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PubMed1986

[Status and tasks of biometry in clinical and experimental research].

The paper starts with reflections on the rôle of biometry in clinical research. Factors which might influence the efficacy of biostatistical consulting of clinicians are dealt with. Primarily, advantages and disadvantages of various behavioral patterns between the medical investigator and the biometrician are discussed. The recruitment and training of new biometricians, organizational structures and material foundations of clinical biometry are regarded as further factors influencing a constructive working practice. The paper ends with considerations on the future of the discipline.

Austria↗
PubMed1993

[Equivalent ultrasonic velocity for intraocular lens implanted eyes in A-mode biometry].

With the standard ultrasonic velocity in commercially available instruments, there is a large difference of the ultrasonic velocity between the ocular medium and the implanted intraocular lens (IOL). If the PMMA or silicon IOL-implanted eye is assessed by using the ultrasonic velocity of the phakic or aphakic eye (1,550 m/s or 1,532 m/s), the error induced by the mismatch of the velocity is considerable. Therefore, we estimated the axial length error of pseudophakic eyes in ultrasonic biometry, and also derived theoretically the overall average sound speed (equivalent ultrasonic velocity, EUV) in IOL-implanted eyes. We found that the EUV (VE) can be estimated from the equation, VE = LV1V2/ T(V1-V2)+LV2], where L is the axial length of the eye, V1 the ultrasonic velocity of aqueous and vitreous body, V2 the ultrasonic velocity of the IOL, and T the central thickness of the IOL. The EUV for a PMMA IOL-implanted eye is approximately 1,560 m/s, and the EUV for a silicon IOL-implanted eye is approximately 1,500 m/s in an eye of standard length (24 mm) and an IOL of standard central thickness (1 mm). However, the EUV is a function of the axial length of the eye (L), the central thickness of the IOL (T), and the sound velocity in the implanted IOL (V2), and thus the EUV can not be applied for all cases. To perform more accurate ultrasonic biometry in pseudophakic eyes, we should rectify the apparent axial length assessed by the aphakic sound speed (1,532 m/s) with the central thickness of the implanted IOL.

Biometry↗
PubMedDate not supplied

Ultrasound fetal biometry charts for a North American Caucasian population.

PURPOSE: This study was done to produce enhanced fetal biometry charts and graphs presenting percentile values as a function of fetal age. METHODS: The relationships between the ultrasound measurements of 10 fetal parameters and menstrual age were determined by a cross-sectional study. Data were obtained from 508 to 790 fetuses. Anatomic structures were scanned and measured 3 times during 1 routine sonographic examination. The study group consisted of 1,396 Caucasian women who had normal singleton fetuses with confirmation of menstrual dates by sonography before 14 weeks and for whom complete pregnancy outcome information was available. For each of the 10 parameters, percentile curves were derived for the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles. RESULTS: Ready-to-use fetal measurement charts and graphs are presented in a format giving the percentile values as a function of fetal age. There were no significant differences between male and female fetuses. CONCLUSIONS: These fetal biometry charts and graphs, obtained from a North American Caucasian population, enhance previously published data.

Abdomen↗
PubMed1991

The relationship between umbilical artery Doppler velocimetry and fetal biometry.

The relationship between peak-systolic/end-diastolic ratio of the umbilical artery waveform and fetal biometry was studied in 127 uncomplicated pregnancies with established dates between 20 and 40 weeks' gestation. At each ultrasonographic examination fetal biometry included measurement of the biparietal diameter, head circumference, abdominal circumference, and femur length. The peak-systolic/end-diastolic ratio was measured by either a continuous or a pulsed-wave method. There were significant linear negative correlations between all the biometric parameters, as well as between the ultrasonographically estimated fetal weight and peak-systolic/end-diastolic ratio. Of the individual ultrasonographic parameters the femur length (for gestations less than 30 weeks) and the abdominal circumference (for gestations greater than or equal to 30 weeks) were found to be best correlated with the peak-systolic/end-diastolic ratio. Regression curves, including the 10th and the 90th percentile, were developed between each biometric parameter (biparietal diameter, head circumference, abdominal circumference, and femur length), as well as between estimated fetal weight and peak-systolic/end-diastolic ratio. The estimated fetal weight nomogram had the best sensitivity (48%) in predicting intrauterine growth retardation. These nomograms should prove most useful in assessing downstream placental vascular resistance in high-risk patients with unknown dates.

