The Role of Three Dimensional Ultrasound In The Evaluation Of The Fetus Obstetrical Sonography 2 Lecture 24 Harry H. Holdorf

3D/4D Ultrasound Imaging of the Fetus Contents Introduction Evaluation of volume measurements Artifacts Parental-Fetal bonding 3D vs. 4D Benefits of 3D/4D imaging Drawbacks of 3D/4D imaging Summary Homework

3D ultrasound is a medical ultrasound technique used during pregnancy, providing three dimensional images of the fetus. Often these images are captured rapidly and animated to produce a 4D ultrasound. There are several different scanning modes in medical and obstetric ultrasound. The standard common obstetric diagnostic mode is 2D scanning.

In 3D fetal scanning, however, instead of the sound waves being sent straight down and reflected back, they are sent at different angles. The returning echoes are processed by a sophisticated computer program resulting in a reconstructed three dimensional volume image of the fetus’s surface or internal organs; allowing one to see width, height and depth of images in much the same way as 3D moves, but no movement is shown.

3D ultrasound was first developed by Olaf von Ramm and Stephen Smith at Duke University in 1987. Clinical use of this Technology is an area of intense research activity especially in fetal anomaly scanning, but there is also popular uses that have been shown to improve fetal-maternal bonding. 4D sans are similar to 3D scans except that they show fetal movement as shown in a video clip (continuous update of data).

If the system is used only in obstetrical applications, the ultrasound energy is limited by the manufacturer below FDA limits for obstetrical ultrasound, whether scanning 2, 3, or 4 dimensionally. While there is no hard evidence for harmful effects of 3D/4D ultrasound, its use in non-medical situations should be undertaken with the understanding that a risk may exist.

Evaluation of Volume Measurements 3D volume imaging is the ability to measure volumes more easily and accurately, compared with using 2D imaging. 3D Sonographic methods provide a more accurate volume measurement than the usual multiple 2D images, regardless of the shape and regularity of objects Specific areas that have been studied include the fetal lung and the prenatal diagnosis of pulmonary hypoplasia, particularly in cases of diaphragmatic hernia. There are volume measurements of the kidneys, liver, spine, thigh, and other extremities, as well as fetal weight. 3D fractional limb volumes have been investigated as a way to predict birth weight and assess overall fetal growth and nutrition during gestation.

Improving the efficiency of the ultrasound practice with three-dimensional ultrasound imaging The measurement of thigh Volume is said to have promise as a useful reference in evaluating fetal growth and nutritional status in utero. 3D ultrasound thigh volume measurements are simple to perform and are more accurate than 2D ultrasound methods for predicting estimated weight during the third trimester. On the other hand, the volume measurement of the placenta, is not an accurate technique for predicting growth-restricted fetuses.

Applications of Three-Dimensional Ultrasound Volumetric evaluation of the fetal lungs also has prompted a large amount to of study using the 3D technique called virtual organ computer-aided analysis. Both 3D multiplanar reconstruction and 3D VOCAL* methods could be used to obtain accurate measurements of fetal lung volumes. VOCAL* does have the advantage of being able to trace out irregular areas of lung parenchymas, such as in cases of diaphragmatic hernia compressing the lung. *A conventional multiplanar technique for three-dimensional (3D) ultrasound measurement of fetal lung volume with a rotational method using VOCAL trade mark (Virtual Organ Computer-aided AnaLysis).

Volume sweeps are best performed with the fetus in transverse section Volume sweeps are best performed with the fetus in transverse section. The ability to measure lung volume with 3D ultrasound has resulted in new nomograms for the normal fetal lung volume at different gestational ages. This method could be an alternative to MRI in imaging the fetal lungs. 3D assessment of fetal lungs was also studied as a factor for isolating the diagnosing of diaphragmatic hernia.

Artifacts The artifacts that occur as a result of volume imaging can be different from those that are familiar in 2D ultrasound. The usual artifacts, such as shadowing and through- transmission, are present in any kind of ultrasound examination, but there also are new artifacts inherent to 3D reconstruction of images. These include motion artifacts such as fetal movement and cardiac motion. It also is important to recognize acoustic shadowing, because it is unlikely to be in the expected location in a reconstructed image. Multiplanar reconstruction of a third trimester fetal face showing an artifact due to fetal movement. There is an indentat* nose on one side best seen in multiplanar plane B (arrow) and transmitted to the surface rendering as an elongated nose on one side (arrow), This is an artifact due to fetal movement during the acquisition and appears on all reconstructed views.

Artifacts As different planes are reconstructed, the shadow may no longer make sense and may be misinterpreted for pathology. Acoustic enhancement behind a cystic structure is also a finding that is an obvious part of a standard ultrasound image, but can be practically unrecognizable in a reconstructed image. The cystic area that has generated the through transmission is unlikely to be located in the usual proximity to the enhanced area in a reconstructed image and may not even appear in the image at all. Other artifacts can be produced, such as apparent limb or facial defects, based on the position of the acquiring data box within the image. Third trimester fetal face showing the shadow from the digits of the hand that is located in front of the face. The shadow of the digits is visualized as an artifact on the face.

