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=20 Ultrasound for the Ultra-challenging Patient

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Ultrasound for the=20 Ultra-challenging Patient =

Health Imaging & = IT

March 1, 2006

Features

By Cheryl Hall Harris, RN=20

Clinical image=20 courtesy of Toshiba
It=92s not = difficult to=20 define the =93difficult-to-image patient.=94 = While large=20 patients are usually the first to spring to = mind,=20 high-risk obstetrics, ovarian cancer patients,=20 transplant candidates and combative patients = pose=20 increased imaging obstacles for sonographers and = physicians alike. But the latest iteration of = ultrasound=20 systems are easing the barriers to imaging a = wide array=20 of challenging patient conditions through = improved=20 harmonics, compound imaging and automated=20 processes.

High-risk = patients =3D=20 complicated issues

The practice of Minnesota Perinatal Physicians = in the=20 Allina Health System in Minneapolis and St. Paul = focuses=20 on high-risk obstetrics, says Medical Director = Manny=20 Gaziano, MD. Ultrasound is key to the practice = because=20 they serve as a referral site for obstetricians = and=20 radiologists for maternal and fetal=20 images.

Gaziano reports that their = Philips=20 Medical Systems iU22 ultrasound system has = improved=20 their ability to scan these complicated = patients. He=20 sees a combination of the skill of the = sonographer=20 coupled with patience and excellent equipment as = essential. Some high-risk women are positioned = on their=20 sides to image through their =93flank=94 rather = than=20 employing standard abdominal views. Or they may = use=20 transvaginal ultrasound to obtain clear images = of a=20 fetus early in pregnancy. The choice of = transducer is=20 another aspect to this specialized field, such = as a=20 transvaginal probe in this case.

While = one type=20 of challenge involves imaging large women, other = =93difficult to image=94 categories include = pregnant women=20 with decreased amniotic fluid that occurs either = with=20 ruptured membranes or if there is an intrinsic = fetal=20 problem such as kidney abnormalities. Additional = imaging=20 complications arise from fetal positions, or = when the=20 placenta is attached to the front wall of the = uterus.=20 Forty percent of the women they image have = uterine=20 tumors that complicate the imaging process, = Graziano=20 says.

Color Doppler is helpful to look = for areas=20 that are difficult to image such as the fetal = kidney, he=20 explains. If they want to make sure that the = fetus has a=20 kidney, they may not be able to determine its = presence=20 on a 2D image. Using color power Doppler = imaging, based=20 on the flow of red blood cells, enables them to = see=20 arterial blood flow to the kidneys thereby = ascertaining=20 that a kidney is present.

=93Features = like=20 adjusting the gain [amplitude of the soundwave]=20 automatically and adjusting harmonics [the = balance of=20 the frequency] automatically, and the = penetration help=20 us in scanning,=94 Graziano says. =93There are = other kinds=20 of automation from the computer that this system = gives=20 us to optimize the images.=94 Although they have = very=20 skilled sonographers and physicians, he says it = is=20 helpful to have some automatic functionality to = save=20 time while improving the image.

Minnesota = Perinatal Physicians has begun using the 3D = capabilities=20 of this system to identify fetal abnormalities = such as=20 cleft lip and palate, abdominal wall defects = such as=20 oomphalocoeles or spinal anomalies such as spina = bifida.

Gaziano=92s particular area of = interest=20 involves women who have had a Cesarean section = to=20 deliver a previous baby. When a woman has a = C-section,=20 she forms a scar, he explains. If she becomes = pregnant=20 subsequently and the placenta implants over the = scar,=20 that placenta tends to invade maternal tissues = and at=20 the time of birth it can cause a major risk of=20 hemorrhage, necessitating hysterectomy or = massive blood=20 transfusions.

=93It is helpful for us to = magnify=20 the area of interest into the scar and then use = very=20 precise color settings to show us the tongues of = blood=20 flow that go where they should not go,=94 = Gaziano=20 concludes. These imaging scans signal the need = for the=20 mother to be delivered in a high-risk perinatal = center=20 and prepare the team for possible=20 problems.

Complex = differential=20 diagnoses

Michael Crade, MD, medical director of = Ultrasonix (a=20 division of Pediatrix Corp.) in Long Beach, = Calif.,=20 describes their private office practice that = performs=20 ultrasound studies primarily for gynecologic = patients.=20 They use a GE Healthcare Voluson 730 ultrasound = to=20 accomplish ovarian cancer screening = studies.

He=20 images complex ovarian growths with color = Doppler,=20 capturing the volume of the mass then rotating = it to=20 isolate vascularity as he performs a = differential=20 diagnosis of the mass. His primary goal is to = diagnose=20 ovarian cancer early, and determine which = patients=20 require surgery and which do not.

