B-Scan: The Reliable, Necessary, Diagnostic
continues to aid retinal specialists in detecting posterior ailments.
JOHN PARKINSON, ASSOCIATE
treatment of patients begins with an understanding of their ailments, and ocular
ultrasound continues to be a reliable technology for uncovering hidden retinal pathologies.
While B-Scan ultrasound may be a mature technology, its usefulness for screening
patients with media opacities, scanning for vitreous hemorrhages and retinal detachments,
or when viewing a variety of other posterior pathologies, makes it an indispensable
piece of equipment.
While utilizing sound beams to create images has been in practice
for years, it is good to find out how other doctors and ultrasonographers in the
field are performing ultrasound. Therefore, the focus of this article will be to
provide feedback from specialists about when they are applying B-Scan technology
in their practices and explain their techniques. Additionally, an ultrasonographer
will provide insights on his technique and offer his perspective about what it is
like to work with retinal specialists on ultrasound analysis.
APPLICATIONS AND TECHNIQUES
Mandy Conway, MD, emphasizes how important it is for new doctors
to learn how to perform ultrasound accurately. She has observed fellows at the university
where she teaches, and often when they use a probe for the first time, she notices
they believe a couple of scans completes the screening for a patient.
"As a physician who teaches younger doctors, it is important to
me to be sure they learn it the right way. If you do this [ultrasound] correctly,
you do sequential probe positions and each of them is labeled, and you do it 2 times,"
explains Dr. Conway.
For her own patients, Dr. Conway utilizes ultrasound when examining
opacities, the configuration and the extent of retinal detachments, vitreous hemorrhages,
choroidal detachments after trauma, and infections such as endophthalmitis. Dr.
Conway also uses ultrasound in clear lenses for special cases of abnormal axial
length that cause pathology in the posterior segment, measuring the length and thickness
of tumors, and occasionally when looking for choroidal osteoma. With lesions, she
is able to scan for size and periodically check for growth over time.
"B-Scan is extremely reliable," summarizes Dr. Conway.
Stephanie Skolik, MD, performs all the ultrasound scanning of
patients herself; she does not have a technician. "For anyone who has a retina that
I cannot visualize, I ultrasound them. I use it any time there is a problem with
the choroid or opacified media. If someone has a vitreous hemorrhage, and I can't
see into the eye, it helps me."
Dr Skolik's technique is to scan directly into the optic nerve,
and then proceed into different quadrants, depending on what the patient's problem
is, to make sure the retina is not detached. If there is a mass or a tumor, she
will have the patient look into that direction so she can get a better image. Dr.
Skolik also has the patient move his or her eye in different directions to help
her ascertain whether blood is moving around in the vitreous or it is a fluttering
Ronald Green, MD, performs screening for all the aforementioned
typical posterior segment problems that are usually screened with ultrasound and
utilizes the axial, transverse, and longitudinal probe positions. He points to how
he uses the transverse and longitudinal positions specifically for viewing lesions.
"The positions place the probe peripherally to the cornea and
limbus, thus minimizing sound attenuation from the lens, and that allows us to get
better resolution," explains Dr. Green. "The transverse and longitudinal scans are
90Þ to one another. This allows us to look at lesions in the eye from different
directions. Each section that we take from 1 probe position is a 2-dimensional scan,
but these scan positions facilitate 3-dimensional thinking during the examination."
AN ULTRASONOGRAPHER'S PERSPECTIVE
Fisher, diagnostic ophthalmic ultrasound specialist, Department of Ophthalmology
at the University of Iowa Hospitals and Clinics, performs ultrasound at about 0.03
mm of resolution. As his sole focus is on ultrasound, he is able to put all his
energies into screenings. A technician's commitment to individual scans can help
the retinal specialist who must focus on several different aspects during exams.
At the University of Iowa, technicians and retinal specialists
go around the entire eye with the probe to ensure a complete screening utilizing
contact ultrasound. "We are setting ourselves up into a routine so we don't miss
anything," says Fisher. "We cover all quadrants and all clock hours of the eye
much like they do in fundoscopy."
According to Fisher, contact ultrasound controls the patient's
gaze and therefore controls the diagnostic field. The contact method also prevents
Technicians' insights can also aid doctors with the diagnostic
challenges. Upon completing a B-Scan, Fisher will write up a report and then discuss
the findings with the doctor.
Fisher talks to the doctor to see that they are both on the same
page as to what they are looking for with the screening.
Fisher believes retinal specialists should educate their technicians,
so they can learn more about the pathologies they are screening.
"Retinal specialists know they can't afford to give 100% of their
time to ultrasound, and they have to work hand and glove with their technician who
is doing their screenings. [Retinal specialists] should show them where the pathology
may lie, how the disease progresses and what they do for treatment," says Fisher.
