Doppler study of uterine vessels

 

What we know:  Doppler study of uterine vessels reflects  downstream impedance to flow is assumed to reflect the endometrial blood flow. We also  know that this study are  usually expressed as the pulsatility index (PI) and the resistance index (RI).

PI is calculated as the peak systolic velocity (PSV) minus end-diastolic velocity divided by the mean.

  RI is the ratio of PSV. Flow velocity waveforms are obtained form the ascending main branch of the uterine artery on the right and lift side of the cervix in a longitudinal plane before it enters the uterus.

Tips of technique:  The gate of the Doppler is positioned  when the vessel with good colour signals is identified on the screen. The PI and RI of the uterine arteries were calculated electronically when three similar, consecutive waveforms of good quality were obtained.  Good uterine blood flow as shown by low PI or RI is correlated with successful pregancy outcome , IVF outcomes in particular.

What to know on the day of transfer of embryo??  Ans:  Researchers have   classified PI measured on the day of ET as low, medium and high in the ranges of 0-1.99, 2.00-2.99 and >3.00, respectively, and reported a 35% implantation failure when PI was >3.0 or 3.3, the uterine Doppler flow indices have a high negative predictive value and sensitivity (in the ranges of 88-100 %,respectively) and a relatively higher range of positive predictive value and specificity (44-56 % and 13-35%’,respectively) when compared with endometrial thickness and pattern.

 

Uterine artery Doppler study may not reflect the actual blood flow to the endometrium as the major compartment of the uterus is the myometrium and there is collateral circulation between uterine and ovarian vessels.

 

:  What about endometrial blood flow?? Can we assess endometrial blood flow?? Ans: Researchers have shown that  2D Doppler study of uterine vessels is poor reflection of subendometrial blood flow by 3D power Doppler in both stimulated and natural cycles as endometrial and subendometrial 3D Doppler flow indices were similar among patients with averaged uterine PI <2.0,2.0-2.99 and >-3.o.

 

Endometrial and subendometrial blood flow by 2D Doppler Endometrial and subendometrial blood flow examined by colour and power Doppler was correlated with implantation or pregnancy rates during IVF treatment. 2D Doppler flow indices of spiral arteries such as PI and PSV are not predictive of pregnancy although several researchers found significantly lower spiral artery PI in pregnant cycles than nonpregnant cycles .Yang et al used a computer software to measure the area and intensity of colour signals present in the endometrium in a longitudinal axis i.e. intraendometrial power Doppler area. Significantly higher EDPA was found in pregnant cycles than non  pregnant cycles. Patients EDPA <5 mm had significantly lower pregnancy rate and implantation rate than those with >5 mm. Contart et al graded endometrial    blood flow by the visualization of power Doppler in the quadrants in the fundal region of the transverse plane but could not demonstrate any predictive value of such grading system.

Presence of endometrial and subendomatrial blood flow can be indentified easily in 2D Doppler ultrasound. Absent endometrial and subendometrial blood flow has been shown to be associated with no pregnancy or a significantly lower pregnancy rate.

Endometrial and subendometrial blood flow by 3D Doppler

3D power Doppler ultrasound with the aid of the VOCAL  (virtual  organ  computer Aided Analysis) measure the endometrial

Volume and indices of blood flow within the endometrium  vascularisation  index (VI), Which measures the ratio of the number of colour voxels, is thought to represent the presence of blood vessels (vascularity) in the endometrium, and this was expressed as a percentage(%) of the endometrial volume. Flow index (FI), THE mean power Doppler signal intensity inside the endometrium, is thought to express the average intensity of flow. Vasculerisation flow index (VFI) is a combination of vascularity and flow intensity .

The subendometrium can be examined through the application of shell imaging which allows the user to generate a vavriable contour that parallels the originally defined surface contour. The  VI, FI and VFI of the subendometrial region are obtained accordingly.The nitraobserver reliability and intra-observer reliability of endometrial and subendometrial blood flow by 3D power Doppler have been confirmed to be high with all measurements obtaining an intra-class correlation of above 0.9 .Studies addressing the role of endometrial and subendometrial blood flow measured by 3D Doppler in IVF treatment

Reserchers the subendometrial blood flow after pituitary downregulation but prior to ovarian stimulation and sgowed that subendometrial VI, FI and VFI were significantly lower in pregnant cyces than nonpregnant ones. Logistic regression analysis found that the subendometrial FI was the strongest predictive factor for the pregnancy outcome among other 3D Doppler flow indices.

Reserchers . performed 3D ultrasound examination on the day of blastocyst transfer avd found that subendometrial FI was significantly higher in pregnant cycles. Subendometrial VI and VFI were similar between pregnant and nonpregnant patients. Wu et at. measured subendometrial biood flow on the day of Hcg and demonstrated that subendometrial VFI was significantly higher in the pregnant group. Subendometrial VI and FI were also similar between pregnant and nonpregnant cycles. Sunbendometrial VFI was superior to subendometrial VI, subendometrial FI and endometrial volume in predicting the successful outcome in the receiver-operating characteristics (ROC) curve analysis.

On the day of oocyte retrival,  dorn et al. Compared the subendometrial blood flow before and after an intravenous administration of Levovist, which is a contrast agent and consists of 99.9 %of D-galactose. All subendometrial 3D Doppler flow indices after the administration of the contrast agent were significantly higher than those without the contrast agent. However, all subendometrial 3D Doppler flow indices with and without the contrast agent were comparable between pregnant and nonpregnant cycles. The results of this study suggested that the use of 3D power Doppler ultrasound under a contrast agent during ivf treatment provided no additional advantage over the conventional 3D power Doppler ultrasound examination.