Crade = explains=20 that blood vessels feeding a tumor appear very = different=20 from their normal counterparts which grow in an = orderly=20 tree-like fashion and taper at the ends. Tumor = vessels=20 grow rapidly, their arteries do not have as much = musculature in the wall of the vessels and they = are=20 larger where musculature is not normal. They = demonstrate=20 bizarre branching and some may empty into a vein = without=20 capillaries in the intervening = space.

Crade uses=20 a technique called =93Tissue Block Ultrasound=94 = to analyze=20 an anatomical volume of 3D images and discern = the=20 relationship between arteries and veins around = the=20 mass.

=93Using a feature GE calls = MagiCut, I can=20 filet the artery open and see the actual wall = becoming=20 smaller then larger then smaller,=94 says Crade. = =93I can=20 see inside the lumen of the vessel and look at = the=20 complexity of the arteries and veins. We have = found that=20 arteries in malignancies have mini-jets of blood = flow=20 just distal to areas of = narrowing.=94

While other=20 clinicians have reported about this rendering of = total=20 percentage of vasculature, Crade describes a = =93beachball=20 sign=94 when tumors are covered with veins and = arteries no=20 matter the direction from which they are=20 viewed.

A correlative benefit of using = these=20 imaging techniques is that women who are found = to have=20 benign tumors are spared surgery with its = possible=20 complications. Crade relates that his study of=20 vascularity using volume ultrasound has = significantly=20 improved his diagnostic=20 confidence.

Combative=20 patients

Peter J. Prokell, MD, president of Fort Worth = Diagnostic=20 Radiology, P.A., describes their hospital-based=20 radiology group where they have been managing = liver=20 transplant patients for about three years. With=20 underlying liver disease caused by a variety of = clinical=20 conditions, these patient are often confused and = combative because they have hepatic = encephalopathy=20 caused by high blood ammonia levels. = Additionally,=20 cirrhotic livers are difficult to penetrate with = ultrasound, and often these patients are=20 overweight.

This department upgraded = their=20 ultrasound imaging system to a Siemens Medical = Solutions=20 Sequoia 512 because they found the image quality = advantageous for their liver and pancreatic = transplant=20 patients.

=93The technical difficulty = increased=20 with liver transplants because we have to = perform a=20 thorough evaluation of the vasculature such as = hepatic=20 artery velocities which is not part of a routine = abdomen=20 exam,=94 explains Prokell. Once they had = improved the=20 quality of their imaging equipment, the second = step was=20 to build additional experience for their = technologists.=20 Using techniques such as re-positioning the = patient or=20 tilting the patient=92s head down may prove = beneficial in=20 the pre-operative evaluation phase of=20 treatment.

However, once the surgery has = been=20 performed, dealing with the operative site that = could=20 include staples, drains and bandages holds = additional=20 challenges.

=93When patients develop = post-operative=20 complications such as hepatic artery stenosis or = venous=20 thrombus, they are usually intubated and = they=92re still,=94=20 Prokell describes. =93But they have distended = abdomens,=20 multiple leads and monitors, and are on a = Triadyne bed=20 with an air mattress covering their sides and = limiting=20 positioning.=94

To image these patients, = they often=20 use different transducers, as well as employ = color=20 Doppler and power Doppler to determine blood=20 flow.

Prokell describes their = technologists as=20 extremely competent and experienced, but he says = that=20 can present difficulties for a department as = well. It=20 can prove challenging to retain good techs, = especially=20 when patients are difficult. Other centers = recruit their=20 experienced technologists away to easier=20 jobs.

Larger patients pose = unique=20 imaging challenges

The heart of the issue with large patients = involves the=20 ability of the sound waves to penetrate to the = area of=20 interest to produce the high-quality images = required for=20 diagnostic purposes. From a physical = perspective, sound=20 wave penetration is challenged by distance and = the type=20 of tissue involved. For example, livers = are=20 difficult to image because they do not transmit=20 soundwaves well. Couple that fact with a few to = several=20 inches of adipose tissue and the problem becomes = clear.

A. Thomas Stavros, MD, FACR, = director of=20 ultrasound for Invision Radiology Imaging = Associates in=20 Englewood, Colo., has been using the Toshiba = America=20 Medical Systems Aplio 80 for a number of years. = He has=20 been evaluating a substantial upgrade that = provides the=20 system with the functionality of the new Aplio = XV with=20 Differential Tissue Harmonic Imaging (DTHI). = This=20 practice involves evaluation of palpable and/or=20 mammographic breast abnormalities as well as to = guide=20 biopsies. Additionally, they do some scans = of=20 other areas of the body.