Adolescent↗
PubMed1997

Predictive value of Doppler umbilical artery velocimetry in a low risk population with normal fetal biometry. A prospective study of 2016 women.

OBJECTIVE: To assess the predictive value of Doppler umbilical artery velocimetry in a low-risk population with normal fetal biometry. STUDY DESIGN: Multicenter prospective study in 17 hospitals with prenatal clinics in France. Two thousand sixteen women who, before 28 weeks gestation were defined as at low risk after routine consultation and after ultrasound. Doppler umbilical artery velocimetry was performed between 28 and 34 weeks gestation. Confounding factors were used to perform multivariate regression. RESULTS: 1903 cases were analysed and 192 (10.1%) had an abnormal Doppler Resistance Index (RI). The abnormal Doppler group contained a significantly higher frequency of severe and moderate small for gestational age infants (SGA), both severe and moderate with a sensitivity of 25.5 and 18.8% respectively. There was no difference in hypertensive disorders or criteria of fetal distress. Mean birth weight was very significantly lower in the abnormal group (162 g). Birth weight was very significantly linked to RI after taking into account confounding variables in the multiple linear regression model (continuous relationship). After multiple logistic regression, the odds ratio associated with an abnormal Doppler result, adjusted for all the confounding factors, was 2.3 (95% CI 1.5-3.7) for moderate SGA and 3.5 (95% CI of 1.8-7.1) for severe SGA. CONCLUSION: Low umbilical Doppler RI is predictive with moderate or severe SGA in a low-risk population with normal fetal biometry, even when the information generally available in clinical practice and ultrasound parameters are taken into account. There is a continuous relationship between RI and birthweight. This predictive value cannot, however, lead to an improvement in neonatal health unless effective measures to prevent SGA exist and umbilical Doppler should not be used in low-risk population on a routine basis.

Birth Weight↗
PubMed1993

First-trimester fetal biometry using transvaginal sonography.

First-trimester fetal biometry using transvaginal sonography is now feasible and desirable due to improved imaging and probe maneuverability. A study of 144 early normal pregnancies with precise dates is presented. Regression models were constructed for the crown-rump length, biparietal diameter, head circumference and abdominal circumference. Error analysis of the technique and calculations was performed. First-trimester fetal biometry may be used for obtaining precise estimates of gestational age and may help to detect early fetal maldevelopment resulting in abnormal growth.

Journal Article↗
PubMed2004

The relation between birth size and the results of refractive error and biometry measurements in children.

AIM: To examine the association of birth parameters with biometry and refraction in Singapore Chinese schoolchildren. METHODS: Chinese children aged 7-9 years (n = 1413) from three schools in Singapore were recruited. Birth parameter information on birth weight, head circumference, length at birth, and gestational age were obtained from standard hospital records. Cycloplegic autorefraction, keratometry and biometry measures (axial length, vitreous chamber depth, lens thickness, and anterior chamber depth) were obtained. RESULTS: Across the normal birthweight range (2.0-4.9 kg), children with birth weights > or =4.0 kg had longer axial lengths (adjusted mean 23.65 mm versus 23.16 mm), compared with children with birth weights <2.5 kg, after controlling for age, sex, school, height, parental myopia, and gestational age. For every 1 cm increment in head circumference at birth, the axial length was longer by 0.05 mm. For every 1 cm increment in birth length, the axial length was longer by 0.02 mm in multivariate analysis. Additional week increases in gestational age till 46 weeks resulted in axial lengths that were longer by 0.04 mm, controlling for age, sex, school, parental myopia, and height. Children with larger birth weights, head circumferences, birth lengths, or gestational ages had deeper vitreous chambers and larger corneal curvature radii; however, there were no significant associations with refraction. CONCLUSIONS: Children who were born heavier, had larger head sizes or lengths at birth, or who were born more mature had longer axial lengths, and deeper vitreous chambers; but there were no differences in refraction at ages 7-9 years, possibly because of the observed compensatory flattening of the cornea.

