Article Date: 9/1/2005

B-Scan: The Reliable, Necessary, Diagnostic Technology
Ultrasound continues to aid retinal specialists in detecting posterior ailments.
JOHN PARKINSON, ASSOCIATE EDITOR

Successful 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 retina.

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

Tom 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 Bell's phenomenon.

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.

CHALLENGING DIAGNOSTICS

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 the hemorrhage.

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 Fisher.

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.

Today's Ultrasound Systems
Here are some B-Scan systems available today.

Accutome Advent. 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 resolution.

 

Innovative Imaging I3SYSTEM-ABD. The 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