The improvements = in=20 imaging resolution for this system are designed = to=20 enhance imaging for larger patients who = previously were=20 not good candidates for ultrasound=20 imaging.

Stavros explains that the issue = with=20 using harmonics in imaging is that the = penetration is=20 often reduced. So even though tissue contrast is = improved, penetration to an area of interest may = be=20 compromised. The Aplio XV is designed as a = hybrid system=20 that is capable of creating a combination of = harmonics=20 with adequate penetration at various depths = while=20 streamlining clinical workflow.

=93I can = toggle=20 through tissue harmonics, so I can have Tissue = Harmonics=20 1 which is just pure tissue harmonics, or A, B, = C or D=20 where I get =85 a greater percentage of = fundamental=20 imaging in the far field with more = penetration,=94 Stavros=20 concludes.

Large patients over 250 pounds = at=20 Harbor-UCLA Medical Center in Torrance, Calif., = are=20 getting the advantage of HiVision8500 from = Hitachi=20 Medical Systems, according to Tom Wright, RDMS, = of=20 Harbor-UCLA Medical Center in Torrance, Calif. = They use=20 a 3.5 Megahertz (MHz) convex array transducer = probe for=20 these patients. =93Because we=92re using a = convex probe,=20 there are more crystals on large transducers and = we get=20 better images than a small vector type=20 transducer.=94

The system features Tissue = Harmonics=20 imaging that uses four levels of penetration to = reduce=20 noise. He describes that they can toggle from a = very=20 fine-grained image to a coarser image and get = more=20 penetration.

=93It also adds compound = scanning=20 which is an improvement on old techniques of = using=20 higher frequencies,=94 Wright says. =93We are = filtering or=20 listening for higher frequencies closer to the=20 transducer and then use the lower frequencies at = the=20 depth, which increases the clarity and gives a = bit more=20 penetration.=94

They also make use of = HiRes, which=20 they use not so much for the truly heavy = patient, but=20 for those in which they are interested in = increasing the=20 resolution of the upper portion of the liver, or = where=20 there is cirrhosis. HiRes reduces the = pixel size=20 so they get higher contrast and better edge=20 enhancement.

Gaziano, who images = high-risk=20 mothers, raises the issue of sensitivity towards = pregnant women who have weight issues besides = those of=20 pregnancy. He explains that they are extremely = sensitive=20 towards these women, so that they do not cause=20 embarrassment or shame because there are = difficulties in=20 imaging their fetuses. This takes staff who can = be=20 caring and reassurance that other factors may = enter into=20 the difficulties with imaging, such as those = mentioned=20 above.

Brette Sember, author of Your = Plus-Size=20 Pregnancy: The Ultimate Guide for the = Full-Figured=20 Expectant Mom, says, =93The most important thing = a=20 clinician can do is realize that many patients = are=20 uncomfortable with their bodies and are = uncomfortable=20 having medical personnel see their bodies. = Adopting an attitude of sensitivity will go a = long way=20 in helping patients feel comfortable. Don't = assume that=20 because you have seen all types of bodies that = patients=20 will know you don't make judgments.=94

In = interviews with plus-sized women contained in = her book,=20 she found there were two common scenarios that = upset=20 women. The first was when an external ultrasound = was=20 attempted and then the sonographer needed to = switch to a=20 vaginal probe. Women were upset when comments = were made=20 such as =93you have too much fat=94 or = =93you=92re too fluffy.=94=20 The others were when women were asked to hold = their=20 pannus (and almost none of the women knew what = that term=20 meant) out of the way. She suggests that = clinicians be=20 matter of fact and friendly, not avoid looking = at the=20 woman=92s face and refrain from using the word=20 =93fat.=94

Finally, she notes, =93Women = reported that=20 they greatly disliked having the ultrasound done = through=20 the navel and found that very painful. = They also=20 reported that this made them feel that it was = being done=20 because of their size and it might be helpful to = explain=20 that sometimes you just can't get a very clear = image=20 because of the way the baby is=20 = positioned.=94

Conclusion

Trends in ultrasound systems include = improvements that=20 not only make imaging easier through automatic=20 functionality, but that also provide advanced=20 capabilities to assist clinicians who care for=20 =93difficult to image=94 patients. Transducer = design has=20 evolved to provide a wide array of imaging = dynamics, and=20 3D tools have proven invaluable in a number of = specific=20 circumstances. While most believe that the = obesity=20 epidemic is the primary reason clinicians have = problems=20 obtaining clear images of the area of interest, = it is=20 only one area of = challenge.