UNDERSTANDING MEDICAL ULTRASOUNDS
This form of imaging is useful in examining organs and blood vessels and in monitoring pregnancies.
Ultrasound use in obstetrics and gynecology has been around since the 1950s. Physicians rely on this type of imaging to identify both common and complex gynecologic issues and conditions as well as the growth of the fetus during pregnancy. We spoke with Dr. Jacques Abramowicz, an obstetrician and gynecologist at the University of Chicago Medicine and an expert in using medical ultrasound to diagnose fetal abnormalities and screening for early detection of ovarian cancer.
What is an ultrasound, exactly?
Medical ultrasound uses very high frequency sound waves to provide an image of soft tissues in the body.
What are some common misconceptions you hear from patients about their ultrasound?
Particularly in pregnancy, the biggest misconception is that once we say we didn’t
see anything wrong, nothing is wrong with the baby. It means that what we saw is OK — we cannot see absolutely everything. For example, there are certain tiny defects, particularly of the heart that cannot be detected by prenatal ultrasound. The heart is the size of a dime or quarter in a term baby, so earlier in pregnancy, it’s even smaller and, thus, it is more difficult to see issues and conditions, if they exist.
What types of ultrasounds are used in obstetrics and gynecology (OB/GYN)?
We use 2D, 3D, 4D, color Doppler and spectral Doppler. Each provides a different type of image.
2D is the most commonly utilized. 3D ultrasounds are computer reconstructions of the various images that were obtained with 2D, and they give us a volume of the organ we’re looking at that we can then manipulate in different directions that the 2D doesn’t allow us to see as clearly.
When do you need to use 3D and other types of ultrasounds?
We don’t need to use 3D all the time if we can get a clear image of what we’re looking at.
For instance, in gynecology, if we don’t know where an intrauterine device (IUD) is located, 2D would give us a general idea but not an exact location. 3D reconstruction allows us to see the whole volume of the uterus, so we could more precisely locate the IUD. Another example would be a tumor in the lower pelvis — sometimes it’s a little difficult to verify if it’s uterine or ovarian. In these cases, 3D allows us to better evaluate the relations between various organs.
4D is real time 3D with movement, which means we see the anatomy in 3D, except it cannot perform reconstruction like 3D can. With 3D/4D, we can identify a problem like a cleft lip. 4D is excellent to examine the surface of the body. But if we need to look at internal organs, it is more difficult because we would have to freeze the image to spot issues better.
When do you need to use Doppler imaging?
We use spectral Doppler imaging to examine certain blood vessels in terms of how fast the blood flows and how much resistance there is to the flow in the organs we are looking at.
Color Doppler helps us visualize the vessels, because the computer adds color to anything that moves — so blood moving in blood vessels is clearly depicted with colored images.
What are some of the various uses of ultrasounds in OB/GYN?
Ultrasounds can be used for ovarian cancer screenings and to examine people with gynecological problems such as pelvic pain, abnormal bleeding, suspected fibroids and many other issues.
In general, we use abdominal ultrasound, which is when we have a probe on the abdomen. We also use vaginal ultrasound if we need to get closer to certain organs of interest, such as the uterus or ovaries.
In obstetrics, ultrasounds are used in a number of ways, including in pregnancy dating, which is typically performed very early in pregnancy. Pregnancy dating means determining the gestational age of the patient and date of delivery. Not all patients know when they become pregnant, so that can be extremely useful to follow the growth of the fetus and determine when the fetus should be delivered.
Ultrasound is also important in looking at the placenta for abnormalities as well as at the cervix to verify length and thickness.
In the first trimester (around 11 to 12 weeks), we will check the back of the neck thickness (called nuchal translucency or NT), which is a screening test for issues in general.
We usually will do an anatomy scan around 18 to 20 weeks, where we look at the various fetal organs. This is when we can need to use 3D to look at the fetal face, to rule out cleft palette and look at the spine to rule out spinal issues.
In the third trimester, we perform a biophysical profile, which means looking at fetal breathing and body movements as well as assessing the amount of amniotic fluid around the baby. This gives us an idea of the fetal health status.
Can parents come just to get an image of their baby for fun?
We do not approve of “souvenir” ultrasound or “entertainment” ultrasound. There are stores in certain malls where you can have a 3D ultrasound, but we (along with the American Medical Association and other professional groups) don’t approve of that. It’s a medical procedure that should be used as such, with a clear indication.
We will give 3D pictures to the parents when it’s within the frame of medical ultrasound. We will give a couple of pictures if the baby is in the right position and if there is enough fluid around the baby.
Are there risks associated with ultrasound?
Although ultrasound is considered safe, it is a form of energy that has the potential to heat and displace tissues. Heat has the potential to cause birth defects, as it has been clearly shown in tests with animals.
The ultrasound practice at UChicago Medicine is accredited by the American Institute of Ultrasound in Medicine. This involves a voluntary peer-review process that determines nationally recognized standards in the performance and interpretation of diagnostic ultrasound examinations are met or exceeded.