Anterior Chamber↗
PubMed2006

Fetal head biometry assessed by fetal magnetic resonance imaging following in utero myelomeningocele repair.

OBJECTIVE: To examine the impact of fetal myelomeningocele (MMC) repair on fetal head biometry and cerebrospinal fluid (CSF) spaces assessed by magnetic resonance imaging (MR) studies. STUDY DESIGN: Axial measurements of intracranial structures were taken at defined anatomical landmarks. Pre- and postnatal head biometry data and CSF spaces obtained from in utero repaired MMC fetuses (n = 22) were compared to the pre- and postnatal measurements of MMC patients that underwent standard neurosurgical MMC repair after birth (n = 16) and a cohort of age-matched control patients (prenatal, n = 52; postnatal, n = 9). RESULTS: In fetuses with MMC, initial MR scans showed an almost complete absence of supratentorial and posterior fossa CSF spaces. No differences in postnatal CSF spaces were found between controls and prenatally repaired MMC newborns. In fetuses with postnatal MMC repair, CSF spaces remained significantly reduced (p < 0.0001). The mean ventricular diameter (VD) increase in the postnatal repaired MMC group was significantly higher compared to the mean percentage of VD increase in the fetal repaired MMC group (6.4 vs. 4.2 mm; p = 0.02). Pre- and postnatal brain thickness measurements were significantly reduced in both MMC populations compared to age-matched normal values (p < 0.0001). In contrast to postnatally repaired patients, in utero repair fetuses showed significant reversal of hindbrain herniation and normalization of the posterior fossa CSF spaces. CONCLUSION: Mid-gestational repair of MMC promotes normalization of extra-axial CSF spaces. Due to progressive ventriculomegaly, brain thickness remains decreased in both prenatal repaired and age-matched non-repaired MMC patients when compared to age-matched normal values. Restoration of CSF volume in the posterior fossa after in utero repair is indicative of reversal of hindbrain herniation.

Brain↗
PubMed2003

Fetal central nervous system biometry on MR imaging.

OBJECTIVE: We sought to compare the biometry of the fetal head on MR imaging with sonographic measurements in fetuses with and without suspected central nervous system abnormalities. MATERIALS AND METHODS: Blinded retrospective measurements of biparietal diameter, head circumference, and cerebellar width obtained on MR imaging were assigned a gestational age on the basis of median sonographic measurements and compared with sonographic and clinical assignment of gestational age in fetuses with no central nervous system abnormalities. In fetuses with central nervous system abnormalities, the same MR measurements were compared with sonographic measurements obtained within 1 week. Single-shot fast spin-echo sequences were obtained. Pearson's product moment correlation coefficients and paired sample t tests were performed. RESULTS: In 22 fetuses with no suspected central nervous system abnormalities, significant correlation was seen in the assignment of gestational age by MR measurements and sonographic gestational age. In 25 fetuses with central nervous system abnormalities, significant correlation was also seen between biparietal diameter and head circumference measurements. The mean biparietal diameter on MR imaging was greater than on sonography in those fetuses with central nervous system abnormalities (p = 0.038). CONCLUSION: MR imaging measurements of biparietal diameter, head circumference, and cerebellar width are strongly correlated to gestational age in fetuses without central nervous system abnormalities. Significant correlation is found between MR imaging and sonographic measurements of biparietal diameter and head circumference in fetuses with central nervous system abnormalities. Larger biparietal diameter measurements were seen with MR imaging than with sonography in the abnormal group. Fetal central nervous system biometry can be performed as part of the MR imaging evaluation of the fetal central nervous system.

Brain↗
PubMed1986

The effect of ventricular dilatation upon biometry of the fetal head.

