Quantification of blood perfusion using 3D power Doppler: anin-vitroflow phantom study

Abstract

Three-dimensional (3D) power Doppler data is increasingly used to assess and quantify blood flow and tissue perfusion. The objective of this study was to assess the validity of common 3D power Doppler 'vascularity' indices by quantification in well characterised in-vitro flow models. A computer driven gear pump was used to circulate a steady flow of a blood mimicking fluid through various well characterised flow phantoms to investigate the effect of the number of flow channels, flow rate, depth dependent tissue attenuation, blood mimic scatter particle concentration and ultrasound settings. 3D Power Doppler data were acquired with a Voluson 530D scanner and 7.5MHz transvaginal transducer (GE Kretz). Virtual Organ Computer-aided Analysis software (VOCAL) was used to quantify the vascularisation index (VI), flow index (FI) and vascularisation-flow index (VFI). The vascular indices were affected by many factors, some intuitive and some with more complex or unexpected relationships (e.g. VI increased linearly with an increase in flow rate, blood mimic scatter particle concentration and number of flow channels, and had a complex dependence on pulse repetition frequency). Use of standardised settings and appropriate calibration are required in any attempt at relating 'vascularity indices' with flow.

The Role of 3-D Ultrasonography in the Evaluation of Menstrual Cycle-Related Vascular Modifications of the Clitoris. A Prospective Pilot Study

“…The 3‐D VOCAL imaging program facilitates the assessment of total blood flow through the quantification (computed algorithms that evaluate the number and intensity of color voxels) of the power Doppler signal within the defined volume of interest and allows the objective evaluation of the total vascular flow within an organ [10]. The different indices (VI—number of color voxels representing the blood vessels in the specific organ; FI—the average intensity of flow inside the specific organ; and VFI—a combination of vascularity and flow) used to define the organ vascularity have been shown to be reliable and reproducible and to correlate with vessel number and volume flow rate in vitro [10,11]. In our study, the clitoral VI, FI, and VFI resulted significantly increased in the periovulatory phase of the menstrual cycle.…”

The three-dimensional ultrasonographic ovarian vascularity of women developing poor ovarian response during assisted reproduction treatment and its predictive value

“…The definition of poor response used were different in this study with Zaidi et al (9) used six or less follicles of varying sizes at oocyte retrieval as cutoff in contrast to the widely used definition with either cycle cancellation or retrieval of three or less oocytes (23). Although this is the unlikely reason for the contrasting findings, we used 3D power Doppler, which does not provide any information on the velocity of blood flow, but both the VI and FI have been shown to provide some information on volume flow and vascularity in in vitro phantom studies (30). A recent study using 2D ultrasound, in a larger population of 136 subjects, also failed to support Zaidi et al's findings with lack of a significant relationship between ovarian response and pulse wave Doppler indices including peak systolic velocity of ovarian stromal vessels (13).…”

Ovarian response to the human chorionic gonadotrophin stimulation test in normal ovulatory women: the impact of regressing corpus luteum

“…1), the program calculated the ratio of color voxels to all voxels; this ratio (%) was expressed as the vascularization index (VI). Raine-Fenning et al (15) observed in an in-vitro flow phantom study that VI increased linearly with an increase in flow rate, suggesting that VI measured with standardized settings is closely related with the blood perfusion in the organ. Vascularized volume (mL) in the ovary was calculated by multiplying the total ovarian volume by the VI.…”