Three-dimensional ultrasound, 2000

Intraexaminer and Interexaminer Variability in 3D Fetal Volume Measurements During the Second and Third Trimesters of Pregnancy

OBJECTIVES

To assess intraexaminer and interexaminer reliability of 3-dimensional fetal sonographic measurements.

METHODS

Three-dimensional fetal organ volumes (head, kidney, total thigh volume, and fractional thigh volume) were acquired during the second and third trimesters, with the addition of placental volume in the second trimester, by 2 different experienced, blinded sonographers. Fifty-eight fetuses were examined from 21 to 39 weeks' gestation. Intraexaminer and Interexaminer reliability was assessed with Bland-Altman plots, and their 95% limits of agreement and intraclass correlation coefficients.

RESULTS

The most significant interexaminer error was observed in the second-trimester kidney volume (95% limits of agreement, ± 110%), and the best agreement was for the third-trimester fractional thigh volume (95% limits of agreement, ± 25%) and second-trimester head volume (95% limits of agreement, -7%-25%). Second- and third-trimester intraclass correlation coefficient results were all greater than 0.75, apart from second-trimester kidney volume intraexaminer (0.374) and interexaminer (0.061) measurements, second-trimester placenta interexaminer measurements (0.390), and third-trimester kidney interexaminer measurements (0.647).

CONCLUSIONS

Three-dimensional fetal sonographic volumes of the head, kidney, total thigh, and placenta have limited reproducibility, and improvements in measurement techniques are needed before they can be used routinely to assess fetal growth. The 3-dimensional fractional thigh volume can be reliably obtained in the late third trimester.

Fetal biometry: how well can offline measurements from three-dimensional volumes substitute real-time two-dimensional measurements?

OBJECTIVES

To assess the feasibility, accuracy and reproducibility of manipulating three-dimensional (3D) volume sets in order to reconstruct optimal two-dimensional (2D) planes for fetal biometry throughout gestation and compare them with those derived from real-time 2D scanning.

METHODS

Sixty-five fetuses were evaluated at a gestational age of 14-41 weeks. For each fetus a duplicate set of seven standard fetal measurements was taken by an experienced operator using 2D ultrasound and then 20 intentionally suboptimal 3D volumes from different predefined angles were captured and stored. These were manipulated and measured. The time taken to complete a full scan, with both 2D and 3D ultrasound, was recorded. All measurement differences were expressed as gestational age-specific Z-scores. For all comparisons Bland-Altman plots were used and limits of agreement were calculated. The means and variances of the measurements were tested with a paired t-test and Pitman's test for differences in variance, respectively. The difference between the time taken to perform a 2D and a 3D scan was tested using the Wilcoxon signed-ranks test.

RESULTS

Mean agreement between 2D and 3D ultrasound measurements was good, with no statistically significant differences (i.e. no systematic error) unless the head was facing anteroposteriorly, or the long axis of the femur was at 60-90° to the transducer. The variance (random error) for 3D measurements was similar to that for 2D measurements. Planes from some volumes could not be extracted (7% for head circumference, 9% for abdominal circumference and 11% for femur length). The median time required to perform a full fetal biometric scan was significantly higher for 3D than for 2D (3:04 min vs 1:57 min, respectively; P < 0.001).

CONCLUSIONS

Fetal measurements derived from 3D volume acquisitions exhibited good agreement with those obtained by real-time 2D scanning, with no extra systematic or random error. However, they were slower to obtain, not all volumes were amenable to extraction of planes and measurements that came from a head facing anteroposteriorly or that were obtained with the long axis of the femur at 60-90° to the transducer were systematically smaller.

Percutaneous renal intervention: comparison of 2-D and time-resolved 3-D (4-D) ultrasound for minimal calyceal dilation using an ultrasound phantom and fluoroscopic control

The rapid advances made by ultrasound in recent years have increasingly taken 3-D ultrasound (3DUS) and 4-D ultrasound (4DUS) from the research setting to the patient's bedside. There are still unexplored areas like renal percutaneous intervention, where 4DUS has yet to be proven an effective tool. Ultrasound-only guidance in renal percutaneous access is used in selected well-dilated pelvi-calyceal systems (PCS), and fluoroscopy is often utilized as an adjunct. Our aim was to compare 2-D and 4-D guidance for punctures, with fluoroscopy as control, using an in vitro ultrasound phantom. Agar and latex were the tissue-mimicking materials used for the construction of the phantom. The latex targets were designed to simulate multidirection-facing minimally dilated renal calyces. Two interventional fellows punctured the "calyces" using first 2DUS and then 4DUS guidance, making use of a different set of targets each time. The time to puncture, time to introduction of wire, quality of puncture (judged on fluoroscopy) and global rating of both modalities were documented. There was no significant difference between the times to puncture using 2DUS (1.8 min) and 4DUS (2 min). Nor was there a significant difference in the quality of puncture. 4DUS had a higher median difficulty rating. The multiplanar reformatted (MPR) longitudinal and transverse images were found to be the most useful for needle guidance. Cross hairs in all MPR images were not just useful in aligning the images on target but also as surrogate targets. The phantom was found to be robust, with only one instance of air introduction after 30 punctures. We have found that 4DUS is at least as good as 2DUS in terms of quality of punctures in vitro. The technology still has some way to go as frame rates, transducer size and resolution improve.

Evolution of fetal ultrasonography

The authors wish to highlight the evolution that has occurred in fetal ultrasound in recent years. A first significant evolution lies in the increasing contribution of first trimester ultrasound for the detection of fetal anomalies. Malformations of several organs and systems have been diagnosed during the first trimester. Furthermore the systematic measurement of the fetal neck translucency has led to increasing rate of detection of aneuploidies and heart malformations. For several years now, three-dimensional (3D) and 4D ultrasound (US) have been used as a complementary tool to 2D US for the evaluation of fetal morphology. This brings an improved morphologic assessment of the fetus. Applications of the techniques are increasing, especially for the fetal face, heart and extremities. The third field where fetal US is continuously providing important information is the knowledge of the natural history of diseases. This has brought significant improvement in the postnatal management of several diseases, especially urinary tract dilatation and broncho-pulmonary malformation.

