Introduction

Measurements have a significant role in many areas of ultrasound practice. Some of the earliest ultrasound measurements were made in the field of obstetrics, originally in A-mode. A small range of measurements was quickly established in regular practice and this range has been considerably developed over the years. The most frequently performed measurements range from nuchal translucency in detecting abnormalities, through crown–rump length, biparietal diameter and femur length for dating, to abdominal circumference (AC) and head circumference (HC) for growth assessment. All of these may affect the management of pregnancy and therefore accuracy and reproducibility of measurements are important.

There is also a long history of measurement in echocardiography. Early measurements were made using the M-mode image and this is still used in modern clinical practice. Echocardiography images a dynamic process; the advantage of M-mode is that it contains information on both distance and time in a single image, so that changes in dimensions during the cardiac cycle may be measured. Cine-loop displays and imaging workstations now provide this temporal information in B-mode in a highly accessible form, facilitating measurement of changes in areas and volumes, e.g. for estimating left ventricular ejection fraction.

Most abdominal and small parts examinations are qualitative. Measurements are sometimes used, ranging from the gall bladder wall and common bile duct (a few millimetres) to the kidneys and liver (centimetres).