The ultrasonograms of 15 patients with moderate to marked fetal hydrocephalus were evaluated retrospectively in an attempt to determine the effect of ventricular dilatation upon biometry of the fetal head in the latter half of pregnancy. In 13 of the 15 cases the age based upon biometry of the fetal head was within one week of the clinical estimate of gestational age based upon the last menstrual period. As accurate head measurements may be useful even in cases of hydrocephalus, these measurements should not be dismissed as being invalid particularly when commensurate with a clinical estimate of gestational age.

Cephalometry↗
PubMed2000

Charts of Thai fetal biometries: 3. Femur length.

A cross-sectional study was conducted in order to construct a new reference chart for Thai fetal femur length (FL). A total of 621 normal pregnant women between 12-41 weeks of gestation and their fetuses were enrolled. Measurements were made once at a randomly assigned gestational age specifically for the purpose of this study only. Femur length data were available in 608 measurements due to unfavorable fetal position in some cases. Linear regression technique was used to model separately the mean and standard deviation as functions of gestational age. Reference centiles were constructed from a combination of both models, assuming the data were normally distributed. A new reference centiles chart for FL is presented and compared with previously published data. While our derived centiles were clearly lower than those from Western studies, they were found comparable with those from a Thai study. This demonstrated the important effect of racial differences between populations on fetal biometries and elucidates the need to develop fetal biometries charts specifically for each region.

Anthropometry↗
PubMed1983

[Biometry--an exact method for the measurement of the axial length of the eye].

High-frequency ultrasound, using a 10 MHz sound probe and an immersion technique, enables the measurement of the axial length of the eye to within an accuracy of 0.1 mm. The total axial length of the anterior surface of the cornea to the vitreoretinal interface is measured by ultrasound. Many authors add a retinal thickness factor to the echographic data. Addition of this retinal factor lowers the accuracy of axial length measurements. Biometry of both eyes can detect unilateral high-grade myopia as the only reason for unilateral exophthalmos. Accurate measurements of anterior chamber depth, lens thickness and axial length are of great diagnostic importance in glaucoma and are useful in the therapeutic management of this condition. Accurate biometry and preoperative calculation of intraocular lens power are indispensable procedures in obtaining optimal post-operative results in patients subjected to intraocular lens implantation.

Anterior Chamber↗
PubMed1998

Biometry of the muscular branches of the median nerve to the forearm.

The aim of this study was to determine the biometry of the muscular branches of the median nerve to the forearm in ten embalmed upper limbs. We measured the length of the forearm and the level of origin of each muscular branch of the median nerve to the forearm from the middle of a line between the medial and lateral epicondyles. The level of origin of each branch was then calculated as a percentage of the length of the forearm. Mean length of the forearm was 25 +/- 2.36 cm (range: 22-29 cm). Although the levels of origin of the proximal and distal nerves to pronator teres, and of the nerves to palmaris longus, flexor carpi radialis and flexor digitorum superficialis, were quite variable (coefficient of variation: CV > 48.61%), the level of origin of the anterior interosseous nerve (CV = 31.24%) and its branches (nerves to flexor pollicis longus and flexor digitorum profundus, CV = 20.06%) was less variable. These results suggest that the anterior interosseous nerve of the forearm is probably the nerve to connect in muscular free transfers in order to restore flexion of the fingers after damage to the flexor tendons to the forearm. We observed Martin-Gruber communications in six out of ten dissections.

Aged↗
PubMed2004

Fetal head biometry following in-utero repair of myelomeningocele.

OBJECTIVE: To evaluate the impact of prenatal myelomeningocele repair on fetal head biometry. METHODS: Fifty fetuses underwent open fetal myelomeningocele repair at our institution between January 1998 and July 2002. All had serial head circumference (HC) and lateral ventricular diameter (VD) measurements taken preoperatively and weekly for 8 weeks after repair. Cortical index (CI) was defined as HC/VD. Measurements were compared with gestational age-matched values from nomograms. One-sample t-test, ANOVA and repeated measures analysis were used to assess HC, VD and CI after fetal repair. RESULTS: Preoperatively, the HC in fetuses with myelomeningocele was smaller than control values (186.4 vs. 198.8 mm, P = 0.0004). Eight weeks' postoperatively this difference had resolved (293 vs. 301.6 mm, P = 0.76). The mean increase in CI after repair was 20% (P = 0.02) compared with the predicted 51% in normal cases. The average increase in VD was 3.9 mm (38.8%, P < 0.001). CONCLUSIONS: Mid-gestational repair of myelomeningocele alters fetal head growth. Increased CI suggests HC changes are not due to ventriculomegaly alone.

