J. Clewes

The interobserver reliability and validity of volume calculation from three‐dimensional ultrasound datasets in the in vitro setting

The primary aim of this validation study was to determine the interobserver reliability and validity of measurements of phantom objects of known volume using conventional and rotational techniques of volume calculation according to measurement technique.

The reliability of virtual organ computer‐aided analysis (VOCAL) for the semiquantification of ovarian, endometrial and subendometrial perfusion

Three‐dimensional power Doppler angiography (3D‐PDA) has been largely used for the subjective assessment of vascular patterns but semiquantification of the power Doppler signal is now possible. We examined the intraobserver and interobserver reliability of the semiquantification of ovarian, endometrial and subendometrial blood flow using 3D‐PDA, virtual organ computer‐aided analysis (VOCAL™) and shell‐imaging.

Determining the relationship between three-dimensional power Doppler data and true blood flow characteristics: an in-vitro flow phantom experiment

Three‐dimensional (3D) ultrasound can be used to acquire power Doppler data which can be quantified to give an objective impression about blood flow within a tissue or organ. Proprietary software can be used to calculate three indices of vascularity: vascularization index (VI), flow index (FI) and vascularization flow index (VFI). Although these indices appear to have a predictive value in the clinical setting and can be shown to vary between different patient populations and over time within the same population, their relationship with true in‐vivo blood flow characteristics has not been established. The objective was to examine the effect of flow rate, vessel number, attenuation and erythrocyte density on these indices.

Evaluation of the effect of machine settings on quantitative three‐dimensional power Doppler angiography: an in‐vitro flow phantom experiment

Three‐dimensional (3D) ultrasound is being used increasingly to acquire and subsequently quantify power Doppler data within the clinical setting. One proprietary software package calculates three 3D vascular indices: the vascularization index (VI), the flow index (FI), and the vascularization flow index (VFI). Our aim was to evaluate how different settings affect the Doppler signal in terms of its quantification by these three indices within a 3D dataset.

The interobserver reliability of three-dimensional power Doppler data acquisition within the female pelvis

To examine the interobserver reliability of three‐dimensional (3D) power Doppler data acquisition from the uterus and ovary.

SonoAVC: a novel method of automatic volume calculation.

To assess the ability of the new software SonoAVC to measure follicular volume and to compare these volume calculations with those made by conventional methods.

The interobserver reliability of off‐line antral follicle counts made from stored three‐dimensional ultrasound data: a comparative study of different measurement techniques

To assess the interobserver reliability of antral follicle counts (AFCs) made from stored three‐dimensional (3D) ultrasound data using conventional two‐dimensional (2D) images, 3D multiplanar view and 3D‐rendered ‘inversion mode’.

Quantitative analysis of antral follicle number and size: a comparison of two‐dimensional and automated three‐dimensional ultrasound techniques

To compare two‐dimensional (2D) ultrasound imaging with automated three‐dimensional (3D) ultrasound imaging for the measurement of antral follicle number and size.

Three‐dimensional ultrasound improves the interobserver reliability of antral follicle counts and facilitates increased clinical work flow

To compare the interobserver reliability of antral follicle counts made using real‐time two‐dimensional (2D) ultrasound with offline counts made from stored three‐dimensional (3D) data and to assess the time required for such counts.

Automated follicle tracking facilitates standardization and may improve work flow

Ultrasound is used to identify pathology and to confirm normality. This requires a subjective interpretation of the image display, which can be modified according to the object or area of interest. Objective assessment of an ultrasound image requires some form of measurement to be made, which should be performable in a reproducible manner and provide a valid result. Ultrasound, therefore, is open to interpretation and is dependent upon the observer regardless of whether a subjective or an objective examination is being made. Automatic data analysis has the potential to remove any observer bias and to reduce the time needed for measurements, but it must be both valid and reliable. This is particularly true within the field of reproductive medicine, with ultrasound being used on a daily basis to follow the ovarian response to gonadotropins in a process known as ‘follicle tracking’1. Each follicle is identified and displayed in its maximum diameter. Two-dimensional measurements are then made and their mean is taken as the true follicular diameter. This is relatively straightforward but follicle tracking becomes more difficult as the number of follicles increases. A typical patient undergoing controlled ovarian stimulation as part of assisted reproduction treatment would be expected to develop somewhere between five and ten follicles within each ovary, although it is not unusual for there to be many more. The validity and reliability of measurements of follicular diameter are likely to reduce as the number of follicles increases, because it becomes increasingly difficult to ensure that every follicle is accounted for. The time required for these measurements also increases as the number of follicles increases, which may adversely affect measurement reliability. Automated measurement of follicular size could potentially address both of these issues and introduce a standard for such measurements2–4. SonoAVC (Automatic Volume Calculation: GE Medical Systems, Zipf, Austria) is a new software program that identifies and quantifies hypoechoic regions within a three-dimensional dataset and provides automatic estimation of their absolute dimensions, mean diameter and volume. Each individual volume is given a specific color and the automated measurements of its mean diameter (relaxed sphere diameter), its maximum dimensions (x, y, z diameters) and its volume are displayed by these colors in descending order of size. An unlimited number of volumes can theoretically be quantified, which makes it an ideal tool for assessment of the ovaries in women undergoing controlled ovarian stimulation. Automated volume measurements require the acquisition of a three-dimensional dataset. This is then displayed using the multiplanar view and a region of interest is selected by manually moving a box to fit the maximum proportions of the ovary. Once the dataset has been correctly positioned, SonoAVC is implemented. The automated analysis takes around 6 s and the individual follicles are then displayed together with their dimensions and relative sizes (Figure 1). Our preliminary experience has shown that the software has great potential and that it provides both reliable and valid measurements of follicles. In a study comparing the automated measurements to those derived from measuring the follicular aspirate5, we found that SonoAVC estimated the volume of a follicle to within ± 0.5 cm3. This was significantly more accurate than were volume measurements derived using algorithms (the sphere and ellipsoid formulae) based on the mean follicular diameter calculated by both twoand three-dimensional techniques. Follicular diameter measurements were also more reliable when made with SonoAVC, which provides two different mean diameters6. The ‘relaxed sphere diameter’ is derived from the automatic volume calculation by assuming that the follicle is spherical and applying the formula used for the estimation of the volume of a sphere. The ‘x, y, z mean diameter’ is calculated by taking the mean of the three perpendicular diameters. The software is formulated to first measure the maximum follicular diameter in the longitudinal or transverse plane and then to measure the two diameters perpendicular to this. This technique