As such, Fisher says doctors should show technicians results
from other tests like angiographs; let them view color photos; and share their surgical
techniques. All this can give technicians a better overall understanding of how
pathologies are diagnosed and treated.
Dr. Conway points to B-Scans' effectiveness in finding tears
in patients with vitreous hemorrhages. She says she can normally view the hemorrhage
without difficulty, but there might be 1 spot that is being occluded because of
Fisher agrees and says the real challenge in screening hemorrhages
is to delve deeper than just to detect the presence of a hemorrhage.
"The goal of ultrasound [in these cases] is to look underneath
that hemorrhage and see if there's pathology that needs to be addressed," explains
In diabetic patients, vitreous can stick to the retina and create
tears, so doctors remain vigilant for that development with ultrasound screenings.
Another potentially difficult screening scenario is when a person
suffers an eye trauma where the eye globe has been penetrated and the retinal specialist
has to scan for foreign objects. Magnetic resonance images (MRI) or computed axial
tomography (CAT) may be considered, but ultrasound is possibly the most effective
in detecting small, foreign objects, and pinpointing its location in the posterior
segment, according to Fisher.
"For objects smaller than 2 mm, ultrasound would probably be much
more reliable because of the averaging problem of the MRI or CAT scan." Fisher also
points out an MRI cannot be used to locate a metallic foreign body.
While there are numerous conditions that can be difficult to detect,
Fisher says one of the more problematic pathologies to screen for is intraocular
lymphoma because it is a rare occurrence, and it is difficult to decipher what is
causing the pathology.
IMPORTANCE OF THE TECHNOLOGY
Having ultrasound in-house means specialists can complete a screening,
reach a diagnosis and administer subsequent treatment.
"It is tremendously important. I would say just about every time
I do an ultrasound it's a decision, of 'do I do surgery or not?'" says Dr. Skolik.
Additionally, owning an ultrasound machine means patients do not
have to go to another office to get screened. Dr. Conway spends her time between
a Tulane University practice and two privately-owned clinics and having B-Scans
in all of those offices helps her serve her patients better. "Had I not had those
machines in those outlying clinics, these people would have traveled somewhere between
30 and 40 miles to get their diagnosis," explains Dr. Conway.
Dr. Skolik works in a rural location in West Virginia and her
local hospital does not have an ultrasound, so she will use the one from her practice
when emergency cases at the hospital call for it. "I will come over, get my machine
and bring it across the parking lot to the ER to be able to ultrasound the eye before
going into the operating room. It's that important," says Dr. Skolik.
B-Scan ultrasound continues to show its significance in the retinal
practice. With its ability to view pathology, whether through a media opacity, or
to scan for other posterior segment pathologies, this established technology
aids retinal specialists and proves it is a necessary diagnostic tool in all practices.
Here are some B-Scan systems available today.
This A/B-Scan offers a multi-frequency probe for B-Scan (7.5 MHz,
12.5 MHz 15.0 MHz). Developed to facilitate optimal imaging of the retina, orbit,
and anterior segment, Accutome states this system can handle all B-Scan techniques.
Whether used as part of a preset scanning mode or set independently to accommodate
a specific scanning technique, settings are adjustable to accommodate the image
Innovative Imaging I3SYSTEM-ABD.
high-resolution A/B-scan may include four modes: 10 MHz globe/orbit B-scan,
20 MHz anterior B-scan, biometry A-scan with multiple IOL formulae, and standardized
diagnostic A-scan. Tumor vascularity and vitreo-macular traction are routinely detected.
The instrument contains a built-in floppy & 750MB Zip drives, 2-year warranty,
on-site clinical training by qualified echographers. All units upgradeable.
NIDEK Echoscan US-2500. This high-resolution instrument can be connected to an A-scan
unit. It has a selectable gain curve including a Log, Linear, and S-Curve. It can
transmit 4 partial images of specific areas. The unit can be integrated with the NIDEK Advanced Vision Information System (NAVIS) for practical data management.
OTI-Scan 2000. 10 MHz, 12 MHz or 20 MHz probes can be used for posterior segment
scanning. UBM (35 MHz or 50 MHz) scans the cornea, anterior chamber and lens, angle
to angle, sulcus to sulcus and peripheral retina. Exams can be exported to computers
(including DICOM) or recorded as digital movies. Data can be archived to CD or DVD.
3D ultrasound available.
Quantel Medical CineScan A/B. Offering
an exquisite analog image with technology and diagnostic capability previously unavailable,
The CineScan represents a true breakthrough for retina specialists according to
the company. The Cineloop and Varigain features significantly reduce exam time.
Options for the system include standardized echography and high frequency of both
anterior and posterior segments.
Retinal Physician, Issue: September 2005