Adult↗
PubMed2006

Cumulative sum (CUSUM) analysis in the assessment of trainee competence in fetal biometry measurement.

OBJECTIVE: To determine the value of cumulative sum (CUSUM) analysis in assessing trainee proficiency in fetal biometry measurement. METHODS: Three primary healthcare doctors with no prior ultrasound training were recruited. Each trainee measured the fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) on 100 consecutive pregnant women. The supervisor repeated the measurements. The CUSUM for each set of trainee measurements was calculated at a set failure rate of 10%. The point at which the graph fell below two consecutive boundary lines indicated the number of examinations required to achieve competence. RESULTS: The CUSUM graphs showed that the rate of learning measurement skills varied among the three trainees. The graph for the CUSUM series for BPD and HC measurement for all trainees fell below two consecutive boundary lines and remained there, indicating competence. The CUSUM series for AC measurement for two of the trainees indicated that competence was achieved; however, for the third trainee, while the graph fell below two consecutive boundary lines, indicating competence, it rose again, crossing two consecutive boundary lines. This indicated a loss of competence and the need for further training. FL measurements for the same trainee never fell below two consecutive boundary lines, indicating failure to achieve competence; the other two achieved competence, but failed to maintain it. CONCLUSIONS: CUSUM is a useful tool for identifying points of competence and for quantifying the duration of ultrasound training required for each trainee. It provides an early indication of performance, and highlights difficulties in individual performance.

Abdomen↗
PubMed1989

The efficacy of fetal sonographic biometry in Down syndrome screening.

Sonographic biometry has been proposed as a second-trimester Down syndrome screening modality. Approaches have relied on the apparent "shortened" femur length of fetuses with Down syndrome. Unfortunately, significant intercenter variation has been reported in the magnitude of this femur length reduction. In an effort to overcome many of these potential biases and better estimate the magnitude of femur length shortening in fetuses with Down syndrome, a retrospective review of femur length differences between 16 Down syndrome and 194 control fetuses was carried out. All scans were performed by one examiner who used the same equipment and measurement technique. A significant reduction in the observed to expected femur length ratio for a given biparietal diameter was identified in the Down versus control fetuses (0.9574 95% confidence interval 0.9197, 0.9952 versus 0.9999 95% confidence interval 0.9913, 1.0086) (p less than 0.008). However, the magnitude of this reduction was not sufficient to permit the use of this sonographic approach as an isolated marker for fetal Down syndrome.

Biometry↗
PubMed1994

The utility of fetal biometry as an adjunct to the multiple-marker screening test for Down syndrome.

OBJECTIVE: Our purpose was to investigate fetal biometry as an adjunct to the multiple-marker screen (maternal age, serum alpha-fetoprotein, estriol, and human chorionic gonadotropin) for Down syndrome. STUDY DESIGN: Fifty-two cases of Down syndrome were compared with 7514 normal fetuses. The measured/predicted femur length ratio had the best discriminant value (1.0 +/- 0.11 vs 0.93 +/- 0.13, p < 0.0001). Multivariate gaussian algorithms were developed and each computed a likelihood ratio for Down syndrome. The trivariate algorithm incorporated the three maternal analytes, whereas the quadrivariate version also included the femur length ratio. The study population included 38 cases of Down syndrome and 1098 euploid controls. The midtrimester risk was the product of the age-related risk and the likelihood ratio. RESULTS: The relative difference in the femur length ratio between normal and affected fetuses was small in comparison to that of the maternal serum analytes. At a risk cutoff of > or = 1:190 the detection rates were similar and actually favored the trivariate algorithm but differed only by one case of Down syndrome. CONCLUSION: The addition of the measured/predicted femur length ratio had a negligible effect on the performance of the multiple-marker screening test.

Adult↗