Influence of Gain Adjustment on 3‐Dimensional Power Doppler Indices and on Spatiotemporal Image Correlation Volumetric Pulsatility Indices Using a Flow Phantom

Abstract

hree-dimensional (3D) power Doppler angiography has offered the potential to examine and quantify organ and tissue blood flow for more than a decade 1 and has generated a great deal of interest, as evident by the 200 or more papers published in the field of obstetrics and gynecology alone. 2,3 It is not only a noninvasive and relatively simple technique but rather safe because it exempts the need for contrast agents or exposure to radiation. Three indices have been proposed using virtual organ computer-aided analysis: the vascularization index (VI), the flow index (FI), and the vascularization-flow index (VFI). 1 Correlation between these indices and perfusion has been shown using both in vitro and ex vivo models, 4-6 but each index is highly dependent on machine settings, 7,8 attenuation, 4,5 and the sampling volume, 9 which limits their use for comparison between patients. 10 Andre H. Miyague, MSc, Nicholas J. Raine-Fenning, PhD, Theo Z. Pavan, PhD, Lukasz T. Polanski, MD, Miriam N. Baumgarten, MD, Carolina O. Nastri, PhD, Wellington P. Martins, PhD Received October 22, 2012, Spatiotemporal image correlation can be used to acquire 3-dimensional power Doppler information across a single cardiac cycle. Assessment and comparison of the systolic and diastolic components of the data sets allow measurement of the recently introduced "volumetric pulsatility index" (vPI) through algorithms comparable with those used in 2-dimensional Doppler waveform analysis. The vPI could potentially overcome the dependency on certain machine settings, such as power, color gain, pulse repetition frequency, and attenuation, since these factors would affect the power Doppler signal equally throughout the cardiac cycle. The objective of this study was to compare the effect of color gain on the vascularization index (VI), vascularization-flow index (VFI), and vPI using an in vitro flow phantom model. We separated gains into 3 bands: -8 to -1 (no noise), -1 to +5 (low noise), and +5 to +8 (obvious noise). The vPI was determined from the 3-dimensional VI or VFI using the formula vPI = (maximumminimum)/mean. Using no-noise gains, we observed that although the VI and VFI increased linearly with gain, the vPI was substantially less dependent on this adjustment. The VI and VFI continued to increase linearly with gain, whereas the vPI decreased slightly using low-noise gains. When gain was increased above the lower limit of obvious noise (+5), the VI and VFI increased noticeably, and there were marked reductions in both vPI values. We conclude that the vPI is less affected by changes in color gain than the VI and VFI at no-noise gains.

Assessment by three-dimensional power Doppler ultrasound of cerebral blood flow perfusion in fetuses with congenital heart disease

“…There are a number of limitations to our study. First, measurements of 3D power Doppler indices based on static volumes are dependent on gain settings and attenuation at acquisition and there have been contradictory reports regarding their reproducibility because of differences in machine settings, ROI, image acquisition and analysis. In this study, therefore, we attempted to keep the acquisition and measurement settings as consistent as possible.…”

Influence of ulipristal acetate therapy compared with uterine artery embolization on fibroid volume and vascularity indices assessed by three-dimensional ultrasound: prospective observational study

“…Furthermore, we did not perform a reproducibility analysis. Finally, 3D power Doppler vascular indices are considered to have limited applicability in obstetrics and gynecology because of their dependency on machine settings, attenuation, heart pulsatility and sample size, resulting in concerns regarding their reproducibility and clinical utility. However, we present a different approach to 3D power Doppler indices; we focused on changes in vascular indices obtained by the same operator on the same settings after different interventions.…”

Placental vascularization alterations in hypertensive disorders complicating pregnancy (HDCP) and small for gestational age with HDCP using three-dimensional power doppler in a prospective case control study

“…Although 3DPD quantification has been widely used in recent studies and publications in the field of obstetrics and gynecology, we acknowledge that PD quantification also has several methodological limitations for assessing vascularization [ 40 , 41 ]. These limitations include the high dependence on gain settings, lack of standardized machine settings [ 42 – 45 ], differences in attenuation [ 46 ], and issues with reproducibility [ 47 – 49 ], which are capable of altering the VI, FI and VFI quantification. A meaningful interpatient comparison of vascularity cannot be made without standardization.…”