purpose, fetal hemodynamic parameters were assessed and tested on spectral- and color Doppler derived data.

Three-dimensional US assessment of hepatic volume, head circumference, and abdominal circumference in healthy and growth-restricted fetuses (Article)

2002-01-01T00:00:00Z

PURPOSE: To establish reproducibility and normal values for fetal hepatic volume and its significance in identification of fetal growth restriction relative to head and upper abdominal circumferences according to a cross-sectional study design. MATERIALS AND METHODS: Pregnant women (n = 135) underwent ultrasonography. The coefficient of variation (CV) for hepatic volume scans obtained at 0 and 20 minutes and hepatic area tracings, performed twice for each scan, was determined (n = 20; range, 23-36 weeks). Normal data for hepatic volume and head and upper abdominal circumferences were obtained (n = 85; range, 20-36 weeks) and related to data from growth-restricted fetuses (birth weight < P5 centile; n = 24; range, 22-36 weeks). RESULTS: CV was 2.9% for volume scans and 1.6% for area tracings. In 85 uncomplicated cases, mean fetal hepatic volume (P50 centile) was 9.7 mL +/- 4.4 (SD) at 20 weeks and 96.4 mL +/- 8.2 at 36 weeks of gestation. In 24 growth-restricted fetuses, hepatic volume, head circumference, and upper abdominal circumference expressed as percentages of the normal P50 centile were 45%, 90%, and 82%, respectively. Mean difference in hepatic volume between fetal growth restriction and normal fetal development, as expressed with the z score, -4.32 +/- 1.4, was significantly different (P <.05) from that for head circumference, -3.04 +/- 1.3, but not from that for upper abdominal circumference, -4.7 +/- 1.2. Fetal hepatic measurement was obtained in 109 pregnancies. CONCLUSION: Acceptable reproducibility exists for hepatic volume determinations. In fetal growth restriction, reduction is more pronounced for hepatic volume than for head or upper abdominal circumference; hepatic volume is a better discriminator than head circumference but not upper abdominal circumference.