It’s not difficult to define the “difficult-to-image patient.” While large patients are usually the first to spring to mind, high-risk obstetrics, ovarian cancer patients, transplant candidates and combative patients pose increased imaging obstacles for sonographers and physicians alike. But the latest iteration of ultrasound systems are easing the barriers to imaging a wide array of challenging patient conditions through improved harmonics, compound imaging and automated processes.
High-risk patients = complicated issues
The practice of Minnesota Perinatal Physicians in the Allina Health System in Minneapolis and St. Paul focuses on high-risk obstetrics, says Medical Director Manny Gaziano, MD. Ultrasound is key to the practice because they serve as a referral site for obstetricians and radiologists for maternal and fetal images.
Gaziano reports that their Philips Medical Systems iU22 ultrasound system has improved their ability to scan these complicated patients. He sees a combination of the skill of the sonographer coupled with patience and excellent equipment as essential. Some high-risk women are positioned on their sides to image through their “flank” rather than employing standard abdominal views. Or they may use transvaginal ultrasound to obtain clear images of a fetus early in pregnancy. The choice of transducer is another aspect to this specialized field, such as a transvaginal probe in this case.
While one type of challenge involves imaging large women, other “difficult to image” categories include pregnant women with decreased amniotic fluid that occurs either with ruptured membranes or if there is an intrinsic fetal problem such as kidney abnormalities. Additional imaging complications arise from fetal positions, or when the placenta is attached to the front wall of the uterus. Forty percent of the women they image have uterine tumors that complicate the imaging process, Graziano says.
Color Doppler is helpful to look for areas that are difficult to image such as the fetal kidney, he explains. If they want to make sure that the fetus has a kidney, they may not be able to determine its presence on a 2D image. Using color power Doppler imaging, based on the flow of red blood cells, enables them to see arterial blood flow to the kidneys thereby ascertaining that a kidney is present.
“Features like adjusting the gain [amplitude of the soundwave] automatically and adjusting harmonics [the balance of the frequency] automatically, and the penetration help us in scanning,” Graziano says. “There are other kinds of automation from the computer that this system gives us to optimize the images.” Although they have very skilled sonographers and physicians, he says it is helpful to have some automatic functionality to save time while improving the image.
Minnesota Perinatal Physicians has begun using the 3D capabilities of this system to identify fetal abnormalities such as cleft lip and palate, abdominal wall defects such as oomphalocoeles or spinal anomalies such as spina bifida.
Gaziano’s particular area of interest involves women who have had a Cesarean section to deliver a previous baby. When a woman has a C-section, she forms a scar, he explains. If she becomes pregnant subsequently and the placenta implants over the scar, that placenta tends to invade maternal tissues and at the time of birth it can cause a major risk of hemorrhage, necessitating hysterectomy or massive blood transfusions.
“It is helpful for us to magnify the area of interest into the scar and then use very precise color settings to show us the tongues of blood flow that go where they should not go,” Gaziano concludes. These imaging scans signal the need for the mother to be delivered in a high-risk perinatal center and prepare the team for possible problems.
Complex differential diagnoses
Michael Crade, MD, medical director of Ultrasonix (a division of Pediatrix Corp.) in Long Beach, Calif., describes their private office practice that performs ultrasound studies primarily for gynecologic patients. They use a GE Healthcare Voluson 730 ultrasound to accomplish ovarian cancer screening studies.
He images complex ovarian growths with color Doppler, capturing the volume of the mass then rotating it to isolate vascularity as he performs a differential diagnosis of the mass. His primary goal is to diagnose ovarian cancer early, and determine which patients require surgery and which do not.
Crade explains that blood