Parental- Fetal Bonding Seeing the fetus in such a real-life form as 3D surface rendering may arouse many emotions from the mother and father, and family members. This type of parental-fetal bonding can sometimes lead to altered behaviors of lifestyle, such as cessation of smoking or cessation or alcohol usage by the mother. There are several studies that compare the effects of 2D ultrasound with 3D and 4D ultrasound scanning on maternal emotional status and bonding. The patients who were examined with 4D ultrasound were more likely to see facial expressions of their fetuses, and hand- to mouth movements compared with patients who were examined with 2D ultrasound. Third trimester fetus yawning, which is easily recognizable by family members viewing the scan.

Bonding 4D ultrasound did not change the antenatal emotional attachment of the mother, compared with patients undergoing conventional 2D ultrasound alone. The 3D ultrasound patients appeared more positively influenced and showed their ultrasound images to greater numbers of people within their family and friends compared with those who had 2D ultrasounds alone. This study suggested that 3D ultrasound may have a greater impact on the maternal-fetal bonding process. At present, there are a number of organizations in business that provide entertainment ultrasound, which is mostly 3D imaging that is done in many cases by nonmedical personnel. The ultrasound community and the major national ultrasound societies have condemned these nonmedical facilities. Late first trimester fetus showing upper extremities and face in a very life-like position.

3D vs. 4D Real-time capacity is not generally available with three-dimensional ultrasound. Real-time three-dimensional ultrasound is also known as 4-D ultrasound. Whereas 3D ultrasound is a static display of various reformatting techniques based on the acquisition of a static volume, 4D ultrasound displays a continuously updated and newly acquired volume in any modality creating the impression of a moving structure.

If it was bread, you will see the whole loaf If it was bread, you will see the whole loaf. The technology has been there for a number of years now but it is the advent of affordable sophisticated computing power that has made this possible at the consumer level.

3D ultrasound is a technique that provides a three-dimensional picture: allows one to see width, height, and depth of images. The 3D images can also be captured and saved for later review. 4D ultrasound is a technique that allows visualization of the unborn baby moving in real-time. With 4D imaging, a three-dimensional image is continuously updated, providing a “live action” view of the fetus.

4D ultrasound presents images with surface detail not possible with 2D ultrasound. 4D ultrasound uses the same high frequency sound waves as 2D. The difference is that the waves are sent into the body at multiple different angles. The reflected waves are then computer processed to reconstitute and produce the life-like image complete with movements.

The time vector (the fourth dimension) makes it possible to perceive a rapid update of eh successive individual images displayed on the monitor at very short intervals which creates the impression of a real time measurement. And enables the user to see fetal motion in almost real-time.

Benefits of 3D/4D imaging 3D/4D ultrasound promises to quite possibly make it easier for doctors to see anomalies. This is, however, a work in progress. The benefit that is certainly already realized through 4D is that it is much easier for parents to see and understand any features, normal or abnormal, that with traditional 2D imaging was very difficult or impossible for them to decipher.

Drawbacks of 3D/4D imaging

Suboptimal volume-rendered images are obtained if there are inadequate amniotic fluids surrounding the structure of interest. This is a major limitation since reduced amniotic fluid volume normally occurs as the fetus progresses towards term. Also, unacceptable surface rendering occurs with unfavorable fetal position and with adjacent or superimposed structures (i.e., limbs, umbilical cord).

In addition, image processing of the volume data may take additional time on the part of the examiner.

Is 3D sonography a good thing? Three-Dimensional ultrasound provides additional diagnostic information for the diagnosis of facial anomalies, especially facial clefts. There is also evidence that 3D ultrasound provides additional diagnostic information in neural tube defects and skeletal malformations.

Additional research is needed to determine the clinical role of 3D/4D ultrasound for the diagnosis of congenital heart disease and central nervous system anomalies. Effects of ultrasound on maternal-fetal bonding; comparison of two-and three-dimensional imaging shows that parents having a 3D exam consistently score higher than those having a 2D ultrasound exam alone for all categories of maternal fetal bonding.

Drawbacks for 3D/4D ultrasound imaging include: Limited usage in the medical community Costly Hard to learn 2D ultrasound just as good as 3D Ultrasound techs do not want to be CT techs

Drawbacks Maternal fetal bonding creates issues with Right to life advocates utilizing bully tactics Commercialization of 3D/4D ultrasounds for non-medial uses

Holdorf has the last word 3D/4D ultrasound was the flavor of the month, or “the next big thing” a few years back. Since then, the high cost of the software, the difficulty to learn the technique, and the resistance of sonographers to become CT techs has made 3D/4D last year’s news. All we are left with is folks prying on parents to pay for “entertainment images” decreasing the profession's creditability.

Homework Submit 20 3D ultrasound images of your choice explaining what each image shows. 10 normal 10 abnormal

Acrania

Holoprosencephaly

Entertainment ultrasound