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At least 145 records · Page 8Linked to original sources
PubMed1976

Precision of ultrasonic fetal cephalometry.

Ultrasonic measurement of the biparietal diameter is a frequently used technique in the assessment of fetal maturity. The popularity of this technique is based partly upon the claim that it can be performed with considerable presicion, but recently published work has not supported this claim. This paper describes a blind clinical trial in which the precision of a single biparietal measurement was determined under normal clinical conditions. The results show that this measurement can be determined with a precision better than +/- 1.6 mm (+/- 2 standard deviations). The clinical significance of this result is discussed.

Cephalometry↗
PubMed1982

Effect of estimating gestational age by ultrasound cephalometry on the specificity of alpha-fetoprotein screening for open neural-tube defects.

A total of 1268 women had a maternal serum alpha-fetoprotein (AFP) screening test for open neural-tube defects between 15 and 22 weeks gestation and a routine ultrasound examination at their first antenatal visit. All had a singleton infant without a neural-tube defect. AFP values were expressed as multiples of the normal median at the relevant gestational age (MoM). The percentage of women with raised maternal serum AFP levels was less when gestation was estimated by the fetal biparietal diameter (BPD) than when the time since the first day of the last menstrual period (LMP) was used; 1.8% compared with 2.3% at a serum AFP cut-off level of 2.5 MoM. Different ultrasound policies were compared for their effect on AFP screening and the best was found to be routine BPD measurement used together with a higher cut-off level than usual. For example, using a cut-off level of 3.0 MoM the detection rate for open spina bifida at 16-18 weeks gestation would be about 88% and the proportion of unaffected singleton pregnancies with raised levels only 0.9%. These results are materially better than those achieved by a policy of scanning only those women with a raised AFP level (79% and 1.4% respectively with a more conventional cut-off level of 2.5 MoM) or, in addition, scanning those with doubtful gestational ages (82% and 1.7% respectively with a cut-off level of 2.5 MoM).

Cephalometry↗
PubMed1972

Ultrasonic fetal cephalometry: percentiles curve.

Measurements by ultrasound of the biparietal diameter of the fetal head during pregnancy are a reliable guide to fetal growth. As a ready means of comparison with the normal we constructed from 4,170 measurements in 1,394 cases a curve showing the percentiles distribution of biparietal diameters for each week of gestation.

Cephalometry↗
PubMed1988

Application of a video image subtraction system to measure and control head position in cephalometry.

Variation in head position in the cephalostat is a potential source of error in cephalometrics as it causes distortion of the radiographic projection of the head. Image subtraction is an electronic technique enabling images to be superimposed and which highlights any differences. Using this method, a study was carried out to assess the reproducibility of the position of the head in the cephalostat. It was also used to find out whether subjects could improve their own head relocation by looking at the monitor and trying to achieve the best possible fit on the original image.

Cephalometry↗
PubMed1991

The effect of beam collimation in lateral radiographic cephalometry.

A study was carried out to compare the image contrast of lateral cephalometric radiographs taken with and without the modified beam collimation and to evaluate the effect of this on the reliability of cephalometric measurements. The findings indicated that the cephalographs taken with modified beam collimation consistently showed a higher image contrast than the cephalographs taken with standard beam collimation. Despite this, however, there was no significant difference in the reliability of cephalometric measurements between the two groups of films.

Cephalometry↗
PubMed1993

A natural head position technique for radiographic cephalometry.

A three-part study was designed in order to test the applicability of the fluid-level method for registration of natural head position. In the first part the fluid-level method was utilized to make two repeated cephalometric radiographs of 33 young adults. The reproducibility of the craniovertical, craniocervical and cervicohorizontal relationships was comparable with previous results with the mirror method. In the second part, the fluid-level method was compared with the mirror method when used by two radiographers for repeated radiographs in 40 subjects. The reproducibility of the craniocervical and cervicohorizontal angles was less accurate with both methods and the only difference between them was a slightly better reproducibility of the craniovertical angle with the fluid-level method for one of the radiographers. In the third part, it was shown that using the fluid level, a patient can be transferred from a standing to a sitting position in the cephalostat without any systematic change in craniovertical, craniocervical or cervicohorizontal relationships.

Adult↗