Three-Dimensional Ultrasound in Small Parts

For longer than 40 years, ultrasound (US) has been a widely used imaging tool in medical practice, which has proved helpful for the diagnosis and staging of diseases. Although three-dimensional ultrasound (3D) US has been available for more than 10 years, it was only through the development of the most recent computer technologies and its adaptation to ultrasound systems, that 3D US has become able to achieve the high level of sensitivity and performance necessary to be considered seriously in clinical practice. 3D US is rapidly turning into a technology with an ever-increasing range of applications in numerous fields because, among other reasons, it helps overcome some of the key limitations related to two-dimensional imaging. 3D US can be used in ultrasonography for small parts, among other medical areas. The assessment of the testicle, parotid, thyroid and parathyroid glands is properly achieved. The multiplanar presentation and niche mode are quite useful to determine the extension--inside or outside the organs-, of nodules, cysts or tumors. The volume measurement is better assessed with 3D US and given this, we can perform studies that follow growth in order to decide medical or surgical treatment. The VOCAL makes it possible to obtain a proper after-treatment follow-up of focal disorders in these small organs. Neovascularization is clearly viewed with 3D US and probably can suggest malignant origin of a neoplasm. 3D US offers a more comprehensive image of anatomical structures and pathological conditions and also permits to observe the exact spatial relationships. We are aware more studies are needed to demonstrate specificity and sensibility of 3D US in particular clinical conditions, not only in small parts but also is some other non-Ob/Gyn applications.

What's new in prenatal screening and diagnosis?

This article provides clinicians with an overview of current methods for prenatal genetic screening and diagnosis. Topics include developments in prenatal screening procedures such as ethnicity-based carrier testing, maternal serum screening, and ultrasonography. Diagnostic alternatives to amniocentesis include chorionic villus sampling and preimplantation diagnosis. Future endeavors such as three-dimensional ultrasonography and fetal cell sorting are discussed.

Quantification of ovarian stromal Doppler signals in postmenopausal women receiving hormone replacement therapy

OBJECTIVE

To investigate the effect of continuous-combined hormone replacement therapy (HRT) on ovarian circulation, we used three-dimensional power Doppler ultrasound to assess ovarian stromal blood flow in postmenopausal women.

DESIGN

Forty healthy, postmenopausal women were enrolled in this prospective, controlled study. They were divided into two groups: the control group (20 patients with no HRT treatment) and the HRT group [initially 20 patients, but later 15 patients who completed the study, using continuous-combined conjugated equine estrogen (0.625 mg/day) plus medroxyprogesterone (5 mg/day)]. All patients underwent transvaginal three-dimensional power Doppler ultrasonography at the time of recruitment and 3 months later. The ovarian stromal flow indices, including vascularization-flow index (VFI), flow index (FI), and vascularization index (VI), were measured. Blood withdrawals for serum follicle-stimulating hormone and estrogen level testing were obtained before and after 3 months of treatment.

RESULTS

All the variables in the hormone profile showed significant difference (P < 0.05) after 3 months of treatment in the HRT group. Of interest, the three-dimensional power Doppler indices of ovarian stromal flow, VFI (0.13 +/- 0.11 --> 0.59 +/- 0.49), FI (30.47 +/- 12.06 --> 38.41 +/- 10.21), and VI (0.31 +/- 0.27 --> 1.12 +/- 0.95) all showed significant increase (P < 0.05) after 3 months of HRT treatment.

CONCLUSIONS

There was a significant increase in ovarian stromal flow indices after 3 months of treatment in the HRT group, but not in the controls. Monitoring the ovarian flow changes by three-dimensional power Doppler may be of clinical importance when HRT is given.

Ovarian stroma flow intensity decreases by age: a three-dimensional power doppler ultrasonographic study

This was a prospective comparative clinical study to test the hypothesis that the flow intensity of the ovarian stroma decreases in the order of the aging process. A total of 100 consecutive women who came to our outpatient clinic for Pap smear examination were recruited. They were divided into three groups. The premenopause group (58 women) had menstruated within the last 3 months and had normal ovaries (no polycystic ovary or any pathologic cyst or mass), as demonstrated on the baseline ultrasound (US) examination. The perimenopause group (20 women) had last menstruated between 3 and 12 months earlier and had normal ovaries. The postmenopause group (22 women) had had no menstrual cycle within the last 12 months and had normal ovaries. Three-dimensional power Doppler US was applied to quantify the blood flow and vascularization within the stroma of the bilateral ovaries. The results showed that the E2 level decreased in the order of: premenopause (mean +/- SD; 40.88 +/- 40.65 pg/mL), perimenopause (22.00 +/- 13.61 pg/mL), then postmenopause (17.25 +/- 16.40 pg/mL). The vascularization index (VI) (6.95 +/- 8.35; 1.11 +/- 0.93; 0.53 +/- 1.75; respectively), flow index (FI) (15.98 +/- 7.59; 12.00 +/- 3.86; 5.18 +/- 5.31; respectively) and vascularization-flow index (VFI) (1.25 +/- 1.59; 0.18 +/- 0.15; 0.09 +/- 0.32; respectively) all decreased significantly in the order of premenopause, perimenopause, then postmenopause. To the best of our knowledge, this is the first study using 3-D power Doppler sonography that proves that the flow intensity decreases along with the aging process in the ovarian stroma.