Currently, 3D ultrasound is widely used for monitoring the course of pregnancy. It allows imaging the developing fetus. With the quality 3D images that this type of ultrasound produces, physicians can clearly assess the health condition of the infant or any anomalies, such as cleft pal­ate, spina bifi da, anencephaly, and cardiac defects. It provides quantifi able nuchal scan mea­surements to facilitate the calculation of the risk of chromosomal defects such as Down syndrome [ 41 ]. In addition, it facilitates gender determina- tion [ 42 ]. 3D ultrasound is not only applied in fetal and gynecologic imaging, but also in other medical procedures such as surgeries or biopsies [ 43 , 44 ]. Moreover, 3D US is being adopted by other medical fi elds such as cardiology and neu­rology [ 45 – 47 ]. Furthermore, it is used in several other fi elds and its application is at the forefront of current medical technology.

the advantages it provides not only in the fi eld

of ART is striking, and instruments as well as

supporting software programs are becoming

more and more user friendly. Operation of the

cessing time has been signifi cantly shortened.

and therapy. Three-dimensional sonography

increasingly acceptable as a diagnostic tool.

myometrial-endometrial junction to form the basal arteries that supply the basal portion of the endometrium and the spiral arteries that continue up towards the endometrium. Endometrial blood fl ow can be determined by colour and power Doppler ultrasound. Power Doppler imaging is more sensitive than colour Doppler imaging at detecting low-velocity fl ow and hence improves the visualisation of small vessels [ 11 ]. In combi- nation with 3D ultrasound, power Doppler can objectively examine both endometrial and suben­dometrial blood fl ow.

Doppler study of uterine vessels refl ecting down­stream impedance to fl ow is assumed to refl ect the endometrial blood fl ow. It is usually expressed as the pulsatility index (PI) and the resistance index (RI) (Fig. 3.1 ). PI is calculated as the peak sys- tolic velocity (PSV) minus end-diastolic velocity divided by the mean, whereas RI is the ratio of PSV minus end-diastolic velocity divided by PSV.

Good uterine blood fl ow as shown by low PI or RI is correlated with successful IVF out­comes [ 12 , 13 ]. Steer et al. [ 12 ] classifi ed 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. Using a PI upper limit of 3.0 [ 12 ] or 3.3 [ 13 ], the uterine Doppler fl ow indices have a high negative pre­dictive value and sensitivity (in the ranges of 88–100 % and 96–100 %, respectively) and a relatively higher range of positive predictive value and specifi city (44–56 % and 13–35 %, respectively) when compared with endometrial thickness and pattern [ 5 ].

Endometrial and subendometrial blood fl ow examined by colour (Table 3.1 ) and power Doppler (Table 3.2 ) was correlated with implan- tation or pregnancy rates during IVF treatment. 2D Doppler fl ow indices of spiral arteries such as PI and PSV are not predictive of pregnancy [ 8 , 19 , 22 ], although Battaglia et al. [ 16 ] and Kupesic et al. [ 23 ] found signifi cantly lower spi- ral artery PI in pregnant cycles than nonpregnant cycles.

Yang et al. [ 18 ] 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 (EDPA). Signifi cantly higher EDPA was found in pregnant cycles than nonpregnant cycles (8.8 mm 2 vs.

3D power Doppler ultrasound with the aid of the VOCAL® (Virtual Organ Computer-Aided Analysis) imaging program for the 3D power Doppler histogram can be used to measure the endometrial volume and indices of blood fl ow within the endometrium (Fig. 3.2 ). Vascularisation index (VI), which measures the ratio of the num­ber of colour voxels to the number of all the voxels, is thought to represent the presence of blood vessels (vascularity) in the endometrium,

The subendometrium can be examined through the application of ‘shell imaging’ which allows the user to generate a variable contour that parallels the originally defi ned surface contour. The VI, FI and VFI of the subendometrial region are obtained accordingly (Fig. 3.3 ). The intra- observer reliability and interobserver reliability of endometrial and subendometrial blood fl ow by 3D power Doppler have been confi rmed to be high with all measurements obtaining an intra­class correlation of above 0.9 [ 25 , 26 ].