Ian R. Johnson

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 individualised birthweight ratio : a more logical outcome measure of pregnancy than birthweight alone

Objective To provide a new outcome measure for pregnancy specifically related to the individual.

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.

Loss of endothelium‐dependent relaxation in myometrial resistance arteries in pre‐eclampsia

Objective To measure endothelium‐dependent relaxation in myometrial resistance arteries and to compare this parameter in nonpregnant and normotensive pregnant women and those with pregnancies complicated by pre‐eclampsia.

Fetal weight estimation by echo-planar magnetic resonance imaging.

Fetal weight was estimated in utero in eleven singleton pregnancies by measurement of fetal volume with echo-planar imaging (EPI), a form of magnetic resonance imaging, and by ultrasound measurements. EPI estimates of fetal volume were closely correlated with actual birthweight (R = 0.97). The median difference (expressed as a percentage of actual birthweight) between actual and EPI-estimated birthweights was 3.0% (range 0.6-9.9); this discrepancy was significantly smaller than that found for ultrasonographic estimates (6.5% [1.7-17.8]; p < 0.01).

The individualised birth weight ratio: a new method of identifying intrauterine growth retardation

Objective To assess the effectiveness of the newly developed individualised birthweight ratio in identifying growth retarded infants.

An assessment of the intrauterine sound intensity level during obstetric echo-planar magnetic resonance imaging

In order to assess the sound level experienced by the fetal ear during obstetric magnetic resonance imaging, a fluid filled stomach was used as an experimental model of the gravid uterus. A better than 30 dB attenuation in intensity was recorded across the frequency band of interest for all patient orientations. This was enough to reduce acoustic sound pressure from a level close to the instantaneous damage threshold (120 dB), to an acceptable level (< 90 dB). Direct mechanical coupling through the patient table was also shown to increase uterine sound pressure levels by as much as 10 dB. Much higher peak pressures could be obtained by tapping of abdomen with the fingers.

Fetal brain activity demonstrated by functional magnetic resonance imaging

Functional magnetic resonance imaging was used to study fetal brain activity. This activity was in response to an auditory stimulus.