The Abdominal and Thoracic circumference -- some historical notes



Most would attribute the use of the Abdominal circumference to Campbell and Wilkin at Kings College Hospital, London, where the techniique of measurement and application in the assessment of fetal growth was discribed in 1975.

The abstract of the article is listed below:

Ultrasonic measurement of fetal abdomen circumference in the estimation of fetal weight. Campbell S, Wilkin D. Br J Obstet Gynaecol 1975 Sep 82:689-97.

Abstract:

A method of estimating fetal weight by ultrasonic measurement of the fetal abdominal circumference is descirbed. Assessment of birth weight predictions on 140 fetuses who were delivered within 48 hours of this measurement showed that the accuracy of predictions varied with the size of the fetus; at a predicted weight of 1 kg, 95 per cent of birth weights fell within 160 g, while at 2 kg, 3 kg and 4 kg the corresponding values were 290 g, 450 g and 590 g respectively. Expressed as a percentage of the predicted weight, confidence limits remained constant throughout the birth weight range. Extrapolation of these data to routine screening of the obstetric population showed that with a single measurement at 32 weeks menstrual age, 87 per cent of babies below the 5th centile would be detected by this method but that the diagnosis rate would fall to 63 per cent at 38 weeks. The false positive diagnosis rate would remain constant between 32 and 38 weeks at just over 1 per cent.


Campbell and Wilkin described their technique as follows " ..... Ultrasound compound B-scans are frst made at different angles to the midline of the maternal abdomen to identify the position of the long axis of the fetal body; where there is marked flexion of the fetal body, it ls helpful to identify a significant length offetal abdominal aorta, or fetal dorsal spine. Scans are then made orthogonal to the long axis of the fetal body and a section across the upper abdomen selected, this is recognised by the typical appearance oft/ic umbilical vein as it passes under the fetal liver.

Usually the umbilical vein can be quickly and easilv recognized from 24 weeks onwards except in about 5% of cases when the fetal spine is directly anterior, which means that the walls of the umbilical vein are not orthogonal to the ultrasonic beam. Under these circumstances we have found the fetal stomach to be the most suitable reference point, it is not so precise a location for when distended it extends over a greater length of the fetal abdomen but it does lie in the upper abdomen to the left of the fetal liver and both umbilical vein and stomach can usually be visualized on the same section. Circumference measurements were made to the nearest millimeter on a Polaroid photograph by means of a map measurer with appropriate correction for picture size In all cases an ultrasonic frequency of 2.5 MHz was used and the velocity calibration set to 1540 metres per second".


Horace Thompson in Denver has described in 1965 measurement of the thoracic circumference as a method for studying fetal growth. The measurement had an accuracy of within 3cm in 90% of the patients. Thompson also introduced the idea of fetal weight estimation basing on the TC and estimates were found to be accurate to within 300 grams in 52% of patients. The resolution of images at that time did not in general allow for very accurate measurement of the fetal trunk.
In:  Thompson HE. Studies of fetal growth by ulttrasound. In: Grossman GC, Holmes JH, Joyner C, Purnell EW, eds. Diagnostic Ultrasound: Proceedings of the First International Conference, University of Pittsburgh, 1965. New York: Plenum Press, 196:416.

William Garrett and David Robinson in Sydney had also reported on measurement of the fetal trunk area as a means to assess fetal size. The group used a Mark II CAL Echoscope which had already incorporated gray scale capabilitiy. They had also reported on gray-scale obstetric scans at the International Biological Engineering meeting in Melbourne in the same year. The method did not catch on until the appearance of gray scaling in other machines (Glasgow, Denver) and in particular the UI Octoson in 1975.
In:  Garrett WJ, Robinson DE. Assessment of fetal size and growth rate by ultrasonic echoscopy. Obstet Gynecol 1971;38:525.


In 1973, Manfred Hansmann in Germany described the use of the thoracic circumference in the assessment of fetal growth. It would appear that without gray scale at that time, the fetal thorax would be a better part of the fetal trunk to be localised. However the measurement was not consistent as a proper landmark has not been identified. The measurement was supposed to be made at a point where the fetal heart pulsations disappear. In view of the conical shape of the fetal chest, reproducibility of the measurement was sometimes in question. The Salvator Levi group in Brussels also published on similar techniques in 1975.
In:  Hansmann M, Voight U. Ultrasonic fetal thoracometry: An additional parameter for determining fetal growth. In: Proceedings of the Second World Congress on Ultrasonics in Medicine, Rotterdam, 1973:47.

Then in 1975 Campbell and Wilkin described the abdominal circumference and defined the proper landmark for measurement: that of the umbilical vein in the fetus. This quickly became a "classic" and had also stood the test of time.

In 1976, the Hansmann group published their paper: Topography of a reference plane for ultrasonic thoracometry. Kugener H, Hansmann M. Z Geburtshilfe Perinatol 1976 Oct 180:313-9, which further described the landmark for the measurement of the thoracic circumference. It was a similar plane as that used for the abdominal circumference.

Abstract:

A method of ultrasonic thoracometry is reported which uses the veins of the fetal liver as landmarks. The fact that the umbilical vein running from the anterior abdominal wall to the "sinus venae portae" is visible in B-scan display is the given presupposition. In a study about topography of the vein system of the fetal liver in 50 cases the description of a so called "sinus-plane" for sonar thoracometry is given. This reference plane is shown to be identical with the "lower apertura of the fetal thorax" recommended by Hansmann and co-workers since 1971. Thereby the nowadays well established method of thoracometry in obstetrical routine work gets a more accurate definition in regard to it's topography. This is not only of theoretical interest but will improve the conditions for more accuracy and reproducibility of the method.




Before the 1980s, the abdominal circumference is usually determined on a polaroid photograph by means of a map measurer or by an average diameter-to-circumference calculation. In the early 80s electronic digitisers and light-pen measuring systems started to appear which could be coupled to the monitor display of a static equipment. With the advent of realtime equipments and digital scan convertors, circumference measurements are made on screen by tracing the outline of the abdomen with a caliper-device (joystick, trackball), a light-pen or computer approximation.




Some historical notes on the Biparietal diameter is here.





Back to History of Ultrasound in Obstetrics and Gynecology.